Roberts Gorden Furnace UHD[X][S][R] 125 User Guide

®
Combat  
UHD-Series  
Tubular Duct Furnace  
(Low Profile Range)  
Installation, Operation  
& Service Manual  
Models UHD[X][S][R]  
75, 100, 125  
Installer  
WARNING  
Please take the time to read and understand  
these instructions prior to any installation.  
Installer must give a copy of this manual to the owner.  
Improper installation, adjustment, alteration, service  
or maintenance can result in death, injury or property  
damage. Read the Installation, Operation and Service  
Manual thoroughly before installing or servicing  
this equipment.  
Owner  
Keep this manual in a safe place in order to provide  
your serviceman with necessary information.  
Installation must be done by a contractor qualified  
in the installation and service of gas-fired heating  
equipment or your gas supplier.  
Roberts-Gordon LLC  
1250 William Street  
P.O. Box 44  
Buffalo, New York 14240-0044  
Telephone: 716.852.4400  
Fax: 716.852.0854  
Toll Free: 800.828.7450  
Quality in Any Language™  
P/N 113000NA 11/08 Orig.  
© 2008 Roberts-Gordon LLC  
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TABLE OF CONTENTS  
SECTION 1: Heater Safety......................................................1 SECTION 10: Operation and Maintenance ..........................23  
1.1 Manpower Requirements .............................................1  
SECTION 2: Installer Responsibility .....................................2  
2.1 Wall Tag.......................................................................2  
10.1 Pre-Start-Up Checks ................................................23  
10.2 Begin Start-Up .........................................................23  
10.3 Complete Start-Up ...................................................25  
2.2 Corrosive Chemicals....................................................2 SECTION 11: User Instructions............................................26  
2.3 National Standards and Applicable Codes ..................2  
SECTION 3: Critical Considerations .....................................3  
3.1 Basic Information.........................................................3  
3.2 Manufactured Units......................................................3  
3.3 Location and Suspension ............................................3  
11.1 User Instructions.......................................................26  
11.2 Heater Operation ......................................................26  
11.3 Common User Controls.............................................26  
11.4 Lighting Instructions..................................................26  
11.5 Simple Troubleshooting.............................................27  
3.4 Minimum Required Installation Clearances .................3 SECTION 12: Servicing.........................................................28  
3.5 Clearances to Combustibles........................................3  
3.6 Ventilation ....................................................................4  
3.7 Gas Supply..................................................................4  
3.8 Electrical Supply..........................................................4  
3.9 Vent..............................................................................4  
SECTION 4: National Standards and Applicable Codes .....5  
4.1 Gas Codes...................................................................5  
12.1 Servicing Instructions...............................................28  
12.2 Burner Maintenance.................................................28  
12.3 Heat Exchanger Maintenance..................................28  
12.4 Gas Valve Maintenance ...........................................28  
12.5 Flue Blower ..............................................................28  
12.6 Venting and Air Intake Pipe......................................28  
12.7 Maintenance Checklist.............................................29  
4.2 Aircraft Hangars ...........................................................5 SECTION 13: Troubleshooting .............................................31  
4.3 Parking Structures and Repair Garages......................5  
4.4 Electrical......................................................................5  
4.5 Venting.........................................................................5  
4.6 High Altitude ................................................................6  
SECTION 5: Duct Heater Installation.....................................7  
5.1 General........................................................................7  
13.1 General ....................................................................31  
13.2 Troubleshooting For Automatic Ignition Burner  
Systems ...................................................................32  
13.3 Troubleshooting for Flame Supervision System .......33  
13.4 Troubleshooting for Gas Valves................................34  
13.5 Troubleshooting for Flue Blower...............................34  
5.2 Shelf Mounting and Suspension..................................8 SECTION 14: Replacement Parts.........................................35  
5.3 Wall Mounting..............................................................8  
SECTION 6: Venting.............................................................. 10  
6.1 Changing Vent and Air Intake Orientation.................. 10  
6.2 Venting....................................................................... 10  
6.3 Vent Installation ......................................................... 10  
6.4 Unvented Operation................................................... 11  
6.5 Horizontal Venting...................................................... 11  
6.6 Vertical Venting.......................................................... 11  
14.1 Gas Valve.................................................................35  
14.2 Burner Compartment ...............................................36  
14.3 Ignition Electrode and Flame Probe.........................37  
14.4 Heat Exchanger .......................................................37  
14.5 Flue Blower Vertical Installation ...............................38  
14.6 Pressure Switch........................................................39  
14.7 Ignition Control.........................................................39  
14.8 Limit Switches ..........................................................39  
6.7 Length Requirements ................................................ 11 SECTION 15: Specifications.................................................40  
6.8 Vent Material.............................................................. 12  
6.9 Replacing an Existing Heater in a Venting System.... 12  
SECTION 7: Air Supply......................................................... 17  
15.1 Dimension Data........................................................40  
15.2 General Technical Data Table ..................................41  
15.3 Technical Data Table ................................................41  
7.1 Separated Combustion Installation............................. 17 SECTION 16: ROBERTS GORDON® COMBAT® UHD-Series  
7.2 Unvented Installation.................................................. 17  
7.3 Building Ventilation..................................................... 17  
7.4 Outside Combustion Air Supply.................................. 17  
SECTION 8: Gas Piping........................................................ 18  
8.1 Connections............................................................... 18  
SECTION 9: Wiring................................................................ 19  
9.1 Positioning Thermostats ............................................ 19  
9.2 Low Voltage Thermostat with One Heater ................. 19  
9.3 Internal Wiring Diagram.............................................20  
9.4 Ladder Wiring Diagram..............................................21  
9.5 Electrical Connection to the Heater ...........................22  
Warranty..........................................................43  
Roberts-Gordon LLC  
© 2008  
All rights reserved. No part of this work covered by the copyrights herein may be reproduced  
or copied in any form or by any means - graphic, electronic, or mechanical, including  
photocopying, recording, taping or information storage and retrieval systems - without the  
written permission of Roberts-Gordon LLC.  
Printed in U.S.A.  
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TABLE OF FIGURES  
Figure 1: Clearances to Combustibles ......................................3  
Figure 2: Air Flow Direction.......................................................7  
Figure 3: Suspension Methods .................................................8  
Figure 4: Shelf-Mounting Methods............................................9  
Figure 5: Wall Shelf Mounting and Suspension ........................9  
Figure 6: Vent and Roof Detail................................................ 13  
Figure 7: Standard Vented Heater - Vertical and Horizontal  
Vent Termination...................................................... 13  
Figure 8: Standard Vented Heater - Common Vertical Vent  
Termination.............................................................. 14  
Figure 9: Separated Combustion Heater - Vertical and  
Horizontal Vent Termination..................................... 15  
Figure 10: Concentric Vent Box............................................... 15  
Figure 11: Concentric Vertical and Horizontal Vent Termination -  
Separated Combustion Heater............................... 16  
Figure 12: Gas Connection ..................................................... 18  
Figure 13: Automatic Burner Control Sequence......................24  
Figure 14: Gas Valve ..............................................................24  
Figure 15: Manual Reset Limit Switch.....................................26  
Figure 16: LED Diagnostic Codes...........................................27  
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SECTION 1: HEATER SAFETY  
SECTION 1: HEATER SAFETY  
Your Safety is Important to Us!  
This symbol is used throughout  
the manual to notify you of  
possible fire, electrical or burn  
hazards. Please pay special  
attention when reading and  
following the warnings in these  
sections.  
Installation, service and quarterly  
inspection of heater must be done by a contractor  
qualified in the installation and service of gas-fired  
heating equipment.  
Read this manual carefully before installation,  
operation or service of this equipment.  
Heaters are not approved for residential  
installations. These instructions, the layout drawing,  
local codes and ordinances and applicable  
standards that apply to gas piping, electrical wiring,  
venting, etc. must be thoroughly understood before  
proceeding with the installation.  
Protective gear is to be worn during installation,  
operation and service. Thin sheet metal parts,  
including the various venting components, have  
sharp edges. To prevent injury, the use of work  
gloves is recommended.  
Before installation, check that the local distribution  
conditions, nature of gas and pressure and  
adjustment of the appliance are compatible.  
1.1 Manpower Requirements  
To prevent personal injury and damage to the  
heater, two persons will be required for installation.  
1
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
SECTION 2: INSTALLER RESPONSIBILITY  
The installer is responsible for the following:  
2.2 Corrosive Chemicals  
To install the heater, as well as the gas and  
electrical supplies, in accordance with applicable  
specifications and codes. Roberts-Gordon  
recommends the installer contact a Local  
Building Inspector or Fire Marshal for guidance.  
Caution: Do not use heater in an area containing  
corrosive chemicals. Avoid the use of corrosive  
chemicals to ensure a longer life of the burner, heat  
exchanger and other parts.  
Roberts-Gordon cannot be responsible for ensuring  
that all appropriate safety measures are undertaken  
prior to installation; this is entirely the responsibility  
of the installer. It is essential that the contractor, the  
sub-contractor, or the owner identifies the presence  
of combustible materials, corrosive chemicals or  
halogenated hydrocarbons* anywhere in the  
premises.  
To use the information given in a layout drawing  
and in the manual together with the cited codes  
and regulations to perform the installation.  
To install the heater in accordance with the  
clearances to combustibles.  
To furnish all needed materials not furnished as  
standard equipment.  
To plan location of supports, vents and air  
intakes.  
* Halogenated Hydrocarbons are a family of chemical  
compounds characterized by the presence of halogen ele-  
ments (fluorine, chlorine, bromine, etc.). These compounds are  
frequently used in refrigerants, cleaning agents, solvents, etc. If  
these compounds enter the air supply of the burner, the life  
span of the heater components will be greatly reduced. An out-  
side air supply must be provided to the burners whenever the  
presence of these compounds is suspected. Warranty will be  
invalid if the heater is exposed to halogenated hydrocarbons.  
To provide access for servicing.  
To provide the owner with a copy of this  
Installation, Operation and Service Manual.  
To never use heater as support for a ladder or  
other access equipment and never hang or  
suspend anything from heater.  
2.3 National Standards and Applicable Codes  
All appliances must be installed in accordance with  
the latest revision of the applicable standards and  
national codes. This refers also to the electric, gas  
and venting installation. Note: Additional standards  
for installations in public garages, aircraft hangars,  
etc. may be applicable.  
To ensure there is adequate air circulation  
around the heater and to supply air for  
combustion, ventilation and distribution in  
accordance with local codes.  
To provide a method that ensures that the air flow  
through the heat exchanger is within the  
acceptable range indicated on the rating plate  
prior to energizing the heater, and that such air  
flow continues at least 90 seconds after the  
heater is de-energized.  
2.1 Wall Tag  
A laminated wall tag is included with the heater as a  
permanent reminder of the safety instructions and  
the importance of the required clearances to  
combustibles. Affix the tag by peeling off the backing  
of the adhesive strips on the rear surface and  
position the tag on a wall near the heater.  
A copy of the wall tag (P/N 91039831) is illustrated  
on the back cover.  
