Liebert Switch POWER PROTECTION STATIC TRANSFER SWITCH User Manual

POWER PROTECTION  
USER MANUAL  
STATIC TRANSFER SWITCH 2  
100-1000 Amp  
50-60 Hz  
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TABLE OF CONTENTS  
i
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ii  
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iii  
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iv  
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FIGURES  
Figure 1  
Figure 26 Control wiring for comms board (see Figure 27 on page 39 for internal modem wiring) . . . . . . 38  
v
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TABLES  
vi  
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IMPORTANT SAFETY INSTRUCTIONS  
Save these instructions  
This manual contains important instructions that should be followed during the installation and  
maintenance of the Liebert Static Transfer Switch 2 (STS2).  
WARNING  
!
The unit is supplied by more than one power source. the Unit contains hazardous voltages if  
any of the input sources are ON, even when the unit is in bypass. To isolate the unit, turn  
OFF and lock out ALL input power sources.  
Verify that all input power sources are de-energized and locked out before making connections  
inside unit.  
Lethal voltages exist inside the unit during normal operation. Only qualified service  
personnel should perform maintenance on the static switch.  
NOTE  
Read the entire manual before installing or operating the system. Adhere to all operating  
instructions and warnings on the unit and in this manual.  
Liebert Corporation neither recommends nor knowingly sells this product for use with life  
support or other FDA-designated “critical” devices.  
The Static Transfer Switch is suitable for indoor use only. Protect the unit from excessive  
moisture and install the unit in an area free from flammable liquids, gases, or corrosive  
substances.  
The unit is designed to operate from solidly grounded AC power sources only. Provide input  
over-current protection in accordance with the unit ratings. Wire and ground the unit  
according to national and local electrical safety codes. All wiring should be installed by a  
qualified electrician.  
Before unit is placed into service for the first time, after equipment relocation, or after the unit  
has been de-energized for an extended period of time, a thorough equipment inspection and  
supervised start-up by qualified service personnel are strongly recommended.  
CAUTION  
!
This unit complies with the limits for a Class A digital device, pursuant to Part 15 Subpart J  
of the FCC rules. These limits provide reasonable protection against harmful interference in a  
commercial environment. This unit generates, uses and radiates radio frequency energy and,  
if not installed and used in accordance with this instruction manual, may cause harmful  
interference to radio communications. Operation of this unit in a residential area may cause  
harmful interference that the user must correct at his own expense.  
WARNING  
!
Locate the center of gravity symbols  
the cabinet.  
and determine the unit’s weight before handling  
1
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OVERVIEW OF MANUAL  
The STS2 Installation, Operation and Maintenance Manual is organized in a logical progression so  
that you can follow the procedures, in the order provided to get your STS2 installed and running.  
Read the entire manual before proceeding with the unpacking and installation of the STS2.  
The major sections are as follows:  
Important Safety Instructions—review the instructions on the previous page before proceeding.  
Support Information—a blank table in which you can enter pertinent data, such as the serial and  
part numbers, which is needed when calling Liebert support.  
Programmable Relay Board Settings Record—a blank table in which you can document your  
Programmable Relay Board settings.  
Input Contact Isolator Settings Record—a blank table in which you can document your Input  
Contact Isolator settings.  
1.0 - Safety Precautions—provides safety warnings that you must review before proceeding.  
2.0 - Unpacking and Inspections—provides instructions for inspecting, unloading, handling and  
removing the STS2 from the shipping pallet.  
3.0 - Location Considerations—provides information regarding environmental considerations for  
where the STS2 is installed.  
4.0 - Locating the STS2—provides instructions for leveling the STS2 and anchoring the unit to the  
floor, should that be required.  
5.0 - Power and Control Wiring—provides instructions wiring the STS2 for power and control con-  
nections.  
6.0 - Options—lists the options available for the STS2.  
7.0 - Installation Drawings—provides outline, seismic and electrical field connection drawings  
required for installing the STS2.  
8.0 - Introduction to STS2 Operations—provides a system description.  
9.0 - Theory of Operation—provides an overview of how the unit works, plus a brief overview of  
some of the components.  
ing the system on and off, completing a maintenance by-pass, and selecting a preferred source.  
11.0 - Alarm and Faults—provides a list of event messages.  
12.0 - Communication Interfaces—discusses the communication ports and provides a list of termi-  
nal and modem commands.  
13.0 - STS2 Touch Screen Display—provides instructions for using the HMI touch screen interface  
for monitoring and managing the STS2.  
14.0 - Operating the LED Display STS2—provides instructions for operating the LED Display  
unit without the touch screen display.  
15.0 - Specifications—provides specifications for the STS2.  
16.0 - Event Message Help Text—provides the help text for the various system event messages.  
This help is also available through the touch screen interface.  
17.0 - Maintenance—briefly discusses routine maintenance, provides proper torque settings for nuts  
and bolts, and provides the Liebert contact information.  
2
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Safety Precautions  
1.0 SAFETY PRECAUTIONS  
Read this manual thoroughly before working with the static transfer switch.  
Be sure to review the warning under Important Safety Instructions on page 1.  
Refer to the Handling Considerations on page 5 before attempting to move the unit.  
Under typical operation and with the doors closed, only normal safety precautions are necessary. The  
area around the static transfer switch should be kept free from puddles of water, excess moisture and  
debris. The vent grate in the front of the system should not be obstructed in order to ensure a smooth  
air flow through the unit for cooling.  
ONLY qualified service personnel should perform maintenance on the static transfer switch. When  
performing maintenance on any part of the equipment under power, service personnel and test equip-  
ment should be located on rubber mats. The service personnel should wear insulating shoes for isola-  
tion from direct contact with the floor.  
Unless all power is removed from the input sources to the unit, one person should never work alone. A  
second person should be on hand to assist and summon help, should an accident occur.  
Three types of messages are used throughout this manual to stress important text. Carefully read the  
information below each Warning, Caution and Note and use professional skills and prudent care  
when performing the actions described in that text.  
A Warning indicates the presence of a possible serious, life-threatening condition. For example:  
WARNING  
!
The unit is supplied by more than one power source. The Unit contains hazardous voltages if  
any of the input sources is ON, even when the unit is in bypass. To isolate the unit, turn OFF  
and lock out ALL input power sources.  
Verify that all input power sources are de-energized and locked out before making connections  
inside unit.  
Lethal voltages exist inside the unit during normal operation. only qualified service personnel  
should perform maintenance on the static switch.  
A Caution indicates a condition that could seriously damage the equipment and possibly injure per-  
sonnel. For example:  
CAUTION  
!
Risk of unit damage  
The input sources to the static switch must be grounded-wye sources. input sources other  
than solidly grounded-wye sources may cause damage to the switch.  
A Note emphasizes important text. If the instructions are not properly followed, the equipment could  
be damaged or may not properly operate. For example:  
NOTE  
Read the entire manual before installing and operating the unit.  
3
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Unpacking and Inspections  
2.0 UNPACKING AND INSPECTIONS  
NOTE  
Read the entire manual before installing and operating the unit. Upon receipt of the Static  
Transfer Switch2, the installer should perform the following steps to assure a high-quality  
installation.  
A high-quality installation begins on the receiving dock. The STS2 and its packaging should be  
inspected when the unit is delivered. If the packaging is not damaged, unpack the unit and conduct  
an internal inspection before beginning the installation process. This section discusses the inspecting  
and unpacking of the STS2.  
2.1  
External Inspections  
1. While the STS2 is still on the truck, inspect the equipment and shipping container(s) for any signs  
of damage or mishandling. Do not attempt to install the system if damage is apparent.  
2. Upon receipt and before unpacking, inspect the shipping crate for damage or mishandling. Check  
the Shock-Watch™ indicator.  
• If the indicator is red, note on shipper’s receipt and check for concealed damage.  
• If any damage as a result of shipping is observed, file a damage claim with the shipper within  
24 hours and contact your local Liebert representative or Liebert Global Services at  
1-800-543-2378 to inform them of the damage claim and the condition of the equipment.  
3. Locate the bag containing the keys for the front access door. The bag is attached to the cabinet.  
4. Compare the contents of the shipment with the bill of lading. Report any missing items to the  
carrier and to Liebert Global Services immediately.  
5. Check the nameplate on the cabinets to verify that the model numbers correspond with the one  
specified. Record the model numbers and serial numbers in the front of this installation manual.  
A record of this information is necessary should servicing be required.  
6. If unit is to be stored before installation, it is recommended to store the unit in a dry environment  
with temperatures in the range of -40°F (-40°C) to 176°F (80°C). Use original packing materials or  
other suitable means to keep the unit clean. When opening the shipping crate, use care not to  
puncture the container with sharp objects.  
2.2  
Unloading and Handling  
CAUTION  
!
Risk of unit damage.  
When moving the unit by forklift, lift the unit from the rear so as to protect the front panel.  
Do not exceed a 15 degree tilt with the forklift.  
Also, if you are moving the unit by forklift or pallet jack after it has been removed from the  
pallet, be aware of the location of the casters and leveling feet so as not to damage them.  
Most STS2 models are contained in one cabinet. The 800–1000 amp units are contained in two cabi-  
nets that are connected together and shipped on one pallet.  
Because the weight distribution in the cabinet is uneven, use extreme care during handling and  
transporting.  
The unit can be moved by forklift or pallet jack.  
See 2.2.2 - Unit Preparation on page 5 for instruction on removing the STS2 from the pallet.  
4
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Unpacking and Inspections  
2.2.1 Handling Considerations  
The static switch is bolted to a wooden shipping pallet to allow handling by forklift equipment or a  
pallet jack.  
Easily Moved — The unit is furnished with integral castors that allow the unit to be rolled into place  
after it has reached its location and is removed from the pallet.  
WARNING  
!
Exercise extreme care when handling static switch cabinets to avoid equipment damage or  
injury to personnel.  
The cabinet can be safely tilted 15 degrees in any direction by forklift.  
If moving the unit up a ramp on its casters or a pallet jack, ensure that the incline does not  
exceed fifteen (15) degrees.  
Locate the center of gravity symbols  
the cabinet.  
and determine the unit’s weight before handling  
Check the unit size and weight — Refer to the cabinet drawings furnished with the unit for size  
and weight. Typical cabinet dimensions are shown in Figures 5 through 7. Typical unit weights are:  
100-250 amp  
400-600 amp  
800-1000 amp  
780 lbs. (354 kg)  
1200 lbs. (544 kg)  
2500 lbs. (1134 kg).  
Plan the route — Review the route over which the unit will be transported to its installation loca-  
tion to ensure that all passages are large enough to accommodate the unit and support the weight.  
Check for any non-negotiable corners or offsets in hallways. Before moving the unit to the intended  
location, review 3.0 - Location Considerations.  
2.2.2 Unit Preparation  
The unit can be removed from the pallet before it is moved to its location.  
Complete the following steps to properly remove the STS2 from the shipping pallet:  
1. Set the pallet in a level area with enough room to maneuver and remove the unit.  
2. Remove the bolts holding the unit to the shipping pallet (located in the base of the unit).  
3. Remove the shipping blocks from under the frame of the unit.  
4. Use a forklift to raise the unit off the pallet and onto the floor. Ensure that the forklift is clear of  
the unit’s casters and leveling feet. Lift the unit from the rear.  
5. Conduct an internal inspection of the unit. See the list below of inspection items.  
2.3  
Internal Inspections  
After the STS2 has been unpacked, conduct an internal inspection:  
1. Verify that all items have been received.  
2. If spare parts were ordered, verify their arrival.  
3. After the Static Transfer Switch has been removed from the pallet, open the door and remove  
cabinet panels to check for shipping damage to internal components.  
4. Check for loose connections or unsecured components in the cabinet(s).  
5. Check for any unsafe condition that may be a potential safety hazard.  
After the STS2 has been inspected and no problems are found, the unit can be moved to its installa-  
tion location. If using a forklift, remember to lift the unit from the rear.  
5
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Location Considerations  
3.0 LOCATION CONSIDERATIONS  
The STS2 should be placed in a clean, cool and dry location. The STS2 requires only front access for  
installation and maintenance. Back or side access is not required. Adequate space is required above  
the unit for conduit (if configured as such) and cooling air flow. This section provides specific informa-  
tion for these considerations.  
The unit is designed with top and bottom cable terminations to allow maximum flexibility in its  
installation. If bottom cable entry is used, sufficient cable bending space must be provided by a raised  
floor or a floor stand.  
For dimensions of each unit, see Figures 5, 6 and 7 in section 7.0 - Installation Drawings on  
page 17. If your unit is equipped with an optional key lockout switch, see Figures 8 through 10 for  
location of that switch.  
3.1  
3.2  
Recommended Minimum Service Clearances  
The recommended service clearances are at the front of the unit. The minimum service clearance  
required by the National Electrical Code (NEC) Article 110-26 is 36 in. (91 cm) for units with voltages  
up to 150 volts to ground and 42 in. (107 cm) for units with voltages over 150 volts to ground. Clear-  
ance of at least 18 in. (46 cm) is required above the unit for cooling air flow.  
Heat Output  
The unit produces minimal heat during normal operation.  
Table 1  
Heat Output  
Heat Output  
BTU/Hr (kW)  
Switch Size  
100 amp  
250 amp  
400 amp  
600 amp  
800 amp  
1000 amp  
2,711 (0.80)  
4,680 (1.37)  
6,972 (2.04)  
10,520 (3.08)  
13,777 (4.03)  
17,390 (5.09)  
3.3  
Operating Environment  
The unit is designed to be installed indoors where the ambient air temperature is in the range of 32°  
and 104°F (0°C and 40°C) with a relative humidity of 0% to 95% non-condensing, up to an altitude of  
4000 feet (1200 meters).  
6
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Location Considerations  
3.4  
Altitude  
The standard units are designed for full load operation up to 4000 feet (1200 m) above sea level. See  
Figure 1 for recommended deratings for altitudes greater than 4000 feet (1200 m).  
Figure 1 Recommended derating for high altitude operation  
100  
98  
96  
94  
92  
90  
88  
86  
Altitude (Feet Above Sea Level)  
Operation at full load at a higher altitude can be accommodated in ambient temperatures less than  
104°F (40°C) ambient. Figure 2 shows the maximum allowable ambient temperature for full load  
operation at altitudes above 4000 feet (1200 m).  
Figure 2 Maximum ambient temperature for full load operation at higher altitudes  
104.0 (40)  
102.2 (39)  
100.4 (38)  
98.6 (37)  
96.8 (36)  
95.0 (35)  
93.2 (34)  
94.1 (33)  
89.6 (32)  
87.8 (31)  
86.0 (30)  
Altitude—Feet  
Table 2  
Altitude conversion—feet to meters  
Feet  
4000  
4500  
5000  
5500  
6000  
6500  
7000  
Meters  
1200  
1372  
1524  
1676  
1829  
1981  
2134  
Feet  
7500  
8000  
8500  
9000  
9500  
10000  
Meters  
2286  
2438  
2591  
2743  
2896  
3048  
Altitude  
Altitude  
7
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Locating the STS2  
4.0 LOCATING THE STS2  
This section provides instructions for leveling the STS2 and anchoring the unit to the floor, should  
that be required.  
For leveling feet details, see Figures 5 through 10.  
4.1  
Leveling and Anchoring the Unit to the Floor  
The STS2 can be anchored to the concrete floor to ensure stability for the unit in the event of seismic  
activity.  
The seismic brackets are an option for the STS2 and are shipped separately from the unit when  
ordered.  
See Figures 11 through 13 for instructions and details for installing seismic anchoring.  
4.2  
4.3  
Leveling of the Static Switch Without Anchoring  
The Static Transfer Switch is furnished with casters and leveling feet. After final positioning of the  
unit, adjust the leveling feet located in each corner of the frame base to level and stabilize the unit.  
Leveling and Anchoring the Static Switch Using Floor Stand  
The STS2 can be installed using the optional floor stand to support the unit instead of using the  
raised floor. The STS2 can be rolled or placed using a lift on to the floor stand.  
After final positioning of the unit, adjust the leveling feet located in each corner of the frame base to  
level and stabilize the unit.  
The floor stand can also be used to ensure the unit’s stability in the event of seismic activity by  
anchoring the STS2 to the floor stand and to the concrete floor .  
The seismic floor stand is shipped separately from the unit when ordered.  
See Figures 33 through 44 for instructions and details for installing seismic floor stand.  
8
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Power and Control Wiring  
5.0 POWER AND CONTROL WIRING  
All power and control wiring should be installed by a qualified electrician. All power and control wir-  
ing must comply with the NEC and applicable local codes. Unless otherwise labeled, use the recom-  
mended tightening torque as shown in Table 25 - Torque tightening.  
The busbars are accessible through the front of the STS2 and designed to allow one-handed tightening.  
Cables can be installed through the top or bottom of the unit through removable conduits plates.  
See Figures 5 through 10 for wiring entrance locations.  
Input wiring also can be installed under a raised floor to optional input junction boxes and cables,  
when used.  
5.1  
Input And Output Power Connections  
If the unit is furnished with input junction boxes, the input power connections are made to the input  
power terminals located in the junction boxes. Input power cables, furnished with the input junction  
boxes, are shipped unattached to the unit for connection between the junction boxes and the bus bars  
provided inside the unit. Input junction box installation is discussed in 5.2 - Input Junction Box  
If input junction boxes are not furnished, the input power connections are made to the bus bars pro-  
vided inside the unit. These bus bars are accessible through the front of the unit.  
Output power connections also are made to the bus bars provided inside the unit. These bus bars are  
accessible through the front of the unit. See Figures 14 to 19 for details on the bus bars.  
WARNING  
!
Risk of electric shock  
Verify that all input power and control circuits are de-energized and locked out before making  
connections inside unit.  
The two input power feeds (sources) to the STS2 should be from two independent sources to avoid a  
common source failure.  
To ensure proper operation of the STS2, the two input sources must be the same nominal voltage level  
and phase rotation.  
For uninterrupted automatic transfer, the two input sources should be synchronized within 15 degrees.  
CAUTION  
!
Risk of unit damage.  
The input sources to the static switch must be grounded-wye sources. Input sources other  
than solidly grounded-wye sources may cause damage to the switch.  
The STS2 is designed for operation with 3 or 4-wire solidly grounded sources only.  
For 4-wire operation, the common source neutral must be connected to the STS2. See Figure 3 on  
page 9 for a typical one-line diagram. Refer to Figures 14 to 19 for electrical field connections on all  
units, with both single and dual output breakers.  
Figure 3 Typical static transfer switch one-line diagram  
SOURCE 1  
SOURCE 2  
SS1
SS2
CB1  
K1  
CB2  
K2  
K2 K3  
CB4  
CB3  
K1 K3  
CB5  
OUTPUT  
9
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Power and Control Wiring  
The input and output power wire size should be based on the upstream overcurrent protection device,  
observing the NEC and local codes.  
The molded case switches contained in the STS2 are typically non-automatic circuit breakers that  
rely on the upstream and/or load overcurrent protection. Upstream overcurrent protection should be  
rated equal to or less than the rating of the STS2 molded case switches.  
The STS2 input and output power and ground and neutral bus bars accommodate a wide range of  
wire sizes. The STS2 bus bars accommodates standard 2 hole lugs.  
Table 3  
Input/output conduit plate specifications  
Max. number and size  
Rating  
100-250A  
400-600A  
800-1000A  
6 — 3" conduit  
9 — 4" conduit  
12 — 4" conduits  
5.2  
Input Junction Box Installation (Optional)  
The input junction box option is available to simplify input connections to the STS2. Two input junc-  
tion boxes and the associated flexible 10 foot long (3 meter) input cables are provided with this option.  
This option is available only with bottom cable entrance, typically when the unit is located on a raised  
floor.  
If the input junction boxes will be used, they either can be shipped with the unit or shipped in  
advance to be installed during the rough-in stage of construction.  
Locate the junction boxes a maximum of 8 feet (2.4 meters) from the planned location of the Static  
Switch.  
Due to a lack of clearance for the cables below the unit, the cables are also shipped loose from the unit  
for installation at the site. The input cables connect from the input junction boxes to the input power  
bus bars inside the STS2.  
The standard configuration for the input junction boxes and cables is for 3-wire-plus-ground feeds. If  
the input neutral is required, special 4-wire-plus-ground input cables and junction boxes are required.  
See Figure 30 for wiring details.  
For preparation purposes, the following tables provide the dimensions and wire sizes for the input  
junction boxes.  
Table 4  
Input junction box dimensions  
Length Width Height  
Inches (mm) Inches (mm) Inches (mm)  
Switch Rating  
100 amp  
16 (406)  
30 (762)  
14 (356)  
16 (406)  
6 (152)  
6 (152)  
250 to 600 amp  
Table 5  
Switch Rating  
100 amp  
250 to 600 amp  
Input junction box terminal wire size range  
Power and Ground Lug Wire Range  
#6 to #2/0 AWG  
(2) #6 AWG to (2) 500 kcmil  
10  
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Power and Control Wiring  
5.3  
System Grounding  
Equipment grounding — Grounding is primarily for equipment and personnel safety, although  
proper grounding also enhances equipment performance.  
All input and output power feeds must include an equipment grounding means as required by the  
NEC and local codes.  
An insulated equipment ground conductor is recommended to run with each input and output power  
feed. The equipment ground conductors should be at least the minimum size conductor per the NEC  
based on the upstream overcurrent protection device.  
WARNING  
!
If conduit is used as a grounding means, adequate electrical continuity must be maintained at  
all conduit connections. The use of isolating bushings with a metal conduit can be a safety  
hazard and is not recommended.  
4-Wire-Plus-Ground Systems — When 4-wire-plus-ground input feeds are utilized, the input power  
sources must be properly grounded. Because the neutral is not switched by the STS2, the neutrals of  
the two power sources are solidly interconnected. The NEC prohibits grounding a power source at  
more than one point. Connecting the neutrals of two grounded power sources together effectively  
grounds each of the sources at more than one point, which allows neutral current to flow on the  
ground system, defeats ground fault protection, creates a safety hazard, and violates the NEC.  
Where possible, the two power sources should be located in close proximity and a single  
neutral-to-ground bond made (as shown in Figure 4 on page 11 or as is typical with a double-  
ended substation).  
Figure 4 Typical one-line diagram of two PDUs and a static transfer switch  
SOURCE 1  
SOURCE 2  
MICB1  
MICB2  
ISOLATION  
TRANSFORMER  
ISOLATION  
TRANSFORMER  
SS1  
SS2  
CB1  
K1  
CB2  
K2  
K2 K3  
CB4  
CB3  
K1 K3  
CB5  
225A  
225A  
225A  
225A  
225A  
225A  
5.4  
Control Wiring Connections  
No control wiring is needed on the standard STS2. Only certain options require external control wir-  
ing. See 6.0 - Options on page 13 for details  
11  
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Power and Control Wiring  
5.5  
Remote Source Selection Wiring  
An optional Remote Source Selection board may be installed in your STS2. This board is installed in  
the same bay as the communications options. See Figures 21 and 22 for the location of these options.  
