Carrier Heating System 48MA 50ME016 040 User Manual
48MA/50ME016-040  
Combination Multizone Heating/Cooling Units  
Gas, Electric, or Glycol Heat  
Installation, Start-Up  
and Service Instructions  
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39  
CONTENTS  
• EVAPORATOR COILS (ZONE COOLING COILS)  
AND GLYCOL HEATING COILS  
Page  
SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . 2  
• CONDENSER AND OUTDOOR-AIR COOLING  
COILS  
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34  
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Unit Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Roof Curb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Roof Openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Rigging Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5  
Unit Positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5  
Removing Shipping Shields . . . . . . . . . . . . . . . . . . 5  
Field-Fabricated Ductwork . . . . . . . . . . . . . . . . . . . . 5  
Condensate Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . 9  
Gas Piping (48MA) . . . . . . . . . . . . . . . . . . . . . . . . . . . 9  
Optional Glycol Connections (50ME) . . . . . . . . . 10  
Field Power Supply Wiring . . . . . . . . . . . . . . . . . . 10  
• UNIT COMMON FEED MINIMUM CIRCUIT AMPS  
Field Control Wiring . . . . . . . . . . . . . . . . . . . . . . . . . 14  
• ZONE THERMOSTATS  
• CONDENSATE DRAINS  
• INDOOR-AIR FILTERS  
• OUTDOOR-AIR INLET SCREENS  
• GAS HEATING SECTION  
• COMBUSTION AIR FAN  
Airflow Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39  
• INDOOR AIRFLOW SWITCH (AFS1)  
• COMBUSTION AIRFLOW SWITCH (AFS2)  
Service Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39  
Time Guardா Control Circuit . . . . . . . . . . . . . . . . . 39  
Capacity Control Pressure Switches (CCP)  
(2-Compressor Units Only) . . . . . . . . . . . . . . . . 39  
Compressor Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39  
• TO ADD OR REMOVE OIL  
Compressor Capacity Control Unloader(s) . . . . 40  
• CONTROL SET POINT  
• PRESSURE DIFFERENTIAL  
• ZONE MODULE CONNECTIONS  
• ACCESSORY REMOTE CONTROL PANEL  
Reheat Humidity Control . . . . . . . . . . . . . . . . . . . . 34  
Optional Economizer . . . . . . . . . . . . . . . . . . . . . . . . 34  
Optional Exhaust Damper . . . . . . . . . . . . . . . . . . . 34  
Crankcase Heater(s) . . . . . . . . . . . . . . . . . . . . . . . . . 40  
Refrigerant Charge . . . . . . . . . . . . . . . . . . . . . . . . . . 40  
• NO CHARGE  
• LOW CHARGE  
START-UP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34-39  
Evaporator Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34  
Compressor Rail Shipping Bolts . . . . . . . . . . . . . 34  
Refrigerant Valves . . . . . . . . . . . . . . . . . . . . . . . . . . 34  
Zone Module Gas Valves (48MA) . . . . . . . . . . . . . 34  
Gas Heat Lighting Procedure (48MA) . . . . . . . . . 35  
• TO SHUT OFF GAS HEAT  
Head Pressure Control . . . . . . . . . . . . . . . . . . . . . . 40  
• MOTORMASTER௡ HEAD PRESSURE CONTROL  
DEVICE  
• FAN CYCLING PRESSURESTAT  
Condenser Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41  
• ADJUSTMENT  
• FAN MOTOR REMOVAL  
• LUBRICATION  
Evaporator Fans and Motor . . . . . . . . . . . . . . . . . . 41  
• MOTOR REMOVAL  
• FAN SHAFT BEARING REMOVAL  
• FAN SPEED ADJUSTMENT  
• PULLEY REMOVAL  
• PULLEY ALIGNMENT  
• BELT TENSION ADJUSTMENT  
• LUBRICATION  
Forced-Draft Blower (48MA) . . . . . . . . . . . . . . . . . 42  
• LUBRICATION  
• AIR SHUTTER ADJUSTMENT  
Zone Module Transformers . . . . . . . . . . . . . . . . . . 42  
Optional Economizer . . . . . . . . . . . . . . . . . . . . . . . . 42  
• THERMOSTAT SETTINGS  
Intermittant Pilots (48MA) . . . . . . . . . . . . . . . . . . . 35  
• ADJUSTMENT  
• PRESSURE ADJUSTMENT (NATURAL GAS)  
Main Burner Adjustment (48MA) . . . . . . . . . . . . . 36  
• ORIFICE ALIGNMENT  
• PRIMARY AIR ADJUSTMENT  
Outdoor-Air Thermostat Adjustment  
(50ME With Electric Heat) . . . . . . . . . . . . . . . . . . 36  
• UNITS WITH 2-ELEMENT HEATERS  
• UNITS WITH 3-ELEMENT HEATERS  
Optional Glycol Heating Coils . . . . . . . . . . . . . . . . 38  
Zone Airflow Adjustment . . . . . . . . . . . . . . . . . . . . 38  
Sequence of Operation . . . . . . . . . . . . . . . . . . . . . 38  
• COOLING  
• HEATING (48MA)  
• HEATING (50ME WITH ELECTRIC HEAT)  
• HEATING (50ME WITH GLYCOL HEATING COILS)  
• OUTDOOR-AIR DAMPER  
• DAMPER POSITION  
• OPERATION  
Optional Exhaust Damper . . . . . . . . . . . . . . . . . . . 42  
Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . 42  
SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39-43  
Cabinet Panels and Grilles . . . . . . . . . . . . . . . . . . 39  
• SIDE PANELS  
START-UP CHECKLIST . . . . . . . . . . . . . . . . . . . . . CL-1  
• TOP PANELS  
• HEATER ACCESS PANELS  
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.  
Book 1 PC 111 Catalog No. 564-840 Printed in U.S.A. Form 48MA/50ME-3SI Pg 1 4-96 Replaces: 48MA/50ME-1SI  
Tab 1c 1d  
1
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CONDENSER SECTION AIRFLOW  
Connection  
CONN  
—
NOTES:  
1. Space required for service and airflow all  
around and above unit is 36 inches.  
2. For additional information see Fig. 4.  
3. Center of gravity is within 6 in. radius of geo-  
metric center of unit.  
4. Maximum allowable pitch of unit is 1  
10 ft in any direction.  
⁄2  
in. per  
Certified dimension drawings available on request.  
DIMENSIONS (ft-in.)  
UNIT  
48MA  
A
B
C
D
E
F
G
H
J
K
L
016-030  
034,040  
7- 23⁄4  
3-05⁄8  
3-915⁄16*  
17-115⁄16  
21- 91⁄16  
2-215⁄16  
4-25⁄8  
13-51⁄2  
13-51⁄2  
0- 91⁄16  
0-111⁄16  
2-10  
3- 45⁄16  
7-33⁄16  
8-63⁄4  
0-31⁄8  
0-31⁄32  
0-31⁄8  
0-215⁄16  
0-31⁄8  
0-71⁄4  
7-11  
*Overall height; includes 13⁄4-in. for fan guards.  