Know your model number. Model number is found  
on the heater and throughout the Installation,  
Operation and Service Manual.  
2
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SECTION 3: CRITICAL CONSIDERATIONS  
SECTION 3: CRITICAL CONSIDERATIONS  
3.1 Basic Information  
3.5 Clearances to Combustibles  
UHD[X][S][R] heaters have automatic ignition  
burners for ON/OFF operation only.  
WARNING  
3.2 Manufactured Units  
Gas-fired, power-vented duct furnace with tubular  
heat exchanger. Units shall have a minimum of 82%  
thermal efficiency. The standard unit shall consist of  
a non-separated combustion design with an  
Fire Hazard  
aluminized heat exchanger. Design and heat  
exchanger alternatives shall be offered as follows:  
• Separated Combustion: A separated  
Some objects can catch fire or explode  
when placed close to heater.  
Keep all flammable objects, liquids and  
vapors the required clearances to  
combustibles away from heater.  
combustion unit shall feature an enclosed,  
sealed burner box. A piece of flexible air duct  
connects this burner box to a flange on the  
cabinet. Combustion air should be ducted from  
outside the heated space, with the ductwork  
connecting to the unit with the use of the flange.  
Failure to follow these instructions can  
result in death, injury or property damage.  
Clearances must be as indicated on Page 3, Figure  
1. If clearances to combustibles are not indicated,  
then installation clearances apply.  
• Stainless Steel Heat Exchanger: A stainless  
steel heat exchanger unit shall consist of heat  
exchanger tubes, heat exchanger tube supports,  
heat exchanger tube plates and vent box  
produced of 409 stainless steel.  
Figure 1: Clearances to Combustibles  
3.3 Location and Suspension  
All models:  
• Must be installed indoors.  
• Must be installed on the positive pressure side of  
the air circulation blower.  
• Must be installed in a level position with  
horizontal discharge.  
• May be mounted on a shelf of non-combustible  
material using shelf mounting brackets.(See  
Page 9, Figure 4 and Page 9, Figure 5 for  
details.)  
Clearance to Vent: 2" (5 cm)  
*18" (46 cm) minimum is necessary for  
servicing.  
• May be suspended from above (See Page 8,  
Figure 3) or from wall brackets of sufficient  
strength to support the heater as listed in the  
Dimension Data Table on Page 40, Section 15.1.  
• Must be installed in a manner which allows  
access to all serviceable components. See Page  
3, Figure 1 for details.  
3.4 Minimum Required Installation Clearances  
Clearances around the heater and vent must be as  
indicated on Page 3, Figure 1 and Page 13, Figure 6  
through Page 16, Figure 11 to ensure access for  
servicing, and correct operation.  
3
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
3.6 Ventilation  
3.8 Electrical Supply  
WARNING  
WARNING  
Carbon Monoxide Hazard  
Heaters may be installed  
vented or unvented.  
Vented heaters must be  
vented outdoors.  
Electrical Shock Hazard  
Unvented heaters must be  
installed in buildings with  
ventilation rates as per  
section 6.4.  
Disconnect electrical and gas supply before  
servicing.  
This appliance must be connected to a  
properly grounded electrical source.  
Failure to follow these  
instructions can result in  
death or injury.  
Failure to follow these instructions can result  
in death or electrical shock.  
It is important to ensure that there is adequate air  
space around the heater to supply air for  
combustion, ventilation and distribution in  
accordance with local and national codes. See Page  
10, Section 6.  
A permanent 120 V /1 Ø/60 Hz electrical supply is  
required for the main electrical power. The heater  
also requires suitable controls in accordance with  
Page 19, Section 9.  
3.7 Gas Supply  
3.9 Vent  
Choose heater orientation to allow for proper  
location of the vent. Each heater must be fitted with  
a correctly sized sealed vent system.  
WARNING  
If vented horizontally, no other appliance may be  
connected to the vent. See Page 10, Section 6.  
Fire Hazard  
Connect gas supply according to Figure 12.  
Do not use gas supply pipe and electrical  
connections to support heater’s weight.  
Gas can leak if not installed properly.  
Failure to follow these instructions can  
result in death, injury or property damage.  
It is important that the gas supply pipe is sized  
correctly to provide the inlet pressure as stated on  
the heater data plate. The gas supply pipe and  
electrical connections must not support any of the  
heater's weight. See Page 18, Section 8.  
4
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SECTION 4: NATIONAL STANDARDS AND APPLICABLE CODES  
SECTION 4: NATIONAL STANDARDS AND APPLICABLE CODES  
4.1 Gas Codes  
4.3 Parking Structures and Repair Garages  
The type of gas appearing on the name plate  
must be the type of gas used. Installation must  
comply with national and local codes and  
requirements of the local gas company.  
Installation in garages must be in accordance  
with the following codes:  
United States: Standard for Parking Structures  
NFPA 88A - latest revision or the Code for Motor  
Fuel Dispensing Facilities and Repair Garages,  
NFPA 30A - latest revision. Canada: Refer to  
CSA B149.1 Natural Gas and Propane  
Installation Code.  
United States: Refer to NFPA 54/ ANSI Z223.1 -  
latest revision, National Fuel Gas Code.  
Canada: Refer to CSA B149.1 Natural Gas and  
Propane Installation Code.  
• In accordance with the Standard for Parking  
Structures NFPA 88A, heaters must be located  
a minimum of 18" (50 cm) below the floor-ceiling  
assembly or 18" (50 cm) above the floor.  
4.2 Aircraft Hangars  
Installation in aircraft hangars must be in  
accordance with the following codes:  
• In accordance with the Code for Motor Fuel  
Dispensing Facilities and Repair Garages,  
NFPA 30A - latest revision, heaters must not be  
installed less than 8' (2.4 m) above the floor.  
United States: Refer to Standard for Aircraft  
Hangars, NFPA 409 - latest revision.  
Canada: Refer to Standard CSA B149.1 Natural  
Gas and Propane Installation Code.  
4.4 Electrical  
• In aircraft storage and servicing areas, heaters  
shall be installed at least 10' (3 m) above the  
upper surface of wings or of engine enclosures  
of the highest aircraft which may be housed in  
the hangar. The measurement shall be made  
from the wing or engine enclosure (whichever is  
higher from the floor) to the bottom of the  
heater.  
The heater must be electrically grounded in  
accordance with the following codes:  
United States: Refer to National Electrical  
®
Code , NFPA 70 - latest revision. Wiring must  
conform to the most current National Electrical  
®
Code , local ordinances and any special  
diagrams furnished.  
• In shops, offices and other sections of aircraft  
hangars communicating with aircraft storage or  
servicing areas, heaters shall be installed not  
less than 8' (2.4 m) above the floor.  
Canada: Refer to Canadian Electrical Code,  
CSA C22.1 Part 1 - latest revision.  
• Suspended or elevated heaters shall be so  
located in all spaces of aircraft hangars that  
they shall not be subject to injury by aircraft,  
cranes, movable scaffolding or other objects.  
Provisions shall be made to assure accessibility  
to suspended heaters for recurrent  
4.5 Venting  
The venting must be installed in accordance  
with the requirements within this manual and  
the following codes:  
United States: Refer to NFPA 54/ANSI Z223.1 -  
latest revision, National Fuel Gas Code.  
maintenance purposes.  
Canada: Refer to CSA B149.1 Natural Gas and  
Propane Installation Code.  
5
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
4.6 High Altitude  
These heaters are CSA-approved (without  
modifications) for installations up to 2000' (610  
m) in US and Canada. CSA approved heaters  
installed above 2000' (610 m) must be de-rated.  
For installations above 2000' (610 m) in US,  
consult factory for information on burner de-  
rating. For installations from 2000' (610 m) to  
4500' (1370m) in Canada, high altitude  
conversion kits are available. Heaters installed  
over 4500' (1370 m) in Canada are not CSA-  
approved and must be approved by the local or  
provincial authority.  
6
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SECTION 5: DUCT HEATER INSTALLATION  
SECTION 5: DUCT HEATER INSTALLATION  
5.1 General  
range shown on Page 7, Section 5.1.3. The minimum  
inlet duct lengths shown on Page 7, Section 5.1.1  
should be observed. Pressure drop through the heat  
exchanger at various air flows is given on Page 7,  
Section 5.1.2.  
To connect the inlet and outlet ducts to the heater,  
Duct-Mate or similar flanges may be slid over the  
duct connector flanges supplied on the unit and  
secured with screws. The connection to the duct  
then can be made using the Duct-Mate clips. The  
ducts must have removable access panels  
upstream and downstream of the heater. These  
panels must be of appropriate size and placement  
so that smoke or reflected light could be observed to  
indicate the presence of leaks in the heat  
Figure 2: Air Flow Direction  
OUTLET DUCT  
exchanger. Covers for these openings should be  
sealed to prevent leakage.  
Any transition into the inlet of the heater should be  
smooth, with a taper of no more than 15 degrees. If  
elbows are required, they should be of either broad  
radius or fitted with properly designed air turns.  
Consult a professional to ensure air turns are  
properly designed.  
AIR FLOW  
INLET DUCT  
The heater must be installed on the positive  
pressure side of the circulating air blower. Air flow  
through the heater must be as shown on Page 7,  
Figure 2 and may not be reversed. The air flow must  
be adjusted such that it is within the acceptable  
5.1.1 Minimum Inlet Duct Length  
Model  
UHD[X][S][R] 75  
UHD[X][S][R] 100 &125  
Duct Length  
32" (81 cm)  
37" (94 cm)  
Duct Size (W X H)  
16 1/8" x 15 7/8" (41 cm x 40 cm)  
21 3/4" x 15 7/8" (55 cm x 40 cm)  
5.1.2 Temperature Rise and Pressure Drop Ranges  
UHD[X][S][R] 75  
UHD[X][S][R] 100  
Temperature PressureDrop  
UHD[X][S][R] 125  
Temperature Pressure Drop  
Airflow  
(CFM)  
850  
Temperature Pressure Drop  
Airflow  
(CFM)  
950  
Airflow  
Rise (°F)  
68.0  
(in wc)  
0.06  
0.10  
Rise (°F)  
(in wc)  
0.05  
0.18  
0.28  
0.39  
0.46  
0.55  
(CFM)  
1,020  
1,650  
2,340  
3,480  
4,240  
4,750  
Rise (°F)  
(in wc)  
0.06  
0.14  
0.27  
0.56  
0.80  
0.98  
78  
50  
31  
26  
24  
22  
92  
57  
41  
28  
23  
20  
1,200  
1,625  
1,965  
2,450  
2,650  
48.3  
36.4  
30.3  
24.4  
1,500  
2,500  
3,000  
3,300  
3,660  
0.16  
0.22  
0.31  
0.36  
22.0  
5.1.3 Air Flow and Temperature Rise Ranges  
Model  
Rate  
Air Flow  
Minimum (CFM)  
Temperature Rise  
(Btu/h)  
75,000  
100,000  
125,000  
Maximum (CFM)  
2,650  
Minimum (°F)  
Maximum (°F)  
UHD[X][S][R] 75  
UHD[X][S][R] 100  
UHD[X][S][R] 125  
850  
950  
1,020  
22  
22  
20  
68  
78  
92  
3,660  
4,750  
7
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
5.2 Shelf Mounting and Suspension  
Do not locate the gas or electrical supply lines  
directly over the path of the flue products from the  
heater.  