See Figure 23 for information on the control wiring for the Remote Source Selection option.  
The Remote Source Selection allows you choose the preferred input source from a remote location.  
Terminal connections allow the customer to remotely select a source to be the preferred source in the  
same process as the local source transfer selection.  
The unit’s preferred source selection and Remote Source Selection are active at the same time, with  
the STS2 following the last request for a preferred source change, regardless of whether it was from  
the local or Remote Source Selection controls.  
A six pin terminal block provides the Remote Source Selection connections. Two pairs of wires are  
used from the switch to trigger the source selection. You can select the type of switch used for this  
remote control. Connections are made to four of the connections, using Form A dry contacts. The con-  
tacts are numbered left to right:  
Table 6  
Contact  
Remote source selection terminal block  
Connection  
Source 1  
1
2
3
4
5
6
Isolated ground  
Source 2  
Isolated Ground  
DO NOT USE  
DO NOT USE  
See 10.3 - Enabling Remote Source Selection for instructions on enabling the Remote Source  
Selection option.  
5.6  
Power Supply  
The STS2 is supplied with redundant power supplies that are designed to operate from a voltage  
range of 200V to 600V. The unit is set at the factory to match the nameplate voltage. Field adjust-  
ments are not necessary. If the unit needs to operate at a voltage other than what is listed on the  
nameplate, contact Liebert Global Service or the local Liebert representative. Table 7 provides trans-  
former tap information.  
Table 7  
Terminal block 1 and terminal block 2 wire connections  
Connect t Connect  
F1  
TB1-XX  
F2  
TB1-YY  
F3  
TB2-XX  
F4  
TB2-YY  
Jumper  
Between  
Voltage  
200  
208  
220  
240  
380  
400  
415  
480  
600  
1
1
2
1
1
1
1
1
1
9
1
1
2
1
1
1
1
1
1
9
1-7  
1-7  
6-8  
1-7  
2-7  
3-7  
4-7  
5-7  
6-7  
10  
12  
11  
8
10  
12  
11  
8
9
9
10  
11  
12  
10  
11  
12  
CAUTION  
!
Using Table 7, ensure that the wiring for the control transformers matches the input voltage  
for the unit.  
Improper wiring could result in blown fuses.  
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Options  
6.0 OPTIONS  
This section discusses the options available for the STS2. The communications options are also dis-  
6.1  
Programmable Relay Board  
The Programmable Relay Board (PRB) provides a means to trigger an external device when an event  
occurs in the STS2. Each PRB has 8 channels. Each channel has two sets of Form-C dry contacts,  
rated 1 Amp @ 30 VDC or 250 mAmp @ 125 VAC.  
Any alarm/event can be programmed to any channel or channels. Up to ten (10) events can be pro-  
grammed to a relay. If multiple events are grouped to one relay, group the events logically to simplify  
troubleshooting when an event is triggered. The same alarm/event can be programmed to more than  
one channel. Up to two Programmable Relay Boards can be installed in the STS2 for a total of 16  
channels. Programming is performed through the touch screen display.  
instructions for reconfiguring the relays. See Figures 21 and 22 for the location of the PRB. See  
Figure 24 for wiring details. Table 8 provides the PRB pinout.  
Table 8  
TB1  
Programmable relay board pinout  
Channel  
Pin No.  
1-3  
C
1
N.C.  
2
N.O.  
3
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
CH1  
4-6  
4
5
6
7-9  
7
8
9
CH2  
CH3  
CH4  
CH5  
CH6  
CH7  
CH8  
10-12  
13-15  
1-3  
10  
13  
1
11  
14  
2
12  
15  
3
4-6  
4
5
6
TB2  
7-9  
7
8
9
10-12  
13-15  
1-3  
10  
13  
1
11  
14  
2
12  
15  
3
4-6  
4
5
6
TB3  
TB4  
7-9  
7
8
9
10-12  
13-15  
1-3  
10  
13  
1
11  
14  
2
12  
15  
3
Key: N.O. = Normally Open; N/C. = Normally Closed; C = Common  
Note: Pin 16 not used on TB1, TB2, and TB3.  
6.2  
Optimized Transfer  
When the STS2 is used as a primary-side switch—on the primary of an isolation transformer—opti-  
mized transfer greatly reduces the transformer magnetization current during automatic transfers  
through a new transfer control algorithm. The Liebert algorithm (patent pending) optimizes the  
transfer timing so that the volt-seconds applied to the downstream transformer primary is balanced,  
minimizing peak saturation current.  
The volt-second balance is achieved by directly computing the volt-second applied to the transformer  
during transfer events and determining the optimum time to turn on the alternate source SCRs in  
order to balance the volt-second within specified tolerance.  
Optimized transfer also seeks to minimize the voltage disturbances while still maintaining trans-  
former flux balance. This unique flux balance algorithm does not just wait for the balance point to  
occur, but will pulse fire the SCRs as soon as possible to minimize the voltage disruption. This results  
in far superior voltage waveforms applied to the load.  
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Options  
6.3  
6.4  
Distribution Cabinet With I-Line Panelboard—100-600A Units Only  
A distribution cabinet with a Square D I-Line panelboard offers space to plug in up to 10 three-pole  
branch circuit breakers (100A-250A). The panelboard is rated at 600A with an overall short-circuit  
rating of 100,000 AIC.  
The full-height cabinet mounts on either the right or left side of the STS2 and is fully enclosed with a  
keylock door and an accent cover that permits access to the panelboard without exposing other por-  
tions of the STS2.  
Input Contact Isolator Board  
The Input Contact Isolator Board (ICI) provides an STS2 module interface for up to eight external  
user alarm or message inputs to be routed through the static transfer switch’s alarm network. The  
eight contacts are normally open dry contacts. When a contact closes, an event is triggered.  
The Input Contact Isolator options are configured through the Input Contact Isolator dialog box,  
which is accessed from the Comm Option dialog box on the touch screen display. You also can pro-  
gram the alarm messages through this dialog box. See Configuring the Input Contact Isolator  
Settings on page 95 for instructions on configuring the connections.  
See Figures 21 and 22 for the location of the ICI. See Figure 25 for wiring details.  
6.5  
Comms Board  
The Comms Board provides a communication interface to Liebert SiteScan, site monitoring product,  
and/or an external or internal modem. SiteLink-12 or SiteLink-4 is required for SiteScan to communi-  
cate with the STS2.  
The Comms Board is equipped with an RS-422 communication port for communication to a Liebert  
SiteScan monitoring system using a 2-wire twisted pair for reliable communication up to 1000 meters  
(3281 feet). Information available from the RS-422 port includes the present switch status informa-  
tion, all monitoring parameters, and all active alarms.  
The Comms Board is equipped with a modem interface for remote reporting of the present switch sta-  
tus information, alarm history information, and the history of status screens that are triggered upon  
a major alarm event. The monitoring system software also supports an auto-dial feature that allows  
the system to automatically dial programmed phone numbers by way of the modem to report desig-  
nated alarm conditions.  
Programming the Comms Board is performed through the touch screen display. See Comm  
Options on page 93 for details.  
See Figures 21 and 22 for the location of the Comms Board.  
See Figure 26 for information on the control wiring.  
6.6  
Internal Modem  
The Internal Modem is an option that must be ordered separately. An external modem is available  
from third party sources. The Internal Modem is capable of dialing out from the STS2 or accepting  
incoming calls and connecting to a remote terminal or computer. Using an ASCII Query and Answer  
format the modem connection can be used to view system status and alarms. The modem provides all  
information normally available on the LCD display of the STS2. No control functions are available via  
the modem, such as making transfers, selecting a preferred source, or changing configurations.  
The modem can also be configured to dial out two different telephone numbers (any combination of  
modem or pager numbers).  
The connection to this modem is through a standard RJ-11 port.  
See Figures 21 and 22 for the location of the internal modem. See Figure 27 for more information  
on the internal modem.  
Programming the modem is performed through the touch screen display, see Configuring the  
Modem on page 94 for details.  
The modem commands are shown in Table 10.  
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Options  
6.7  
Network Interface Card (NIC)  
An OpenComms Network Interface Card (NIC) enables the STS2 to communicate to a network man-  
agement system (NMS). The NIC provides the internal hardware and software to communicate, via  
SNMP, to any I.P.-based Ethernet network through an RJ-45 connector using Category 5 cabling.  
The NIC provides redundant paths for communications that make it possible to connect to a Building  
Management System (BMS) using Modbus, while simultaneously communicating to a NMS through  
SNMP. A terminal block provides the connection to Modbus.  
See Figures 21 and 22 for the location of the NIC.  
See Figure 28 control wiring information.  
If you have questions about the NIC, refer to the OpenComms Network Interface Card Installation  
and Users Guide.  
6.8  
6.9  
LED Display  
A light-emitting diode display is available to replace the standard liquid crystal display touch screen  
control. The display provides monitoring and control throuh a series of LEDs and buttons. LEDs alert  
you when a problem occurs. A PC running terminal emulation solfware conneted to the RS-232 port is  
needed to access the data and configuration settings.  
Remote Source Selection  
The Remote Source Selection allows the preferred input source to be chosen from a remote location. A  
user supplied normally open dry contact allows the user to remotely select a source to be the preferred  
source in the same process as the local source transfer selection.  
The unit’s preferred source selection and Remote Source Selection are active at the same time, with  
the STS2 following the last request for a preferred source change, regardless of whether it was from  
the local or Remote Source Selection controls.  
See 10.3 - Enabling Remote Source Selection for instructions on enabling the Remote Source  
Selection.  
See Figures 21 and 22 for the location of the Remote Source Selection option.  
trol wiring.  
6.10 Key Lockout Switch  
The key lockout switch activates a software lockout of the touch screen display to prevent manual  
transfers and configuration changes. When locked out, the touch screen becomes a read only display.  
A key is needed to do manual transfers or change settings.  
The alarm silence button is not disabled when in the lockout position.  
The switch is located behind the front door but can be operated without opening the front door. See  
Figures 8 to 10 for the key lockout location on each unit.  
See 14.1.4 - Key Lockout Switch for instructions on using the key lockout switch.  
6.11 Redundant Output Breaker  
An output plug-in, non-automatic circuit breaker is provided which allows redundancy in the output  
power path. The breaker is connected in parallel with the output plug-in non-automatic circuit  
breaker.  
15  
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Options  
6.12 Input Junction Boxes and Cables  
Two input power junction boxes and interconnecting cables provide under floor connection for the two  
input power feeds. Power terminal blocks are provided in each junction box for the connection of the  
input power conductors and a parity-sized ground conductor. The junction boxes are NEMA 1 enclo-  
sures. A main input cable assembly is provided for connection between the unit and the junction box.  
The cable length between the unit and junction box is 10 feet (3 meters) long.  
See 5.2 - Input Junction Box Installation (Optional) on page 10 for more information and specifi-  
cations. See Figure 30 for wiring details.  
6.13 Seismic Floor Anchors  
Seismic anchors are available for anchoring the unit to a concrete floor to meet seismic Zone 4  
mation. Installation details are provided in Figures 11 through Figure 13 on page 25.  
6.14 Seismic Floor Stand  
Seismic floor stands in four heights—18", 24", 30" and 36" (457mm, 610mm, 762mm and 914mm)—  
are available for the STS2. The stands can be fastened to the floor to meet seismic Zone 4 require-  
ments. See 4.0 - Locating the STS2 and Figures 33 through 44 for instructions and details for  
installing seismic floor stands.  
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Installation Drawings  
7.0 INSTALLATION DRAWINGS  
Figure 5 Outline drawing: 100 – 250 amp STS2  
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Installation Drawings  
Figure 6 Outline drawing: 400 – 600 amp STS2  
18  
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Installation Drawings  
Figure 7 Outline drawing: 800 – 1000 amp STS2  
19  
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Installation Drawings  
Figure 8 Outline drawing: 100 – 250amp STS2 with a key lockout switch option  
20  
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Installation Drawings  
Figure 9 Outline drawing: 400 – 600 amp STS2 with a key lockout switch option  
21  
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Installation Drawings  
Figure 10 Outline drawing: 800 – 1000 amp STS2 with the key lockout switch option  
22  
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Installation Drawings  
Figure 11 Seismic anchor drawing: 100 – 250 amp STS2  
S I D E W A L L  
23  
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Installation Drawings  
Figure 12 Seismic anchor drawing: 400 – 600 amp STS2  
S I D E W A L L  
24  
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Installation Drawings  
Figure 13 Seismic anchor drawing: 800 – 1000 amp STS2  
S I D E W A L L  
25  
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Installation Drawings  
Figure 14 Electrical field connections drawing: 100 – 250 amp STS2 with single output breaker  
26  
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Installation Drawings  
Figure 15 Electrical field connections drawing: 100 – 250 amp STS2 with dual output breakers  
27  
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Installation Drawings  
Figure 16 Electrical field connections drawing: 400 – 600 amp STS2 with single output breaker  
28  
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Installation Drawings  
Figure 17 Electrical field connections drawing: 400 – 600 amp STS2 with dual output breakers  
29  
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Installation Drawings  
Figure 18 Electrical field connections drawing: 800 – 1000 amp STS2 with single output breaker  
30  
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Installation Drawings  
Figure 19 Electrical field connections: 800 – 1000 amp STS2 with dual output breakers  
31  
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Installation Drawings  
Figure 20 Circuit breaker schedule  
32  
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Installation Drawings  
Figure 21 Control connection location diagram: 100 – 600 amp STS2  
33  
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Installation Drawings  
Figure 22 Control connection location diagram: 800 – 1000 amp STS2  
34  
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Installation Drawings  
Figure 23 Control wiring for remote source selection option  
35  
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Installation Drawings  
Figure 24 Control wiring for the programmable relay board option  
36  
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Installation Drawings  
Figure 25 Control wiring for the input contact isolator board option  
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Installation Drawings  
Figure 26 Control wiring for comms board (see Figure 27 on page 39 for internal modem wiring)  
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Installation Drawings  
Figure 27 Control wiring for the internal modem option  
T O T E L E P H O N E L I N E  
M O D E M L I N E C O M M U N I C A T I O N S  
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Installation Drawings  
Figure 28 Control wiring for the network interface card (NIC) option  
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Installation Drawings  
Figure 29 Control wiring for the RS-232 port  
41  
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Installation Drawings  
Figure 30 Outline drawing for input junction box  
42  
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Installation Drawings  
Figure 31 Color LCD touch screen display  
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Installation Drawings  
Figure 32 LED display  
44  
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Installation Drawings  
Figure 33 Installation drawing, seismic floor stand 100-250A  
45  
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Installation Drawings  
Figure 34 Installation drawing, seismic floor stand 100-250A  
46  
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Installation Drawings  
Figure 35 Installation drawing, seismic floor stand 100-250A  
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Installation Drawings  
Figure 36 Installation drawing, seismic floor stand 100-250A  
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Installation Drawings  
Figure 37 Installation drawing, seismic floor stand 400-600A  
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Installation Drawings  
Figure 38 Installation drawing, seismic floor stand 400-600A  
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Installation Drawings  
Figure 39 Installation drawing, seismic floor stand 400-600A  
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Installation Drawings  
Figure 40 Installation drawing, seismic floor stand 400-600A  
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Installation Drawings  
Figure 41 Installation drawing, seismic floor stand 800-1000A  
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Installation Drawings  
Figure 42 Installation drawing, seismic floor stand 800-1000A  
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Installation Drawings  
Figure 43 Installation drawing, seismic floor stand 800-1000A  
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Installation Drawings  
Figure 44 Installation drawing, seismic floor stand 800-1000A  
56  
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Introduction to STS2 Operations  
8.0 INTRODUCTION TO STS2 OPERATIONS  
8.1 System Description  
A STS2 provides an automatic, seamless transfer between input power sources to an output load. The  
STS2 monitors the input sources, to ensure each source is operating within set parameters, as well as  
ensure that each source is within acceptable tolerances for a transfer between sources to be com-  
pleted.  
The STS2 contains two static transfer switches in one enclosure to allow the unit to transfer its load  
between the two input sources without disruption to the output for longer than 1/4 cycle.  
If a problem is detected with a primary (Preferred) input source and defined trigger points are  
reached, the STS2 automatically switches the input to the other (Alternate) input source. The STS2  
continues to monitor both sources and can automatically transfer the load back to the preferred  
source, if so configured, when that source returns to acceptable operating parameters.  
The system control logic automatically monitors the input sources and power output to ensure that  
they are operating within acceptable tolerances. The system logic manages the transfer between  
sources.  
The STS2 front panel contains either a Color Graphical Display on an LCD touch screen or an LED  
display.  
The Color Graphical Display provides a menu-driven operator interface, and a display of system infor-  
mation, status information, a one-line diagram (Mimic) of the STS2, active alarms, and alarm history  
information.  
The menu selections provide control of the preferred source, manual transfer initiation. Buttons pro-  
vide for audible alarm silence and reset.  
Through the touch screen, specific voltage, current and environmental parameters can be configured  
to trigger events that can sound an alarm, write to a history log and either transfer sources or inhibit  
a transfer.  
In units not equipped with the touch screen, LEDs provide the user with the ability to monitor the  
STS2 and quickly assess problems.  
Preferred input source selection, alarm reset and alarm silencing are done through buttons on the  
touch screen, or push buttons with the LED display.  
Communication options can be installed in the Color Graphical Display (LCD) unit only. These  
options provide external communication with the STS2 through a modem, a network card, a program-  
mable relay board, a contact isolator, or an RS-422 port to Liebert’s SiteScan.  
8.1.1 Redundancy  
Redundancy within the STS2 prevents one component from being a single point of failure, should a  
problem occur. Redundant circuits and components are used to eliminate single points of failure.  
Since the STS2 has two input sources, no single component failure can cause a loss of power to the  
load. Redundant power supplies are provided which feed a DC dual-bus used throughout the unit to  
prevent any single-point power supply failure modes.  
Three separate redundant control logic modules are built into the system. Each contains the logic nec-  
essary to run the STS2, and control all transfers.  
Redundant fans are provided if a primary fan fails. The redundant fans turn on to prevent overheat-  
ing inside of the unit.  
Should the front panel interface fail, either touch screen or LEDs, the control logic continues to oper-  
ate and the unit would transfer should a problem be detected on the preferred source. Information on  
the monitoring parameters would be available through the remote communication options, if avail-  
able, or the DB9 (RS-232) connector located next to the LCD display behind the front door. See  
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Introduction to STS2 Operations  
8.1.2 Reliability and Agency Requirements  
The STS2 is designed for high reliability and high availability with a critical bus Mean Time Between  
Failure (MTBF) exceeding 1,000,000 hours.  
The STS2, Control/Power Module, and all its options are designed, tested and certified, where appli-  
cable, to meet agency requirements as follows:  
• UL 1008: Transfer Switch Equipment, for UL and ULc listing  
• UL1459: Telephone equipment (Modem)  
• NEC  
• FCC Part 15 EMI emission limits for Class A computing devices.  
The STS2 uses conservatively rated components, minimizing the need to go to maintenance bypass.  
All maintenance and repair work can be done through the front panel of the unit. This access makes  
repairs and maintenance easier.  
Gating and control logic are partitioned so that failure of one source’s gating or sensing logic does not  
prevent the switch from transferring to the other source.  
All control and logic components are mounted separate from the power components. The STS2 is  
designed to minimize the exposure of hazardous voltages to allow safe servicing of the unit while the  
load is energized.  
All electrical components requiring normal maintenance are replaceable without de-energizing the  
load, as long as one source is available. Solid-state switching devices are packaged to allow safe repair  
of those devices without having to de-energize the load. All non-automatic switches or circuit breakers  
are the plug-in or draw-out type to allow replacement without de-energizing the load. All solid-state  
power switching devices are rated to prevent hazardous device failure in power systems with avail-  
able fault currents up to the defined limits, as listed in 15.1.5 - Electrical Requirements.  
8.1.3 Factory Backup and Service Assistance  
Because improper installation can cause a system to fail, a Liebert Global Services service technician  
should thoroughly inspect the unit to ensure it is properly installed and its operating parameters are  
properly configured.  
Once the STS2 is properly installed, you, as the on-site operator, can easily monitor the unit’s opera-  
tion utilizing the touch screen or LEDs.  
If you need assistance, or have questions, you can contact Liebert for technical support at  
1-800-LIEBERT (800-543-2378).  
8.2  
Modes of Operation  
8.2.1 Normal (Preferred Source)  
Under normal operating conditions, the STS2 routes power from the preferred input source to the out-  
put load. The unit monitors the voltage current and phase of each source to ensure that both are oper-  
ating within set tolerances, and that the alternate source is available, should a transfer be required  
8.2.2 Transfer  
Should the preferred source fail or be outside acceptable voltage limits, the STS2 transfers the input  
to the alternate source until the problem is rectified in the preferred source. The unit can be set to  
automatically transfer the input back to the preferred source, or only allow the transfer to be done  
manually.  
8.2.3 Transfer Inhibit  
For a transfer to be completed between input sources, the sources must meet certain parameters, or  
the transfer cannot take place. Uninterrupted transfer between sources is inhibited due to input  
source failure, sources out of sync, switch failure, or the unit is in bypass mode.  
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Introduction to STS2 Operations  
8.2.4 Bypass  
The static transfer switch can be manually bypassed to allow the power from a source to directly flow  
to the output load. This bypass allows the unit’s electronics to be serviced without dangerous voltages  
being present.  
The STS2 includes key-interlocked maintenance bypass breakers that allow either input source’s elec-  
tronics to be bypassed for maintenance without interruption of power to the load. The maintenance  
bypass allows all electronics to be isolated from the input, output, and bypass connections. Bypass  
instructions are available from the touch screen and are discussed later in this manual.  
8.3  
Operator Controls  
The STS2 is equipped with an interface to configure and monitor the unit either locally or remotely.  
The Color Graphical Display is a touch screen LCD that provides a color diagram (Mimic) that dis-  
plays the current status of the unit. System parameters are displayed and help is available to define  
events. See Figure 45 below and Figure 31. The touch screen menus allow the operator to initiate  
source transfers, view event and history logs, and view bypass and other operational instructions.  
Figure 45 STS2 touch screen display  
Mimic  
Event controls  
Event Display  
Display Panel  
and  
Help Screen  
Menu Options  
Touch screen control buttons allow you to reset alarms, silence the audible alarm, review configura-  
tions, event and history logs, preferred source, startup and bypass procedures, and the help menu.  
Qualified personnel, with a password, can use these menus to configure parameters, select a pre-  
ferred source, and do manual source transfers.  