Fig. 1 — Base Unit Physical Data and Dimensions; 48MA Units  
3
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CONDENSER SECTION AIRFLOW  
Connection  
CONN  
—
NOTES:  
1. Space required for service and airflow all  
around and above unit is 36 inches.  
2. For additional information see Fig. 5.  
3. Center of gravity is within 6 in. radius of geo-  
metric center of unit.  
4. Maximum allowable pitch of unit is 1  
10 ft in any direction.  
⁄2  
in. per  
Certified dimension drawings available on request.  
DIMENSIONS (ft-in.)  
UNIT  
50ME  
A
B
C
D
E
F
G
H
J
016-030  
034,040  
7- 23⁄4  
3-09⁄16  
3-915⁄16*  
17-115⁄16  
21-91⁄16  
2-215⁄16  
4-25⁄8  
13-51⁄2  
13-51⁄2  
3-71⁄16  
7-33⁄16  
8-63⁄4  
0-31⁄8  
0-215⁄16  
0-31⁄8  
0-71⁄4  
7-11  
4-4  
*Overall height; includes 13⁄4-in. for fan guards.  
Fig. 2 — Base Unit Physical Data and Dimensions; 50ME Units  
4
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AIRFLOW  
*Factory supplied (with accessory roof curb).  
†Field supplied (when using accessory roof curb).  
NOTE: Dimensions are in inches.  
Fig. 3 — Roof Curb Detail  
Rigging Unit — Inspect unit for shipping damage, and  
file any damage claim immediately with transportation  
company.  
Lift unit with cables and spreader bars, using lifting brack-  
ets provided (Fig. 1 and 2). Lift one unit at a time, keep unit  
upright, and do not drop. Unit weights are given in Table 1.  
Unit center of gravity is within 6 in. of unit’s geometric cen-  
ter. Eyebolts may be removed after unit is in final position.  
Field-Fabricated Ductwork — Supply- and return-  
air openings are shown in Fig. 4 and 5. To simplify supply-  
air connection, a zone duct plenum may be field fabricated  
as shown in Fig. 7. It is recommended that this plenum be  
installed prior to unit positioning.  
It is recommended that the unit be supported on blocks  
temporarily while the duct plenum is installed, rather than  
installing the plenum while the unit is suspended. The duct  
plenum may be installed once the unit is located in its final  
position, but it is much easier to install the plenum prior to  
unit final placement.  
Zone supply-air duct openings on the base unit have tab  
slot connections similar to those shown in Fig. 7 except that  
the end partitions are hemmed. Hem is positioned so that the  
1-in. flange at entering end of field-fabricated plenum will  
force-fit between hem and adjacent unit frame.  
Standard flexible duct connections between duct plenum  
and duct system may be used. Follow applicable codes.  
IMPORTANT: Do not drill or punch holes in unit frame  
or panels; damage to internal components or wiring  
may result.  
Unit Positioning — When lowering unit onto roof curb,  
do not exceed the out-of-symmetry tolerances given in  
Fig. 4 and 5. Be sure unit is level or is pitched within speci-  
fied tolerances. Units have drains on both sides and may be  
pitched to either side.  
Insulate any supply-air ducts passing through uncondi-  
tioned spaces and cover with a vapor barrier. Separate ducts  
with insulation if they run parallel for more than 5 ft. This  
will prevent heat transfer between zones.  
Removing Shipping Shields (Fig. 6)  
1. Remove shield over flue outlet grille (48MA only).  
2. Remove shields (sheet metal covers) located in the outdoor-  
air inlet screen tracks behind the louvers. If the screens  
are removed for this procedure, be sure to replace them  
before replacing the louvered assembly.  
Install a manual balancing damper in each zone duct to  
provide the required zone airflow.  
The return-air duct connection consists of 4 sheet metal  
flanges as shown in Fig. 1, 2, 4, and 5.  
5
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Table 1 — Physical Data  
UNIT 48MA/50ME  
016  
024  
028  
030  
034  
040  
Zone Modules (Quantity)  
Nominal Cooling Capacity (tons)  
8
15  
8
20  
10  
25  
10  
28  
12  
30  
12  
37  
OPERATING WEIGHT (lb)  
Base Unit 48MA  
Base Unit 50ME (with electric heat)  
Roof Curb  
3395  
2995  
506  
3815  
3415  
506  
4075  
3675  
506  
4080  
3680  
506  
5340  
4900  
630  
5710  
5270  
630  
REFRIGERANT CHARGE — R-22 (lb)  
28  
32  
43  
43  
57  
66.1  
COMPRESSOR  
Reciprocating Hermetic, 1725 Rpm  
No. 1 Type  
06DE537  
06DE824  
6...2  
06DE537  
6...2  
06DE537  
6...2  
06DE537  
6...2  
06EE250  
4...1  
Cylinders...Unloaders  
No. 2 Type  
Cylinders (have no unloaders)  
System Oil Charge (pints)  
6...2  
—
06DA824  
6
06DA824  
6
06DA537  
6
06DA537  
6
06EA250  
4
—
11  
18  
18  
18  
18  
31  
Unloader Settings (psig)  
Compressor No. 1 Only  
71.0 ± 1.5  
Loads  
—
Unloader No. 2  
Unloads  
57.5 ± 2.5  
—
Loads  
Unloads  
75.0 ± 1.5  
62.5 ± 2.5  
75.5 ± 1.5  
58.0 ± 2.5  
Unloader No. 1  
100,83,67  
50,33,17  
100,80,60  
40,20  
100,80,60  
40,20  
100,83,67  
50,33,17  
100,75,  
50,25  
Capacity Steps (%)  
100,67,33  
CONDENSER FANS  
Propeller, Direct Drive  
Motor Hp...Rpm...Frame (NEMA)  
No. 1  
1...1075...56 (Single phase)  
1...1140...56 (3 phase)  
No. 2  
No. 3  
—
16,500  
—
15,000  
—
15,000  
—
15,000  
1...1140...56 (3 phase)  
Nominal Cfm  
24,000  
23,000  
EVAPORATOR FANS*  
Number...Size (in.)  
Cfm (Nominal)  
Centrifugal, Belt Drive  
2...15 × 15  
6000  
2...15 × 15  
8000  
2...15 × 15  
10,000  
10...1725  
—
2...15 × 15  
3...15 × 9  
12,000  
3...15 × 9  
12,000  
10,000  
10...1725  
—
Std  
Alt  
5...1725  
—
71⁄2...1725  
—
15...1725  
20...1725  
15...1725  
20...1725  
Motor Hp...Rpm  
Fan Pulley  
Outside Diameter (in.)  