WARNING  
Crush Hazard  
The heater must be installed in a location that is  
readily accessible for servicing.  
Use 3/8" threaded rod  
minimum.  
The heater must be installed in accordance with  
clearances to combustibles as indicated on the wall  
tag and in this manual.  
Failure to follow these  
instructions can result in  
death, injury or property  
damage.  
5.3 Wall Mounting  
Four suspension points (3/8" nuts) are located on  
the top of the heater. Drop rods must be 3/8"  
diameter mild steel.  
For typical suspension, See Page 9, Figure 5. Wall  
mounted heaters blowing parallel to the wall can  
only be installed with the service door away from the  
wall.  
When handling or supporting the heater from below,  
ensure that the weight is taken at the support points.  
For typical suspension, See Page 8, Figure 3.  
For typical shelf mounting on existing shelf, See  
Page 9, Figure 4.  
The wall mounting brackets must be attached to a  
suitable wall using all mounting holes. Screw sizes  
less than 3/8" may not be used. In order for the wall  
mounting brackets to adequately carry the weight of  
the heater, it must be installed according to best  
building practices.  
The gas or electrical supply lines must not be used  
to support the heater.  
Figure 3: Suspension Methods  
Ensure all suspension  
hardware is torqued to  
a minimum of 20 ft lbs.  
Channel  
Unistrut  
Nut  
NOTE: Duct supports  
not shown.  
Washer  
Duct supports  
and duct are  
Nut  
3/8"  
Threaded  
Rod  
not provided by  
manufacturer.  
Cone Point  
Set Pin  
Window  
Clamp  
3/8"  
Threaded  
Rod  
Nut  
Washer  
Unistrut  
Support Points  
Riv  
Nut  
8
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SECTION 5: DUCT HEATER INSTALLATION  
Figure 4: Shelf-Mounting Methods  
Existing cabinet screws must be re-used.  
Description  
Part Number  
Qty.  
Shelf Mounting Bracket Kit 12011000K  
Shelf Mounting Bracket  
Screw #10 x 1/2"  
Type AB Phil HWH Z  
11111510  
94311008  
2
2
Shelf Mounting  
Brackets  
Figure 5: Wall Shelf Mounting and Suspension  
Wall Shelf Mounting  
Wall Suspension Mounting  
Shelf  
Mounting  
Brackets  
3/8" Fasteners  
(Fasten to  
Wall Mounting  
Bracket)  
Wall Mounting  
Bracket Arm  
(Right & Left)  
5/16" x 3 1/2" Bolt  
5/16" Flat Washer  
5/16" Locknut with Nylon Insert  
Torque to 40 in lb (4.5 Nm).  
Wall Mounting  
Bracket Diagonal  
Wall Mounting  
Bracket Vertical  
Hardware provided to construct mounting bracket assembly only.  
Description  
Part Number  
Qty.  
Description  
Part Number  
12011002K  
12011001K  
12011000K  
Qty.  
Wall Suspension Mounting Bracket Kit  
Wall Mounting Bracket Arm Left  
Wall Mounting Bracket Arm Right  
Wall Mounting Bracket Vertical  
Wall Mounting Bracket Diagonal  
5/16" x 3 1/2" Bolt  
5/16" Lock Nut with Nylon Insert  
5/16" Flat Washer  
5/16" Lockwasher  
12011001K  
111WALL1  
111WALL1  
111WALL2  
111WALL3  
97213925  
92114000  
95211600  
96411600  
Wall Shelf Mounting Bracket Kit  
Wall Suspension Mounting Bracket Kit  
Shelf Mounting Bracket Kit  
1
1
2
2
6
6
6
6
1
1
9
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
SECTION 6: VENTING  
sheet metal screws.  
For single wall venting, pressure sensitive aluminum  
tape or silicone sealant must be used to seal all  
joints.  
WARNING  
Carbon Monoxide Hazard  
Aluminum tape shall have a minimum temperature  
rating of 400° F (204° C) and meet SMACNA AFTS-  
100-73 standards. High temperature silicone sealant  
must have a minimum temperature rating of 480° F  
(250° C).  
Heaters may be installed  
vented or unvented.  
Vented heaters must be  
vented outdoors.  
Unvented heaters must be  
installed in buildings with  
ventilation rates as per  
section 6.4.  
6.2.1 United States Requirements  
Vent must terminate at least 3' (.9 m) above any  
forced air inlet located within 10' (3.1 m).  
Failure to follow these  
instructions can result in  
death or injury.  
Vent must terminate at least 4' (1.2 m) below,  
4' (1.2 m) horizontally from, or 1' (.3 m) above any  
door, operable window, or gravity air inlet into any  
building.  
6.1 Changing Vent and Air Intake Orientation  
The heater is sold with rear horizontal vent and air  
intake connections as standard. (Only separated  
combustion models have air intake connection). If  
vertical vent and air intake connections are required,  
follow the instructions on Page 38, Section 14.5.  
NFPA 54/ANSI Z223.1 - latest revision, National  
Fuel Gas Code specifies a 4' (1.2 m) horizontal vent  
terminal clearance from gas and electric meters,  
regulators and relief equipment.  
6.2.2 Canadian Requirements  
6.2 Venting  
The vent shall not terminate within 6' (1.8 m) of a  
mechanical air supply inlet to any building.  
This heater must be vented in accordance with the  
rules contained in this manual and with the following  
national codes and any state, provincial or local  
codes which may apply: United States: Refer to  
NFPA54/ANSI Z223.1 - latest revision, National Fuel  
Gas Code; Canada: Refer to CSA B149.1 Natural  
Gas and Propane Installation Code.  
The vent shall not terminate within 3' (.9 m) of a  
window or door that can be opened in any building,  
any non-mechanical air supply inlet to any building,  
or of the combustion air inlet of any other appliance.  
Any portion of vent pipe passing through a  
combustible wall must have a listed thimble to  
conform with the above codes.  
6.3 Vent Installation  
Maintain clearances to combustibles at all times for  
safety. Clearances are the required distances that  
combustible objects must be away from the heater  
to prevent serious fire hazard. See Page 3, Figure  
3.5. For vented units, the vent must terminate  
outside of the building.  
Vents must be fully sealed and correctly sized for  
the model. If the vent passes through a wall or  
ceiling of combustible material, it must be enclosed  
by a listed thimble and be separated from the  
thimble by at least a 2" (5 cm) air gap.  
The heater may be installed unvented in  
certain circumstances according to building  
ventilation codes. Refer to the above codes and  
Page 11, Section 6.4 for further information.  
Unvented operation also requires compliance with  
the clearances to combustibles given on Page 3,  
Figure 1.  
The bottom of the vent or air intake terminal shall not  
be located less than 1' (.3 m) above grade level.  
For separated combustion models, vents and air  
intakes must be a fully sealed system and correctly  
sized for the model. Vent should be assembled as  
detailed on Page 13, Figure 6 through Page 16,  
Figure 11. The joints between the vent terminal and  
the roof or wall must be properly sealed. If the vent  
passes through a wall or ceiling of combustible  
material, it must be enclosed by a listed thimble and  
be separated from the thimble by at least a 2" (5 cm)  
air gap.  
The vent shall not terminate less than 7' (2.1 m)  
above grade where located adjacent to public  
walkways.  
Vent terminal must be installed at a height sufficient  
to prevent blockage by snow and building materials  
protected from degradation by flue gasses.  
Vent terminal must be beyond any combustible  
overhang.  
Secure all joints with corrosion resistant #8 x 3/8"  
10  
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SECTION 6: VENTING  
Vents and air intakes must be adequately  
supported so that the heater does not bear the  
weight of the pipes.  
States); 3 cfm per 1000 Btu/h firing rate (Canada).  
WARNING: Combustion by-products contain a  
For vent termination See Page 13, Figure 6 through chemical known to the State of California to cause  
Page 16, Figure 11.  
cancer and birth defects or other reproductive harm.  
6.3.1 Standard Vented Heaters  
(Models UHD[X][R] 75 - 125)  
The vent must be fitted with a low resistance  
terminal. See Page 13, Figure 6 through Page 13,  
Figure 7. Standard vented heaters do not allow  
outdoor air intake for combustion air.  
6.5 Horizontal Venting  
Horizontally vented heaters must be individually  
vented.  
Vent pipe must be sloped ¼" (.6 cm) downward for  
every 1' (.3 m). For vent lengths greater than 5' (1.5  
m), condensation will form. Insulation is  
recommended and condensation drains may be  
desired.  
6.3.2 Separated Combustion Heaters  
(Models UHD[X]S[R] 75 - 125)  
In noncombustible walls only, vent terminal  
(P/N 02537801-1P) may be used.  
The heaters are designed to be installed as  
separated combustion heaters. The vent and air  
intake are run as separate pipes to the wall or roof  
terminals. See Page 15, Figure 9. As an option, the  
vent and air intake are run as separate pipes to a  
concentric vent box and a concentric vent/air intake  
pipe penetrates the wall or roof. See Page 15,  
Figure 10 and See Page 16, Figure 11.  
For separated combustion installation, the vent and  
air intake must be fitted with an individual and  
correctly sized sealed system and the vent and air  
intake must terminate at approved wall and roof  
terminals.  
For 4'' (10 cm) vents in either combustible or  
noncombustible walls, use vent terminal (P/N  
90502100) or equivalent insulated vent terminal.  
Follow the manufacturer's instructions for proper  
installation.  
Instead of an insulated vent terminal, a listed thimble  
(with 2" (5 cm) air gap) may be used with a 4" (10  
cm) vent cap (P/N 90502102).  
6.6 Vertical Venting  
Vertically-vented standard-vented heaters can be  
common vented (up to four heaters).  
Separated combustion units may not be common  
vented. See Page 10, Section 6.  
For vent lengths greater than 5' (1.5 m),  
condensation will form. Insulation is recommended  
and condensation drains may be desired. Venting  
through the top of the heater cabinet is not  
recommended if vent lengths are longer than  
10' (3 m). In this case, vent from the rear of the  
heater cabinet then run the vent vertically and use a  
condensate drain at the bottom of the vertical vent.  
Vent pipe must be sloped 1/4'' (.6 cm) for every  
1' (.3 m).  
6.4 Unvented Operation  
WARNING  
Carbon Monoxide Hazard  
Heaters may be installed  
vented or unvented.  
Vented heaters must be  
vented outdoors.  
For 4'' (10 cm), an approved vent cap  
(P/N 90502102) must be used.  
Unvented heaters must be  
installed in buildings with  
ventilation rates as per  
section 6.4.  
For 6'' (15 cm) common vent, an approved vent cap  
(P/N 90502103) must be used.  
For common vertical venting of more than two  
heaters, See Page 14, Figure 8.  
Failure to follow these  
instructions can result in  
death or injury.  