LED display units do not have the color LCD display. Instead of the touch screen, these units are  
monitored by a series of LEDs and controlled by a series of push buttons.  
Both units can be accessed from a terminal, or a PC running terminal emulation software, that is  
attached to the unit. Through the RS-232 access, you can monitor and configure the unit, plus  
remotely select a preferred source. See 12.1 - Using the RS-232 Port on page 76 for instructions on  
using the RS-232 interface.  
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Theory of Operation  
9.0 THEORY OF OPERATION  
9.1 General Description  
The STS2 contains all the equipment necessary to prevent an interruption in power flow to the AC  
load, should your primary source fail.  
9.1.1 STS2 Static Transfer Switch  
The STS2 is a 3 pole, double-throw, solid state automatic transfer switch that is fed from two sources.  
The Preferred source is the input source that normally carries the load when both sources are avail-  
able. The preferred source is selectable by the user from the LCD panel or an optional Remote Source  
Selection. The unselected source is referred to as the Alternate source and carries the load if the pre-  
ferred source should fail or if a manual transfer is initiated.  
The unit uses Silicon Controlled Rectifiers (SCRs) connected in paralleled, opposing pairs to function  
as an AC switch configuration. Three pairs of SCRs connect the AC load to the selected preferred  
input source as long as the preferred source is available. A second set of SCRs stands ready to trans-  
fer the AC load to the alternate input source should the preferred source fail. The switching action is  
a very fast, break-before-make with less than a 1/4 cycle break in the AC waveform.  
During static switch transfers and retransfers, the conduction state of the SCRs is carefully moni-  
tored and controlled to prevent a current path from one source to the other. This technique prevents a  
faulted source from feeding into the other good source.  
9.1.2 Source Transfer  
The STS2 allows manually initiated transfers between the two sources, providing the alternate  
source is within acceptable voltage limits and phase tolerances with the preferred source. You begin a  
manual transfer by selecting the inactive source as the preferred source. On a manual transfer, the  
STS2 transfers between the two sources with less than one (1) millisecond interruption of power to  
the load. The transfer can only be completed when both sources are available and synchronized  
within the user-adjustable phase synchronization window. For sources where the two frequencies are  
not exactly in phase, manually-initiated transfers are delayed by the STS2 until the two sources are  
within the defined phase synchronization window.  
Source selection can also be done remotely using the Remote Source Selection option, if installed.  
9.1.3 Automatic Transfer/Retransfer  
If the preferred source is out of voltage and/or frequency limits, the load is automatically transferred  
to the alternate source. The default transfer voltage limits comply with the limits of the IEEE Std.  
446-1995 computer voltage tolerance envelope.  
If the unit is so configured, the load is retransferred automatically to the preferred source after the  
preferred source returns to within the acceptable voltage and frequency limits for at least the defined  
retransfer time delay, and is in phase with the alternate source. You can enable and disable auto-  
matic retransfer to the preferred source through a user configuration setting.  
Automatic Retransfer Inhibited  
If the system makes five transfers from the preferred source to the alternate source in a five minute  
period, automatic retransfers back to the preferred source is disabled.  
To clear this alarm condition, you must assign the alternate source as the preferred source.  
Also, the UV detection thresholds may need adjustment. See Source Set Points on page 90 for  
instructions on setting the UV detection.  
This alarm also is cleared if the unit transfers to the preferred source due to an alternate source AC  
volt failure (i.e., an emergency transfer.)  
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Theory of Operation  
9.1.4 Emergency Transfer  
To ensure that power remains connected to the load, the STS2 automatically performs an emergency  
transfer from one input source to the other when an outage occurs on the existing source. The auto-  
matic transfer takes place if the other source’s voltage is within acceptable limits, and regardless of  
the phase difference between the two sources.  
Emergency transfers occur with a loss of power on the output of less than 4 ms.  
Emergency transfers from the alternate source to the preferred source are not affected by the Auto  
Retransfer Enabled/Disabled or Retransfer Delay user settings.  
9.1.5 Load Current Transfer Inhibit  
The STS2 senses the load current. If the load current exceeds the preset level deemed to represent a  
load inrush or fault condition, the unit’s logic disables manual and automatic transfers, even if the  
selected source’s input voltage is outside the acceptable limits. This event triggers an I-Peak alarm. If  
so configured, the Load Current Transfer Inhibit is automatically reset after the current and voltage  
return to within normal parameters. This reset provides continued protection against a source fail-  
ure. The Load Current Transfer Inhibit also can be programmed to require a manual reset. See  
step 14. on page 92 under the Source Set Points heading for details.  
9.1.6 SCR Failure  
The STS2 continuously monitors the status of the SCR switching devices for proper operation. In the  
event of a shorted SCR on the input source powering the load, the STS2 automatically triggers an  
alarm and trips open the other source isolation breaker. In the event of a shorted SCR on the other  
input source, the STS2 automatically triggers an alarm and trips open the other source isolation  
breaker.  
In the event of an open SCR, the switch automatically triggers an alarm and transfers the load to the  
other source. All open and shorted SCR alarm conditions are latched and require the system to be  
repaired and reset to restore normal operation.  
9.1.7 On/Off Sequence  
The STS2 contains no master On/Off push button control. When connected to the input sources, the  
unit’s logic power comes on automatically. The touch screen display (if so equipped) is active as long  
as at least one input source is energized and the Control Power Disconnect (located inside the static  
switch) is on.  
9.2  
Detailed Component Description  
9.2.1 Controls  
Operator Interface  
The STS2 Color Graphical Display unit contains a touch screen color LCD to provide the operator  
interface to control and configure the operation of the unit and quickly diagnose problems. A pass-  
word and an optional keylock, if installed, are provided for security.  
The LED Display unit includes push-buttons for source transfer, alarm reset and audible alarm  
silence.  
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Theory of Operation  
Hardware  
• The STS2 operator interface in the Color Graphical Display unit is designed to provide all of the  
information required to configure and monitor the unit’s operation.  
• The control logic performs automatic operations with minimal operator interface.  
• Each STS2 unit is equipped with either a color LCD touch screen or a panel of LEDs and push  
buttons.  
• The STS2 can have optional communication ports installed. See 6.0 - Options and 12.0 - Com-  
munication Interfaces on page 76 for more information on communication options.  
• On LED Display units, the RS-232 interface is used for configuration and status and event log  
monitoring. The RS-232 interface can also be used with the Color Graphical Display units, if nec-  
essary.  
Firmware  
The operator interface enables you to monitor the STS2, to configure set points for transfers, monitor  
system parameters and access event and history logs. The firmware is accessible through the LCD  
touch screen (if installed) or the RS-232 interface. The firmware includes:  
• View and set the preferred source.  
• View and configure set points.  
• View alarms, faults and status.  
Additionally, the Color Graphical Display unit provides:  
• The mimic graphical representation of the systems operation.  
• Menu driven monitoring and configuration.  
• Step-by-step instructions to assist you in the start-up, shut-down and bypass operations.  
• Help on event messages.  
• Touch screen alarm reset and silence buttons.  
Events in the system, both faults and alarms, are detected and displayed on the LCD. See 11.0 -  
Alarm and Faults on page 71 for more information on events.  
• A set of event masks can be configured through the LCD to trigger a system response to an event.  
• Report event conditions from other components of the system.  
• Monitor and report changes in event condition states. If the event condition’s state changes from  
inactive to active, a new event is detected. If the transition is from active to inactive, the event con-  
dition has cleared.  
• Process new faults and alarms, and clear inactive alarms.  
• Provide the alarm reset and silence options.  
9.2.2 Circuit Breakers  
Three circuit breakers provide total isolation of the solid-state switching devices with an input  
breaker for each source and a load isolation breaker. Two breakers provide for maintenance bypass-  
ing of the solid-state switching devices to either input source.  
All switches in the STS2 are plug-in types, which allows any switch to be replaced without de-energiz-  
ing the output bus. The Merlin Gerin breakers have an interlock in the plug-in base, which prevents  
the switch from being withdrawn in the CLOSED position. The switch trips OPEN before it discon-  
nects from the plug-in base.  
See 15.2.5 - Circuit Breakers for specifications and more information pertaining to the circuit  
breakers. See Figure 14 to Figure 19 for circuit breaker locations. The circuit breaker schedule is  
provided in Figure 20.  
9.2.3 SCRs  
Brick-type SCRs are used rated to carry the full 100% rated load. Because the unit is a fuseless design  
with non-automatic circuit breakers, overcurrent protection is provided by upstream circuit breakers.  
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Theory of Operation  
9.2.4 Logic Modules  
The logic contains three separate redundant logic modules. The modules contain the logic necessary  
to run the STS2 and control transfers and shunt trips under all circumstances, without any outside  
assistance once set-up and started properly.  
9.2.5 Audible Alarm  
An audible alarm is installed on the control board. This alarm is triggered by an alarm condition  
detected on the unit. The alarm can be turned off from the touch screen (Color Graphical Display  
units) or by a push button (LED Display units). Turning off the audible alarm does not clear or reset  
the condition that triggered the alarm.  
9.2.6 RS-232 Port  
An RS-232 serial port is provided to allow an external terminal to be connected as another user inter-  
face. See 12.1 - Using the RS-232 Port on page 76 for more information on using the RS-232 port.  
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Operating Instructions for the Touch Screen Interface  
10.0 OPERATING INSTRUCTIONS FOR THE TOUCH SCREEN INTERFACE  
CAUTION  
!
Before unit is placed into service for the first time, after equipment relocation, or after the  
equipment has been de-energized for an extended period of time, a thorough equipment  
inspection and supervised start-up by qualified personnel are strongly recommended. Contact  
your local Liebert representative or Liebert Global Services at 1-800-543-2378 to arrange for  
equipment inspection and start-up.  
After the initial equipment start-up, the following operating guidelines can be used for standard  
equipment operation. These guidelines should be reviewed for any special equipment modifications,  
special site conditions, or company policies that may require changes to the standard equipment oper-  
ation.  
All programmable functions are preset at the factory to enable the unit to be brought up without the  
need to enter all selectable parameters.  
This section refers to the LCD touch screen display. This display is discussed in more detail later in  
NOTE  
If the front panel of your STS2 is comprised of LEDs and push buttons instead of the touch  
screen interface, refer to 14.0 - Operating the LED Display STS2 for operating instructions.  
See Figures 14- 19 for circuit breaker locations.  
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Operating Instructions for the Touch Screen Interface  
10.1 Normal System Turn-On  
NOTE  
If your STS2 is connected to a PDU with a Wye configuration, enable the Wye Output  
Transformer before starting the system. This setting can be made from the touch screen. Refer  
1. Ensure that all STS2 breakers—CB1, CB2, CB3, CB3A (if supplied), CB4, and CB5—are in the  
OFF position.  
a. Ensure that the key interlocks for CB1 and CB2 have their bolts retracted.  
b. Ensure that the key interlocks for CB4 and CB5 have their bolts extended, thus preventing  
CB4 or CB5 from being turned ON.  
2. Source/input power should be applied to both STS2 inputs.  
The touch screen control panel should become active and operate properly when at least one of the  
inputs is energized is closed.  
3. Verify that nominal input voltages are applied to both inputs (Source 1 and Source 2).  
The input voltages, selected preferred source, breaker and switch status, and alarms are indi-  
cated on the Mimic screen.  
Figure 46 STS2 touch screen display  
Mimic  
Sources  
Static  
Transfer  
Switch  
Event controls  
Event display  
4. Close CB1.  
5. Verify that Source 1 voltages are nominal and CB1 breaker status is correctly indicated on the  
Monitor/Mimic screen.  
6. Close CB2.  
7. Verify that Source 2 voltages are nominal and CB2 breaker status is correctly indicated on the  
Mimic screen.  
8. Verify that boxes for the preferred source and corresponding static transfer switch are  
highlighted on the Mimic screen, indicating which side of the Static Transfer Switch is on.  
9. Close Output Breaker CB3 (and CB3A in redundant output configurations).  
10. Verify CB3, the Output box, and the Load box are highlighted, indicating that CB3 is closed and  
the Output and Load are energized.  
NOTE  
For redundant output switch units, CB3 descriptions apply to CB3 and CB3A.  
11. Press the RESET button on the touch screen to reset any previous alarms.  
12. Verify in the Event Display and the Mimic that there are no active alarms.  
If any active alarms are displayed, refer to 11.0 - Alarm and Faults for a description of the  
alarms and possible causes. All active alarm conditions should be corrected before proceeding.  
13. Turn on the load equipment following the load equipment manufacturer’s recommendations.  
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Operating Instructions for the Touch Screen Interface  
10.2 Manual Transfer / Preferred Source Selection  
The Source Transfer option (Source Xfers) in the touch screen menu allows you to select a preferred  
source. Transfers are only permitted when the voltage and current are within their proper operating  
range and the sources are synchronized. The Source Transfer screen indicates the synchronization  
between the two sources, while the voltage and frequency are displayed on the Mimic. See Figure 47.  
Transfer is inhibited if the deviation exceeds the parameter set in the Source Set Points. See User  
NOTE  
If one source will be de-energized for an extended period (hours or days), set the unit to bypass  
mode for the remaining source. Without using bypass, if a failure occurs in the switch  
components for remaining source, the STS2 does not have a second source to switch to and the  
load would not receive power. See Maintenance Bypass on page 67 for bypass instructions.  
If your system contains the LED front panel instead of the LCD touch screen, refer to 14.2.2 - Man-  
ual Transfer / Preferred Source Selection for instructions on this procedure.  
Figure 47 Source transfer screen  
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Operating Instructions for the Touch Screen Interface  
To manually select the preferred source:  
1. Verify that the input breakers CB1 and CB2 are closed.  
2. Select SOURCE XFERS from the menu bar.  
The Select Preferred Source screen is displayed in the Event Display.  
3. Check the Mimic to verify that Source 1 and Source 2 input voltages are correct.  
4. Select SOURCE 1 or SOURCE 2 as your preferred source.  
When conditions are correct, the switch transfers the load to the alternate source by selecting the  
alternate source as the preferred source.  
This source is now monitored as the preferred source throughout the various configurations set up  
through the touch screen.  
5. Verify that the correct source is designated as the preferred source and that the input source  
changes to the desired source.  
The Mimic is updated to indicate the new preferred source. The source is now highlighted with blue  
and that source is labeled as the preferred source.  
If the Transfer Inhibit message is displayed, check for alarm messages on the Active Status window.  
Correct alarm conditions before attempting a source transfer.  
NOTE  
The preferred source may also be changed via the optional Remote Source Selection option,  
thereby initiating a transfer remotely.  
10.3 Enabling Remote Source Selection  
If your system is equipped with the optional Remote Source Selection option, it must be enabled.  
If you your system includes the Color Graphical Display:  
1. Select CONFIG from the menu bar.  
2. Select SYSTEM SETTINGS from the Configuration menu.  
3. Select SYSTEM OPTIONS from the System Settings menu.  
4. Select YES for the REMOTE SOURCE SELECT choice.  
If your system contains the LED display or you are configuring the system from the RS-232 port, see  
12.1 - Using the RS-232 Port on page 76 for instructions on using the that interface.  
10.4 Maintenance Bypass  
The STS2 is equipped with two key-interlocked, bypass breakers, CB4 and CB5, to allow manual  
bypass of the switch electronics for either input source in the event of switch failure or for mainte-  
nance of the switch. Refer to the static transfer switch one-line diagram (Figure 3). While operating  
on maintenance bypass, all voltages are removed from the STS2 electronics to facilitate safe repair,  
without de-energizing the load using a make-before-break switching sequence.  
However, the unit can be bypassed using a make-before-break switching sequence only to the same  
source to which that the switch is connected, as indicated by the highlighted static transfer switch box  
on the Mimic screen.  
In the event of source or switch failure, the unit should be bypassed only to the current input source.  
For convenience, instructions for the bypass procedure can be displayed on the touch screen by select-  
ing the BYP. PROC option from the menu bar.  
The Mimic is used to verify the status of the unit during the bypass procedures. In the unlikely event  
that the Color Graphical Display is not available, open the front door and look through the slots in the  
control door. If you can see green LEDs on the gate driver board through that slot, then the unit is  
connected to the source referenced on the label below that slot. See Figure 48.  
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Operating Instructions for the Touch Screen Interface  
Figure 48 Gate board viewing slot locations  
Touch Screen  
Viewing Slot for  
the Source 1  
Gate Drive Board  
Viewing Slot for  
the Source 2  
Gate Drive  
Board  
GREEN LEDS ON THE  
GATE DRIVER BOARD  
ARE VIEWABLE  
THROUGH THIS SLOT  
INDICATE THAT THE  
STS IS ON SOURCE 1  
GREEN LEDS ON THE  
GREEN LEDS ON THE  
GATE DRIVER BOARD  
GATE DRIVER BOARD ARE  
VIEWABLE THROUGH THIS  
SLOT INDICATE THAT THE  
STS IS ON SOURCE 2  
ARE VIEWABLE THROUGH  
THIS SLOT INDICATE THAT  
THE STS IS ON SOURCE 1  
If the Color Graphical Display is not available, you can still use the following bypass procedures,  
ignore the steps to check the display, and check the LEDs .  
If your system contains the LED display, see 14.2.3 - Maintenance Bypass.  
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Operating Instructions for the Touch Screen Interface  
10.4.1 Bypass Procedures for Source 1  
To bypass the switch for Source 1:  
NOTE  
If you wish to bypass the Source 1 static transfer switch but Source 2 is presently active, you  
must first transfer to Source 1. See Manual Transfer / Preferred Source Selection on  
1. Verify Source 1 is supplying power via the Mimic.  
• If the Color Graphical Display is not available, check the gate driver board LEDs through the  
slots in the control panel. See Figure 48.  
2. Remove interlock key from CB5 and place it in the CB4 interlock.  
3. Open the alternate source input breaker CB2.  
4. Rotate and remove the interlock key.  
5. Insert the key in the CB4 bypass breaker interlock.  
6. Rotate interlock keys in CB4 bypass breaker interlock to retract interlock.  
7. Close bypass breaker CB4.  
8. Verify the breaker status on the Mimic screen.  
9. Open source input breaker CB1.  
10. Rotate the interlock key and remove it to lockout the breaker.  
11. Secure the key, per your site’s lockout/tagout procedure.  
12. Open output breakers CB3 and CB3A (if supplied) to remove power from static switch.  
To return to the normal mode:  
1. Remove the key from CB5 and insert it in the CB1 breaker interlock.  
2. Rotate key to retract interlock.  
3. Close source input breaker CB1.  
4. Verify the Source 1 and CB1 breaker status on the Mimic screen.  
5. Close output breakers CB3 and CB3A (if supplied).  
6. Verify CB3 and CB3A breaker status and STS SOURCE 1 and OUTPUT boxes are highlighted on  
the Mimic screen.  
7. Open bypass breaker CB4.  
8. Rotate the keys in CB4 interlock to extend the interlock.  
9. Remove the proper key from CB4 interlock and insert it into CB2 breaker interlock.  
10. Rotate the key to retract the CB2 breaker interlock.  
11. Close source input breaker CB2.  
12. Verify the STS SOURCE 2 box and CB2 breaker status on the Mimic screen.  
• If the Color Graphical Display is not available, check the gate driver board LEDs through the  
slots in the control panel. See Figure 48.  
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Operating Instructions for the Touch Screen Interface  
10.4.2 Bypass Procedures for Source 2  
To bypass the switch for Source 2:  
NOTE  
To bypass the Source 2 static transfer switch when Source 1 is presently active, you must first  
1. Verify Source 2 is supplying power via the Mimic.  
• If the Color Graphical Display is not available, check the gate driver board LEDs through the  
slots in the control panel. See Figure 48.  
2. Remove the interlock key from CB4 and place it in CB5 interlock.  
3. Open the alternate source input breaker CB1.  
4. Rotate and remove the interlock key.  
5. Insert the key in the CB5 bypass breaker interlock.  
6. Rotate interlock keys in the CB5 bypass breaker interlock to retract the interlock.  
7. Close bypass breaker CB5.  
8. Verify the breaker status on the Mimic screen.  
9. Open source input breaker CB2.  
10. Rotate the interlock key and remove it to lockout the breaker.  
11. Secure the key, per your site’s lockout/tagout procedure.  
12. Open output breakers CB3 and CB3A (if supplied) to remove power from static switch.  
To return to normal mode:  
1. Insert the key in the CB2 breaker interlock.  
2. Rotate the key to retract the interlock.  
3. Close source input breaker CB2.  
4. Verify Source 2 and CB2 breaker status on the Mimic screen.  
5. Close output breakers CB3 and CB3A (if supplied).  
6. Verify CB3 and CB3A breaker status and STS SOURCE 2 and OUTPUT boxes are highlighted on  
the Mimic screen.  
7. Open bypass breaker CB5.  
8. Rotate the keys in CB5 interlock to extend the interlock.  
9. Remove the proper key from CB5 interlock and insert it into CB1 breaker interlock.  
10. Rotate the key to retract the CB1 breaker interlock.  
11. Close source input breaker CB1.  
12. Verify the STS SOURCE 1 box and CB1 breaker status on the Mimic screen.  
• If the Color Graphical Display is not available, check the gate driver board LEDs through the  
slots in the control panel. See Figure 48.  
10.5 Normal System Shutdown  
The STS2 can be shut down from either the static switch mode or the bypass mode.  
10.5.1 Shutdown in Static Transfer Switch Mode  
When the STS2 is operating on static transfer switch mode (not maintenance bypass mode):  
1. Turn off the load equipment per manufacturer’s recommendations.  
2. Open CB3 to turn off the static switch output.  
• Open CB3A if the static transfer switch has a redundant output configuration.  
3. Open the input switches CB1 and CB2.  
4. To completely de-energize the unit, turn OFF power to both inputs to the STS2.  
10.5.2 Shutdown in Maintenance Bypass Mode  
When the Static Transfer Switch is operating on bypass:  
1. Turn off the load equipment per manufacturer’s recommendations.  
2. Open the bypass switch (CB4 or CB5) to turn off the static transfer switch output.  
3. To completely de-energize the unit, turn OFF the power to both inputs to the STS2.  
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Alarm and Faults  
11.0 ALARM AND FAULTS  
Alarms and faults are events that are triggered when the operation of the static transfer switch falls  
outside of the defined parameters. These events can also be triggered by: user actions, such as chang-  
ing configurations, clearing logs, etc.; failed components such as a fan failure, an SCR that is open or  
closed, etc.; and system status, such as open circuit breakers, load on alternate source, etc. These  
events can provide a warning or trigger the system to make a change, such as switch sources or the  
recording of a history log.  
The STS2 monitoring system detects and annunciates a comprehensive set of fault and alarm condi-  
tions. Faults and alarm messages are can be viewed on the LCD touch screen or via the RS-232 port.  