Bore (in.)  
Std  
Fan Belt Number...Size  
Alt  
10.6  
13⁄16  
1...3V630  
—
10.6  
13⁄16  
1...3V630  
—
8.0  
13⁄16  
2...3V560  
—
8.0  
13⁄16  
2...3V560  
—
8.0  
8.0  
111⁄16  
111⁄16  
2...3V630  
3...3V670  
2...3V630  
3...3V670  
Motor Pulley  
Factory Installed  
Std  
Outside Diameter (in.)  
Alt  
5.3  
—
6.0  
—
5.0  
—
5.0  
—
5.0  
6.0  
5.0  
6.0  
Bore (in.)  
11⁄8  
13⁄8  
13⁄8  
1095  
—
13⁄8  
1095  
—
15⁄8  
15⁄8  
Std  
Resulting Fan Rpm  
Alt  
880  
—
18 ± 2.5  
1300  
995  
—
18 ± 2.5  
1300  
1095  
1320  
21 ± 2.5  
1550  
1095  
1320  
21 ± 2.5  
1550  
Shaft Center Line Distance (in.)  
Maximum Fan Rpm  
18 ± 2.5  
1300  
18 ± 2.5  
1300  
CONDENSER COOLING COIL  
Face Area (sq ft)  
Corrugated Fins/in. ...Rows  
Thermostatic Expansion Valve, Hot Gas Bypass  
6.8  
13...2  
6.8  
6.8  
6.8  
10.2  
10.2  
13...3  
13...2  
13...2  
13...2  
13...2  
EVAPORATOR COILS (zone)  
Number...Face Area (sq ft/ea)  
Corrugated Fins/in. ...Rows  
Solenoid Valve and Capillary Tube for each  
8...2.12  
13...3  
8...2.12  
13...3  
10...2.12  
13...3  
10...2.12  
13...3  
12...2.01  
12...3  
12...2.01  
15...3  
HEATING SECTION (48MA)  
Rise Range  
One Heat Assembly in Each Zone Module  
25 F to 55 F at 0.75 in. wg ESP  
Total  
432  
54  
432  
54  
540  
54  
540  
54  
648  
54  
648  
54  
Input (1000 Btuh)  
Each Module  
Total  
Each Module  
324  
324  
405  
405  
40.5  
2...38  
486  
486  
Bonnet Cap.† (1000 Btuh)  
Burner Spud Qty...Size  
40.5  
2...38  
40.5  
2...38  
40.5  
2...38  
40.5  
2...38  
40.5  
2...38  
OPTIONAL HEATING SECTION (50ME Electric)  
Electric Heaters  
Qty...Elements (each)**  
Nichrome, Open-Wire Resistance Element in Each Zone Module  
8...2 or 3 10...2 or 3 10...2 or 3 12...2 or 3  
8...2 or 3  
12...2 or 3  
OPTIONAL HEATING SECTION  
(50ME Glycol Coil)  
One Heating Coil in Each Zone Module  
Maximum Allowable Inlet Temperature (F)  
Maximum Allowable Flow, Each Coil (Gpm)  
Solution Mixture  
200  
6
20% Glycol  
30  
Maximum Allowable Working Pressure (Psig)  
Total Internal Volume (Gal)  
2.61  
2.61  
3.15  
3.15  
3.76  
3.76  
PRESSURE SWITCHES  
Cutout  
Low-Pressure (Psig)  
Cut-in  
29 ± 5  
39 ± 5  
400 ± 5  
300 ± 5  
Cutout  
High-Pressure (Psig)  
Cut-in  
Indoor Airflow Switch (AFS1)  
Factory Setting (cfm)  
Adjustment Range (cfm)  
6000  
4000-6000  
9000  
6000-9000  
INDOOR AIR FILTERS  
Standard Qty...Size (in.)  
High Efficiency (optional)  
Qty...Size (in.)  
12...20 × 25 × 2  
12...20 × 25 × 2 (36.5% Efficient)  
OUTDOOR AIR FILTERS  
Qty...Size (in.)  
2...20 × 25 × 1  
2...32 × 35 × 1  
LEGEND  
ESP  
NEMA  
—
—
External Static Pressure  
National Electrical Manufacturers Association  
*Standard unit shipped with standard motor, pulley, and belt(s); alternate unit shipped with alternate motor, pulley, and belt(s).  
†The heating efficiency rating is a product thermal efficiency rating determined under continuous operating conditions independent of any installed system.  
**See Field Power Supply Wiring section on page 10 and Table 4 for details.  
6
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EVAPORATOR (ZONE MODULE) AIRFLOW  
Connection  
CONN  
—
*Not used on 48MA016,024 (8 zone module units).  
NOTES:  
1. For additional information, see Table 1 and Fig. 1.  
1
2. Maximum allowable unit pitch is  
⁄2  
in. per 10 ft in any direction.  
3. Remove shipping brace before assembling curb section (location  
shown).  
DIMENSIONS (ft-in.)  
UNIT  
48MA  
A
B
C
D
E
F
G
H
J
016-030  
034,040  
18-21⁄8  
21-97⁄8  
7- 3  
7-113⁄4  
11-9  
14-13⁄4  
5-61⁄4  
6-77⁄16  
7-27⁄8  
8-43⁄16  
1-109⁄16  
2- 91⁄8  
2-29⁄16  
6-03⁄8  
6-81⁄2  
0- 71⁄2  
0-105⁄16  
3-1  
Fig. 4 — Roof Curb Physical Data and Dimensions; 48MA Units  
7
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EVAPORATOR (ZONE MODULE) AIRFLOW  
Connection  
CONN  
—
*Not used on 50ME016,024 (8 zone module units).  
END DETAIL  
(034,044 12-ZONE MODULES)  
NOTES:  
1. For additional information, see Table 1 and Fig. 2.  
1
2. Maximum allowable unit pitch is  
⁄
2
in. per 10 ft in any direction.  
3. Remove shipping brace before assembling curb section (location  
shown).  
DIMENSIONS (ft-in.)  
UNIT  
50ME  
A
B
C
D
E
F
G
H
J
016-030  
034,040  
18-21⁄8  
21-97⁄8  
7- 3  
7-113⁄4  
11-9  
14-13⁄4  
5-61⁄4  
6-77⁄16  
7-27⁄8  
8-43⁄16  
1-109⁄16  
2- 91⁄8  
2-29⁄16  
6-03⁄8  
6-81⁄2  
0- 71⁄2  
0-105⁄16  
3-1  
Fig. 5 — Roof Curb Physical Data and Dimensions; 50ME Units  
8
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Do not interconnect drains. Make each trap a minimum of  
4 in. deep. Insulate trap against freeze-up or use flexible  
material.  