A vent shall not extend less than 2' (.6m) above the  
highest point where it passes through a flat roof of a  
building.  
This heater is not approved to be installed in  
residential buildings.  
6.7 Length Requirements  
For unvented operation in commercial installations,  
sufficient building ventilation must be provided in the  
amount of 4 cfm per 1000 Btu/h firing rate (United  
If using vent lengths greater than 5' (1.5 m),  
condensation will form in the vent pipe. Insulation  
11  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
and additional sealing measures (high temperature  
silicone at all seams) are required.  
Do not operate a summer exhaust fan. Close  
fireplace dampers.  
The entire vent should be insulated with foil faced  
fiberglass insulation (1/2" thick, 1-1/2# density  
minimum).  
4. Follow the lighting instructions. Place the  
appliance being inspected in operation.  
Adjust thermostat so that the appliance will  
operate continuously.  
6.7.1 Maximum Vent Lengths  
Model UHD[X][S][R] 75, 100, 125  
Number of Elbows  
5. For any appliance having a draft hood, test for  
draft hood appliance spillage at the draft hood  
relief opening after five minutes of main burner  
operation. Use the flame of a match or candle.  
40 ft (12.2 m)  
35 ft (10.7 m)  
30 ft (9.1 m)  
25 ft (7.6 m)  
1
2
3
4
5
20 ft (6.1 m)  
6. After it has been determined that each  
appliance connected to the venting system  
properly vents when tested as outlined above,  
return doors, windows, exhaust fans, fireplace  
dampers and any other gas-burning appliances  
to their previous conditions of use.  
6.8 Vent Material  
Vent material may be single wall 26 ga. (minimum)  
galvanized steel or equal thickness stainless steel.  
Completely seal all joints, refer to Page 10, Section  
6.3.  
If penetrating a combustible wall or roof, a listed  
thimble with 2" (5 cm) clearance must be used.  
Where local codes permit, a single section of type  
B-1 vent material may be used at the roof or wall  
penetration instead of a thimble. Ensure vent  
manufacturer's clearance from vent material is  
maintained. Seal annular space of the type B-1 vent  
as well as all joints in the remaining vent.  
7. If improper venting is observed during any of  
the above tests, the venting system must be  
corrected by a contractor qualified in the  
installation and service of gas-fired equipment  
or your local gas supplier. If the venting must be  
resized, use appropriate tables in (US)  
Appendix G of NFPA 54/ANSI Z223.1 - latest  
revision, National Fuel Gas Code (US) or  
Standard CSA B149.1 Natural Gas and  
Propane Installation Code (Canada) to  
6.9 Replacing an Existing Heater in a Venting  
System  
determine minimum size. All vent corrections  
must be in accordance with the appropriate  
local codes and the NFPA 54/ANSI Z223.1 -  
latest revision, National Fuel Gas Code (US) or  
Standard CSA B149.1 Natural Gas and  
Propane Installation Code (Canada).  
When replacing an existing heater in a venting  
system, the venting system may not be properly  
sized to vent the new heater. The following steps  
must be followed with each appliance connected to  
the venting system placed in operation, while any  
other appliances connected to the venting system  
are not in operation.  
1. Seal any unused openings in the venting  
system.  
2. Inspect the venting system for proper size and  
horizontal pitch, as required by the NFPA 54/  
ANSI Z223.1 - latest revision, National Fuel  
Gas Code (US) or Standard CSA B149.1  
Natural Gas and Propane Installation Code  
(Canada) and these instructions. Determine  
that there is no blockage or restriction, leakage,  
corrosion and other deficiencies which could  
cause an unsafe condition.  
3. Close all building doors and windows and all  
doors between the space in which the  
appliance(s) connected to the venting system  
are located and other spaces of the building.  
Turn on clothes dryers and any exhaust fans,  
such as range hoods and bathroom exhausts  
so that they shall operate at maximum speed.  
12  
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SECTION 6: VENTING  
Figure 6: Vent and Roof Detail  
Figure 7: Standard Vented Heater - Vertical and Horizontal Vent Termination  
Model  
Vent Diameter  
Part Number  
UHD[X][R] 75 - 125  
4" (10 cm)  
90502102  
13  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
Figure 8: Standard Vented Heater - Common Vertical Vent Termination  
14  
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SECTION 6: VENTING  
Figure 9: Separated Combustion Heater - Vertical and Horizontal Vent Termination  
Air Intake &  
Vent Diameter  
Model  
Part Number  
UHD[X]S[R] 75 - 125  
4" (10 cm)  
90502102  
Figure 10: Concentric Vent Box  
Toward  
Outside  
Seal joint between single wall  
and Type B vent with silicone sealant.  
6" (15 cm) Single  
Wall Inlet Air Pipe  
(By Others)  
Concentric  
Combustion Air  
Vent Box  
to Heater  
Use 3 sheetmetal  
Use 3 sheetmetal  
screws equally  
screws equally  
Exhaust  
from Heater  
spaced around joint.  
spaced around collar.  
4" (10 cm) Single  
Wall Vent Pipe  
(By Others)  
15  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
Figure 11: Concentric Vertical and Horizontal Vent Termination - Separated Combustion Heater  
Description  
Concentric Vent Kit  
Part Number  
UHVK1  
Qty.  
Concentric Vent Box Top & Side Assembly  
Concentric Vent Box Bottom Assembly  
Screw #6 x 3/8 Self Drilling  
4" (10 cm) Vent Terminal with Baffle Plate  
6" (15 cm) Combustion Air Terminal  
90504113  
90504112  
91119100  
90502102R  
90502103  
1
1
14  
1
1
16  
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SECTION 7: AIR SUPPLY  
SECTION 7: AIR SUPPLY  
7.1 Separated Combustion Installation  
When installed as a separated combustion heater  
(UHD[X]S[R]), the air for combustion is drawn in  
from outside the building.  
7.2 Unvented Installation  
It is important to ensure that there is adequate fresh  
air supply at all times for both combustion and  
heating requirements in accordance with local and  
national codes.  
WARNING: Combustion by-products contain a  
chemical known to the State of California to cause  
cancer and birth defects or other reproductive harm.  
7.3 Building Ventilation  
Where ventilation is required, air must be taken from  
an outside point where it is not likely to be  
contaminated or obstructed.  
7.4 Outside Combustion Air Supply  
If outside combustion air supply is required,  
separated combustion model (UHD[X]S[R]) heaters  
must be used.  
Caution: If the building has a slight negative  
pressure or corrosive contaminants such as  
halogenated hydrocarbons are present in the air, an  
outside combustion air supply to the heater is  
required. Seal all combustion air pipe joints.  
The flexible air supply duct may have to be insulated  
to prevent condensation on the outer surface. The  
outside air terminal must not be more than 1' (31  
cm) above the vent terminal.  
7.4.1 Length Requirements  
Follow the constraints listed on Page 11, Section  
6.7.  
17  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
SECTION 8: GAS PIPING  
• Gas supply pipe work is run in medium or heavy  
gauge tubing in compliance with local and  
national codes.  
• Meter and service must be large enough to  
handle all the burners being installed plus any  
other connected load. The gas pipe which feeds  
the system must be large enough to supply the  
required gas with a maximum pressure drop of  
1/2" wc. When gas piping is not included in the  
layout drawing, contact the local gas supplier.  
• An isolating valve and union connection should  
be used and fitted into the supply adjacent to the  
heater.  
Fire Hazard  
Connect gas supply according to Figure 12.  
Do not use gas supply pipe and electrical  
connections to support the heater’s weight.  
• A minimum 1/8" NPT plugged tapping  
accessible for test connection must be installed  
immediately upstream of the gas supply  
connection to the heater.  
Gas can leak if not installed properly.  
Failure to follow these instructions can  
• For suspended heaters, an approved metal  
flexible connection between the isolating valve  
and the heater may be used. To reduce  
pressure loss, use one pipe size larger than  
the heater gas connection.  
IMPORTANT - The complete installation must be  
purged and tested for gas soundness in accordance  
with local and national codes.  
Caution: Do not high pressure (in excess of 1/2 psi  
[14" wc]) test the gas piping with the burner  
connected. Close manual shut-off valve during any  
pressure testing equal to or less than 1/2 psi (14"  
wc).  
result in death, injury or property damage.  
A gas meter is connected to the service pipe by the  
gas supply company. An existing meter should be  
checked, preferably by the company, to ensure that  
the meter is adequate for the rate of gas supply  
required.  
Installation pipes must be fitted in accordance with  
local and national codes. Pipes of smaller size than  
the heater inlet gas connection should not be used.  
8.1 Connections  
Connect the heater to the gas supply ensuring that  
the final connections are as follows:  
Check the pipe and tubing ends for leaks before  
placing heating equipment into service. When  
checking for gas leaks, use a soap and water  
solution; never use an open flame.  
Figure 12: Gas Connection  
• Hold gas  
nipple securely  
with pipe  
wrench when  
attaching the  
flexible gas  
connector.  
Do not bend flexible  
gas connector  
sharply.  
• Do not twist  
flexible gas  
connector.  
• Ensure all  
joints are  
gas tight.  
18  
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SECTION 9: WIRING  
SECTION 9: WIRING  
All heaters are equipped with thermostat  
connections suitable to power a 24 V thermostat.  
Heater must be wired and electrically grounded in  
accordance with local codes. In the absence of local  
WARNING  
codes in accordance with: United States: refer to  
®
National Electrical Code NFPA 70 - latest revision;  
Canada: refer to Canadian Electrical Code CSA  
C22.1 Part I - latest revision.  
Electrical Shock Hazard  
Disconnect electrical and gas supply before  
9.1 Positioning Thermostats  
servicing.  
A room thermostat should be mounted on a  
vibration-free wall or column at a height of  
approximately 5' (1.5 m) from the floor to measure  
the ambient temperature. It should be clear of both  
cold drafts and the direct path of warm air from the  
heater.  
This appliance must be connected to a  
properly grounded electrical source.  
Failure to follow these instructions can  
result in death or electrical shock.  
Avoid mounting thermostat on outside walls or in  
areas directly exposed to radiant heat or sunlight.  
Install wall tag in a visible location near thermostat.  
See Page 2, Section 2.1 for wall tag details.  
All heater models require constant 120 V/1Ø/ 60 Hz  
power supply. Check heater rating plate for electrical  
rating for proper circuit sizing. For servicing, a  
disconnect switch of proper electrical rating should  
be installed in the vicinity of the heater.  