On the LCD touch screen, the events are shown in the Status Display panel in the lower left corner of  
the touch screen and written to the Event log. You can touch a message to view a definition of an  
event and a tip for troubleshooting. See 13.0 - STS2 Touch Screen Display for more information on  
the touch screen.  
If you are monitoring the system through the RS-232 port, see Table 10 - Terminal Commands on  
page 77 for the commands to view event logs, and alarm and fault lists.  
Event actions can be triggered by the settings configured from the Event Masks. See 11.1 - Event  
Mask for more information.  
Faults — A fault indicates that a component of the STS2 has failed or has been damaged. In the  
Event Display, faults are indicated in red.  
Alarms — An alarm is an event caused by a significant abnormal system condition. In the Event Dis-  
play, alarms are indicated in yellow. The setpoints for many of the alarms are configurable through  
the User Settings. Many alarms clear themselves when the condition is resolved. If an alarm event  
mask is set to latch, the alarm messages remain active until the alarm condition has been corrected  
and the RESET button is pushed. See 11.1 - Event Mask for more information on latching.  
When the system is furnished with an optional internal or external modem and a telephone line is  
connected to the modem, the system can be programmed to automatically dial out upon occurrence of  
any of certain designated alarms. The auto-dial feature can be configured for alarms using the Event  
Mask option in the touch screen. See Configuring the Modem on page 94 for instructions on for  
setting up your modem.  
11.1 Event Mask  
The STS2 gathers, processes and reports faults and alarms, collectively referred to below as events.  
The Event Mask dialog box allows you to set the system’s response for specific alarms and faults that  
are generated.  
The following mask types are available for each event:  
Latch — If a latch is enabled for the selected event, that event remains active even if the originat-  
ing event condition clears. A latched event may only be cleared by pushing the RESET button  
(ALRMRST on the LED units).  
Dial Out — If the selected event is triggered, the system automatically calls the specified tele-  
phone numbers through the modem. For example, a page could be sent or an event could be sent  
to a external terminal, via the modem. See Communication Interfaces on page 76 for more  
information on configuring communications options.  
Event Log — The selected event is date/time stamped and recorded to the Event Log when the  
event is triggered.  
Audible — If the selected event is triggered, an audible beeper or horn is sounded by the STS2.  
The beeper continues while this event is active or latched, or until the SILENCE button (NOAUD  
on the LED units) is pushed. This button must be pushed with the ALRMRST button on the LED  
units.  
See Event Masks on page 88 for instructions on setting the mask type via the touch screen display.  
tion using the RS-232 port.  
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Alarm and Faults  
11.2 Event and History Logs  
The system tracks events through the Events Log and tracks significant events through the History  
Logs. These logs allow you to quickly spot trends or diagnose problems that the unit may have had.  
Both logs are written in nonvolatile memory.  
The logs can be accessed from the touch screen menu or the RS-232 port. See 13.6.2 - Logs for more  
instructions on viewing the logs from the touch screen. See Table 10 - Terminal Commands on  
page 77 for the RS-232 interface commands used to access the logs.  
11.2.1 Event Log  
The events are tracked in sequence of occurrence. The sequence of occurrence is identified by date,  
time, and frame number. The last 512 events are stored in a nonvolatile memory and can be viewed  
from the Event Log.  
Event logs wrap, meaning when the log is full, the oldest event is deleted when a new event is written  
to the log.  
The Event Log tracks:  
• # — the sequence number in which the event occurred since the log was last cleared.  
Message — the event that occurred, such as Ambient Over temp., Source 1 Fail, etc.  
Type — either a Fault or Alarm. See 11.0 - Alarm and Faults on page 71 for further details on  
these events.  
ID — the event identifier.  
Date and Time — when the event occurred.  
Faults — the number of fault events logged.  
Alarms — the number of alarm events logged.  
User Alarms — the number of alarm events logged that were triggered by user-created alarms,  
such as those alarms created with the Input Contact Isolator settings.  
Total — the sum of all the events currently logged.  
11.2.2 History Log  
When a designated major alarm occurs, the History Status buffer is frozen, capturing 64 sequential  
frames before and after the alarm condition. When the History Status buffer is frozen, a History Log  
is created.  
Two History Logs are available to track major alarms. This log includes the triggering event plus the  
surrounding events, and the system voltages, currents, frequency, power, source selection and  
breaker positions at the time of the event. The History Log displays the 64 sequential frames, in  
4-millisecond intervals, of the Present Status screens surrounding the event.  
If you are viewing the log from the touch screen, the Mimic and the Event Display show the data that  
was present as the alarm was triggered. The data is displayed as frames are played.  
The History Log allows you to replay the events leading up to the alarm and the events right after the  
alarm to see the status of the switch at that time and diagnose the cause of the alarm. The History  
Log is triggered when certain events are tripped that have the Freeze option enabled.  
You can run through the frames sequentially. The sequence of the events is identified by date, time,  
and frame number. The History Log frames are stored in a nonvolatile memory buffer that is continu-  
ously overwritten until a designated fault condition occurs. When the fault occurs to trigger a freeze,  
the History Log stores the next 23 frames, then freezes until it is reset. The History Log then keeps 40  
frames before the fault, the frame where the fault occurred, plus the next 23 frames.  
The History Log should not be reset until the fault condition that caused the buffer to freeze is  
reviewed and investigated by a qualified service technician. After the alarm condition has been cor-  
rected, the History Log can be cleared.  
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Alarm and Faults  
The History Log has the following fields:  
Replay Rate — indicates how long it takes for the replay to play. Use the UP and DOWN buttons  
to set the time.  
Status — the status of the STS2 at the point of the current frame in the replay. The History log  
has three statuses: Frozen, Not Frozen and Retrieving Data, please stand by.  
Critical Event — The event which triggered this log to be written. The event is indicated in red on  
the bar graph.  
Frame Number — the current frame in the replay. A negative number indicates the replay is at a  
point before the triggering event occurred.  
11.3 Alarm Notes  
The I-PK on Source 1 and I-PK on Source 2 alarms inhibit automatic transfer due to an overload or  
load fault. These alarms can be set for either auto or manual alarm reset.  
In the auto reset mode, the alarm is reset as soon as the load current and source voltage return to nor-  
mal, and transfers are no longer inhibited. In manual mode, the alarm remains active and transfers  
are inhibited until the conditions return to normal and the user manually presses the RESET button  
(ALRMRST button on LED units). In either case, the cause of the Source 1 or Source 2 I-Peak over-  
load should be investigated and resolved (such as by reducing the overload condition or clearing the  
output fault) before returning the switch to normal operation.  
These events indicate a device failure. The device must be replaced and the system must be restarted  
for the fault to clear. A shorted SCR automatically trips open a source input switch (CB1 or CB2) to  
prevent transfers in the event of an SCR failure. The SCR failure must be investigated and repaired  
before returning the switch to normal operation. Both source input switches must be opened (such as  
when the unit is placed in maintenance bypass for servicing) before a shorted or open SCR alarm can  
be reset.  
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Alarm and Faults  
11.4 List of Messages  
Table 9 lists available event messages, a definition of the event, and the functions that are activated  
with the event by default. The functions are indicated as follows:  
D — The indicated event initiates the Auto-Dial sequence through the optional modem.  
A — The indicated event activates the Audible alarm.  
F — The indicated event triggers a Freeze of the History Log.  
L — The indicated event Latches. A latched alarm remains displayed until the alarm condition  
has cleared and the RESET (ALRMRST) button has been pressed.  
E — By default, all faults and alarms are written to the Event Log. Changing this setting is only  
available for the LED units and is set through the RS-232 port. See Setting Event Masks with  
All of these functions, except Freeze, can be reconfigured to trigger for each event, using the Event  
Mask option. See 11.1 - Event Mask on page 71. The Freeze function is hard-coded and cannot be  
changed for a event.  
If the front panel of your STS2 contains LEDs and push buttons instead of the touch screen interface,  
you can view these messages via the RS-232 port. See 12.1.1 - Connecting and Using a  
Terminal on page 77 for the commands to view the event messages on a PC terminal.  
An LED is used to indicate the presence of any active fault or alarm. Refer to 14.0 - Operating the  
LED Display STS2 for more information about the LEDs.  
.
Table 9  
ID  
Event Messages  
Alarm Message  
Description/Cause  
Action  
001  
S1 SCR SHORT  
One or more of the SCRs for Source 1 have shorted and  
failed.  
D, F, A, E  
002  
S2 SCR SHORT  
One or more of the SCRs for Source 2 have shorted and  
failed.  
D, F, A, E  
003  
004  
005  
S1 SCR OPEN  
One or more of the SCRs for Source 1 is open.  
One or more of the SCRs for Source 2 is open.  
D, F, A, E  
D, F, A, E  
D, A, E  
S2 SCR OPEN  
PRIMARY FAN FAIL  
A primary cooling fan has failed and the unit is now being  
cooled by a secondary fan, which is not monitored.  
006  
007  
008  
009  
010  
011  
012  
013  
014  
015  
016  
017  
018  
019  
020  
021  
022  
023  
CONTROL MODULE FAIL  
PWR SPLY DC A FAIL  
PWR SPLY DC B FAIL  
PWR SPLY S1 AC FAIL  
PWR SPLY S2 AC FAIL  
PWR SPLY LOGIC FAIL  
OUT VOLT SENSE FAIL  
S1 VOLT SENSE FAIL  
S2 VOLT SENSE FAIL  
S1 SCR SENSE FAIL  
S2 SCR SENSE FAIL  
S1 CURR SENSE FAIL  
S2 CURR SENSE FAIL  
S1 GATE DRIVE FAIL  
S2 GATE DRIVE FAIL  
INTERNAL COMM FAIL  
EXTERNAL COMM FAIL  
CB1 SHUNT TRIP FAIL  
Control logic module has failed.  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
D, A, E  
A, E  
Power supply DC bus A has failed.  
Power supply DC bus B has failed.  
Power supply Source 1 AC has failed.  
Power supply Source 2 AC has failed.  
A power supply module has failed.  
The output volt sense module failed  
The Source 1 volt sense module failed.  
The Source 2 volt sense module failed.  
The Source 1 SCR sense module failed.  
The Source 2 SCR sense module failed.  
The Source 1 SCR current module failed.  
The Source 2 SCR current module failed.  
The Source 1 gate drive module failed.  
The Source 2 gate drive module failed.  
Internal CAN communications failed.  
Options CAN communications failed.  
CB1 shunt trip failed.  
A, E  
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Alarm and Faults  
Table 9  
ID  
Event Messages  
Alarm Message  
CB2 SHUNT TRIP FAIL  
HEATSINK OVERTEMP  
S1 UV  
Description/Cause  
CB2 shunt trip failed.  
Action  
D, A, E  
A, E  
024  
064  
067  
068  
069  
070  
071  
072  
073  
074  
075  
076  
077  
078  
079  
080  
081  
082  
083  
084  
085  
086  
087  
088  
089  
090  
091  
092  
093  
Heatsink has exceeded the recommended temperature.  
Source 1 under voltage, fast detection.  
Source 1 under voltage, slow detection.  
Source 1 over voltage  
A, E  
S1 UV (RMS)  
L, A, E  
A, E  
S1 OV  
S1 OF/UF  
Source 1 over frequency/under frequency  
Source 1 failure.  
A, E  
S1 FAIL  
A, E  
S2 UV  
Source 2 under voltage, fast detection.  
Source 2 under voltage, slow detection.  
Source 2 over voltage.  
A, E  
S2 UV (RMS)  
A, E  
S2 OV  
A, E  
S2 OF/UF  
Source 2 over frequency/under frequency.  
Source 2 failure.  
A, E  
S2 FAIL  
A, E  
S1 OVERCURRENT  
S2 OVERCURRENT  
S1 I-PEAK  
Source 1 over current.  
A, E  
Source 2 over current.  
A, E  
I-PK on Source 1.  
A, F, E  
A, F, E  
A, E  
S2 I-PEAK  
I-PK on Source 2.  
SOURCES OUT OF SYNC  
LOAD ON ALT SOURCE  
AUTO REXFER INHIBIT  
CB1 (S1) OPEN  
CB2 (S2) OPEN  
CB4 (S1 BYP) CLOSED  
CB5 (S2 BYP) CLOSED  
CB3 (OUTPUT) OPEN  
CB3A (OUTPUT) OPEN  
S1 PHASE ROT ERROR  
S2 PHASE ROT ERROR  
TRANSFER INHIBITED  
OUTPUT UV  
Source 1 and Source 2 are out of synchronization.  
The output load is running on the alternate source.  
Automatic retransfer is inhibited.  
Source 1, Circuit Breaker 1 is open.  
Source 2, Circuit Breaker 2 is open.  
Source 1 on bypass, Circuit Breaker 4 is closed.  
Source 2 on bypass, Circuit Breaker 5 is closed.  
Output circuit breaker (CB3) is open.  
Output circuit breaker (CB3A) is open.  
Source 1 phase rotation error.  
A, E  
A, E  
A, E  
A, E  
A, E  
A, E  
A, E  
A, E  
A, E  
Source 2 phase rotation error.  
A, E  
Transfer inhibited.  
A, E  
Output is under voltage.  
D, F, A, E  
120  
121  
122  
123  
124  
125  
126  
127  
INPUT CONTACT #1  
INPUT CONTACT #2  
INPUT CONTACT #3  
INPUT CONTACT #4  
INPUT CONTACT #5  
INPUT CONTACT #6  
INPUT CONTACT #7  
INPUT CONTACT #8  
Input Contact # x is an optional alarm input. The alarm name  
can be programmed with an alarm name from the Input  
Contactor Isolator settings option under the Comm Options.  
page 95. The alarm is sent to Monitor DSP. The LCD logs  
the alarm with the programmed name. Monitor DSP logs it  
with the generic name which is how it is reported to the SVT  
query.  
A, E  
128  
129  
CONFIG MODIFIED  
A set point configuration has changed.  
A, E  
A, E  
PASSWORD CHANGED  
The password for touch screen access has been modified  
and saved.  
130  
131  
132  
133  
134  
TIME REPROGRAMMED  
DATE REPROGRAMMED  
EVENT LOG CLEARED  
HIST LOGS CLEARED  
HIST LOGS FULL  
The system’s time has been reset and saved.  
The system’s date has been reset and saved.  
The event log has been erased.  
A, E  
A, E  
A, E  
A, E  
A, E  
Both History Logs have been erased.  
Both History Logs have been written and no more history logs  
can be written without clearing one of the logs.  
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Communication Interfaces  
12.0 COMMUNICATION INTERFACES  
The STS2 monitoring system offers several choices for communications.  
The RS-232 terminal port is standard on all units. The port is located inside the front door, to the left  
of the touch screen/LED front panel mounting as shown in Figure 29. This port is primarily used as  
an alternate user interface to configure, control, and diagnose the system, especially for systems that  
do not include the HMI touch screen. Commands for the RS-232 port are shown in Table 10.  
Several other communications options are also available. Those options are located a Communica-  
tions compartment to the right of the touch screen/LED front panel and are accessible when the front  
panel door is open. See Figures 21 and 22 for the location of the communications options.  
Connections to the communication ports are made by wiring to terminal boards located in the Com-  
munications compartment. The communications options listed below reference the control wiring  
drawing for each option.  
• Internal modem (optional) — the connection to this modem is through a standard RJ-11 port. This  
port automatically dials the programmed telephone number when a designated alarm occurs.  
Automatic dial attempts are made to the first phone number at periodic intervals for 30 minutes.  
After that time, auto dial attempts are made to the second phone number at periodic intervals for  
the next 30 minutes. The process is repeated until a successful connection is made. Upon success-  
ful connection, the system transmits the status information and then hangs up. System status  
and history information can be requested and date and time can be changed through the modem.  
The modem commands are shown in Table 10 on page 77. See Figure 27 for more information on  
the internal modem.  
• Network Interface Card (NIC) (optional) — the NIC provides connectivity to any TCP/IP-based  
Ethernet network to allow the device to communicate with network management systems (NMS)  
via SNMP. Events can be transmitted to the NMS to provide remote status monitoring, plus fault  
and alarm detection. The NIC includes an RJ-45 port for an Ethernet connection, via Category 5  
cable.  
The NIC can also integrate the system with an existing Building Management System (BMS) or  
out-of-band monitoring, using Mobus, a standard multi-drop protocol. The NIC has redundant  
communication paths that make it possible to connect to a BMS using Modbus while simulta-  
neously communicate to a NMS through SNMP  
See Figure 28 for more information on the NIC. If you have questions about the NIC, refer to the  
OpenComms Network Interface Card Installation and Users Guide.  
• Input Contact Isolator (ICI) Board (optional) — provides an interface for up to eight user inputs.  
External messages and alarms can be routed to the unit, via the ICI.  
uring the connections. See Figure 25 for wiring details.  
• Programmable Relay Board (PRB) (optional) — up to two PRBs can be installed in the STS2 to  
route STS2 events to external devices.  
and instructions for reconfiguring the relays. See Figure 24 for wiring details.  
• Comms Board (optional) — includes a terminal block to provide a DTE connection to an external  
modem. This board also provides a direct connection to a SiteScan terminal, via an RS-422.  
SiteLink-12 or SiteLink-4 is required for SiteScan to communicate with the STS2. See Figure 26  
for wiring details.  
Data link requirements are Full Duplex Asynchronous RS-232 format.  
Communications options are also discussed in 6.0 - Options.  
12.1 Using the RS-232 Port  
The RS-232 port is configured with a baud rate of 9600 with 8 Data Bits, 1 Stop Bit, No Parity, and no  
hardware handshaking.  
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12.1.1 Connecting and Using a Terminal  
An RS-232 connection can be used to connect the STS2 to either a terminal or a PC running terminal  
emulation software. If you are unsure of the cable pin out, see 15.2.10 - Terminal Port Connec-  
tions.  
1. Connect the terminal to the STS2 by plugging the cable from the terminal into the RS-232 port.  
This connection can be made at any time.  
2. After making the connection, verify the communications link by pressing <ENTER> on the  
terminal keyboard.  
The interface communications system responds as indicated below:  
Repeating command -->  
Illegal command!  
<?> or <HELP?> displays the RS-232 command set  
<?> <command> or <HELP?> <command> displays specific help for the command  
SVTP-Control >  
The SVTP-Control > prompt indicates that RS-232 communications are established.  
• If you receive no response or prompt, verify that the connector is properly plugged into the  
port and the PC or terminal serial interface is working properly.  
3. Enter the desired commands, as listed in Table 10.  
For additional help type <?> <command> or <HELP?> <command>  
Refer to the corresponding menu options in the 13.0 - STS2 Touch Screen Display for more details  
about the commands.  
Some terminal commands require a password to function. Use the PWD command and a valid pass-  
word to gain access.  
Table 10 Terminal Commands  
Keys  
Function  
Displays this help menu or specific help with a command  
Displays active alarms  
?
AA?  
AF?  
Displays active faults  
CEL  
Clears the event log  
CHL  
DATE?  
DATE  
EL?  
Clears the history logs  
Displays current system date  
Sets system date  
Displays the entire event log  
HELP?  
HLn?  
Displays this help menu or specific help with a command  
Displays the history log #n, if frozen  
Logs user out of unprotected mode  
Displays the preferred source  
LOGOUT  
PS?  
PS n  
Sets the preferred source to #n  
Allows users to access protected commands  
Modem only. Ends the session and hangs up the modem.  
Silences the horn  
PWD  
QUIT  
SH  
SPT?  
SPTx  
Displays all current setpoints  
Displays current setpoints for group x. See 12.1.2 - Configuring the STS2 via the  
Terminal for a description of groups.  
SR?  
Displays status reports  
Displays current system time  
Sets system time  
TIME?  
TIME  
UPMDR?  
VER?  
Displays metering data  
Displays firmware versions  
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Communication Interfaces  
12.1.2 Configuring the STS2 via the Terminal  
The SPT command is used to configure the systems setpoints. The SVT syntax for the setpoints con-  
sists for four parameters:  
SPT [group] [item] [value]  
where the parameters are:  
• SPT — is the terminal command that is used to configure setpoints.  
group — the group under the setpoint command which contains the desired settings.  
item — the item number within the selected group.  
value — the desired value for this item.  
Only the specific options words listed in this section use a hexadecimal value. Other settings, depend-  
ing on what they are, use other input types. For example, System ID uses a text string, nominal volt-  
ages and currents use standard numeric integers, and modem baud rate uses an enumeration where  
0 = 2400, 1 = 9600, & 2 = 19200 bps.  
NOTE  
Spaces are placed between each parameter, but not between characters or numbers in a  
parameter. Using an underline here to represent a space, an example of a the syntax is:  
SPT_2_6_0081. 0081 is the value parameter.  
This section provides instructions for setting these parameters, with an example of building an SPT  
command for System and User settings.  
Groups Parameter  
The setpoints are grouped for ease of configuration. For example, Event Masks are group 4 and Sys-  
tem Settings are group 2. The numbers shown below are entered for the group parameter. For exam-  
ple, start of a System Settings command is SPT 2.  
The group parameters are:  
1 = System Ratings  
2 = System Settings  
3 = User Settings  
4 = Event Mask Settings  
For example, the start of a System Settings command is SPT 2, where SPT is the system setpoints  
command and 2 is the group parameter for System Settings.  
Event Mask parameters.  
Item Parameter  
Each setting within the group is indexed by an item number as shown below in Table 12. These item  
numbers are also displayed on the terminal when you list the configuration setting for a particular  
group  
Continuing with the example, to configure an Options_1 setting under System Settings, the command  
would begin with SPT 2 6  
where 6 is the value Options_1. Note the space between each parameter.  
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Value Parameter  
Item settings, depending on what they are, use various value types.  
Table 11 provides a list of the possible value types and their description.  
Table 11  
Value types  
Type  
Definition  
Numeric  
Scaled  
An integer numeric value in the units indicated by the item name. For example, a  
System Voltage Rating of 480 would indicate 480 volts.  
Similar to the Numeric, this value type is an integer that has been scaled, usually to  
remove decimal points that would normally appear within the value. In this case, a  
value of 2.5 may actually be input as simply 25. For all Scaled types, the scaling  
appears in Table 12.  
String  
Certain settings are represented by alphanumeric character strings, such as setting  
the System Model Number to STS2.  
Enumeration  
Bit-packed  
This type uses an indexed list to represent possible choices. One example is the  
Modem Baud Rate which uses a value of 0 to select 2400 bps, 1 for 9600 bps, and 2  
for 19200 bps.  
This type of value uses a hexadecimal binary word, where each of the sixteen bits in  
the word has the value of 1 (True) or 0 (False). Although somewhat difficult to use, it  
packs a large amount of data within a single entry. A detailed description of this type  
Event Masks  
This type is a specially formatted and is used to customize the behavior of each fault  
page 83 for instructions on configuring Event Mask parameters.  