Condensate Drains — Pipe nipples covered with foam  
rubber insulation are shipped in unit return air filter section  
(6 nipples in units 48MA, 4 nipples in units 50ME). Install  
a nipple in each drain connection on both sides of unit. See  
Fig. 1 and 2 for drain locations. Be sure foam rubber seals  
space between nipple and base rail opening to prevent rain  
leaks.  
Connect a drain line to drain connection under outdoor air  
inlet grilles on both sides of unit. These drains need not be  
trapped.  
Install a trapped drain line on remaining connections on  
lowest side of unit depending on unit pitch. If unit is level,  
a trapped drain may be installed at each connection if de-  
sired. Cap or plug unused connections on high side of unit  
to prevent airflow between unit interior and outdoors.  
Gas Piping (48MA) — Unit is equipped for use with  
type of gas shown on nameplate. Refer to latest edition of  
ANSI Z223.1. Unit main gas connection and alternate gas  
connection locations are shown in Fig. 1, 4, and 8. Do not  
use gas supply pipe smaller than unit gas connection. Maxi-  
mum allowable natural gas supply pressure is 10.0 in. wg;  
minimum allowable natural gas supply pressure for full rate  
input is 5.0 in. wg.  
1
Pitch pipe ⁄4 in. per 15 ft. Pitch all horizontal pipe runs  
upward to risers and from risers upward to meter. Install a  
dirt and moisture pocket (drip leg) at each section of vertical  
pipe run. Use only ground joint unions to ensure leakfree  
joints. Use only pipe joint compounds that are resistant to  
the action of liquefied petroleum gases.  
OUTDOOR AIR INLET  
(ONE ON EACH SIDE OF UNIT)  
FLUE OUTLET  
SHIPPING SHIELD  
COVER  
(BEHIND LOUVERS)  
(48MA ONLY)  
Fig. 6 — Shipping Shield Locations  
(016-030 Units Shown)  
DIMENSIONS (in.)  
UNIT  
48MA,50ME  
016,024  
028,030  
034,040  
A*  
B*  
75⁄8  
75⁄8  
75⁄8  
73⁄4  
75⁄16  
53⁄4  
*Typical; both ends.  
NOTE: Dimension to suit job requirements. Twelve inches will bring  
duct plenum to bottom of roof curb.  
Fig. 7 — Field-Fabricated Zone Duct Plenum Detail  
9
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All units have a main power supply terminal board in the  
power and condensing control box. The electric resistance  
heater power supply terminal board(s) (if unit is so equipped)  
on 50ME units is located in the heater control box at front  
of unit. See Fig. 2, 5, and 9.  
All terminal boards are suitable for use with copper or  
aluminum wire.  
Connect electrical conduit (a threaded pipe nipple) shipped  
with unit to threaded fitting in roof curb and bottom of main  
power and condensing section control box. Route main power  
wires through conduit to terminal board in box as shown on  
unit label wiring diagram and in Fig. 9.  
When installing 48MA,50ME040 units with optional 20-hp  
motor, the electrical conduit interconnecting the curb and con-  
trol box power wire openings will not accommodate alumi-  
num wire of the size that may be required. If aluminum wire  
cannot be accommodated, an external transition box and short  
lengths of no. 300 kcmil, 75 C copper wire from the tran-  
sition box to the unit main power connection are  
recommended.  
Voltage to compressor terminals during compressor op-  
eration must be within voltage range indicated on unit name-  
plate. Phases must be balanced within 2%.  
*Shutoff valve not used except where required by code.  
Properly cap any gas connection not being used.  
Fig. 8 — Suggested Gas Piping (48MA)  
Unit has factory-installed gas shutoff valves. Install gas  
shutoff valve external to unit if required by code (Fig. 8).  
After piping is complete, pressurize gas line and check for  
leaks with soap and water solution.  
Do not use an open flame when checking for gas leaks.  
Optional Glycol Connections (50ME) — Each zone  
module has its own glycol heating coil and 115-v solenoid  
valve. Heating coils are connected in parallel to common sup-  
ply and return manifolds. Supply manifolds are equipped with  
bleed cocks. Supply and return connections are shown in  
Fig. 2 and 5. Unit does not have internal pressure relief for  
part-load operation. Maximum allowable system working pres-  
sure is 30 psig. Unit ratings are based on 20% glycol solu-  
tions. Install solution supply apparatus in accordance with  
application requirements, and mix glycol solution percent-  
age in accordance with glycol manufacturer’s recommenda-  
tions. Freeze-up protection is not factory installed.  
Field Power Supply Wiring — When installed, unit  
must be electrically grounded in accordance with local codes  
or, in the absence of local codes, with the National Electrical  
Code (NEC).  
LEGEND  
EQUIP  
GND  
TB  
—
—
—
Equipment  
Ground  
Terminal Board  
Unit has a circuit breaker for each compressor, each fan  
motor, and for each 50ME electric resistance heater assem-  
bly (if unit is so equipped). If required by local code, pro-  
vide an additional disconnect switch in accordance with code  
being followed.  
*208/230 v units only.  
Fig. 9 — Field Power Supply Details  
10  
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Use the following formula to determine the percent volt-  
age imbalance.  
IMPORTANT: If the supply voltage phase imbalance  
is more than 2%, contact your local electric utility com-  
pany immediately.  
% Voltage Imbalance:  
max voltage deviation from average voltage  
= 100 ×  
average voltage  
Unit failure as a result of operation on improper line volt-  
age or excessive phase imbalance constitutes abuse and may  
cause damage to electrical components. See Tables 2-5 for  
unit, electric heater, and 50ME electrical application elec-  
trical data.  
Each 50ME electric heat unit is fitted with a heating lock-  
out circuit (if equipped with optional heat). If any zone mod-  
ule is operating on mechanical cooling (compressor is op-  
erating), the heating element in each zone module is locked  
out and cannot be energized.  
On 50ME units, cooling power supply wires and electric  
heater power supply wires (if applicable) must be sized ac-  
cording to the cooling MCA (Minimum Circuit Amps) val-  
ues and heating MCA values shown on unit nameplate and  
in Tables 3-5. These wires may be powered by a common  
power supply (i.e., a pull-box junction), if desired. The com-  
mon power supply wires from the main power source to the  
junction must be sized according to the common MCA val-  
ues shown in Table 5.  
EXAMPLE: Supply voltage is 460-3-60.  
AB = 452 v  
BC = 464 v  
AC = 455 v  
452 + 464 + 455  
Average Voltage =  
3
1371  
3
=
= 457  
Determine maximum deviation from average voltage.  
(AB) 457 − 452 = 5 v  
(BC) 464 − 457 = 7 v  
(AC) 457 − 455 = 2 v  
Maximum deviation is 7 v.  