9.2 Low Voltage Thermostat with One Heater  
24 Volt  
Thermostat  
Terminal  
Strip  
R
R
G
W
C
Gas  
W
Supply  
Electrical  
Supply  
19  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
9.3 Internal Wiring Diagram  
L2 L1  
WHITE  
BLACK  
FLUE  
BLOWER  
GREEN  
WHITE  
GREEN  
GAS VALVE  
3
4
1
5
BLACK  
TRANSFORMER  
WHITE  
GREEN  
BLUE  
YELLOW  
YELLOW  
BLUE  
BROWN  
PRESSURE SWITCH  
BLUE  
3
6
1
2
4
5
R = 24 VAC TO THERMOSTAT (RED)  
R
G
W
C
ORANGE  
ORANGE  
LIMIT SWITCH (UHD 300, 350, 400 ONLY)  
G = MANUAL FAN INPUT FROM THERMOSTAT (GREEN)  
ORANGE  
W = HEAT DEMAND INPUT FROM THERMOSTAT (WHITE)  
ORANGE  
C = COMMON GROUND TO THERMOSTAT  
MANUAL RESET LIMIT SWITCH (RESIDENTAL UNITS ONLY)  
LIMIT SWITCH  
IGNITION MODULE  
THERMOSTAT INPUT: FIELD SUPPLIED  
SENSE  
BLACK  
BLACK  
BLACK  
ELECTRODE  
CMB BLOWER  
ACC  
L1  
BLACK  
IMPORTANT:  
For field wiring into service junction box, or if any of the original wire supplied with the heater  
must be replaced, it must be replaced with wiring material having a temperature rating of at least 105 °C  
(221 °F) and 600 V. For supply connections, use No. 14 AWG or larger wires.  
20  
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SECTION 9: WIRING  
9.4 Ladder Wiring Diagram  
120 VAC  
FLUE BLOWER  
TRANSFORMER  
GAS VALVE  
PRESSURE SWITCH  
2
5
3
1
FLAME  
SENSOR  
6
4
FLAME  
IGNITION  
MODULE  
LIMIT SWITCH (UHD 300, 350, 400 ONLY)  
LIMIT SWITCH  
SPARK  
ELECTRODE  
MANUAL RESET LIMIT SWITCH  
(UHD 75 - 125 ONLY)  
THERMOSTAT CONNECTION  
FLUE BLOWER  
IMPORTANT:  
For field wiring into service junction box, or if any of the original wire supplied with the heater  
must be replaced, it must be replaced with wiring material having a temperature rating of at least 105 °C  
(221 °F) and 600 V. For supply connections, use No. 14 AWG or larger wires.  
21  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
9.5 Electrical Connection to the Heater  
Flexible Conduit  
BX Connector  
Burner  
L1  
L2  
Ground  
Connect wires together  
with suitable approved  
wire connectors.  
Junction Box  
Green to Ground  
White to L2  
Black  
White  
Green  
Black to L1  
IMPORTANT: Junction box is not provided with heater.  
Conduit can also be attached directly to heater with wire junction made within the heater cabinet.  
22  
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SECTION 10: OPERATION AND MAINTENANCE  
SECTION 10: OPERATION AND MAINTENANCE 10.2 Begin Start-Up  
10.2.1 Before Operating the Heater  
WARNING  
To ensure that all the controls are in safe working  
order, operate the heater for the first time with the  
isolating gas valve turned off and power supply  
turned on.  
1. Turn off the isolating gas valve.  
2. Turn up the thermostat above room  
temperature. The automatic ignition  
sequence will now begin as described  
on Page 24, Figure 13.  
There will be no ignition of the burner and lockout  
will occur, which proves the controls are operating  
correctly.  
Explosion Hazard  
Installation, service and annual inspection  
must be done by a contractor qualified in  
the installation and service of gas-fired  
heating equipment or your gas supplier.  
Turn off gas and electrical supplies before  
performing service or maintenance.  
Failure to follow these instructions can  
result in death, injury or property damage.  
Read this manual carefully before installation,  
operation, or service of this equipment. All  
components are accessed via the door secured by  
four sheet metal screws. Opening the door exposes  
live electrical connections and hot components.  
10.1 Pre-Start-Up Checks  
All pre-start-up checks must be carried out before  
lighting the heater.  
Ensure that the heater and all controls are suitable  
for the gas, pressure and electrical supply to which  
they are to be connected.  
10.1.1 Electrical Checks  
1. Check that all site wiring is connected in  
accordance with the appropriate wiring diagram  
on Page 20, Section 9.3.  
10.1.2 Gas Supply  
All aspects of the gas installation including the gas  
meter must be inspected, tested for gas tightness  
and purged in accordance with local and national  
codes.  
Ensure that the air is fully purged from the heater  
inlet pipe up to the main gas valve inlet test nipple.  
10.1.3 Mechanical Checks  
1. Check that the flue (and air intake for separated  
combustion units) is installed in accordance  
with these instructions and local regulations.  
23  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
Figure 13: Automatic Burner Control Sequence  
Burner Sequence for Ignition Control  
START  
RUN  
SHUT DOWN  
Thermostat 24 V  
Flue Blower  
30 Seconds Purge*  
NO  
30 Seconds Post  
P
Pressure  
Switch  
C
NC  
ts = 10 Seconds  
Ignition Spark  
Start Gas Valve  
Flame Signal  
*Purge time begins at pressure switch change over.  
Required Incoming Signals  
If at any stage the flame fails, the control will retry  
for ignition. The control has four trials for ignition  
before a one hour lockout.  
Signals Output By Control  
Figure 14: Gas Valve  
END VIEW  
TOP VIEW  
Regulator  
C
ON  
OFF  
Outlet  
Gas Inlet  
Pressure  
Description  
Gas Valve NG  
Gas Valve LP  
Part Number  
90032505  
90032506  
Inlet Pressure  
24  
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SECTION 10: OPERATION AND MAINTENANCE  
10.2.2 Start-Up the Gas Valve (All Gases)  
10.2.2.1 Check Burner Gas Pressure  
10.3 Complete Start-Up  
1. Remove the plug in the outlet (burner) pressure Ensure that all covers are fitted correctly and all test  
points are properly sealed.  
test point and connect a pressure tap and a  
manometer.  
10.3.1 Instruction to the User  
2. With the burner firing, measure the pressure on  
the manometer. To adjust the burner pressure, Explain the controls of the heater to the user  
including how to turn it on and off, using the controls  
fitted on site.  
Give this manual to the user.  
Ensure that the user is shown and understands the  
importance of maintaining clearances to  
combustibles on Page 3, Figure 1 and the user  
instructions on Page 26, Section 11 through Page  
27, Section 11.5 and all warnings defined in this  
manual.  
remove the regulator cover from the valve and  
turn the regulator adjustment screw to set the  
required burner pressure as stated in the  
Technical Data Tables for the correct gas and  
model on Page 41, Section 15.3.  
IMPORTANT: If the correct burner pressure cannot  
be reached, then check the inlet pressure to the  
valve with the burner firing. See Technical Data  
Tables on Page 41, Section 15.3 for inlet pressure  
requirement.  
Do not continue to adjust the regulator if the  
pressure is not changing.  
If the inlet pressure is too low to allow correct burner  
pressure setting, then the gas inlet pressure must be  
corrected before completing the start-up.  
Check Gas Rate  
1. After burner pressure adjustment, allow the  
heater to operate for at least 15 minutes and  
then re-check settings. Adjust pressure setting  
if necessary.  
2. Check gas flow rate at gas meter.  
3. Turn off heater and electrical supply.  
4. Remove the manometer and refit all covers to  
the valve and tighten the screw of the outlet  
pressure tap.  
10.2.3 Pressure Switch  
The pressure switch is factory pre-set for each  
model and is not adjustable.  
10.2.4 Turning Off the Heater  
Set the thermostat to the "OFF" position or lowest  
setting and the main burner will stop.  
10.2.5 External Controls  
External controls may include time switch, interlock  
switch, room thermostat and frost thermostat.  
Operate each control to ensure that they function  
correctly. Set the switches (if fitted) and  
thermostat(s) to the users’ requirements.  
25  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
SECTION 11: USER INSTRUCTIONS  
11.3 Common User Controls  
11.3.1 Manual Reset Limit Switch  
WARNING  
WARNING  
Explosion Hazard  
Explosion Hazard  
Installation, service and annual inspection  
must be done by a contractor qualified in  
the installation and service of gas-fired  
heating equipment or your gas supplier.  
Do not make more than one attempt to  
restart the heater if manual reset limit switch  
locks out.  
Turn off gas and electrical supplies before  
performing service or maintenance.  
The vent or heat exchanger may be blocked.  
The fault must be traced and repaired.  
Failure to follow these instructions can  
result in death, injury or property damage.  
Failure to follow these instructions can  
result in death, injury or property damage.  
11.1 User Instructions  
The UHD[X][S][R] Series heaters are fully automatic  
and operate from the external controls fitted on site.  
The only user control at the heater is the Manual  
Reset Limit Switch - See Page 26, Section 11.3.1  
The limit thermostat is located inside the access  
door of the heater. See Page 37, Section 14.3. This  
control protects against excessive heat build-up  
inside the burner compartment.  
Figure 15: Manual Reset Limit Switch  
11.2 Heater Operation  
Reset Button  
When the heater has been switched on by the  
thermostat installed on site, the main burner will  
automatically turn on.  
The burner control box will control the safe ignition  
of the flame.  
All heaters require a constant gas and electricity  
supply which must not be interrupted during the  
normal operation of this heater.  
To reset manual reset limit switch, press reset  
button. NOTE: To reset, the switch must be cool.  
Description  
Part Number  
Manual Reset Limit Switch  
90412106  
11.4 Lighting Instructions  
11.4.1 To Turn On Heater  
1. Ensure that the electrical and gas supplies to  
the heater are on. Check that the on site  
controls are "ON".  
IMPORTANT: The thermostat setting must be above  
the ambient temperature for the heater to operate.  
2. The automatic firing sequence will begin as  
described on Page 24, Figure 13. The heater  
will now operate automatically under the control  
of the on site controls.  
26  
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SECTION 11: USER INSTRUCTIONS  
11.4.2 To Turn Heater Off  
Set the thermostat to the "OFF" position.  
The burner will turn off immediately.  
To restart, turn the thermostat above room  
temperature.  
11.5 Simple Troubleshooting  
Some possible reasons for the heater not operating  
are:  
1. Gas supply not "ON".  
2. Electricity supply not "ON".  
3. The time and/or temperature controls are not  
"ON".  
4. A limit switch may have operated. This may be  
caused by an interruption of the electrical  
supply, failure of the distribution fan or vent or  
heat exchanger blockage.  
If a temperature limit switch persistently trips, there  
is a fault which must be investigated by a contractor  
qualified in the installation and service of gas-fired  
heating equipment.  
11.5.1 Simple Troubleshooting (Burner Faults)  
If the burner fails to ignite for any reason, it will retry  
for ignition (four trials total). After four unsuccessful  
ignition trials, the control will put the heater into  
lockout for one hour.  
Lockout should not occur during normal operation of  
the heater and indicates there is a fault condition  
which must be corrected. There is an LED light on  
the ignition control that flashes codes to assist in  
fault correction. See Page 27, Figure 16 for LED  
indication codes.  
Figure 16: LED Diagnostic Codes  
LED INDICATION FAULT MODE  
Slow Flash  
Fast Flash  
2 Flashes  
3 Flashes  
4 Flashes  
Normal Operation - No call for heat.  
Normal Operation - Call for heat.  
Ignition Lockout - No flame detected.  
Airflow Fault - Pressure switch open or closed.  