Table 12 shows the various groups, the settings contained within, and the type of value it requires.  
Table 12 Group settings and values  
Group  
Item:  
1
Description  
Input Volts (PDU)  
Volts  
Value Type  
Integer  
Value Notes  
Set per system spec.  
Group 1:  
System  
Ratings  
2
Integer  
Set per system spec.  
Set per system spec.  
Desired freq. x 10 (600 = 60 Hz)  
[Not supported at this time]  
14 Character max.  
3
Current  
Integer  
4
Frequency  
Scaled  
1
Language  
Enumeration  
String  
2
System Model Number  
System ID Number  
System Tag Number  
System Order Number  
Options_1  
Group 2:  
System  
Settings  
3
String  
8 Character max.  
4
String  
8 Character max.  
5
String  
8 Character max.  
6
Bitpacked  
String  
14 Character max.  
7
Autodial Primary Line  
Autodial Secondary Line  
Autodial Pager Number  
Autodial Pager PIN  
Modem Init String  
Modem Baud Rate  
Modem LGS Check - Day  
Modem LGS Check - Time  
Comms Options 1  
Comms Options 2  
20 Character max.  
8
String  
20 Character max.  
9
String  
20 Character max.  
10  
11  
12  
13  
14  
15  
16  
String  
10 Character max.  
Group 2  
(cont.)  
String  
20 Character max.  
Enumeration  
Bitpacked  
Bitpacked  
Bitpacked  
Bitpacked  
0 = 2400, 1 = 9600, & 2 = 19200 bps  
See section 12.1.3.  
See section 12.1.3.  
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Communication Interfaces  
Table 12 Group settings and values (continued)  
Group  
Item:  
Description  
Value Type  
Value Notes  
SRC1 Fast Undervoltage  
Setpoint  
1
Integer  
In % of nominal below nominal  
Group 3:  
User  
Settings  
SRC1 Slow Undervoltage  
Setpoint  
2
3
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
Integer  
In % of nominal below nominal  
In number of lines cycles  
In % of nominal above nominal  
In 1/4 lines cycles  
SRC1 Slow Undervoltage  
Detect Delay  
SRC1 Overvoltage  
Setpoint  
4
SRC1 Overvoltage Detect  
Delay  
5
SRC1 I peak Transfer  
Setpoint  
6
x 10  
SRC2 Fast Undervoltage  
Setpoint  
7
In % of nominal below nominal  
In % of nominal below nominal  
In number of lines cycles  
In % of nominal above nominal  
In 1/4 lines cycles  
SRC2 Slow Undervoltage  
Setpoint  
8
SRC2 Slow Undervoltage  
Detect Delay  
9
SRC2 Overvoltage  
Setpoint  
10  
11  
12  
13  
14  
SRC2 Overvoltage Detect  
Delay  
SRC2 I peak Transfer  
Setpoint  
x 10  
Max. Transfer Phase  
Angle  
In degrees  
Output Frequency  
Deviation  
Freq. in Hz x 10  
15  
16  
17  
ReTransfer Delay Time  
Horn Volume  
Integer  
In seconds  
Integer  
Range: 1-10  
CriticalOptionEnabling  
Bitpacked  
See section 12.1.3.  
Non-Critical Option  
Enabling  
18  
Bitpacked  
See section 12.1.3.  
See section 12.1.4.  
See section 12.1.4.  
1 to  
63  
Event Mask settings for  
faults  
Event Mask  
Event Mask  
Group 4:  
Event Mask  
Settings  
64 to  
143  
Event Mask settings for  
alarms  
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Communication Interfaces  
12.1.3 Setting Bitpacked Options with the Terminal  
Five sets of options and features settings are available through the terminal to control the system  
operation.  
Under System Settings for the SPT command, these items denote which options are INSTALLED:  
• 6 — Options_1  
• 14 — Comms Options 1  
• 15 — Comms Options 2  
Under User Settings, for the SPT command, these items denote which features are ENABLED:  
• 17 — Critical Option Enabling  
• 18 — Non-Critical Option Enabling  
The value parameter settings are in the form of a bit-packed word (in hexidecimal notation). In other  
words, each bit indicates a particular setting for the option or feature. The bit assignments for the  
options and features are as follows:  
Options_1  
bit0 —HasDualOutputBreaker  
bit1 — HasPDU  
bit2 — Has4PoleTransferSwitch  
bit3 — HasShuntTrip  
bit4 — HasWyeOutputXfmr  
bit5 — HasExternalPrecisionTimeSource  
bit6 — HasSFA  
bit7 — HasRemoteSourceSelect  
bit8 through bit15 — not used (set to 0)  
Comms Options 1  
bit0 — HasIntModem  
bit1 — HasExtModem  
bit2 — HasNIC  
bit3 — not used (set to 0)  
bit4 — HasSiteScan  
bit5 — not used (set to 0)  
bit6 — not used (set to 0)  
bit7 — HasOpenCommsDigitalInputBrd  
bit8 — HasOpenCommsDigitalOutputBrd_1  
bit9 — HasOpenCommsDigitalOutputBrd_2  
bit10 — HasRemoteStatusPanelBrd_1  
bit11 — not used (set to 0)  
bit12 — not used (set to 0)  
bit13 — not used (set to 0)  
bit14 — EnableDialIn  
bit15 — EnableDialOut  
Comms Options 2  
bit0 — EnablePager  
bit1 — EnableOCDINormallyClosed  
bit2-3 — OCDO1Assignment (0=User Defined, 1=Standard Set or 2=AS400)  
bit4-5 — OCDO2Assignment (0=User Defined, 1=Standard Set or 2=AS400)  
bit6 through bit15 — not used (set to 0)  
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Critical Option Enabling  
bit0—EnableManual_IPeakReset  
bit1—EnableAutoRestart  
bit2 through bit15 - not used (set to 0)  
Non-Critical Option Enab  
bit0 — EnableAutoReXfer  
bit1 through bit15 — not used (set to 0)  
The bits are set in reverse order, from bit 15 on the left to bit 0 (zero) on the right. The bits are  
grouped in four sets of four bits each, as such:  
0000 0000 0000 0000  
|................................|  
bit 15.........................bit 0  
Since each bit represents a setting, a bit can be enabled or disabled:  
1 = installed option or enabled feature  
– or –  
0 = option not installed or feature not enabled  
Enabling or disabling the bits in each group creates a binary value for that group. For example, if the  
fourth bit in a group is set to 1, the group group’s binary value is 0001.  
Each group is translated into a hexidecimal equivalent. The group with the value of 0001 has a hex  
equivalent of 1.  
You can use this table to help with the conversion:  
Table 13 Binary-Hexadecimal Conversions  
Hex  
Equivalent  
Hex  
Equivalent  
Binary value  
0000  
Binary value  
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
1010  
1011  
1100  
1101  
1110  
1111  
0001  
0010  
0011  
0100  
0101  
0110  
0111  
1000  
1001  
The hex value for each group is entered in the command as four digits.  
To summarize the procedure:  
1. Set each bit position.  
2. Convert the binary value each group into its hex equivalent.  
3. Enter the hex values for each group, in order, into the command for the value parameter.  
The following example explains how the conversion is completed.  
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Communication Interfaces  
Putting the Terminal Command Together  
For example, a unit only has the Remote Source Selection and Dual-Output Breaker options installed.  
Checking the bits list under Options_1 on page 81, bits 7 and 0 each must be set to 1 to indicate  
that these options are installed.  
The bit setting is as follows, starting with bit 15 on the left and going down to bit 0:  
0000 0000 1000 0001  
With the bits combined in groups of four, the binary settings can be translated into hexidecimal val-  
ues.  
The first two groups in the sample equal zero (0). In the third group, 1000 in binary translates to 8 in  
hex. In the fourth group, 0001 in binary translates to 1 in hex.  
In hex this equates to (digits in the value parameter cannot have spaces between them):  
0081  
So your command to indicate that the Remote Source Selection and the Dual-Output Breaker are  
installed would be:  
SPT 2 6 0081  
12.1.4 Setting Event Masks with the Terminal  
The event masks can be customized via a terminal. The command SPT4?<ENTER> displays all faults  
and alarms, along with their associated event masks. A plus sign (+) means that particular event  
mask is enabled, while a minus sign (-) means that mask is disabled.  
Refer to 11.1 - Event Mask on page 71 for more information on event masks and their associated  
flags.  
Unlike the System and User Settings, mask values are set by designated letters, not hex values. How-  
ever, as with other RS-232 interface settings, four parameters are passed. See 12.1.2 - Configuring  
The syntax for configuring event masks is:  
SPT 4 ID ±D±L±S±E±A  
• SPT — is the terminal command used to configure setpoints.  
• 4 — setting (group parameter) for event masks, under System Settings.  
ID — event ID. The ID is the item parameter for this command. The ID numbers for each event  
are listed with the events in Table 9 on page 74.  
• D,L,S,E,A — the event masks: Dial, Latch, Summary, Event log, and Audible. The masks are the  
value parameter for the command.  
Each mask type must be preceded by a plus sign (+) to enable it, or a minus sign (-) to disable it.  
NOTE  
NO spaces are placed between each mask listed above.  
Only the mask that is passed (enabled) is applied when the event occurs.  
Note that the Summary and Event Log event masks are only configurable for the LED units.  
To set the event masks for a particular event:  
1. Enter the command. Examples and descriptions are provided below.  
2. Press ENTER.  
After the new settings are entered, the new results for that event ID are displayed.  
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Communication Interfaces  
Examples of Event Mask Settings  
• To latch event #001, S1 SCR SHORT, use SPT 4 1 +L.  
• To disable event #128, CONFIG MODIFIED, from sounding the horn, use SPT 4 100 -A.  
• To enable event #012, OUT VOLT SENSE FAIL, to Dial and go into the Event Log, use  
SPT 4 12 +D+E.  
• To disable all masks for event #120, INPUT CONTACT #1, use SPT 4 120 -D-L-S-E-A.  
To breakdown this syntax for the last example:  
• SPT — SVT command  
• 4 — group parameter, identifying System Setting group under which the Event Mask settings  
reside.  
• 120 — item parameter. In this command, that is the event ID.  
• -D-L-S-E-A — value parameter. In this case, the minus sign (-)disables all masks for the INPUT  
CONTACT #1 event.  
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STS2 Touch Screen Display  
13.0 STS2 TOUCH SCREEN DISPLAY  
The STS2 can be configured with a Color Graphical LCD touch screen display that allows you to  
quickly check the status of the unit and identify problems.  
A touch screen LCD is available through the front of the STS2. This screen provides a graphical  
(Mimic) display of the switch’s operation, plus system information including system parameters,  
alarms and faults.  
The LCD provides a color, back-lit touch screen as a user interface. In addition to the Mimic and the  
system parameters, the screen provides a series of menus to allow you to configure the STS2, includ-  
ing the control of the preferred source, auto/manual retransfer selection, alarm notification, and other  
system setpoints. The touch screen also provides buttons to reset alarms and turn off audible alarms,  
such as a horn.  
13.1 Display Overview  
The STS2 Color Graphical Display provides three areas of information, plus buttons and a series of  
menu choices.  
The Color Graphical Display contains the following features:  
Mimic — a graphical diagram of the status of the unit.  
Event controls — allow you to reset alarms and turn off audible alarms.  
Event Display — displays any active alarm or fault condition, in real-time.  
Menus — provide choices and configuration settings in dialog boxes or information in the display  
panel.  
Display panel — provides additional information, depending on the menu choice that was last  
selected. This information includes event help text, and startup and bypass procedures.  
Figure 49 STS2 touch screen display  
Mimic  
Event Controls  
Display Panel  
Event Display  
Menu Options  
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STS2 Touch Screen Display  
13.2 Menu Overview  
The touch screen menu provides access to configuration settings and more device information.  
The CONFIG (Configuration) and LOGS menus provide multiple choices through pop-up menus. The  
SOURCE XFER menu selection allows you to select the preferred source. The other menu choices pro-  
vide information in the display panel. The menu choices are discussed later in this manual.  
All programmable functions are preset at the factory to default settings. These settings enable the  
unit to be brought up without the need to enter all selectable parameters. The menus allow the set-  
tings to be customized.  
Figure 50 Menus  
Logs  
Config menu  
Event Log  
System Rating  
History Log 1  
History Log 2  
Event Masks  
User Settings  
System Settings  
Comm Options  
System Options  
System ID  
NOTE  
Some menu choices display a keyboard or keypad on the touch screen. Enter data on the  
touch screen.  
Click OK to save the data that you have entered.  
Use the back arrow button (<-) to delete unwanted characters. This button functions like  
a backspace key on a keyboard.  
Figure 51 Keyboard and keypad displays  
Backspace  
Backspace  
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STS2 Touch Screen Display  
13.2.1 Security  
Because the STS2 Color Graphical Display provides access to various configuration and monitoring  
choices, a password or key lockout switch may be used to protect access to certain changes, including:  
• Change configuration settings.  
• Clear logs.  
• Make a source transfer.  
• Reset an alarm.  
Without entering the password or enabling changes with the key lockout switch, you still can:  
• View the display, including the mimic, status and event help.  
• View logs.  
• View the startup and bypass procedures.  
• Use the SILENCE button to turn off the audible alarm.  
Using the Optional Key Lockout Switch  
An optional key lockout switch for the STS2 enables or disables the ability to make changes on the  
STS2. The key lockout switch is mounted on the front door. See Figures 8 through 10 for location of  
the key lockout switch.  
• To disable the changes, turn the key to the top of the switch, toward the closed padlock.  
• To enable changes turn the key to the horizontal position, toward the open padlock.  
Figure 52 Key lockout switch.  
Changes disabled  
Changes enabled  
Using the Password  
If the unit is not equipped with a keylock, a password is required when you attempt to:  
• Save changes in the CONFIG menu choices.  
• Transfer sources.  
• Reset active alarms.  
• Clear logs.  
When a password is requested, a keyboard is displayed on the touch screen. After you enter the pass-  
word, select OK.  
The password is case-sensitive. Password access times out after ten (10) minutes, and must be reen-  
tered to save changes. The time-out period cannot be changed.  
To set or reset the password:  
1. Select SYSTEM SETTINGS from the CONFIG menu.  
2. Select SYSTEM ID form the SYSTEM SETTINGS menu.  
3. Click PASSWORD.  
A keyboard is displayed.  
4. Enter a password.  
The password must be four (4) alpha-numeric characters and is case sensitive.  
5. Click OK.  
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STS2 Touch Screen Display  
13.3 Mimic Display  
The Mimic display provides a color diagram of the operation of the STS2. This display imitates the  
power flow through the static transfer switch and indicates source status, breaker status, switch sta-  
tus, source voltage and current readings, output power measurements, and active alarm messages.  
13.4 Event Controls  
The STS 2 detects events when certain thresholds are passed or certain problems occur. The alarm  
controls allow you to acknowledge the existence of these events.  
• RESET — All latched events whose conditions have cleared are removed from the Event Display.  
Faults and alarms that remain active, or are not recoverable, are not affected when this button is  
selected. This button is also used to perform manual I-Peak resets and manual retransfers.  
• SILENCE — turns off the audible alarm (horn or beeper) without resetting the triggering event.  
This setting does not permanently turn off the horn. The alarm sounds again when the next event  
with an audible alarm setting is triggered.  
Active events are shown in the Event Display, whereas cleared events can be reviewed via the Event  
Log.  
13.5 Event Display  
The Event Display lists the condition of the STS2 in real-time. Both nominal system parameters and  
alarm messages are displayed in the Event Display. You can touch any message in the Event Display  
to display more information in the Display Panel to the left. The selected status is displayed in bold  
type.  
13.6 Menu bar  
As previously mentioned, the menu bar provides both configuration choices and information. The  
choices under the Config and Log menus access additional dialog boxes, while the other menu choices  
only show information in the display panel.  
13.6.1 Configuration Menu  
When you select the CONFIG (Configuration) menu choice, a pop-up menu is dis-  
played with four choices.  
System Ratings used to configure frequency, voltage and currents settings for  
the STS2.  
Event Mask allows you to configure system’s response for events.  
User Settings allows you to configure operations for the STS2.  
System Settings accesses another pop-up menu to configure communication and  
system choices and the system ID.  
Each of these choices accesses a separate dialog box.  
System Ratings  
The System Ratings menu is used to set the nominal line frequency, nominal voltage and nominal  
current at which the system operates when it is installed. These settings are configured when the sys-  
tem is initialized at the factory or under maintenance and should not be changed by the user.  
Event Masks  
The STS2 gathers, processes and reports faults and alarms, collectively referred to below as events.  
The Event Mask dialog box allows you to set the system’s response for specific alarms and faults that  
are generated. See 11.0 - Alarm and Faults for more information on events and 11.1 - Event Mask  
for the definitions of the Event Mask types.  
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STS2 Touch Screen Display  
To set the event masks:  
1. Access the Event Mask dialog box:  
a. Select CONFIG.  
b. Select EVENT MASK from the pop-up menu.  
The Event Mask dialog box is displayed. See Figure 53.  
2. Select the mask settings for each fault and alarm.  
a. Select YES to enable the setting,  
– or –  
b. Select NO to disable the setting.  
3. Select SAVE to keep the settings.  
Figure 53 Event mask dialog box  
User Settings  
The User Settings choice allows you to adjust the user-accessible switch settings. Access is limited to  
qualified personnel via system security.  
To access the User Settings dialog box:  
1. Select CONFIG.  
2. Select USER SETTINGS from the pop-up menu.  
The User Settings dialog box is displayed. See Figure 54. The top six buttons access a series of sec-  
ondary dialog boxes to configure the various settings.  
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STS2 Touch Screen Display  
Figure 54 User settings dialog box  
Source Set Points  
The Source 1/2 Set Points allows you to configure trigger points for each input source (1 or 2) for the  
STS2 via a keypad dialog or HI/LO dialog box. The source numbers do not designate the source as the  
preferred or alternate source. The numbers simply identify the input source. See 10.2 - Manual  
Transfer / Preferred Source Selection to set the preferred source.  
The Set Points are based on values in relation to the nominal voltage required for the STS2. UV refers  
to under voltage, meaning the amount of voltage below the nominal voltage. OV refers to over voltage,  
or the amount of voltage over the nominal voltage.  
Fast UV Setting (%) if the voltage drops below this set percentage of the nominal voltage, the  
STS2 transfers from the current source to the opposite source.  
Slow UV Setting (%) if the voltage remains this set percentage below the nominal voltage for  
the period of the slow detection delay, the STS2 transfers from the current source to the opposite  
source.  
Slow UV detection delay the number of cycles that the source must remain below the Slow UV  
Setting before the STS2 transfers.  
OV Setting (%) if the voltage exceeds this set percentage of the nominal voltage for the period of  
the OV detection delay, the STS2 transfers from the current source to the opposite source.  
OV Detection Delay the number of cycles that the source must remain above the OV Setting  
before the STS2 transfers sources.  
I-PK Xfer Lockout if current from the source exceeds this threshold, the STS2 disables source  
transfers, and has to be reset either manually or automatically. The type of reset is configured  
under the User Settings.  
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STS2 Touch Screen Display  
To configure the set points for each source:  
1. Select SOURCE 1/2 SET POINTS from the User Settings dialog box.  
The Source 1/2 Set Points dialog is displayed.  
Figure 55 Source setpoints  
2. Select 1 to configure the settings for Source 1.  
3. Configure the settings using the keypad or dialog box that is displayed when you touch a button.  
Table 14 Set Point Parameters  
Button  
Range  
Default  
Comments  
Fast UV Setting (%)  
-10 to -30% of Nominal  
voltage rating  
-20%  
Set in increments of 1%.  
Slow UV Setting (%)  
Slow UV detection delay  
OV Setting (%)  
-5 to -20%  
-10%  
Set in increments of 1%.  
Units: Line Cycle  
1-60 cycles  
+5% to +20%  
1-255 cycles  
5 cycles  
+10%  
Set in increments of 1%.  
Units: 1/4 Line Cycle  
OV Detection Delay  
I-PK Xfer Lockout  
3 cycles  
0 – 3.0 multiplied by  
the unit current rating.  
2.5 * Unit  
Current Rating  
I-peak xfer lockout detection point.  
Units: Amps RMS. Select the HI or  
LO buttons to configure your setting.  
4. Select 2 for Source 2.  
5. Configure the settings, as described in step 3.  
6. Select SAVE to keep the settings for both sources.  
The Set Points dialog is closed and the User Settings dialog is displayed.  
7. Select MANUAL MAX XFER PHASE ANGLE.  
A keypad is displayed.  
This setting configures the maximum allowed phase difference between the sources and applies to  
all manual transfers as well as any auto retransfer.  
a. Configure this setting with a range of +/- 1-30 degrees.  
The default setting is +/-15 degrees and the resolution is 1 deg.  
b. Select OK to save the setting.  
The setting is now displayed in the adjacent field in the User Settings dialog box.  
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STS2 Touch Screen Display  
8. Select FREQUENCY TRIP POINT.  
A keypad is displayed.  
This choice verifies that the source is running at the proper frequency. This choice sets the fre-  
quency deviation in the frequency that triggers the frequency trip point alarm. The frequency  
deviation setting is the allowable frequency variation from nominal (60.0 or 50.0 Hz) before acti-  
vating the frequency deviation alarm. The frequency setting applies to both input sources.  
a. Configure this setting with a range of 0.1 – 3.0 Hz  
The default setting is 0.5 and the resolution is 0.1.  
b. Select OK to save the setting.  
9. Select RETRANSFER DELAY.  
A keypad is displayed.  
With the secondary source being used, this setting sets the length of time the switch waits until  
attempting to transfer back to the preferred source.  
a. Configure this setting with a range of 1 to 60 seconds.  
The default setting is three (3) seconds and the resolution is 1 second.  
b. Select OK to save the setting.  
The setting is now displayed in the adjacent field in the User Settings dialog box.  
10. Select AUDIO LEVEL.  
A dialog box is displayed with HI and LO settings.  
This choice sets the loudness of the horn or beeper that is sounded for audible alarms.  
a. Configure this setting with a range of 1–10 (ten).  
The default setting is 5. The settings have an increment of 1 (one).  
b. Select OK to save the setting.  
The setting is now displayed in the adjacent field in the User Settings dialog box.  
You can select TEST to briefly sound the alarm to judge its volume.  
11. Select DISPLAY BRIGHTNESS.  
A dialog box is displayed with HI and LO settings.  
This choice sets the brightness for the touch screen.  
a. Configure the Contrast and Brightness settings with a range of 1 – 10 (ten).  
b. Select OK to save the settings.  
12. Set the AUTO REXFER ENABLE choice.  
The auto retransfer enable setting determines whether the switch automatically returns the pre-  
ferred source after that source is restored.  
• Select YES to enable the automatic transfer.  