Determine percent voltage imbalance:  
UNIT COMMON FEED MINIMUM CIRCUIT AMPS —  
The unit common feed MCA is calculated on the basis of  
either: the sum of the cooling MCA plus 1⁄2 heating MCA on  
7
% Voltage Imbalance = 100 x  
457  
2
= 1.53%  
units with 2 heating elements per zone module (or ⁄3 heat-  
ing MCA on units with 3 heating elements per zone module)  
or the sum of the evaporator fan motor full load amps, per  
NEC, plus the full heating MCA, whichever is larger. Field  
wiring must conform to NEC limitations for Type T wire.  
This amount of phase imbalance is satisfactory as it is below  
the maximum allowable 2%.  
Table 2 — Unit 48MA Electrical Data  
VOLTAGE  
RANGE  
COMP  
NO. 1  
COMP  
NO. 2  
OFM  
FLA  
COMBUSTION  
POWER  
SUPPLY  
IFM  
UNIT  
Voltage  
FAN MOTOR  
48MA (3 Ph, 60 Hz)  
Min Max RLA LRA RLA LRA No. 1 No. 2 No. 3  
FLA  
Hp  
FLA MCA MOCP  
208/230  
187  
414  
518  
187  
414  
518  
187  
414  
518  
187  
414  
518  
254 63.6 266  
508 28.6 120  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
16.2 109.6  
125  
60  
016  
024  
028  
030  
460  
575  
—
—
6.2  
6.2  
6.2  
6.2  
—
—
—
—
1.8  
1.8  
1.8  
1.8  
5
6.6  
5.6  
49.8  
39.8  
632 22.8  
96  
45  
208/230  
460  
254 44.4 170 44.4 170  
24.2 137.5  
150  
70  
508 19.9  
632 15.7  
77 19.9  
62 15.7  
77  
62  
7.5 11.0  
9.0  
62.2  
49.4  
575  
60  
208/230  
460  
254 63.6 266 44.4 170  
30.8 168.1  
200  
90  
508 28.6 120 19.9  
632 22.8 96 15.7  
77  
62  
10  
10  
13.0  
10.5  
76.1  
60.4  
575  
70  
208/230  
460  
254 63.6 266 63.6 266  
508 28.6 120 28.6 120  
30.8 187.3  
200  
100  
90  
13.0  
10.5  
84.5  
67.5  
575  
632 22.8  
96 22.8  
96  
15  
20  
15  
20  
15  
20  
15  
20  
15  
20  
15  
20  
46.2 210.8  
61.0 224.6  
225  
250  
100  
125  
90  
208/230  
460  
187  
414  
518  
187  
414  
518  
254 63.6 266 63.6 266  
508 28.6 120 28.6 120  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
21.0  
94.5  
034  
040  
6.2  
6.2  
1.8  
1.8  
26.6 100.5  
16.0  
21.3  
75.6  
80.6  
575  
632 22.8  
96 22.8  
96  
100  
300  
300  
150  
150  
125  
125  
46.2 247.7  
61.0 261.5  
21.0 116.7  
27.0 122.7  
208/230  
460  
254 80.0 345 80.0 345  
508 38.5 150 38.5 150  
632 31.4 120 31.4 120  
16.0  
95  
575  
21.3 100  
LEGEND  
MOCP  
OFM  
RLA  
—
—
—
Maximum Overcurrent Protection  
Outdoor (Condenser) Fan Motor  
Rated Load Amps  
COMP  
FLA  
IFM  
LRA  
MCA  
—
Compressor  
Full Load Amps  
—
—
—
—
NOTES:  
Indoor (Evaporator) Fan Motor  
Locked Rotor Amps  
1. Combustion air fan is a 115-1-60 motor on all units.  
2. Condenser fan motor no. 1 is a 208/230-1-60 speed control motor  
on all units.  
Minimum Circuit Amps  
11  
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Table 3 — Unit 50ME Electrical Data  
VOLTAGE  
RANGE  
COMP  
NO. 1  
COMP  
NO. 2  
OFM  
FLA  
POWER  
SUPPLY  
IFM  
FLA  
UNIT  
VOLTAGE  
50ME  
(3 Ph, 60 Hz)  
Min  
Max  
254  
508  
632  
254  
508  
632  
254  
508  
632  
254  
508  
632  
RLA  
LRA  
266  
120  
96  
RLA  
LRA  
No. 1  
No. 2  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
No. 3  
Hp  
MCA  
MOCP  
125  
60  
208/230  
460  
187  
414  
518  
187  
414  
518  
187  
414  
518  
187  
414  
518  
63.6  
28.6  
22.8  
44.4  
19.9  
15.7  
63.6  
28.6  
22.8  
63.6  
28.6  
22.8  
16.2  
6.6  
109.6  
49.5  
016  
024  
028  
030  
—
—
6.2  
—
5
575  
5.6  
39.6  
45  
208/230  
460  
170  
77  
44.4  
19.9  
15.7  
44.4  
19.9  
15.7  
63.6  
28.6  
22.8  
170  
77  
24.2  
11.0  
9.0  
138.0  
61.9  
150  
70  
6.2  
6.2  
6.2  
—
—
—
7.5  
10  
10  
575  
62  
62  
49.2  
60  
208/230  
460  
266  
120  
96  
170  
77  
30.8  
13.0  
10.5  
30.8  
13.0  
10.5  
46.0  
61.0  
19.8  
26.6  
16.0  
21.3  
46.2  
61.0  
19.8  
26.6  
16.0  
21.3  
168.9  
75.8  
200  
90  
575  
62  
60.2  
70  
208/230  
460  
266  
120  
96  
266  
120  
96  
188.0  
84.5  
200  
100  
90  
575  
67.3  
15  
20  
15  
20  
15  
20  
15  
20  
15  
20  
15  
20  
210.8  
224.6  
94.5  
225  
250  
100  
125  
90  
208/230  
460  
187  
414  
518  
187  
414  
518  
254  
508  
632  
254  
508  
632  
63.6  
28.6  
22.8  
80.0  
39.3  
31.4  
266  
120  
96  
63.6  
28.6  
22.8  
80.0  
39.3  
31.4  
266  
120  
96  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
6.6  
3.0  
2.4  
034  
040  
6.2  
6.2  
100.5  
75.6  
575  
80.6  
100  
300  
300  
150  
150  
125  
125  
247.7  
261.5  
118.5  
124.5  
95  
208/230  
460  
345  
150  
120  
345  
150  
120  
575  
100  
LEGEND  
NOTE: Condenser fan motor no. 1 is a 208/230-1-60 speed control  
motor on all units.  