Temperature Limit or  
Manual Reset Limit Switch Open  
5 Flashes  
Steady On  
Flame Sense Error - Gas valve not energized.  
Internal Control Failure  
27  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
SECTION 12: SERVICING  
3. Remove the ignition electrode and flame probe.  
Check condition of ignition electrode and flame  
probe. Clean off any deposits which may have  
been formed, check condition of ceramic  
insulators. Replace as required.  
WARNING  
12.3 Heat Exchanger Maintenance  
The heat exchanger will remain clean unless a  
problem has developed with combustion. Inspect the  
heat exchanger. Look for signs of overheating at the  
front tubes which may indicate burner over firing or  
persistently low air flows.  
Explosion Hazard  
Installation, service and annual inspection  
must be done by a contractor qualified in  
the installation and service of gas-fired  
heating equipment or your gas supplier.  
12.4 Gas Valve Maintenance  
Turn off gas and electrical supplies before  
performing service or maintenance.  
No regular maintenance is required on this device.  
To change gas control valves, See Page 35, Section  
14.1.  
Failure to follow these instructions can  
result in death, injury or property damage.  
Do not repair or disassemble gas valve.  
Replace faulty gas valves with replacement parts  
sold and supplied by Roberts-Gordon.  
12.1 Servicing Instructions  
After start-up, the heater will require maintenance to  
be carried out annually. If the heater is used in a  
12.5 Flue Blower  
dirty or dusty area, more frequent maintenance may The flue blower should not require maintenance.  
be required.  
However, if the air pressure switch is causing burner  
lockout, then remove the flue blower from the vent  
box by unscrewing the three screws at the mounting  
plate. Remove the four screws attaching the  
mounting plate to the fan inlet (See Page 38,  
Section 14.5). Ensure that the fan is free to run and  
that the fan wheel is clean.  
IMPORTANT: After any maintenance or repair work,  
always test fire the heater in accordance with the  
start-up instructions on Page 23, Section 10 through  
Page 25, Section 10.3.1 to ensure all safety systems  
are in working order before leaving the heater to  
operate. Minor faults may be traced by using the  
troubleshooting charts on Page 31, Section 13  
through Page 34, Section 13.5.  
12.6 Venting and Air Intake Pipe  
Inspect all venting and air intake pipe. Ensure that  
all seams are sealed and suspension points secure.  
Repair suspension points if any part of the venting  
or combustion air pipe is sagging. Check to make  
sure any insulation is not missing or in poor  
IMPORTANT: Check all gas pipes and pipe joints to  
ensure there are no cracks or gas leaks. Any cracks  
in the pipes or pipe joints must be repaired.  
condition. Replace as required. Check all venting  
and air intake components to ensure they are in  
good condition, gas tight and corrosion-free.  
IMPORTANT: Inspect all suspended components  
and hardware. Ensure that they are in good  
condition, properly tightened, and corrosion free.  
12.2 Burner Maintenance  
1. Open the door and remove the burner  
compartment cover. See Page 36, Section  
14.2.  
2. Clean any deposits from the main burner which  
may have formed in the injectors or venturi of  
the burner. See Page 36, Section 14.2.  
28  
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SECTION 12: SERVICING  
12.7 Maintenance Checklist  
Installation Code and Annual Inspections: All  
®
installations and service of ROBERTS GORDON  
WARNING  
equipment must be performed by a contractor  
qualified in the installation and service equipment  
sold and supplied by Roberts-Gordon and conform  
to all requirements set forth in the ROBERTS  
®
GORDON manuals and all applicable  
governmental authorities pertaining to the  
installation, service and operation of the equipment.  
Explosion Hazard  
Installation, service and annual inspection  
must be done by a contractor qualified in  
the installation and service of gas-fired  
heating equipment or your gas supplier.  
To help facilitate optimum performance and safety,  
Roberts-Gordon recommends that a qualified  
contractor annually inspect your ROBERTS  
GORDON equipment and perform service where  
necessary, using only replacement parts sold and  
supplied by Roberts-Gordon.  
®
Turn off gas and electrical supplies before  
performing service or maintenance.  
Failure to follow these instructions can  
result in death, injury or property damage.  
The Vicinity of the Heater Do not store or use flammable objects, liquids or vapors near the heater.  
Immediately remove these items if they are present.  
See Page 3, Section 3.  
Vehicles and Other  
Objects  
Maintain the clearances to combustibles.  
Do not hang anything from, or place anything on, the heater.  
Make sure nothing is lodged in between the heat exchanger tubes.  
Immediately remove objects in violation of the clearances to combustibles.  
See Page 3, Section 3.  
Vent Pipe/Terminals  
Venting must be intact. Using a flashlight, look for obstructions, cracks on the  
pipe, gaps in the sealed areas or corrosion.  
The area must be free of dirt and dust.  
Remove any carbon deposits or scale using a wire brush.  
If the vent terminal has a screen built in, remove any dirt, dust or deposits  
from the screen.  
See Page 17, Section 7.  
Combustion Air Intake  
Pipe  
Intake pipe and inlet must be intact. Look for obstructions, cracks on the pipe,  
gaps in the sealed areas or corrosion.  
The area must be free of dirt and dust.  
Clean and reinstall as required.  
Heat Exchanger  
Make sure there are no cracks.  
Make sure there is no sagging, bending or distortion.  
Clean or replace as required.  
See Page 18, Section 8.  
29  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
Gas Line and Shut-off  
Valves  
Check for gas leaks.  
See Page 18, Section 8.  
Burner Observation  
Window  
Make sure it is clean and free of cracks or holes.  
Clean and replace as required.  
Flue Blower Scroll, Wheel Compressed air or a vacuum cleaner may be used to clean dust and dirt.  
and Motor  
Inshot Burners and  
Orifices  
Clear obstructions (even spider webs will cause problems).  
Carefully remove any dust and debris from the burner.  
Direct-Spark Igniter  
Replace if there are cracked ceramics, excessive carbon residue, or erosion  
of the electrode.  
The electrode gap should be 1/8" (3.2 mm).  
Thermostat  
There should be no exposed wire or damage to the device or wiring.  
See Page 19, Section 9.1.  
Suspension Points  
Make sure the heater is hanging securely.  
Look for signs of wear on the suspension materials or ceiling.  
See Page 8, Figure 3.  
Silicone Tubing  
Gas Valve  
Ensure tight, secure fit on all pressure fittings at pressure switch,  
burner partition, and blower outlet.  
Verify that cap covering pressure regulator adjustment screw is secure and  
has not been tampered with.  
Verify all wiring connections.  
Condensate Drain  
(when installed)  
Flush drain and clear any obstructions.  
Ductwork  
Consult an indoor air quality professional for proper cleaning procedures.  
Air Circulation Blower  
For a complete inspection, refer to the manufacturers installation, operation  
and service manual.  
Wall Tag  
If wall tag is present, make sure it is legible and accurate. Please contact  
®
Roberts-Gordon LLC or your ROBERTS GORDON independent distributor if  
you need a wall tag. See Page 2, Section 2.1.  
30  
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SECTION 13: TROUBLESHOOTING  
SECTION 13: TROUBLESHOOTING  
13.1 General  
WARNING  
Explosion Hazard  
Installation, service and annual inspection  
must be done by a contractor qualified in  
the installation and service of gas-fired  
heating equipment or your gas supplier.  
START  
Turn off gas and electrical supplies before  
performing service or maintenance.  
Are gas & electrical  
No  
Turn on supplies.  
supplies on?  
Failure to follow these instructions can  
result in death, injury or property damage.  
Yes  
UHD 75: Press in reset  
button on manual reset limit  
switch. UHD 100 - 125: Wait  
10 - 15 minutes for limit  
switch to cool. Does fan  
stop running?  
Is ignition control showing a  
"4 flashes" LED code?  
Fan and limit switch are  
operating normally.  
Yes  
Yes  
No  
Replace temperature limit  
switch.  
No  
Burner has locked out due  
to ignition failure. Use  
Troubleshooting for Automatic  
Ignition Burner Systems  
section to test burner.  
Is ignition control showing a  
"2 flashes" LED code?  
Yes  
No  
Use Troubleshooting for  
Flue Blower section to test  
fan.  
Does the flue blower run?  
No  
Yes  
With external controls (i.e.  
thermostat) on, does the  
burner continue through the  
heating cycle?  
The limit switch has  
tripped. See Manual Reset No  
Has burner “Locked Out”?  
No  
No  
Replace limit switch.  
Limit Switch Figure.  
Yes  
Yes  
Use Troubleshooting for  
Automatic Ignition Burner  
Systems section to test burner.  
Ensure air flow through the  
heat exchanger is  
appropriate per the rating  
plate.  
Yes  
If problems persist, contact  
Roberts-Gordon, LLC at  
www.rg-inc.com  
Heater Operating  
TROUBLESHOOT ENDS.  
No  
31  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
13.2 Troubleshooting For Automatic Ignition Burner Systems  
START  
Are gas & electrical  
Turn on supplies.  
No  
supplies on?  
Yes  
Are external controls  
(i.e. Thermostat) on?  
No  
Turn on controls.  
UHD 75: Press in reset  
button on manual reset limit  
switch. UHD 100 - 125: Wait  
10 - 15 minutes for limit  
switch to cool. Does fan  
stop running?  
Yes  
Is ignition control showing a  
"4 flashes" LED code?  
Fan and limit switch are  
operating normally.  
Yes  
Yes  
No  
Replace temperature limit  
switch.  
No  
Does flue blower run?  
Is 120 V supply at fan  
Flue blower faulty;  
No  
Yes  
connections?  
replace  
No  
Burner control faulty or wiring  
connections faulty. Repair  
or replace as required  
Yes  
Check for too much vent/air inlet duct. Check for blockage in  
vent and combustion air circuit. Check for faulty air pressure  
switch. Check pressure switch hoses for leaks or cracks.  
Do not attempt to circumvent pressure switch circuit to  
place unit in operation.See Pressure Switch section for details.  
Does air pressure switch  
No  
change over?  
Yes  
Is ignition lead okay and  
connected?  
Is spark electrode okay?  
Wait 30 - 40 seconds.  
Does ignition spark  
operate?  
Ignition control faulty;  
replace.  
See Ignition Control section.  
No  
Yes  
No  
Yes  
Is the gas valve operating?  
To test valve, See  
Troubleshooting for Gas  
Valves section.  
Replace valve.  
Does the flame light?  
No  
Yes  
Trace fault in supervision  
system. See  
Is the flame current at  
least 1 μAmp DC when  
the flame ignites?  
Is ignition control showing  
a "2 flashes" LED code?  
Yes  
Yes  
Troubleshooting  
for Flame Supervision  
System section.  
No  
If problems persist, contact  
Roberts-Gordon LLC at  
www.rg-inc.com  
Heater Operating  
TROUBLESHOOT ENDS.  
No  
For optimum heater performance, use only replacement parts sold and supplied by Roberts-Gordon.  
Conduct start-up procedure as shown on Page 23, Section 10.  