• Select NO to disable the automatic transfer. The setting requires transfers be done manually.  
13. Set the AUTO RESTART ENABLE choice.  
This setting determines whether the STS2 can be started automatically when power is restored  
after it has been lost.  
• Select YES to enable the automatic restart.  
• Select NO to disable the automatic restart. This settings requires a manual restart of the STS2.  
14. Select a setting for the I-PEAK RESET.  
• Select AUTO to configure the static transfer switch to automatically reset when a fault clears  
and the voltage and current are normal.  
• Select MAN to require a manual reset of the static transfer switch when fault clears and the  
voltage and current are normal.  
CAUTION  
!
Risk of equipment damage and personnel injury.  
Use of Auto Restart is site specific. Do not enable auto restart unless the infrastructure is  
designed for unattended operation and there is no chance of equipment or personnel harm by  
automatic re-energizing of the system.  
Consult with your Liebert site Engineer as to whether Auto restart should be enabled.  
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STS2 Touch Screen Display  
System Settings  
The System Settings choice under the Config menu displays another pop-up menu with three choices:  
Comm Options  
System Options  
System ID  
To access the System Settings menu:  
1. Select CONFIG from the menu bar.  
2. Select SYSTEM SETTINGS from the Config menu.  
Comm Options  
The Comm Options dialog box allows you to configure the communications settings for the STS2.  
• Select COMM OPTIONS from the System Settings Menu.  
The Comm Options dialog box is displayed. See Figure 56.  
• An option can be enabled by selecting YES.  
• An option can be disabled by selecting NO.  
• An option can be configured by selecting the adjacent option button to display a separate con-  
figuration dialog box.  
The instructions for configuring the communications options are provided in this section.  
Figure 56 Comm options dialog box  
Option  
buttons  
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STS2 Touch Screen Display  
Configuring the Modem  
The Modem dialog box allows you to configure the optional, internal modem or an external modem  
that is connected to the static transfer switch. Only one modem can be utilized by the STS2.  
The dialog box contains a series of choices that access either a keypad or a secondary dialog to config-  
ure settings. Auto dial can also be configured for the modem to be triggered by events, as set up in the  
Event Mask choices.  
Designated major alarms activate the auto dial modem sequence. Automatic dial attempts are made  
to the first number three times, at 30 seconds between attempts. If connection is not established in  
that time period, the system automatically rolls over to the second number. Auto dial attempts are  
made again three more times at 30 seconds between attempts. The process is repeated until a success-  
ful connection is made. Upon successful connection, the system transmits a present status data,  
including all active alarms messages. After transmission, the modem automatically hangs up and  
returns to the auto-answer mode.  
To configure the modem:  
1. Select MODEM from the Comm Options menu.  
The Modem dialog box is displayed.  
Figure 57 Modem dialog box  
2. Select the type of modem that the STS2 will be using:  
• Select INT if the STS2 will be communicating via an internal modem.  
• Select EXT if the STS2 will be communicating via an external modem.  
3. Select the PRIMARY LINE choice to enter the primary telephone number for the modem to dial  
when an alarm is triggered.  
4. Enter the number in the keypad dialog box.  
5. Select OK to save the telephone number. The number is displayed in the field adjacent to the  
Primary Line choice.  
6. Select the SECONDARY LINE choice to enter the secondary telephone number for the modem to  
dial when an alarm is triggered.  
7. Enter the number in the keypad dialog box.  
8. Select OK to save the telephone number. The number is displayed in the field adjacent to the  
Secondary Line choice.  
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STS2 Touch Screen Display  
9. Select INIT. STRING to configure the initialization string.  
This string configures the parameters of the modem.  
• This setting only needs to be configured if an external modem is used. Check your modem’s  
documentation for this setting.  
• The string for the internal modem set by the manufacturer and does not need to be changed.  
10. Select BAUD RATE to display a dialog with the baud rate choices:  
• For an external modem, select from 2400 bps, 9600 bps or 19200 bps.  
• An internal modem only supports 2400 bps.  
11. Configure the MODEM HEALTH CHECK.  
The Health Check verifies that the modem is working properly. This setting allows you to enable  
the check and set when it is run.  
a. Select the button to display the Modem Health Check dialog box, from which you can access  
further dialogs to set the time and days that the check is run.  
b. Select SAVE to keep the settings.  
The Health Check dialog box is closed and the Modem dialog box is again active.  
c. Select YES in the Modem dialog box to activate the Modem Health Check.  
If you select NO, the Modem Health Check is not run.  
12. Configure AUTO DIAL IN.  
Auto Dial In allows a user to dial into the STS2 through the modem to check status and access the  
system via a hyperterminal connection.  
a. Select YES to activate the dial in feature.  
b. Select NO to deactivate the dial in feature.  
13. Configure AUTO DIAL OUT.  
Auto Dial Out allows the STS2 to automatically dial out to a system to notify a user of an event or  
status.  
a. Select YES to activate the dial out feature.  
b. Select NO to deactivate the dial out feature.  
14. Select SAVE to keep the modem configuration settings.  
15. Select YES in the Comm Options dialog box to activate the settings.  
You are returned to the Comm Options dialog box.  
Configuring Pager Support  
Pager support will be implemented in an upcoming update of the system. This support will trigger the  
system to call a pager when specified events occur. This menu choice will allow you to enter the tele-  
phone number and PIN for the pager that you want the system to call.  
Configuring the Input Contact Isolator Settings  
The Input Contact Isolator (ICI) is an optional, eight-channel input board for up to eight external user  
alarm or message inputs to be routed to the static transfer switch’s alarm network.  
The contact is set to either be normally open or normally closed. When a contact closes or opens, an  
event is triggered. See 6.4 - Input Contact Isolator Board for more information on the ICI.  
The Input Contact Isolator options are configured through the Input Contact Isolator dialog box,  
which is accessed from the Comm Options dialog box. The Input Contact Isolator dialog box contains  
eight choices to match the eight channel input board. You can label each button to identify the event  
associated with the contact. When the dialog box is accessed, each button flashes to display the Input  
Contact Isolator number and the user entered label. This label also appears in the Display Panel  
when an event related to an Input Isolator Connector is triggered.  
The Input Contact Isolator dialog box allows you to:  
• Label the input contact assignments for your setup.  
• Set the delay for an external event triggering an alarm.  
• Review the isolator contact assignments, once the labels are entered.  
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STS2 Touch Screen Display  
The delay allows you to set the number of seconds which a condition needs to persist to trigger an  
alarm.  
These input alarms can also be configured to activate a programmable relay output, which is dis-  
To configure the Input Contact Isolator relays:  
1. Select INPUT CONTACT ISOLATOR from the Comm Options menu.  
The Input Contact Isolator dialog box is displayed.  
Figure 58 Input contact isolator dialog box  
2. Select INPUT CONTACT 1.  
A keyboard is displayed to allow you to enter the name of the alarm.  
3. Enter the name of the alarm set for that input. For example, a fan problem could be indicated by  
naming the button FAN.  
4. Select OK on the keyboard to keep your label.  
5. Select DELAY.  
A keypad is displayed prompting you for a delay time, in seconds, for a condition to exist before  
the alarm is triggered.  
6. Enter the delay value. The range for the values are from 0 (zero) to 99.9 seconds.  
7. Select OK on the keypad to keep your setting.  
The value you entered is displayed in the field adjacent to the corresponding input contact.  
8. Repeat steps 2 to 7 for each input contact.  
9. Select SAVE after you have configured all input contacts.  
Be sure to select Save even if you have accessed this dialog only to change a setting.  
This information is not saved if control power is removed.  
11. Select OK in the Comm Options dialog box to activate the settings.  
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STS2 Touch Screen Display  
Configuring the Programmable Relay Board Settings  
The STS2 can contain up to two Programmable Relay Boards (PRB) that can trigger an external  
device when an event occurs in the static transfer switch. For example, if Source 1 fails, an external  
light flashes.  
See 6.1 - Programmable Relay Board for more information on the PRBs.  
The Programmable Relay Board dialog box with two options: STANDARD SET and USER DEFINED  
SET. The STANDARD SET are the factory-configured settings.  
The STANDARD SET for the Programmable Relay Board settings are:  
Table 15 Standard Settings for Programmable Relays  
Relay  
Setting  
SOURCE 1 FAIL  
Definition  
1
2
3
4
5
6
Source 1 failure.  
Source 2 failure.  
SOURCE 2 FAIL  
BYPASS CB4 CLOSED  
BYPASS CB5 CLOSED  
TRANSFER INHIBIT  
OUT OF SYNC  
Switch (CB4) is closed, Source 1 is bypassed.  
Switch (CB 5) is closed, Source 2 is bypassed.  
A transfer between Source 1 and Source 2 is being restrained.  
The phase difference between sources 1 and 2 exceeds the  
allowable threshold for transfer,  
7
8
EQUIP OVER TEMP  
blank  
The ambient temperature of the STS2 exceeds the  
recommended threshold for operation.  
No setting.  
The USER DEFINED SET allows you to assign faults and alarms to each contact on the relay boards.  
Utilizing the USER DEFINED SET, you can also select Input Contact Isolators to associate with a  
programmable relay.  
In addition individual events, three other assignment choices are available:  
• SELECT ALL sends a summary event to the selected relay whenever any event occurs. If this set-  
ting is selected for a relay, no other event needs to be assigned for that relay.  
• ON SOURCE 1 or ON SOURCE 2 can be assigned to a relay to send a notification when that  
source is being used by the load.  
Once configured, the static transfer switch continuously checks the status of the items defined for  
each contact and updates the state of the relay.  
To configure your programmable relay boards for user defined settings:  
1. Select PROG. RELAY BOARD # x from the Comm Options dialog box, where x is the  
corresponding board number.  
The Prog. Relay Board dialog box is displayed.  
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STS2 Touch Screen Display  
Figure 59 Programmable relay board dialog box  
2. Select your configuration settings.  
• Select STANDARD SET to use the settings configured at the factory. See Go to step 4.  
• Select USER DEFINED SET to configure your own settings. Go to step 3.  
If you enter a user defined settings, this information is not saved if control power is removed.  
3. To define your relay board settings:  
a. Select a Programming Relay.  
b. Select an event you want associated with the relay. That fault is placed in the Relay column.  
You can associate up to ten (10) events with one relay. If you do so, you should group the  
events logically to simplify troubleshooting when an event is triggered.  
4. Select SAVE to keep the settings.  
5. Select OK for the applicable Programmable Options Board option in the Comm Options dialog box  
to activate the settings.  
Configuring the Network Interface Card  
An optional Liebert OpenComms Network Interface Card (NIC) can be installed in the STS2 to pro-  
vide Ethernet connectivity via an RJ-45 port.  
Ethernet cabling is the responsibility of the customer. Category 5 cabling is required.  
See 6.7 - Network Interface Card (NIC) for more information on the NIC.  
See the OpenComms Network Interface Card Installation and Users Guide for configuration instruc-  
tions for the card.  
If the optional OpenComm NIC is installed in the STS2:  
• Select YES for the Network Interface Card option in the Comm Options dialog box to activate the  
card.  
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STS2 Touch Screen Display  
SiteScan Configuration  
An optional RS-422 port, contained in the Comms Board, can be installed in the static transfer switch  
to provide communications with Liebert’s SiteScan. SiteScan is Liebert’s system monitoring software  
that allows you to utilize a PC to monitor the static transfer switch’s status and check alarms. See  
6.5 - Comms Board for more information on this board.  
If the STS2 will be connected to SiteScan:  
• Select YES for the SiteScan choice in the Comm Options dialog box to activate the card.  
Saving Your Communications Configurations  
To save you communications configuration settings:  
1. When you have completed the Comm Options configurations, ensure you have selected YES for all  
the settings that you want activated.  
2. Select SAVE to keep the settings.  
Whenever you make modifications to the any of the Comm Options, select SAVE to keep the changes.  
System Options  
Most System Options are configured at the factory. However, you may need to set two of the choices  
after the unit is installed: Wye Output Transformer and Remote Source Selection.  
• Select SYSTEM OPTIONS from the System Settings Menu.  
The System Options dialog box is displayed.  
• An option is enabled by selecting YES.  
• An option is disabled by selecting NO.  
Figure 60 System options  
Dual Output Breaker  
This selection is set at the factory. The choice is set to YES to enable both output breakers (CB3 and  
CB3A) when two are installed in the unit. If only one output breaker (CB3) is installed, the setting is  
set to NO.  
PDU  
This selection is set at the factory. This setting allows the LCD to draw the Mimic accordingly and  
display PDU specific metering and alarm information.  
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STS2 Touch Screen Display  
4 Pole Transfer Switch  
This selection is set at the factory to indicate whether the system is a 3 pole or 4 pole unit.  
Shunt  
This selection is set at the factory.  
Wye Output Transformer  
The Wye Output Transformer controls the firing of the SCRs on startup, which minimizes the inrush  
into PDU transformers. Output breakers and PDU input breakers have to be closed when you start  
up the system. Based on whether the input side of the PDU transformer is configured as a Wye or  
Delta changes the firing sequence of the SCRs.  
If the STS2 is connected to a PDU configured as a Wye:  
• Select YES for the Wye Output Transformer choice in the System Options dialog box.  
Remote Source Selection  
If your system is configured with the optional Remote Source Selection, it must be enabled from the  
System Options menu. See 5.5 - Remote Source Selection Wiring for more information.  
If the system is utilizing Remote Source Selection:  
• Select YES for the Remote Source Selection choice in the System Options dialog box to activate  
the option.  
System ID  
Most of the settings for System ID are set by Liebert either at the factory or when the unit is  
installed.  
Order No., System Tag No., System ID No. and Model No. are the numbers used to identify and track  
the system.  
Language, Time and Date are synchronized with the location of the unit.  
The only configurable field is the Password. See Using the Password on page 87 for more informa-  
tion on configuring and using the password.  
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STS2 Touch Screen Display  
13.6.2 Logs  
Two types of logs are kept by the STS2: Event Log and History Log.  
Event Log  
The Event Log tracks the alarms and faults of the STS2.  
See 11.0 - Alarm and Faults for more information on these events and see 11.2.1 - Event Log for  
more information on the Event Log and definitions of the fields displayed in the Event Log screen.  
Figure 61 Event log  
To use the Event Log:  
1. Select LOGS from the menu bar to open the Logs menu.  
2. Select EVENT LOG from the menu.  
3. Use the UP and DOWN buttons to scroll through the event list.  
4. Select OK to close the Event Log. The data remains in the log.  
History Log  
Two History Logs are available to track major alarms. If so configured, an alarm freezes the history  
buffer. When the History Status buffer is frozen, a History Log is created that can be accessed from  
the HISTORY LOG x choices in the LOGS menu.  
See 11.2.2 - History Log for more information on the History Logs and definitions of the fields dis-  
played in the History Log screen.  
Figure 62 History log  
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STS2 Touch Screen Display  
To use the History Log:  
1. Select LOGS from the menu bar to open the Logs menu.  
2. Select either HISTORY LOG 1 or HISTORY LOG 2 from the menu.  
3. Select the appropriate buttons to replay the log:  
• Select PREV to go to the previous frame in the sequence.  
• Select NEXT to go to the next frame in the sequence.  
• Move the green cursor to the location from which you would like to play the sequence of  
events.  
• Select REPLAY to play the frames automatically from the point of the cursor.  
• Select STOP to halt the replay.  
• Select RESET to return to the first frame in the log.  
4. Select EXIT to close the History Log. The data remains in the log.  
• Use CLEAR HLOGS to remove the data from both history logs.  
NOTE  
Event and History Logs are protected by security. The password or a disabled key lockout is  
required on such equipped units to clear these logs.  
13.6.3 Source Transfers  
The Source Transfer choice (SOURCE XFERS) allows you to manually select a preferred source.  
To switch the primary source, refer to the instructions in 10.2 - Manual Transfer / Preferred  
13.6.4 Startup Procedure  
You can access instructions for starting the STS2 from the menu bar.  
• From the menu bar, select STARTUP PROC.  
These instructions are also provided on 10.1 - Normal System Turn-On for Color Graphical display  
units and 14.2.1 - Normal System Turn-On for LED Display units.  
13.6.5 Bypass Procedure  
You can access instructions for bypassing the static transfer switch from the menu bar.  
• From the menu bar, select BYP. PROC.  
The instructions are provided in the display panel.  
Bypass procedures are also discussed in 10.4 - Maintenance Bypass for Color Graphical display  
units and 14.2.3 - Maintenance Bypass for LED Display units.  
13.6.6 Help  
You can select an event in the Event Display to display more information about that event in the Dis-  
play Panel. This same help is also available in 16.0 - Event Message Help Text.  
13.6.7 Logo  
The Logo menu choice shows the Liebert and Emerson logo in the Display panel.  
13.7 Cleaning the LCD Touch Screen  
If the touch screen requires cleaning, use a pre-moistened towelette designed for cleaning CRTs, or  
dampen a soft, non-abrasive cloth with a very mild cleaning solution.  
Do not spray the cleaner directly onto the touch screen, as drips may run down into the screen and  
damage the equipment.  
Close all menus and dialog boxes before cleaning the touch screen.  
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Operating the LED Display STS2  
14.0 OPERATING THE LED DISPLAY STS2  
Certain models of the STS2 do not include the LCD Color Graphical Display with the touch screen  
interface. This display is replaced by an LED front panel to allow you to monitor the unit and alert  
you when a problem occurs. The LED panel can be replaced with the Color Graphical Display, if  
desired. Instructions for using the LCD are in 13.0 - STS2 Touch Screen Display.  
You can use a PC running terminal emulation software connected to the RS-232 port to access the  
data and configuration settings that are available in the Color Graphical Display touch screen.  
See 12.1 - Using the RS-232 Port for instructions on setting up and using a terminal with the unit.  
14.1 LEDs and Buttons and Key Lockout Switch  
The LED Display unit is monitored and controlled through a series of LEDs and buttons and an  
optional key lockout switch. This section includes illustrations of the LEDs, buttons and key lockout  
switch, plus tables providing definitions of these components.  
14.1.1 Front Panel Controls  
The front panel contains the LEDs to monitor the STS2, plus selection buttons to choose the preferred  
source. Figure 63 provides a breakdown of the front panel.  
Table 16 on page 104 defines the LEDs and the push buttons on the display.  
Figure 63 LED display  
4
(E)  
~
~
(A)  
1
(C)  
(H)  
1
~
3
(J)  
(G)  
3A  
2
(I)  
~
~
2
(B)  
(D)  
(F)  
5
(L)  
(K)  
(M)  
(N)  
PS211002  
Rev. 0  
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Operating the LED Display STS2  
14.1.2 LED and push button description  
The following table defines the LEDs and pushbuttons in the LED display:  
Table 16 LED and push button description  
Symbol LED  
Description  
Action  
A green LED is lit if the Source 1 input power is present. This LED  
only indicates that power is present to the power supply; it does not  
indicate if the power is within the programmed tolerances of the unit.  
A
B
Green  
Source 1 power is present  
A green LED is lit if the Source 2 input power is present. This LED  
only indicates that power is present to the power supply; it does not  
indicate if the power is within the programmed tolerances of the unit.  
Green  
Source 2 power is present  
A green LED is lit if Source 1 power is within the programmed  
tolerance for all phases.  
C
D
Green  
Green  
Source 1 within tolerance  
Source 2 within tolerance  
A green LED is lit if Source 2 power is within the programmed  
tolerance for all phases.  
E
F
Green  
Green  
Source 1 SCRs on  
Source 2 SCRs on  
A green LED is lit when the SCRs for Source 1 are closed.  
A green LED is lit when the SCRs for Source 2 are closed.  
A yellow (amber) LED is lit when source transfers are inhibited  
(locked out) by a hardware condition. Connect a PC terminal to the  
STS2 to locate the exact cause. See 12.0 - Communication  
Interfaces for PC terminal commands.  
G
Yellow  
Source transfer inhibited  
Push button to select Source 1 A green LED is lit if the button has been pushed to set Source 1 as  
as the preferred source the preferred source.  
H
I
Green  
Green  
Green  
Push button to select Source 2 A green LED is lit if the button has been pushed to set Source 2 as  
as the preferred source  
the preferred source.  
A green LED is lit to indicate that power is present on the output  
load.  
J
Output power is present  
Push this button to turn off the horn that is sounded for an alarm.  
This button does not reset an alarm condition, unless pushed  
simultaneously with “M” button.  
K
L
Alarm silence button  
Symbol to indicate the K and M  
must be pushed at the same  
time to reset alarm  
Push this button simultaneously with the “K” button to reset an alarm  
condition. An alarm can only be reset if the hardware condition  
permits a reset.  
M
Alarm reset push button  
A red LED is lit when an alarm condition is present in the STS2.  
Connect a PC terminal to the STS2 to locate the exact cause. See  
12.0 - Communication Interfaces for PC terminal commands.  
N
1
Red  
Alarm present  
CB1 closed  
A green LED is lit if CB1 is closed, indicating power is flowing to the  
static transfer switch from Source 1.  
Green  
A green LED is lit if CB2 is closed, indicating power is flowing to the  
static transfer switch from Source 2.  
2
3
Green  
Green  
Green  
CB2 closed  
CB3 closed  
CB3A closed  
A green LED is lit if the output breaker/switch is closed.  
A green LED is lit if the output breaker/switch is closed. CB3A is  
installed on units with dual output breakers.  
3A  
4
5
Yellow  
Yellow  
CB4 closed  
CB5 closed  
A yellow LED is lit if the Source 1 bypass breaker/switch is closed.  
A yellow LED is lit if the Source 2 bypass breaker/switch is closed.  
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Operating the LED Display STS2  
14.1.3 Event Controls  
When an alarm is triggered, a red LED is lit in the control panel. A pair of buttons allows you to turn  
off the horn and reset the alarm.  
14.1.4 Key Lockout Switch  
An optional key lockout switch for the STS2 enables or disables all push button inputs, except for the  
alarm silence button. The key lockout switch is mounted on the front of the unit. See Figures 8 to 10  
for the key lockout switch location on each unit.  
• To disable the buttons, turn the key to the top of the switch, toward the closed padlock icon.  
• To enable all of the buttons, except the alarm silence, turn the key to the horizontal position,  
toward the open padlock icon.  
Figure 64 Key lockout switch.  
Changes disabled  
Changes enabled  
14.2 Operations  
This section discusses the system turn-on, shut-down and bypass procedures for LED-based STS2.  
If your unit has an LCD touch screen, see10.0 - Operating Instructions for the Touch Screen  
Interface for instructions these procedures.  
14.2.1 Normal System Turn-On  
NOTE  
If your STS2 is connected to a PDU with a Wye configuration, enable the Wye Output  
Transformer before starting the system. This configuration can be done from a PC terminal.  
Refer to 12.1 - Using the RS-232 Port for instructions.  