COMP  
FLA  
—
—
—
—
—
—
—
—
Compressor  
Full Load Amps  
IFM  
Indoor (Evaporator) Fan Motor  
Locked Rotor Amps  
LRA  
MCA  
MOCP  
OFM  
RLA  
Minimum Circuit Amps  
Maximum Overcurrent Protection  
Outdoor (Condenser) Fan Motor  
Rated Load Amps  
Table 4 — Electric Resistance Heater Data  
NOMINAL  
VOLTAGE  
(3 Ph, 60 Hz)  
ELECTRIC  
HEAT kW  
(Unit Total)  
UNIT  
50ME  
HEATING ELEMENTS  
PER ZONE MODULE  
FLA PER  
HEATING ELEMENT  
MCA  
(Each Circuit)  
MOCP  
(Each Circuit)  
43/ 53  
57/ 70  
87/106  
2
2
3
13.0/14.4  
17.3/19.2  
17.3/19.2  
150/166  
200/221  
150/166  
175/175  
225/225  
175/175  
208/230  
016,024  
53  
70  
2
2
3
7.2  
9.6  
9.6  
83  
111  
166  
90  
125  
175  
460  
575  
106  
106  
3
7.7  
133  
150  
54/ 66  
72/ 88  
108/132  
2
2
3
13.0/14.4  
17.3/19.2  
17.3/19.2  
188/207  
250/276  
188/207  
200/225  
275/300  
200/225  
208/230  
028,030  
034,040  
66  
88  
2
2
3
7.2  
9.6  
9.6  
103  
138  
207  
110  
150  
225  
460  
575  
132  
132  
3
7.7  
166  
175  
65/ 79  
87/106  
129/158  
2
2
3
13.0/14.4  
17.3/19.2  
17.3/19.2  
225/249  
150/165  
225/249  
250/250  
175/175  
250/250  
208/230  
79  
106  
158  
2
2
3
7.2  
9.6  
9.6  
124  
166  
249  
125  
175  
250  
460  
575  
158  
3
7.7  
199  
200  
LEGEND  
NOTES:  
1. Heaters are rated at 230 v, 460 v, and 575 v.  
2. Terminal boards provided for heater power wire connections are  
suitable for use with copper or aluminum wire.  
FLA  
—
—
—
Full Load Amps  
MCA  
Minimum Circuit Amps  
MOCP  
Maximum Overcurrent Protection  
12  
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Table 5 — Unit 50ME Electrical Application Data  
MCA  
UNIT  
50ME  
kW  
(Unit  
Total)  
Heating  
Circuit  
NOMINAL  
VOLTAGE  
Unit  
Common  
Feed  
Cooling  
IFM  
Hp  
Size  
016  
1
2
43/ 53  
57/ 70  
87/106  
150.0/165.6  
200.0/220.9  
150.0/165.8  
—
—
184.8/192.6  
216.7/237.6  
316.7/348.3  
208/230  
109.8/109.8  
150.0/165.8  
5
53  
70  
106  
82.9  
110.5  
165.8  
90.9  
117.1  
172.4  
460  
575  
49.5  
39.6  
—
—
106  
132.5  
138.1  
43/ 53  
57/ 70  
87/106  
150.0/160.6  
200.0/220.9  
150.0/165.8  
—
—
213.0/220.8  
238.0/248.5  
342.2/359.0  
208/230  
138.0/138.0  
150.0/165.8  
024  
028  
030  
7.5  
10  
10  
15  
20  
15  
20  
53  
70  
82.9  
110.5  
165.8  
103.4  
121.5  
176.8  
460  
575  
61.9  
49.2  
—
106  
106  
132.5  
—
141.5  
54/ 66  
72/ 88  
108/132  
188.0/207.1  
250.0/276.1  
188.0/207.1  
—
—
262.9/272.5  
293.9/307.0  
419.6/445.0  
208/230  
168.9  
188.0/207.1  
66  
88  
132  
102.8  
138.0  
207.1  
127.2  
151.0  
220.1  
460  
575  
75.8  
60.2  
—
—
132  
165.6  
176.1  
54/ 66  
72/ 88  
108/132  
188.0/207.1  
250.0/276.1  
188.0/207.1  
—
—
282.0/291.6  
313.0/326.0  
438.7/464.0  
208/230  
188.0  
188.0/207.1  
66  
88  
132  
102.8  
138.0  
207.1  
135.9  
153.5  
222.6  
460  
575  
84.5  
67.3  
—
—
132  
165.6  
177.7  
65/ 79  
87/106  
129/158  
225.0/248.5  
150.0/165.6  
225.0/248.5  
—
323.3/335.1  
360.8/376.4  
510.9/543.2  
208/230  
210.8  
150.0/165.1  
225.0/248.5  
79  
106  
158  
124.3  
165.1  
248.5  
156.7  
185.4  
268.3  
460  
575  
94.5  
75.6  
—
—
158  
198.8  
214.8  
034  
65/ 79  
87/106  
129/158  
225.0/248.5  
150.0/165.1  
225.0/248.5  
—
337.1/348.9  
374.6/391.2  
524.6/558.0  
208/230  
224.6  
150.0/165.1  
225.0/248.5  
79  
106  
158  
124.3  
165.6  
248.5  
162.7  
192.2  
275.1  
460  
575  
100.5  
80.6  
—
—
158  
198.8  
220.1  
65/ 79  
87/106  
129/158  
225.0/248.5  
150.0/165.1  
225.0/248.5  
—
360.2/372.0  
397.7/412.8  
547.7/579.0  
208/230  
247.7  
150.0/165.1  
225.0/248.5  
79  
106  
158  
124.3  
165.6  
248.5  
178.9  
199.5  
282.4  
460  
575  
116.7  
95.0  
—
—
158  
198.8  
227.5  
040  
65/ 79  
87/106  
129/158  
225.0/248.5  
150.0/165.1  
225.0/248.5  
—
374.0/385.8  
411.5/426.6  
561.5/592.8  
208/230  
261.5  
150.0/165.1  
225.0/248.5  
79  
106  
158  
124.3  
165.6  
248.5  
148.9  
205.5  
288.4  
460  
575  
122.7  
100.0  
—
—
158  
198.8  
232.5  
LEGEND  
IFM  
MCA  
—
—
Indoor (Evaporator) Fan Motor  
Minimum Circuit Amps  
13  
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quick-connect type multiplexing terminals. This prevents over-  
loading the nest control transformers. Factory-supplied jump-  
ers with quick-connect terminals are shipped in the zone con-  
trol and thermostat panel compartment.  
Under no circumstances shall the transformer power from  
one Class II circuit be interconnected with any other circuit.  
Field Control Wiring  
ZONE THERMOSTATS — Install a Carrier approved ac-  
cessory zone thermostat assembly in each zone according to  
installation instructions included in the accessory. Locate each  
thermostat assembly in the space where it will sense average  
zone temperature.  