32  
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SECTION 13: TROUBLESHOOTING  
13.3 Troubleshooting for Flame Supervision System  
To measure flame current, connect a 0 - 50 μA DC meter in series with the flame probe. If the meter  
reads negative values, then reverse the test leads.  
START  
Connect a DC ammeter in  
series with the flame probe.  
Use General  
Troubleshooting section to  
trace the fault.  
Is the flame present and  
at least 1 μA DC flame  
current?  
No  
Yes  
Yes  
Yes  
Is the connecting lead  
damaged? Is the flame probe  
damaged or touching earthed  
components?  
Is there a current flowing in  
the flame probe circuit with  
no flame present?  
Repair or replace as  
Yes  
required.  
No  
Is inlet burner gas pressure  
correct? Is live and neutral  
polarity correct? Is  
Does “lockout” occur when  
there is a flame present?  
Yes Replace ignition control.  
flame probe circuit correct?  
No  
Repair or replace as  
required.  
No  
If problems persist, contact  
Roberts-Gordon LLC at  
www.rg-inc.com  
Heater Operating  
TROUBLESHOOT ENDS.  
No  
NOTE: Minimum flame probe current 1 μA DC. Typical flame probe current 3-5 μA DC.  
33  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
13.4 Troubleshooting for Gas Valves  
START  
Is gas pressure at inlet of the  
valve correct for gas type?  
Fault elsewhere.  
Correct pressure problem.  
No  
Note pressure found.  
Yes  
Valve or ignition control  
faulty. Replace with  
one of correct type.  
Does gas pressure at outlet  
of the valve rise when  
valve turns on?  
No  
Yes  
Does gas pressure at  
outlet of valve return to zero or  
lower when valve turns off?  
Valve faulty.  
Replace with one of  
correct type.  
No  
Yes  
If problems persist, contact  
Roberts-Gordon LLC at  
www.rg-inc.com  
Valve Operating  
TROUBLESHOOT ENDS.  
No  
13.5 Troubleshooting for Flue Blower  
START  
Does flue blower run  
automatically when there  
is a call for heat?  
Correct power  
supply problem.  
No  
Yes  
Blower motor faulty.  
Replace with correct type.  
Yes  
Does blower turn on and  
off while burner is firing  
continuously?  
Check blower motor leads  
for loose connections.  
Yes  
No  
If problems persist, contact  
Roberts-Gordon LLC at  
www.rg-inc.com  
Blower Operating  
TROUBLESHOOT ENDS.  
No  
For optimum heater performance, use only replacement parts sold and supplied by Roberts-Gordon.  
Conduct start-up procedure as shown on Page 23, Section 10.  
34  
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SECTION 14: REPLACEMENT PARTS  
SECTION 14: REPLACEMENT PARTS  
Burner Components  
All serviceable burner parts are accessed by the  
door on the side of the heater. Remove the  
sheetmetal screws.  
WARNING  
14.1 Gas Valve  
Remove the gas supply pipe at the heater inlet.  
Follow steps in Section 14.2 and Section 14.2.1 to  
remove gas valve/manifold.  
Explosion Hazard  
Replace in reverse order. Verify that the gas flow  
direction of the valve is correct. Use a minimum  
amount of gas seal on the thread joint. Check that  
all the joints are leak free. Reset gas valve. See  
Page 25, Section 10.2.2.  
Installation, service and annual inspection  
must be done by a contractor qualified in  
the installation and service of gas-fired  
heating equipment or your gas supplier.  
Turn off gas and electrical supplies before  
performing service or maintenance.  
IT IS IMPORTANT THAT ONLY THE CORRECT  
GAS VALVE IS USED WHEN REPLACING  
THESE CONTROLS.  
Failure to follow these instructions can  
result in death, injury or property damage.  
See warnings and notes on Page 28, Section 12  
before removing or replacing parts.  
NOTE: Separated combustion  
model shown.  
Flexible Air Duct  
C
ON  
OFF  
Description  
Gas Valve, NG (Models UHD[X][S][R] 75 - 125)  
Gas Valve, LP (Models UHD[X][S][R] 75 - 125)  
Part Number  
90032505  
90032506  
35  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
14.2 Burner Compartment  
Burner  
The burner compartment is a sealed  
compartment. Following any work,  
re-seal the compartment with the  
gas pipe rubber seal fully in place  
and all screws fitted and tight.  
Compartment  
Cover  
Viewing port  
for flame probe  
Flame Probe  
Ignition Electrode  
Remove flexible  
air duct from spigot  
NOTE: Separated combustion  
model shown.  
Remove screws and  
pull off burner cover  
14.2.1 Burner Injectors  
Ensure gas tight fitting  
of injectors.  
Manifold  
Ensure correct alignment  
with burners.  
Remove manifold  
screws and pull  
out manifold  
Ensure all pipe joints are  
gas tight.  
Manifold  
Inshot  
Burners  
Unscrew  
Orifices  
Orifices  
Manifold  
Mounting  
Bracket  
Grommet  
Marking  
Folded  
Hem  
MODEL  
UHD[X][S][R] 75  
UHD[X][S][R] 100  
UHD[X][S][R] 125  
Orifice Quantity  
Natural Gas (G20)  
Orifice Marking  
P/N  
5
6
7
49  
46  
46  
91930049  
91930046  
91930046  
Propane (G31)  
Orifice Marking  
P/N  
1.15 mm  
1.25 mm  
1.25 mm  
91930115  
91930125  
91930125  
36  
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SECTION 14: REPLACEMENT PARTS  
14.3 Ignition Electrode and Flame Probe  
Inshot  
Burners  
Manual Reset  
Limit Switch  
(Position may vary.)  
Flame  
Probe  
Flame  
Probe  
Limit  
Switch  
Burner Compartment  
Front Views  
Ignition  
Electrode  
Ignition  
Electrode  
.120  
(3 mm)  
spark  
gap  
Inshot  
Burners  
To replace the electrode or flame probe, remove the electrical lead and screw.  
Pull out from mounting. Refit in reverse ensuring that the gap to burner is as shown in the  
front view of the burner compartment.  
Description  
Spark Electrode  
Automatic Ignition Flame Probe  
Transformer  
Ignition Module  
Inshot Burners UHD[X][S][R] 75  
Inshot Burners UHD[X][S][R] 100  
Inshot Burners UHD[X][S][R] 125  
Limit Switch  
Part Number  
90427411  
90439300  
90436900K  
90434008  
92000002  
92000002  
92000002  
90412104  
90412106  
Qty  
1
1
1
1
5
6
7
1
Manual Reset Limit Switch (75 only)  
1
14.4 Heat Exchanger  
The heat exchanger consists of a six-pass design with 1.5" outer diameter [aluminized steel] [409 stainless  
steel] tube. The tube plates are made of [aluminized steel] [409 stainless steel]. The tube supports are  
made of [galvannealed steel] [409 stainless steel].  
37  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
14.5 Flue Blower Vertical Installation  
To remove the blower, remove  
screws securing the fan and  
mounting plate to the vent box.  
To remove the blower from the  
mounting plate, remove screws.  
Intake &  
Exhaust  
Covers  
Refit in reverse order.  
Mounting Plate  
to Vent Box  
fixing screws  
To change the vent and air  
intake orientation from back to  
top, remove the blower and  
mounting plate as above.  
Air Intake  
Gaskets  
Adaptor  
Vent Box  
Remove intake (if applicable)  
and exhaust covers from top of  
the heater.  
Mounting Plate  
to Flue Blower  
screws  
Rotate the blower, mounting  
plate and gasket clockwise until  
the flue adapter lines up with  
the top hole. Secure screws.  
Air Intake Adapter  
Intake &  
Exhaust  
Covers  
If applicable, remove the flexible  
air duct from the air intake  
adapter on the back.  
Gasket  
Flexible Air  
If applicable, remove the air  
intake adapter from the back of  
the heater and install in the  
appropriate hole on top.  
Duct  
Reconnect the flexible air duct.  
Install intake and exhaust  
covers over the back holes.  
Mounting Plate  
to Vent Box  
fixing screws  
NOTE: Separated combustion model shown.  
MODEL  
UHD[X][S][R] 75  
UHD[X][S][R] 100  
90710405  
UHD[X][S][R] 125  
Flue Blower P/N  
90710404  
90710405  
IT IS IMPORTANT THAT ONLY THE CORRECT FLUE BLOWER SPECIFIED FOR EACH MODEL TYPE  
IS USED WHEN REPLACING THESE ITEMS.  
Carry out a start-up after working on or changing a flue blower. See Page 26, Section 11.  
38  
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SECTION 14: REPLACEMENT PARTS  
14.6 Pressure Switch  
Pull off 3 way connector. Spring open plastic clips of mounting cradle. Replace with correct type of pressure  
switch for model. The pressure switches are color coded for each pressure setting.  
Carry out a start-up after working on or changing a pressure switch. See Page 23, Section 10.  
MODEL  
UHD[X][S][R] 75  
90439810  
black  
UHD[X][S][R] 100  
90439810  
black  
UHD[X][S][R] 125  
90439803  
gray  
Pressure Switch Kit P/N  
Color Code  
.35  
.35  
.41  
Set Point in wc  
90439850  
90439850  
90439850  
Pressure Switch Snap Ring P/N  
14.7 Ignition Control  
The control mounts to the heat exchanger plate. Pull out ignition cable and wiring from board, noting their  
positions. Release the four mounting standoffs. Refit in reverse. Ensure correct location of ignition cable  
and all other wiring.  
14.8 Limit Switches  
14.8.1 Removal and Replacement  
1. Remove the electrical connections to the switch.  
2. Unscrew the two screws securing the switch.  
3. Fit a new switch with two screws.  
4. Reconnect the electrical connections and test operation.  
39  
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17.63"  
(45 cm)  
B
4 x 3/8" Captive Nuts  
Provided  
Air Intake  
(UHD[X][S][R] only;  
Optional Position)  
18.25"  
(46 cm)  
16.63"  
(42 cm)  
Flue  
6"  
(15 cm)  
(Optional Position)  
C
6.75"  
(17 cm)  
B
E
B
20.25"  
( 51 cm)  
E
6"  
(15 cm)  
A
(15 cm)  
6"  
Thermostat  
Connection  
Electrical  
Supply  
1.8"  
(5 cm)  
1.5"  
(4 cm)  
3.3"  
(8 cm)  
28.5"  
(72 cm)  
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SECTION 15: SPECIFICATIONS  
15.2 General Technical Data Table  
UHD[X][S][R] UHD[X][S][R]  
UHD[X][S][R]  
125  
Model  
A
75  
100  
Full Load Amps @ 115 V  
1
2
950  
2
Minimum Air Volume  
CFM  
850  
1020  
92 (33)  
0.06  
°C)  
Temperature Rise @ Minimum Air Volume  
Heat Exchanger Pressure Drop @ Minimum Air Volume  
Maximum Air Volume  
°F (  
in wc  
CFM  
°C)  
68 (20)  
0.06  
2650  
22 (-6)  
0.36  
78 (26)  
0.05  
3660  
4750  
20 (-7)  
0.98  
Temperature Rise @ Maximum Air Volume  
Heat Exchanger Pressure Drop @ Maximum Air Volume  
Flue Size/Air Intake**  
°F (  
22 (-6)  
0.55  
in wc  
in (cm)  
4 (10)-All models  
*Do not exceed the maximum length of flue stated or heater may not operate properly.  