This section provides instructions to turn on your STS2. The LEDs provide the basic information  
required to ensure proper operation. To monitor metering data, use a PC terminal.  
1. Ensure that all STS2 breakers—CB1, CB2, CB3A (if supplied), CB3, CB4, and CB5—are in the  
OFF (open) position.  
a. Ensure that the key interlocks for CB1 and CB2 have their bolts retracted.  
b. Ensure that the key interlocks for CB4 and CB5 have their bolts extended, thus preventing  
CB4 or CB5 from being turned ON.  
c. Ensure that the circuit breakers respective LEDs are off.  
2. Source/input power should be applied to both STS2 inputs.  
Check that the green LEDs for each source are lit.  
3. Verify that nominal input voltages are applied to both inputs (Source 1 and Source 2).  
Check that the green LEDs monitoring the sources are lit indicating the sources are within  
acceptable tolerances.  
NOTE  
For redundant output switch units, CB3 descriptions apply to CB3 and CB3A.  
4. Close CB1.  
The green LED monitoring CB1 turns on.  
5. Close CB2.  
The green LED for CB2 turns on.  
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Operating the LED Display STS2  
6. Verify that the preferred source LED (green) (LED_PREFx) is lit for the source that you want the  
switch to be using.  
7. Verify that the green LED for the corresponding SCR (STS1 or STS2) is lit, indicating that the  
SCR is closed.  
8. Close Output Breaker CB3 (and CB3A in a redundant output configuration).  
9. Verify the CB3 LED is lit, indicating that CB3 is closed and the output and load are energized.  
• In a redundant output configuration, verify the CB3A LED is lit, indicating that CB3A is  
closed and the output and load are energized  
10. Press the Reset and Silence buttons simultaneously to reset any previous alarms.  
11. Verify that no red or yellow (amber) LEDs are lit indicating an active alarm, transfer is inhibited  
or a bypass circuit breaker is closed.  
If the alarm LED remains lit, check the PC terminal to identify the alarm. Refer to 11.0 - Alarm  
and Faults for a description of the alarms and possible causes. All active alarm conditions should  
be corrected before proceeding.  
12. If the unit is supplied with an output distribution cabinet, close output breakers as required.  
13. Turn on the load equipment following the load equipment manufacturer’s recommendations.  
14.2.2 Manual Transfer / Preferred Source Selection  
The preferred source buttons allow you to change the preferred source. Transfers are only permitted  
when the voltage and current are within their proper operating range and the sources are synchro-  
nized. Transfer is inhibited if the deviation exceeds the parameter set in the Source Set Points.  
NOTE  
If one source will be de-energized for an extended period (hours or days), set the unit to bypass  
mode for the remaining source. Without using bypass, if a failure occurs in the switch  
components for remaining source, the STS2 does not have a second source to switch to and the  
load would not receive power. See 14.2.3 - Maintenance Bypass on page 107 for bypass  
instructions.  
To manually select the preferred source:  
1. Ensure that the Transfer Inhibit (NOXF) LED is not lit.  
If the Transfer Inhibit LED is lit:  
• Check to see if the red alarm LED is lit.  
• If the alarm LED is lit, check the alarm messages on a PC terminal.  
• Correct alarm conditions before attempting a source transfer.  
NOTE  
When the remote source selection option (Remote Control) is activated, a change of state  
(Remote Preferred Source Selection) may initiate a transfer if the appropriate contacts are  
closed.  
2. Verify that the LEDs are lit for both sources, indicating power is present and within acceptable  
tolerances.  
3. Verify that the LEDs for the SCRs (STS1 and STS2) are lit.  
4. Verify that the input breakers CB1 and CB2 are closed.  
• Verify that their respective LEDs are lit.  
5. Push the Preferred Source button for the desired source. See Table 16 on page 104.  
The Preferred Source (LED_PREFx) LED turns on for that source.  
When conditions are correct, the switch transfers the load to the alternate source by selecting the  
alternate source as the preferred source.  
This source is now monitored as the preferred source throughout the various configurations set up  
through the PC terminal.  
6. Check the LEDs to verify that the correct source is designated as the preferred source and that  
the input source changes to the desired source and the output (OUT) LED remains lit.  
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Operating the LED Display STS2  
14.2.3 Maintenance Bypass  
The STS2 is equipped with two key-interlocked, bypass breakers, CB4 and CB5, to allow manual  
bypass of the switch electronics for either input source in the event of switch failure or for mainte-  
nance of the switch. Refer to the static transfer switch one-line diagram (Figure 3). While operating  
on maintenance bypass, all voltages are removed from the STS2 electronics to facilitate safe repair,  
without de-energizing the load using a make-before-break switching sequence.  
However, the unit can be bypassed using a make-before-break switching sequence only to the same  
source to which that the switch is connected.  
In the event of source or switch failure, the unit should be bypassed only to the current input source.  
Bypass Procedures for Source 1  
If transfer to Source 2 is not desired:  
1. Follow the instructions to transfer the load to Source 1, if it is not the currently used source.  
2. Remove the interlock key from CB5 and place it in CB4 interlock.  
3. Open the alternate source input breaker CB2.  
The CB2 LED is turned off.  
4. Rotate and remove the interlock key.  
5. Insert the key into the CB4 bypass breaker interlock.  
6. Rotate interlock keys in the CB4 bypass breaker interlock to retract the interlock.  
7. Close bypass breaker CB4.  
The LED for CB4 turns on.  
8. Open source input breaker CB1.  
9. Rotate the interlock key and remove it to lockout the breaker.  
The LED for CB1 turns off.  
10. Open the output breakers CB3 and CB3A (if supplied) to remove power from static switch.  
The LEDs for CB3 and CB3A (if supplied) turn off.  
11. Verify that the output (OUT) LED is lit.  
Power is now flowing directly from the source to the load, without passing through the static transfer  
switch.  
To return to the normal mode:  
1. Verify that the LEDs for Source 1 are on, indicating that the source is supplying power and is  
operating within acceptable tolerances.  
2. Remove the key from CB5 and insert it in the CB1 breaker interlock.  
3. Rotate key to retract interlock.  
4. Close source input breaker CB1.  
The LED for CB1 turns on.  
5. Close the output breakers CB3 and CB3A (if supplied).  
The LEDs for CB3 and CB3A are lit.  
6. Open bypass breaker CB4. Rotate keys in CB4 interlock to extend interlock.  
The LED for CB4 is turned off.  
7. Remove proper key from CB4 interlock and insert it in CB2 breaker interlock.  
8. Rotate the key to retract CB2 breaker interlock.  
9. Close source input breaker CB2.  
The LED for CB2 is turned on.  
10. Verify that the output LED is lit.  
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Operating the LED Display STS2  
Bypass Procedures for Source 2  
If transfer to Source 1 is not desired:  
1. Follow the instructions to transfer the load to Source 2, if it is not the currently used source.  
2. Remove the interlock key from CB4 and place it in CB5 interlock.  
3. Open the alternate source input breaker CB1.  
The LED for CB1 is turned off.  
4. Rotate and remove the interlock key.  
5. Insert the key into the CB5 bypass breaker interlock and rotate the interlock keys in CB5 bypass  
breaker interlock to retract the interlock.  
6. Close bypass breaker CB5.  
The LED for CB5 is turned on.  
7. Open source input breaker CB2.  
The LED for CB2 is turned off.  
8. Rotate the interlock key and remove it to lockout the breaker.  
9. Open output breakers CB3 and CB3A (if supplied) to remove power from static switch.  
The LEDs for CB3 and CB3A (if supplied) turn off.  
10. Verify that the output LED is lit.  
Power is now flowing directly from the source to the load, without passing through the static transfer  
switch.  
To return to normal mode:  
1. Verify that the LEDs for Source 2 are on, indicating that the source is supplying power and is  
operating within acceptable tolerances.  
2. Insert key in the CB2 breaker interlock.  
3. Rotate key to retract interlock.  
4. Close source input breaker CB2.  
The LED for CB2 is turned on.  
5. Close output breakers CB3 and CB3A (if supplied).  
The LEDs for CB3 and CB3A (if supplied) turn on.  
6. Open bypass breaker CB5.  
The LED for CB5 is turned off.  
7. Rotate keys in CB5 interlock to extend interlock.  
8. Remove the proper key from CB5 interlock and insert it in CB1 breaker interlock.  
9. Rotate key to retract CB1 breaker interlock.  
10. Close source input breaker CB1.  
The LED for CB1 is turned on.  
11. Verify that the output LED is lit.  
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Operating the LED Display STS2  
14.2.4 Normal System Shutdown  
The STS2 can be shut down from either the static switch mode or the bypass mode.  
Shutdown in Static Transfer Switch Mode  
When the Static Transfer Switch is operating on static transfer switch mode (not mainte-  
nance bypass mode):  
1. Turn off the load equipment per manufacturer’s recommendations.  
2. Open CB3 to turn off the static switch output.  
• Open CB3A if the static transfer switch is a redundant output configuration.  
The LEDs for CB3 and CB3A (if supplied) and the output (OUT) are turned off.  
3. Open the input switches CB1 and CB2.  
The LEDs for CB1 and CB2 are turned off.  
4. To completely de-energize the unit, turn OFF the power to both inputs to the STS2.  
Shutdown in Maintenance Bypass Mode  
When the Static Transfer Switch is operating on bypass:  
1. Turn off the load equipment per manufacturer’s recommendations.  
2. Open the bypass switch (CB4 or CB5) to turn off the static transfer switch output.  
The LED for the bypass switch is turned off.  
The output (OUT) LED is turned off.  
3. To completely de-energize the unit, turn OFF the power to both inputs to the STS2.  
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Specifications  
15.0 SPECIFICATIONS  
This section provides the specifications for the STS2.  
15.1 System Configuration  
The STS2 can be set in several different configurations, according to the model and location. The con-  
figuration is set at the factory and does not need to be changed by the customer. These configurations  
apply to both units, the Color Graphical Display and an LED Display.  
15.1.1 Frequency  
The STS2 accepts input frequencies of 50 Hz and 60 Hz. The frequency shall be within +/- 0.5 Hz of  
the nominal frequency.  
15.1.2 Input/Output Voltage  
The STS2 models are available to handle various voltages.  
The input voltage must be three phase AC (3 or 4 wire-plus-ground). The STS2 is designed to accept  
an input neutral from each source. The neutral is switched in the 4-pole static transfer switch only.  
The voltage shall be within +/- 10% of the nominal voltage.  
The output voltage shall be three phase AC (3 or 4 wire-plus-ground). Nominal output voltage shall be  
same as input voltage.  
The following table provides nominal voltages, listed according to frequency  
Table 17 Input/Output Voltage  
60Hz  
50 Hz  
[L-L/L-N]  
200/115V  
208/120V  
220/127V  
240/139V  
380/220V  
400/230V  
415/240V  
480/277V  
600/346V  
[L-L/L-N]  
200/115V  
208/120V  
220/127V  
240/139V  
380/220V  
400/230V  
415/240V  
15.1.3 System Current Ratings  
These ratings are based upon continuous switch current rating. These ratings are for all voltages and  
frequencies. All units are 100% continuous current rated.  
Table 18 System Current Ratings  
Current  
100  
250  
400  
600  
800  
1000  
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Specifications  
15.1.4 Grounding  
Refer to 5.3 - System Grounding for specifications and instructions regarding grounding.  
15.1.5 Electrical Requirements  
Table 19 Electrical Requirements  
Item  
Requirement  
Maximum Continuous Current  
Load Power Factor Range  
Load Crest Factor  
100, 250, 400, 600, 800, 1000 amps  
0.75 to 1.0, leading or lagging  
Up to 3.5  
Source Voltage Distortion  
Up to 10% THD with notches and ringing transients  
125% for 30 minutes 100A-400A  
125% for 10 minutes 600A-1000A  
150% for 2 minutes  
Overload Capability  
500% for 0.25 sec.  
Table 20 Unit Short Circuit Withstand Capability  
Unit Voltage  
Unit Amps  
100-250A  
400-600A  
800-1000A  
100-250A  
400-600A  
800-1000A  
100-250A  
400-600A  
800-1000A  
Withstand Capability  
100kA  
100kA  
100kA  
65kA  
208-240V  
380-480V  
600V  
100kA  
65kA  
25kA  
25kA  
42kA  
15.1.6 Input Surge Suppression  
The STS2 is equipped with transient voltage surge suppression on each input for maximum surge  
suppression. The surge suppression is capable of protecting the STS2 from operating outside of toler-  
ances due to surges as defined by IEC 1000-4-5 (1.2/50uS surge, 2kV CM and 1kV DM) as required  
under EN 50091-2.  
15.1.7 Response Time  
A dual level fast/slow transfer threshold is used for under voltage detection to allow the STS2 to be  
compatible with UPSs and generators. The voltage thresholds and the slow transfer delay time is  
user-adjustable. The fast transfer delay time is less than 4 ms.  
The over voltage detection uses a single threshold, with programmable level and delay time.  
See User Settings on page 89 for instructions on configuring these settings.  
15.1.8 Environmental Requirements  
See 3.0 - Location Considerations for details concerning environmental requirements for the  
STS2.  
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Specifications  
15.2 System Components  
All STS2 models provide two static transfer switches within one enclosure, with the ability to transfer  
between two input sources to a single output.  
All STS2s are configured with either an LCD Color Graphical Interface touch screen display or LEDs  
for monitoring and configuring the unit.  
This section lists the common components and the differences for both types of units.  
15.2.1 Frame and Enclosure  
The complete STS2 is housed in a freestanding enclosure. The cabinet is a NEMA type 1 enclosure  
and meets IP20 requirements. The cabinet is structurally designed to handle lifting from the base.  
The frame is designed to accommodate floor stands.  
Table 21 Frame Sizes  
Rating  
Width  
30 in (76 cm)  
Depth  
32 in (81 cm)  
Height  
76.77 in (195 cm)  
76.77 in (195 cm)  
76.77 in (195 cm)  
100 – 250A 3 pole  
400 – 600A 3 pole  
800 – 1000A 3 pole  
38 in (96 cm)  
84 in (213 cm)  
32 in (81 cm)  
32 in (81 cm)  
The distributed floor weight for STS2 is less than 150 lbs./sq. ft. (660kg/m²).  
The required service access is only from the front of the unit.  
The STS2 can be tipped 15° in any direction without falling over.  
15.2.2 Castors, Leveling and Seismic Anchoring  
The frame includes heavy-duty swivel castors for ease of installation, plus permanent leveling feet for  
final installation.  
The unit also can be fastened to the floor using optional seismic anchors to meet seismic Zone 4  
requirements. See 4.0 - Locating the STS2 and Figures 11 through 13 for instructions and details  
for installing seismic anchoring.  
15.2.3 Cooling  
The STS2 100 – 600A units utilize convection air cooling for the enclosure with forced air cooling of  
the heat sinks. The 800-1000A units are fan cooled using low-velocity fans to minimize audible noise.  
All fans are redundant so that a single fan failure cannot cause temperatures to increase beyond  
acceptable limits.  
Air intake is through screened protective openings in the front of the unit. A standard furnace filter is  
installed behind the openings.  
By opening the front door, the filter can be changed easily without exposing personnel to high voltage.  
The size of the filter is 1 in. x 25 in. x 25 in. (2.54 cm x 63.5 cm x 63.5 cm).  
The air exhaust is through the top of the unit.  
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Specifications  
15.2.4 Access  
The STS2 is designed so all repairs and maintenance can be done from the front or top of the unit. All  
components that may need repair or replacement during routine field maintenance are safely  
accessed with the units in bypass without removing power from the unit. These components include:  
• All electronic PCB assemblies  
• Power supply assemblies  
• All fuses  
• All circuit breaker plug-in modules  
• Fans  
• SCRs  
All power connections are designed to maintain proper connection torque over the lifetime of the unit  
without any maintenance. The integrity of the connections can be checked via infrared scanning  
safely from the front or top of the unit.  
All other components including power cables and connections, circuit breaker bases, etc. are replace-  
able from the front or top of the unit only, but this requires all power to be removed from the unit for  
safety. Although routine re-torquing of the power connections is not required, if maintenance of these  
connections is needed, complete removal of power is required from the unit for safety reasons.  
WARNING  
!
Lethal voltages exist inside the unit during normal operation. Only qualified service  
personnel should perform maintenance on the static switch.  
The unit is supplied by more than one power source. The unit contains hazardous voltages if  
any of the input sources is ON, even when the unit is in bypass. To isolate the unit, turn OFF  
and lock out ALL input power sources.  
Verify that all input power sources are de-energized and locked out before making connections  
inside unit.  
15.2.5 Circuit Breakers  
The STS2 is equipped with five molded-case, plug-in, non-automatic circuit breakers. The breakers  
are UL listed for use up to 600 VAC and CE marked. The plug-in feature of the breaker includes an  
interlock, which prevents the breaker from being unplugged without being in the OFF (open) position.  
Mechanical interlocks are provided on the breakers to prevent improper maintenance bypassing of  
the solid-state switch. A bypass breaker cannot be closed unless the solid-state switch is connected to  
the same input source and only one bypass breaker can be closed at a time. All breakers are equipped  
with N.O. and N.C. auxiliary switches for monitoring of the breaker positions. The two input breakers  
for the solid-state switching devices also are equipped with 48 VDC shunt trips to allow for control by  
the STS2 logic. See the Circuit Breaker Schedule in Figure 20.  
15.2.6 Cable Entrance  
Removable conduit termination plates are provided in the top and bottom of the STS2 for termination  
of the two source input conduits or raceways and/or the output conduits or raceways.  
15.2.7 Doors  
A removable key lock hinged front door provides access to the circuit breakers.  
15.2.8 Color Graphical Display or LED Display  
The display is located in the front of the unit. Front panel display is either an LCD touch screen dis-  
play for monitoring and configuring the unit, or an LED panel to monitor the unit's status.  
See Figure 31 for a drawing of the touch screen display. See Figure 63 for the layout of the LED dis-  
play.  
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Specifications  
15.2.9 RS-232 Port  
The unit is equipped with an RS-232 port for connecting a terminal or PC.  
See Figure 29 for the port’s location.  
See 12.1 - Using the RS-232 Port for instructions on using a PC terminal with the unit.  
15.2.10Terminal Port Connections  
The system has an asynchronous serial port configured as Data Terminal Equipment for terminal  
access only (half duplex). The CPU services the terminal port with no handshaking. The serial port  
conforms to RS-232 levels with a data format of 9600 Baud, 1 start bit, 8 data bits, and no parity bits.  
The serial port is 1000 Volt DC isolated (non-SELV) and ESD protected to 15kV air discharge. The  
connector is a 6 Pin MTA plug with connections shown below.  
Table 22 MTA Plug Pinout  
Pin  
1
Signal Name  
ISO_GND  
Function / Comments  
Isolated service terminal ground  
2
ISO_TXD  
ISO_RXD  
NC  
Isolated service terminal transmit output  
Isolated service terminal receive input  
No Connection  
3
4
5
NC  
No Connection  
6
NC  
No Connection  
A DB9 male connector is added and connected parallel to the 6 position header. It is configured as  
DTE.  
Table 23 DB9 Pinout  
Pin  
1
Signal Name  
Function / Comments  
NC  
No Connection  
2
ISO_RXD  
ISO_TXD  
NC  
Isolated service terminal transmit output  
Isolated service terminal receive input  
No Connection  
3
4
5
ISO_GND  
NC  
Isolated service terminal ground  
No Connection  
6
7
NC  
No Connection  
8
NC  
No Connection  
9
NC  
No Connection  
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Specifications  
15.2.11RS-232 Interface Parameters  
The service terminal interface parameters are the following settings and cannot be changed.  
Table 24 RS-232 Settings  
Parameter  
Setting  
Interface  
Baud Rate  
Parity  
RS-232 Using EIA Voltage Levels  
9600  
None  
Number of Data Bits  
Number of Stop Bits  
Hardware Flow Control  
Terminator  
8
1
Off  
<CR> <LF>  
Not supported  
Full duplex  
Off  
Handshaking  
Structure  
Local Echo  
15.2.12Maintenance Bypass  
The STS2 is configured to allow the unit’s electronics to be bypassed to either input source for mainte-  
nance without interruption of power to the load.  
The STS2 is furnished with key-interlocked maintenance bypass breakers to configure the bypass.  
STS2 units have all electronics isolated from the input, output, and bypass connections to allow safe  
servicing of any components without access to hazardous voltages when the unit is in maintenance  
bypass.  
See 10.4 - Maintenance Bypass on page 67 for instructions using the Color LCD Graphical Display  
15.2.13Fuseless Design  
All STS2 units are fuseless and are UL rated for use with upstream circuit breakers only.  
15.2.14Options  
The following options are available for the STS2:  
Optimized Transfer  
LED Display  
Redundant Output Breaker  
Network Interface Card (NIC)  
Seismic Floor Stand - 18", 24", 30" and 36"  
Export Crating  
Distribution Cabinet With I-Line Panelboard  
Input Junction Boxes and Cable  
Comms Board w/SiteScan and Modem Interface Internal Modem  
Input Contact Isolator Board  
Programmable Relay Board  
Remote Source Selection  
Key Lockout Switch  
See 6.0 - Options for more information.  
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Event Message Help Text  
16.0 EVENT MESSAGE HELP TEXT  
Key:  
ALL CAPS = event message displayed in the Event Display panel in the lower left corner of the LCD display.  
Indented text = help text shown in the Display Panel in the lower right corner of LCD display.  
BOLD = commands that are sent through the RS-232 port.  
S1 SCR SHORT  
Source 1 SCR Short.  
One or more of the SCRs for Source 1 has shorted. Transferring between sources has been inhibited.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event and the system status surrounding it have been written to a History Log if the History Logs were not already full.  
This event was also written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
S2 SCR SHORT  
Source 2 SCR Short.  
One or more of the SCRs for Source 2 has shorted. Transferring between sources has been inhibited.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event and the system status surrounding it have been written to a History Log if the History Logs were not already full.  
This event was also written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
S1 SCR OPEN  
Source 1 SCR Open.  
One or more SCRs on Source 1 is open. Transferring between sources has been inhibited.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
STS2 output has been transferred to Source 2.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event and the system status surrounding it have been written to a History Log if the History Logs were not already full.  
This event was also written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
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Event Message Help Text  
S2 SCR OPEN  
Source 2 SCR Open.  
One or more SCRs on Source 2 is open. Transferring between sources has been inhibited.  
STS2 output has been transferred to Source 1.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event and the system status surrounding it have been written to a History Log if the History Logs were not already full.  
This event was also written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
PRIMARY FAN FAIL  
Primary Fan Failure  
One of the primary cooling fans for the STS2 has failed. The alternate fans are now running. The alternate fans are not  
monitored.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
CONTROL MODULE FAIL  
Control logic module has failed.  