Thermostat heat anticipator settings are indicated for each  
permitted zone module connection arrangement illustrated  
in Fig. 11-28.  
To Join Modules of the Same Nest Into the Same Zone (i.e.,  
modules no. 1 and 2) — Install field-supplied jumpers on  
thermostat connections (screw terminals) Y to Y and W2 to  
W2 as shown in Fig. 11. Connect thermostat wires to ter-  
minal connections of first module in zone (for consistency).  
Two-stage cooling may be obtained in this example as shown  
in Fig. 12 (using a 2-stage thermostat).  
Route thermostat cable or equivalent single leads of no.  
18 AWG (American Wire Gage) colored wire from thermo-  
stat subbase terminals through opening on base unit  
(Fig. 1, 2, 4, and 5) to low-voltage thermostat connections  
on zone control board (Fig. 10). Use no. 16 AWG wire for  
lengths exceeding 50 ft.  
ZONE MODULE CONNECTIONS — Any module may be  
controlled independently or jointly with another module or  
modules. Modules are combined into nests that form indi-  
vidual Class II circuits (40 va) as follows:  
To Join Modules Not of the Same Nest Into the Same Zone  
(i.e., modules no. 2 and 3) — Install the factory-supplied jump-  
ers on quick-connect terminals 6 to 1, 7 to 2, and 8 to 3 as  
shown in Fig. 13. Note that module no. 1 is independently  
controlled by its own thermostat (in Fig. 13).  
Modules no. 1 and 2, 3 and 4, 5 and 6, 7 and 8, 9 and 10  
(028-040 units), 11 and 12 (034,040 units).  
The control signal can be transferred from one nest  
to another nest by using factory-supplied jumpers on  
LEGEND  
AFS  
CR  
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
Airflow Switch  
Control Relay  
ECR  
ECT  
GV  
Economizer Relay  
Economizer Outdoor-Air Thermostat  
Gas Valve (not used on 50ME units)  
Heater Contactor  
Heater Relay  
HC  
HR  
IFC  
Indoor (Evaporator) Fan Contactor  
Liquid Line Solenoid  
Master Cooling  
LLS  
MC  
MCR  
MH  
Master Cooling Relay  
Master Heating  
MHR  
MU  
Master Heating Relay  
Master Unit  
MUR  
NC  
Master Unit Relay  
Normally Closed  
NO  
Normally Open  
NS  
Night Setback  
SW  
Switch  
TRAN  
Transformer  
Quick-Connect Type Terminals (for multiplexing)  
Screw-Type Terminals  
NOTE: Twelve-zone unit shown. Eight-zone units have modules  
1-8 only. Ten-zone units have modules 1-10 only.  
Fig. 10 — Zone Control Board Component Location  
14  
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Fig. 10 — Zone Control Board Component Location (cont)  
15  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1 and 2  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1 and 2  
2. Set heat anticipator (HA1) at .26.  
Screw Terminal  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 11 — 48MA; One-Stage Heat, One-Stage Cool — 2 Nested Modules, Joint Zone Control  
16  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1 and 2  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1 and 2  
2. Set heat anticipator (HA1) at .26.  
Screw Terminal  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 12 — 48MA; One-Stage Heat, Two-Stage Cool — 2 Nested Modules, Joint Zone Control  
17  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, and 3  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, and 3  
2. Set heat anticipators (HA1) at .13.  
Screw Terminal  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 13 — 48MA; One-Stage Heat, One-Stage Cool — One Independent Module, 2 Joint Modules Zone Control  
18  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, and 3  
Stage 2 — Second stage of modules 2 and 3  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, and 3  
Screw Terminal  
2. Set heat anticipators (HA1) at .13.  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 14 — 48MA; One-Stage Heat, One-Stage Cool; One-Stage Heat, Two-Stage Cool Combination  
19  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, 3, and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
2. Set heat anticipator (HA1) at .26.  
Screw Terminal  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 15 — 48MA; One-Stage Heat, One-Stage Cool — 4 Module Joint Zone Control  
20  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, 3, and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
2. Set heat anticipators (HA1) at .13.  
Screw Terminal  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 16 — 48MA; One-Stage Heat, One-Stage Cool — One Independent Module, 3 Joint Modules Zone Control  
21  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — Modules 1 and 3  
Stage 2 — Modules 2 and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
Screw Terminal  
2. Set heat anticipator (HA1) at .26.  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 17 — 48MA; One-Stage Heat, Two-Stage Cool — 4 Module Joint Zone Control  
22  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — Module 3  
Stage 2 — Module 2 and 4  
If thermostat wires are interchanged, the reverse may be  
obtained.  
TH  
TRAN  
HEATING  
Screw Terminal  
Stage 1 — First stage of modules 2, 3, and 4  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
2. Set heat anticipator (HA1) at .13.  
Field Wiring  
Fig. 18 — 48MA; One-Stage Heat, Two-Stage Cool — 3 Module Joint Zone Control  
23  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, 3, and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
2. Set heat anticipators (HA1) as follows:  
Screw Terminal  
MODULE(S)  
SETTING  
.26  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
1, 3  
2
.13  
4
.13  
Field Wiring  
Fig. 19 — 48MA; One-Stage Heat, One-Stage Cool — 2 Independent Modules, 2 Joint Modules Zone Control  
24  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1 and 2  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1 and 2  
Stage 2 — Second stage of modules 1 and 2  
Screw Terminal  
2. Set heat anticipator 1 (HA1) at .26, and set heat anticipator 2 (HA2)  
at 1.14.  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 20 — 50ME; Two-Stage Heat, One-Stage Cool — 2 Modules, Joint Zone Control  
25  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1 and 2  
Stage 2 — Second stage of modules 1 and 2  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1 and 2  
Stage 2 — Second stage of modules 1 and 2  
Screw Terminal  
2. Set heat anticipator 1 (HA1) at .26, and set heat anticipator 2 (HA2)  
at 1.14.  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 21 — 50ME; Two-Stage Heat, Two-Stage Cool — 2 Modules, Joint Zone Control  
26  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, and 3  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, and 3  
Stage 2 — Second stage of modules 1, 2, and 3  
Screw Terminal  
2. Set heat anticipator 1 (HA1) at .13, and set heat anticipator 2 (HA2)  
at .57 (both thermostats).  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 22 — 50ME; Two-Stage Heat, One-Stage Cool — One Independent Module, 2 Joint Modules Zone Control  
27  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, and 3  
Stage 2 — Second stage of modules 2 and 3  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, and 3  
Stage 2 — Second stage of modules 1, 2, and 3  
Screw Terminal  
2. Set heat anticipator 1 (HA1) at .13, and set heat anticipator 2 (HA2)  
at .57 (both thermostats).  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 23 — 50ME; Two-Stage Heat, One-Stage Cool; Two-Stage Heat, Two-Stage Cool Combination  
28  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, 3, and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
Stage 2 — Second stage of modules 1, 2, 3, and 4  
Screw Terminal  
2. Set heat anticipator 1 (HA1) at .26, and set heat anticipator 2 (HA2)  
at 1.14.  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 24 — 50ME; Two-Stage Heat, One-Stage Cool — 4 Module Joint Control  
29  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, 3, and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
Stage 2 — Second stage of modules 1, 2, 3, and 4  
Screw Terminal  
2. Set heat anticipator 1 (HA1) at .13, and set heat anticipator 2 (HA2)  
at .57 (both thermostats).  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 25 — 50ME; Two-Stage Heat, One-Stage Cool — One Independent Module, 3 Joint Modules Zone Control  
30  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — Modules 1 and 3  
Stage 2 — Modules 2 and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
Stage 2 — Second stage of modules 1, 2, 3, and 4  
Screw Terminal  
2. Set heat anticipator 1 (HA1) at .26, and set heat anticipator 2 (HA2)  
at 1.14.  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
Field Wiring  
Fig. 26 — 50ME; Two-Stage Heat, Two-Stage Cool — 4 Module Joint Zone Control  
31  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — Module 3  
Stage 2 — Module 2 and 4  
If thermostat wires are interchanged, the reverse may be  
obtained.  