15.3 Technical Data Table  
UHD[X][S][R]  
75  
UHD[X][S][R]  
Model  
UHD[X][S][R] 125  
100  
Total Input  
Total Output  
Efficiency  
(Btu/h) x (1000)  
(Btu/h) x (1000)  
%
75  
100  
125  
61.5  
82  
102.5  
82-All models  
Natural Gas (G20) Data - Inlet Pressure 5.0 in wc Min., 14 in wc Max.  
Burner Pressure in. wc 3.5  
LPG / Propane (G31) Data - Inlet Pressure 12.0 in wc Min., 14 in wc Max.  
Burner Pressure in. wc 10.0  
2.6  
9.1  
3.3  
10.0  
41  
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UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL  
42  
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®
®
SECTION 16: ROBERTS GORDON COMBAT UHD-SERIES WARRANTY  
®
®
SECTION 16: ROBERTS GORDON COMBAT UHD-SERIES WARRANTY  
®
®
®
The ownership of the ROBERTS GORDON COMBAT  
UHD-Series is moved or transferred. This warranty is  
nontransferable.  
Roberts-Gordon is not permitted to inspect the damaged  
controller and/or component parts.  
READ YOUR INSTALLATION, OPERATION AND  
SERVICE MANUAL  
If you have questions about your controller, contact your  
installing professional. Should you need Replacement  
Parts or have additional questions, call or write:  
Roberts-Gordon  
1250 William Street  
P. O. B ox 4 4  
ROBERTS GORDON WILL PAY FOR:  
Within 24 months from date of purchase by buyer or 27  
months from the date of shipment by Roberts-Gordon  
(whichever comes first), replacement parts will be  
provided free of charge for any part of the product which  
fails due to a manufacturing or material defect.  
Roberts-Gordon will require the part in question to be  
returned to the factory. Roberts-Gordon will, at its sole  
discretion, repair or replace after determining the nature  
of the defect and disposition of part in question.  
®
ROBERTS GORDON Replacement Parts are warranted  
for a period of 18 months from date of shipment from  
®
Roberts-Gordon or the remaining ROBERTS GORDON  
®
COMBAT UHD-Series warranty.  
Buffalo, New York 14240-0044  
716.852.4400  
On the web at: www.rg-inc.com  
®
ROBERTS GORDON WILL NOT PAY FOR:  
Service trips, service calls and labor charges.  
Shipment of replacement parts.  
Roberts-Gordon' liability, and your exclusive remedy,  
under this warranty or any implied warranty  
Claims where the total price of the goods have not  
been paid.  
Damage due to:  
(including the implied warranties of merchantability  
and fitness for a particular purpose) is limited to  
providing replacement parts during the term of this  
warranty. Some jurisdictions do not allow limitations on  
how long an implied warranty lasts, so this limitation may  
not apply to you. There are no rights, warranties or  
conditions, expressed or implied, statutory or otherwise,  
other than those contained in this warranty.  
• Improper installation, operation or maintenance.  
• Misuse, abuse, neglect, or modification of the  
ROBERTS GORDON COMBAT UHD-Series in any  
way.  
®
®
®
®
• Use of the ROBERTS GORDON COMBAT UHD-  
Series for other than its intended purpose.  
Roberts-Gordon shall in no event be responsible for  
incidental or consequential damages or incur liability  
for damages in excess of the amount paid by you for  
• Incorrect gas or electrical supply, accident, fire, floods,  
acts of God, war, terrorism, or other casualty.  
®
®
the ROBERTS GORDON COMBAT UHD-Series.  
Some jurisdictions do not allow the exclusion or limitation  
of incidental or consequential damages, so this limitation  
• Improper service, use of replacement parts or  
accessories not specified by Roberts-Gordon.  
®
• Failure to install or maintain the ROBERTS GORDON or exclusion may not apply to you. This warranty gives  
®
you specific legal rights, and you may also have other  
COMBAT UHD-Series as directed in the Installation,  
rights which vary from jurisdiction to jurisdiction.  
Operation and Service manual.  
®
®
• Relocation of the ROBERTS GORDON COMBAT  
Roberts-Gordon shall not be responsible for failure to  
perform under the terms of this warranty if caused by  
circumstances out of its control, including but not limited  
to war, fire, flood, strike, government or court orders, acts  
of God, terrorism, unavailability of supplies, parts or  
power. No person is authorized to assume for Roberts-  
Gordon any other warranty, obligation or liability.  
UHD-Series after initial installation  
®
®
• The use of the ROBERTS GORDON COMBAT  
UHD-Series in a corrosive atmosphere containing  
contaminants.  
®
®
• The use of the ROBERTS GORDON COMBAT  
UHD-Series in the vicinity of a combustible or  
LIMITATIONS ON AUTHORITY OF  
REPRESENTATIVES:  
No representative of Roberts-Gordon, other than an  
Executive Officer, has authority to change or extend these  
provisions. Changes or extensions shall be binding only if  
confirmed in writing by Roberts-Gordon's duly authorized  
Executive Officer.  
explosive material.  
®
®
• Any defect in the ROBERTS GORDON COMBAT  
UHD-Series arising from a drawing, design, or  
specification supplied by or on behalf of the  
consumer.  
• Damage incurred during shipment. Claim must be  
filed with carrier.  
WARRANTY IS VOID IF:  
®
®
The ROBERTS GORDON COMBAT UHD-Series is not  
installed by a contractor qualified in the installation and  
service of gas-fired heating equipment.  
You cannot prove original purchase date and required  
annual maintenance history.  
The data plate and/or serial number are removed,  
defaced, modified or altered in any way.  
43  
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®
Wa r m A i r H e a t i n g  
OWNER WARRANTY REGISTRATION CARD  
Mail or Fax to:  
Roberts Gordon LLC • 1250 William Street, P.O. Box 44 • Buffalo, NY 14240-0044 • Phone: 716-852-4400 • Fax: 716-852-0854  
Toll Free: 800-828-7450 • www.rg-inc.com  
About the Owner:  
Name:__________________________________________________________________________________________________  
Address:______________________________________City:_________________________State:__________Zip Code:________  
Phone:_________________________ Fax:_________________________ E-mail:______________________________________  
About the Installer:  
Name:__________________________________________________________________________________________________  
Address:______________________________________City:_________________________State:_________Zip Code:_________  
Phone:__________________________Fax:_________________________E-mail:______________________________________  
Purchased From (if different than installer):  
Name:__________________________________________________________________________________________________  
Address:______________________________________City:_________________________State:__________Zip Code:________  
Phone:_________________________ Fax:_________________________ E-mail:______________________________________  
About your Heater:  
Model#:_______________________ Serial #:___________________________ Fuel:____________Installation Date:__________  
Type of Installation (check one):  
o Automotive  
o Manufacturing  
o Warehouse  
o Recreational  
o Aircraft  
o Public Building  
o Office  
o Retail  
o Agricultural  
o Other______________  
Installation Code and Annual Inspections: All installations and service of ROBERTS GORDON® equipment must be performed by a  
contractor qualified in the installation and service of equipment sold and supplied by Roberts-Gordon and conform to all  
requirements set forth in the ROBERTS GORDON® manuals and all applicable governmental authorities pertaining to the  
installation, service and operation of the equipment.  
To help facilitate optimum performance and safety, Roberts-Gordon recommends that a qualified contractor annually inspect your  
ROBERTS GORDON® equipment and perform service where necessary, using only replacement parts sold and supplied by  
Roberts-Gordon.  
These products are not approved for residential use.  
© 2008 Roberts-Gordon LLC - All rights reserved. No part of this work covered by the copyrights herein my be reproduced or  
copied in any form or by any means – graphic, electronic, or mechanical, including photcopying,  
recording, taping, or information storage and retrieval systems – without written permission of  
Roberts Gordon LLC.  
Printed in the U.S.A.  
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Attach this information to the wall near the ROBERTS GORDON® heater  
®
Read the Installation, Operation and Service Manual thoroughly before installation, operation or service.  
OPERATING INSTRUCTIONS  
WARNING  
1. STOP! Read all safety instructions on this information sheet.  
2. Open the manual gas valve in the heater supply line.  
3. Turn on electric power to the heater.  
4. Set the thermostat to desired setting (above ambient temperature).  
The automatic starting sequence begins.  
TO TURN OFF THE HEATER  
1. Turn the thermostat/time switch to 'OFF' or lowest setting. The burner  
will turn 'OFF' immediately, but fans will continue to cool heat exchanger  
until the fan thermostat switches off.  
Fire Hazard  
Some objects can catch fire or explode when placed  
close to heater.  
IF THE HEATER WILL NOT OPERATE, TO ENSURE YOUR SAFETY,  
FOLLOW THESE INSTRUCTIONS TO SHUT DOWN YOUR HEATER  
Keep all flammable objects, liquids and vapors the  
required clearances to combustibles away from  
heater.  
1. Set the thermostat to off or the lowest setting.  
2. Turn off electric power to the heater.  
3. Turn off the manual gas valve in the heater supply line.  
4. Call your installer/contractor qualified in the installation and  
service of gas-fired heating equipment.  
Failure to follow these instructions can result in  
death, injury or property damage.  
Clearances to Combustibles  
Top  
Top  
Left  
Right  
Left  
Right  
Bottom  
Bottom  
Models 75 - 125  
Models 150 - 400  
150 - 400  
75 - 125  
Models  
6"  
6"  
31"*  
6"  
1"  
1"  
1"  
18"*  
2"  
Top  
Bottom  
Right  
Left  
Vent  
2"  
* Clearance needed for servicing.  
Roberts-Gordon LLC  
1250 William Street  
P.O. Box 44  
Telephone: 716.852.4400  
Fax: 716.852.0854  
Toll Free: 800.828.7450  
Buffalo, NY 14240-0044 USA  
Installation Code and Annual Inspections:  
All installation and service of ROBERTS GORDON® equipment must be performed by a contractor qualified in the installation and service of equipment sold and supplied by Roberts-Gordon and  
conform to all requirements set forth in the ROBERTS GORDON® manuals and all applicable governmental authorities pertaining to the installation, service and operation of the equipment. To help  
facilitate optimum performance and safety, Roberts-Gordon recommends that a qualified contractor conduct annual inspections of your ROBERTS GORDON® equipment and perform service  
where necessary, using only replacement parts sold and supplied by Roberts-Gordon.  
For installations at elevations above 2000' (610 m), the appliance shall be derated 4% for each 1000' (305 m) of elevation above sea level.  
Further Information:Applications, engineering and detailed guidance on systems design, installation and equipment performance is available through ROBERTS GORDON® representatives. Please  
contact us for any further information you may require, including the Installation, Operation and Service Manual.  
This product is not for residential use.  
© 2008 Roberts-Gordon LLC  
www.rg-inc.com  
Printed in U.S.A.  
P/N 91039831  
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