One of the control modules on the control board has failed.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
PWR SPLY DC A FAIL  
Power Supply DC Bus A Failed  
The primary power supply is no longer providing DC power to the control board and the touch screen.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
PWR SPLY DC B FAIL  
Power Supply DC Bus B Failed  
The secondary power supply is no longer providing DC power to the control board and CAN options.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
PWR SPLY S1 AC FAIL  
Power Supply Source 1 AC Failed  
The AC input power to the power supplies from Source 1 has failed. The power supplies are now operating on AC power  
from Source 2. The AC input from Source 1 is still good.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
PWR SPLY S2 AC FAIL  
Power Supply Source 2 AC Failed  
The AC input power to the power supplies from Source 2 has failed. The power supplies are now operating on AC power  
from Source 1. The AC input from Source 2 is still good.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
PWR SPLY LOGIC FAIL  
Power Supply Module Failed  
The power supply logic module contained in the primary power supply has failed.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, is so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
OUT VOLT SENSE FAIL  
Output Voltage Sense Module Failed  
The module contained on the snubber monitoring the output voltage has failed.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
S1 VOLT SENSE FAIL  
Source 1 Voltage Sense Module Failed  
The module contained on the snubber monitoring the input voltage from Source 1 has failed.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S2 VOLT SENSE FAIL  
Source 2 Voltage Sense Module Failed  
The module contained on the snubber monitoring the input voltage from Source 2 has failed.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the STS2 system from a terminal,  
type CA and press RETURN on your keyboard.  
S1 SCR SENSE FAIL  
Source 1 SCR Sense Module Failed  
The module contained on the snubber monitoring the SCRs for Source 1 has failed.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the STS2 system from a terminal,  
type CA and press RETURN on your keyboard.  
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Event Message Help Text  
S2 SCR SENSE FAIL  
Source 2 SCR Sense Module Failed  
The module contained on the snubber monitoring the SCRs for Source 2 has failed.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the STS2 system from a terminal,  
type CA and press RETURN on your keyboard.  
S1 CURR SENSE FAIL  
Source 1 Current Sense Failure  
The module monitoring the current from Source 1 has failed. This module is contained on the left side gate driver board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Events Log, is so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the STS2 system from a terminal,  
type CA and press RETURN on your keyboard.  
S2 CURR SENSE FAIL  
Source 2 Current Sense Failure  
The module monitoring the current from Source 2 has failed. This module is contained on the right side gate driver board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Events Log, is so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the STS2 system from a terminal,  
type CA and press RETURN on your keyboard.  
S1 GATE DRIVE FAIL  
Source 1 Gate Drive Failure  
The gate drive module for an SCR for Source 1 has failed. This module is contained on the right side gate driver board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the STS2 system from a terminal,  
type CA and press RETURN on your keyboard.  
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Event Message Help Text  
S2 GATE DRIVE FAIL  
Source 1 Gate Drive Failure  
The gate drive module for an SCR for Source 2 has failed. This module is contained on the left side gate driver board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
INTERNAL COMM FAIL  
Internal CAN Communications Failed  
Communications have failed in the CAN bus between the control board and the touch screen control.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
EXTERNAL COMM FAIL  
External Communications Failed  
Communications have failed between the control board and the CAN options.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the unit from a  
terminal, type SH and press RETURNRETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
CB1 SHUNT TRIP FAIL  
Circuit Breaker 1 Shunt Trip Failure  
Circuit Breaker 1 failed to trip open when the control issued a command for the circuit breaker to trip.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
CB2 SHUNT TRIP FAIL  
Circuit Breaker 2 Shunt Trip Failure  
Circuit Breaker 2 failed to trip open when the control issued a command for the circuit breaker to trip.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
Contact Liebert for technical support at 1-800-LIEBERT (800-543-2378).  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
HEAT SINK OVERTEMP  
Heat Sink Over Temperature  
The system heat sink temperature has exceeded the design limits.  
Take immediate steps to cool the unit. Remove obstructions from the air inlet in the front of the unit. Remove and replace  
the air filter behind the front door. A standard furnace filter can be used.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
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Event Message Help Text  
S1 UV  
Source 1 Under Voltage (fast detection).  
The input voltage from Source 1 dropped below a set percentage of the nominal voltage, as set in the Fast UV set point  
under the User Settings. An S1 Fail alarm was also issued and source transfer has been inhibited.  
The load of the STS2 has been transferred to Source 2.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S1 UV (RMS)  
Source 1 Under Voltage (slow detection).  
The input voltage from Source 1 remained below a set percentage of the nominal voltage for a designated period, as set in  
the Slow UV Setting and Slow UV Detection Delay set points configured under the User Settings. An S1 Fail alarm was  
also issued and source transfer has been inhibited.  
The load of the STS2 has been transferred to Source 2.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The alarm is latched and must be reset after the voltage returns to the nominal voltage. If the Reset option is not configured  
for AUTO (automatic reset), then the reset action must be done manually. When the voltage is within acceptable  
parameters, touch the RESET button on the touch screen. If you are accessing the unit from a terminal, type CA and press  
RETURN on your keyboard.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
S1 OV  
Source 1 Over Voltage.  
The input voltage from Source 1 exceeded a set percentage of the nominal voltage, as set in the OV Setting and OV  
Detection Delay set points configured under the User Settings. An S1 Fail alarm was also issued and source transfer has  
been inhibited.  
The load of the STS2 has been transferred to Source 2.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
S1 OF/UF  
Source 1 Over Frequency/Under Frequency  
The frequency for Source 1 is running outside the acceptable operating range, as set in the Frequency Trip Point under  
User Settings. An S1 Fail alarm was also issued and source transfer has been inhibited.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S1 FAIL  
Source 1 Failure  
Source 1 has failed due to under voltage (UV), over voltage (OV), or running over or under frequency (OF/UF). This alarm  
is a companion to S1 UV, S1 UV (RMS), S1 OV and S1 OF/UF.  
The load of the STS2 has been transferred to Source 2.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event has been written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S2 UV  
Source 2 Under Voltage (fast detection).  
The input voltage from Source 2 dropped below a set percentage of the nominal voltage, as set in the Fast UV set point  
under the User Settings. An S2 Fail alarm was also issued and source transfer has been inhibited.  
The load of the STS2 has been transferred to Source 1.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
S2 UV (RMS)  
Source 2 Under Voltage (slow detection).  
The input voltage from Source 2 remained below a set percentage of the nominal voltage for a designated period, as set in  
the Slow UV Setting and Slow UV Detection Delay set points configured under the User Settings. An S2 Fail alarm was  
also issued and source transfer has been inhibited.  
The load of the STS2 has been transferred to Source 1.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The alarm is latched and must be reset after the voltage returns to the nominal voltage. If the Reset option is not configured  
for AUTO (automatic reset), then the reset action must be done manually. When the voltage is within acceptable  
parameters, touch the RESET button on the touch screen. If you are accessing the unit from a terminal, type CA and press  
RETURN on your keyboard.  
This event was written to the Event Log, if so configured.  
S2 OV  
Source 2 Over Voltage.  
The input voltage from Source 2 exceeded a set percentage of the nominal voltage, as set in the OV Setting and OV  
Detection Delay set points configured under the User Settings. An S2 Fail alarm was also issued and source transfer has  
been inhibited.  
The load of the STS2 has been transferred to Source 1.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S2 UF/OF  
Source 2 Under Frequency/Over Frequency  
The frequency for Source 2 is running outside the acceptable operating range, as set in the Frequency Trip Point under  
User Settings. An S2 Fail alarm was also issued and source transfer has been inhibited.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
S2 FAIL  
Source 2 Failure  
Source 2 has failed due to under voltage (UV), over voltage (OV), or running with an over or under frequency (OF/UF).  
This alarm is a companion to S2 UV, S2 UV (RMS), S2 OV and S2 OF/UF.  
The load of the STS2 has been transferred to Source 1.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S1 OVERCURRENT  
Source 1 Overcurrent  
STS2 is running on Source 1 and an overload condition has occurred on one or more phases.  
Note: The overload setpoint is a single fixed number--101%. An overload condition is detected when the measured load  
current is equal to or greater than the setpoint.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S2 OVERCURRENT  
Source 1 Overcurrent  
STS2 is running on Source 2 and an overload condition has occurred on one or more phases.  
Note: The overload setpoint is a single fixed number--101%. An overload condition is detected when the measured load  
current is equal to or greater than the setpoint.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
S1 I-PEAK  
Current Peak on Source 1  
The peak current from Source 1 has exceeded the set point as defined in the I-PK Xfer Lockout setting under User  
Settings.  
Transferring to Source 2 has been inhibited.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event and the system status surrounding it have been written to a History Log if the History Logs were not already full.  
This event was also written to the Event Log, if so configured.  
If this alarm is configured to automatically reset under the set points for User Settings, the alarm clears itself when the I-  
Peak condition clears.  
If this alarm is set for manual reset mode, the alarm continues to show as active after the current returns to nominal, still  
inhibiting transfers. You will need to manually reset the alarm. If configured to be a latching alarm, press RESET on the  
display. If you are accessing the unit from a terminal, type CA and press RETURN on your keyboard.  
The alarm has triggered a message to be sent to the modem, if so configured.  
S2 I-PEAK  
Current Peak on Source 2  
The peak current from Source 2 has exceeded the set point as defined in the I-PK Xfer Lockout setting under User  
Settings.  
Transferring to Source 1 has been inhibited.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event and the system status surrounding it have been written to a History Log if the History Logs were not already full.  
This event was also written to the Event Log, if so configured.  
If this alarm is configured to automatically reset under the set points for User Settings, the alarm clears itself when the I-  
Peak condition clears.  
If this alarm is set for manual reset mode, the alarm continues to show as active after the current returns to nominal, still  
inhibiting transfers. You will need to manually reset the alarm. If configured to be a latching alarm, press RESET on the  
display. If you are accessing the unit from a terminal, type CA and press RETURN on your keyboard.  
The alarm has triggered a message to be sent to the modem, if so configured.  
SOURCES OUT OF SYNC  
Sources out of synchronization.  
The phase difference between Source 1 and Source 2 has exceeded the deviation as set for MANUAL MAX XFER PHASE  
ANGLE under User Settings.  
A manual transfer cannot take place while the sources are not synchronized.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
LOAD ON ALT SOURCE  
STS2 load on the alternate source.  
The static transfer switch is running on the alternate power source. Check the Event Log to determine the reason for the  
transfer from the preferred source.  
Another event has caused the system to transfer to the alternate source. The system returns the load to the preferred  
source either automatically or manually, depending on how the system is configured.  
In automatic reset mode, the STS2 automatically retransfers to the preferred source after the causal condition clears.  
In manual reset mode, the system remains on the alternate source after the causal event clears until you select RESET  
from the touchscreen, or enter CA (Clear Alarms) from a service terminal.  
Pressing the RESET button to returns the unit to the preferred source. Ensure that the condition that triggered the  
switch has been rectified before returning to the preferred source.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
AUTO REXFER INHIBIT  
Automatic Retransfer Inhibited.  
The system made five transfers from the preferred source to the alternate source in the last five minutes. As a result,  
automatic retransfers back to the preferred source is now disabled.  
To clear this alarm condition, assign the alternate source as the preferred source.  
This alarm also is cleared if the unit transfers to the preferred source due to an alternate source AC volt failure (i.e., an  
emergency transfer.)  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
CB1 (S1) OPEN  
Circuit Breaker 1 (for Source 1) Open  
Circuit Breaker 1 is not closed. CB1 is only assigned to Source 1.  
Check that the Circuit Breaker 1 switch is in the desired position.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
CB2 (S2) OPEN  
Circuit Breaker 2 (for Source 2) Open  
Circuit Breaker 2 is not closed. CB1 is only assigned to Source 2.  
Check that the Circuit Breaker 2 switch is in the desired position.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
CB4 (S1 BYP) CLOSED  
Circuit Breaker 4 (Source 1 Bypass Breaker) Closed  
Circuit breaker 4 is not open. The input from Source 1 is bypassing the static transfer switch.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
CB5 (S1 BYP) CLOSED  
Circuit Breaker 5 (Source 2 Bypass Breaker) Closed  
Circuit breaker 5 is not open. The input from Source 2 is bypassing the static transfer switch.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
CB3 (OUTPUT) OPEN  
Circuit Breaker 3 (Output breaker) Open  
Circuit breaker 3 is not closed. This circuit breaker is assigned to the output load. The power flow to the load cannot flow  
through the static transfer switch.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
CB3A (OUTPUT) OPEN  
Circuit Breaker 3A (Output breaker) is Open (Optional)  
Circuit breaker 3A is not closed. This circuit breaker is assigned to the output load. The power flow to the load cannot flow  
through the static transfer switch.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S1 PHASE ROT ERROR  
Source 1 Phase Rotation Error  
A phase rotation error condition exists on Source 1. Check the phase sequence (ABC) of Source 1.  
Transferring to Source 1 has been inhibited.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
S2 PHASE ROT ERROR  
Source 2 Phase Rotation Error  
A phase rotation error condition exists on Source 2. Check the phase sequence (ABC) of Source 2.  
Transferring to Source 1 has been inhibited.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
TRANSFER INHIBITED  
Transfer Inhibited  
Uninterrupted transfer between sources is inhibited due to input source failure, sources out of sync, switch failure, or the  
unit is in bypass mode.  
Check the Event Log for the event or events that may have caused the alarm.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
OUTPUT UV  
Output Undervoltage  
The voltage being supplied to the load has dropped below the acceptable nominal voltage. Check the input voltage from  
both sources.  
This event and the system status surrounding it have been written to a History Log if the History Logs were not already full.  
This event was also written to the Event Log, if so configured.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
INPUT CONTACT #1  
Input Contact Isolator #1  
Occurrence of the indicated external event has been detected by Input Contact Isolator #1 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
INPUT CONTACT #2  
Input Contact Isolator #2  
Occurrence of the indicated external event has been detected by Input Contact Isolator #2 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
INPUT CONTACT #3  
Input Contact Isolator #3  
Occurrence of the indicated external event has been detected by Input Contact Isolator #3 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
INPUT CONTACT #4  
Input Contact Isolator #4  
Occurrence of the indicated external event has been detected by Input Contact Isolator #4 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
INPUT CONTACT #5  
Input Contact Isolator #5  
Occurrence of the indicated external event has been detected by Input Contact Isolator #5 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
INPUT CONTACT #6  
Input Contact Isolator #6  
Occurrence of the indicated external event has been detected by Input Contact Isolator #6 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
INPUT CONTACT #7  
Input Contact Isolator #7  
Occurrence of the indicated external event has been detected by Input Contact Isolator #7 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
INPUT CONTACT #8  
Input Contact Isolator #8  
Occurrence of the indicated external event has been detected by Input Contact Isolator #8 of the Open Comms Digital Input  
option board.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event, with its assigned name, was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
CONFIG MODIFIED  
Configuration Modified  
A set point has been updated and saved.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
PASSWORD CHANGED  
Access Password Changed  
The password for accessing the HMI (touch screen) options has been updated and saved.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The alarm has triggered a message to be sent to the modem, if so configured.  
The event was written to the Event Log, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
TIME REPROGRAMMED  
System Time Reprogrammed  
The system’s time setting has been updated and saved.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
DATE REPROGRAMMED  
System Date Reprogrammed  
The system’s date setting has been updated and saved.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Event Message Help Text  
EVENT LOG CLEARED  
Event Log Cleared  
All past alarms and faults are no longer recorded in the system’s event log.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
This event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
HIST LOGS CLEARED  
History Logs Cleared  
Both History Logs have been erased and the logs are now available to record future events.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
HIST LOGS FULL  
History Logs Full  
The history buffer has reached its capacity for both history logs. No further history logs can be written until the logs are  
cleared. The History Logs were frozen by the occurrence of two designated faults or alarms.  
Both history logs have been frozen by significant events. These logs contain valuable diagnostic data regarding those  
events which may be useful if service is required. Once the logs have been analyzed and the causes for freezing them  
have been resolved, the history logs should be cleared to make them available for capturing future events.  
To clear the History Logs, select the CLEAR HLOG button under the LOGS > HISTORY LOG 1 or LOGS > HISTORY LOG  
2 menus to clear the History Status buffer after the alarms have been resolved.  
If you are accessing the unit from a terminal, type CHL and press RETURN to clear the History Logs.  
Press SILENCE on the touch screen to turn off the audible alarm, if so configured. If you are accessing the STS2 system  
from a terminal, type SH and press RETURN on your keyboard to turn off the audible alarm.  
The event was written to the Event Log, if so configured.  
The alarm has triggered a message to be sent to the modem, if so configured.  
If configured to be a latching alarm, press RESET on the display. If you are accessing the unit from a terminal, type CA and  
press RETURN on your keyboard.  
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Maintenance  
17.0 MAINTENANCE  
WARNING  
!
Only qualified service personnel should perform maintenance on the static switch.  
Lethal voltages exist inside the unit during normal operation.  
The unit is supplied by multiple ac power sources. disconnect and lock-out all power sources  
before working inside unit.  
Minimal periodic maintenance of the STS2 is required. As with all electrical distribution components,  
the system should be regularly inspected for electrical connection integrity, signs of excessive temper-  
atures, dirt accumulation, and proper system operation.  
17.1 Proper Tightening of Nuts and Bolts  
The recommended tightening torque for all nuts and bolts is as shown below, unless otherwise  
labeled. All power connections are designed to remain at proper torque throughout the lifetime of the  
unit.  
Table 25 Torque tightening  
Grade 5 -Imperial  
Grade 8.8 -metric  
Electrical Connections with  
Belleville Washers  
in-lb  
(pound-inch)  
N-m  
(Newton-meter)  
in-lb  
(pound.inch)  
N-m  
(Newton.meter)  
Bolt Shaft Size  
10-32  
25  
53  
3
35  
80  
4
1/4-20  
6
9.0  
5/16-18  
3/8-16  
107  
192  
428  
12  
22  
48  
180  
240  
480  
20.4  
27.1  
54.3  
1/2-13  
17.2 Testing the STS2  
The STS2 includes comprehensive system alarms and fault detection to identify operational prob-  
lems. To increase the degree of confidence of proper system operation, periodic transfer tests can be  
easily performed. For instructions for changing the preferred source and switching sources:  
• For a Color Graphical Display unit, see 10.2 - Manual Transfer / Preferred Source  
17.3 Changing the Air Filter  
A standard furnace filter is installed behind the air intake in the front door. The air intake allows air  
to circulate to cool the unit. Replace the filter when it becomes dirty and impedes air flow. The fre-  
quency of changing or cleaning the filter depends on the location in which the unit is located.  
The size of the filter is 1 in. x 25 in. x 25 in. (2.54 cm x 63.5 cm x 63.5 cm).  
137  
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Maintenance  
SUPPORT INFORMATION  
To contact Liebert Global Services for information or repair service in the United States, call  
1-800-LIEBERT (1-800-543-2378). Liebert Global Services is available to assure fast repair of your  
unit with minimal downtime. Liebert Global Services offers a complete range of start-up services,  
repair services, preventive maintenance plans, and service contracts.  
For repair or maintenance service outside the 48 contiguous states, contact Liebert Global Services, if  
available in your area. For areas not covered by Liebert Global Services, the authorized distributor is  
responsible for providing qualified factory-authorized service. Additional telephone numbers and  
e-mail contact information is on the back page of this manual.  
Please have the following information available.  
Part Number:  
Serial Number:  
Date Purchased:  
Date Installed:  
Location:  
Current Rating:  
Frequency:  
Voltage:  
138  
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Maintenance  
PROGRAMMABLE RELAY BOARD SETTINGS RECORD  
The optional Programmable Relay Board (PRB) has eight channels to report events to an external  
device. Up to ten (10) events can be programmed to each channel. See 6.1 - Programmable Relay  
Board for more information on the PRB.  
If your STS2 has the PRB option installed, list the settings below for future reference. If control power  
is lost in the STS2, the settings are not saved.  
Channel 1:  
Channel 2:  
Channel 3:  
Channel 4:  
Channel 5:  
Channel 6:  
Channel 7:  
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Maintenance  
Channel 8:  
Channel 9:  
Channel 10:  
PRB Notes:  
140  
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Maintenance  
INPUT CONTACT ISOLATOR SETTINGS RECORD  
The Input Contact Isolator board (ICI) provides an STS2 module interface for up to eight external  
user alarm or message inputs to be routed through the static transfer switch’s alarm network. See  
6.4 - Input Contact Isolator Board for more information on the ICI.  
If your STS2 has the ICI option installed, list the settings below for future reference. If control power  
is lost in the STS2, the settings are not saved.  
Channel 1:  
Channel 2:  
Channel 3:  
Channel 4:  
Channel 5:  
Channel 6:  
Channel 7:  
Channel 8:  
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Maintenance  
142  
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POWER PROTECTION  
USER MANUAL  
STATIC TRANSFER SWITCH 2  
The Company Behind the Products  
Technical Support/Service  
Web Site  
With over a million installations around the globe,  
Liebert is the world leader in computer protection  
systems. Since its founding in 1965, Liebert has  
developed a complete range of support and  
protection systems for sensitive electronics:  
www.liebert.com  
Monitoring  
800-222-5877  
Outside the US: 614-841-6755  
Single-Phase UPS  
800-222-5877  
Environmental systems—close-control air  
conditioning from 1 to 60 tons  
Power conditioning and UPS with power  
ranges from 300 VA to more than 1000 kVA  
Outside the US: 614-841-6755  
Three-Phase UPS  
800-543-2378  
Integrated systems that provide both  
environmental and power protection in a  
single, flexible package  
Environmental Systems  
800-543-2778  
Monitoring and control—from systems of any  
size or location, on-site or remote  
Outside the United States  
614-888-0246  
Service and support through more than 100  
service centers around the world and a 24/7  
Customer Response Center  
Locations  
United States  
1050 Dearborn Drive  
P.O. Box 29186  
While every precaution has been taken to ensure the  
accuracy and completeness of this literature, Liebert  
Corporation assumes no responsibility and disclaims all  
liability for damages resulting from use of this information  
or for any errors or omissions.  
Columbus, OH 43229  
Italy  
Via Leonardo Da Vinci 8  
Zona Industriale Tognana  
35028 Piove Di Sacco (PD)  
+39 049 9719 111  
© 2005 Liebert Corporation  
All rights reserved throughout the world. Specifications  
subject to change without notice.  
Fax: +39 049 5841 257  
Asia  
7/F, Dah Sing Financial Centre  
108 Gloucester Road, Wanchai  
Hong Kong  
® Liebert and the Liebert logo are registered trademarks  
of Liebert Corporation. All names referred to are  
trademarks or registered trademarks of their respective  
owners.  
852 25722201  
SL-20620 (6/05) Rev. 5  
Fax: 852 28029250  
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