TH  
TRAN  
HEATING  
Screw Terminal  
Stage 1 — First stage of modules 2, 3, and 4  
Stage 2 — Second stage of modules 2, 3, and 4  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
2. Set heat anticipator 1 (HA1) at .13, and set heat anticipator 2 (HA2)  
at .57.  
Field Wiring  
Fig. 27 — 50ME; Two-Stage Heat, Two-Stage Cool — 3 Module Joint Zone Control  
32  
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LEGEND  
*One for each module.  
C
—
—
—
—
—
—
—
—
Contactor  
NOTES:  
CR  
GV  
HA  
HR  
TC  
Control Relay  
Gas Valve  
1. COOLING  
Heat Anticipator  
Heating Relay  
Thermostat, Cooling  
Thermostat, Heating  
Transformer  
Stage 1 — First stage of modules 1, 2, 3, and 4  
HEATING  
TH  
TRAN  
Stage 1 — First stage of modules 1, 2, 3, and 4  
Stage 2 — Second stage of modules 1, 2, 3, and 4  
Screw Terminal  
2. Set heat anticipators as follows:  
Quick-Connect Terminal  
Factory Control Wires  
Printed Circuit  
SETTING  
MODULE(S)  
HA1  
.26  
HA2  
1, 3  
2, 4  
1.14  
.57  
Field Wiring  
.13  
Fig. 28 — 50ME; Two-Stage Heat, One-Stage Cool — 2 Independent Modules, 2 Joint Modules Zone Control  
33  
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ACCESSORY REMOTE CONTROL PANEL — This central-  
station control can be set to override zone thermostat mode  
settings to lock out heating or cooling for the entire unit. The  
DAY/NIGHT switch and damper position knob provide in-  
space, central control of damper position. Panel also houses  
the filter light to indicate reduced airflow and need for clean  
filters. See Fig. 29. Install remote control panel in accor-  
dance with instructions shipped with this accessory.  
START-UP  
After unit is installed, perform the following checks and  
procedures, and complete Start-Up Checklist on page CL-1.  
Evaporator Fan — Fan belt and pulley are shipped at-  
tached to fan assembly. The factory-installed pulley pro-  
vides fan speeds as shown in Table 1. Adjust fan belt(s) as  
described in Evaporator Fans and Motor section on page 41.  
Also see Zone Airflow Adjustment section on page 38.  
Reheat Humidity Control — Control is achieved in  
any module by wiring a humidistat in parallel with the cool-  
ing thermostat. If zone thermostat drops below setting of heat-  
ing thermostat because the humidistat is closed (cooling coil  
is energized), the heating mode will be energized to reheat  
the air in order to maintain zone space temperature. A typi-  
cal humidistat hookup is shown in Fig. 30.  
Compressor Rail Shipping Bolts — Loosen ship-  
ping bolts beneath compressor rails so that rails float freely.  
Do not loosen or remove bolts that attach compressors to  
rails.  
Refrigerant Valves — Open compressor discharge serv-  
ice valve. Check that the suction service, hot gas shutoff,  
and the liquid line shutoff valves are also open. See Fig. 31.  
Optional Economizer — Adjust optional economizer  
as described in Optional Economizer section on page 42.  
Zone Module Gas Valves (48MA) — Each zone mod-  
ule has its own combination gas valve and pressure regula-  
tor to which gas is supplied by one of the 2 main manual gas  
valves (Fig. 32).  
Optional Exhaust Damper — Adjust optional ex-  
haust damper as described in Optional Exhaust Damper sec-  
tion on page 42.  
LEGEND  
APS  
MCR  
MHR  
MUR  
NC  
—
—
—
—
—
—
Air Pressure Switch  
Master Cooling Relay  
Master Heating Relay  
Master Unit Relay  
Normally Closed  
Terminal (Circuit Board,  
Field or Accessory Conn.)  
Accessory or Field Wiring  
Factory Wiring  
OR  
NO  
Normally Open  
Circuit Board Run  
Fig. 29 — Remote Control Panel Accessory Connections  
34  
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The heating thermostat energizes a 115-v solenoid by means  
of a gas valve relay and the pilot lights. The main burner  
comes on after the pilot is proven.  
The safety switches (airflow switches 1 and 2, pilot flame  
sensor, door switch, and limit switches) are in series with  
the gas valve.  
Gas Heat Lighting Procedure (48MA)  
1. Purge gas supply line of air. Make sure unit main manual  
and zone module gas valves have been off for 5 minutes  
before proceeding.  
2. Set each zone thermostat to the lowest setting.  
3. Turn zone module and main manual gas valves to ON  
position, and secure door of burner compartment.  
4. Turn on unit main power supply. Set control circuit serv-  
ice switch in condensing control box at ON position. Evapo-  
rator fan will be energized.  
5. Set zone thermostat to call for heat. Pilot will light. The  
main burner will come on after the pilot is proven.  
NOTE: A time-delay relay will shut unit down in 180 sec-  
onds if main manual gas valve is not open.  
LEGEND  
TO SHUT OFF GAS HEAT — Set control circuit service  
switch at OFF position. Shut off unit power supply only if  
necessary. Remove heating controls compartment access door.  
Shut off main manual gas valves and pilot manual gas valves.  
HA  
HU  
TC  
TH  
—
—
—
—
Heat Anticipator  
Humidistat  
Screw Terminal  
Printed Circuit  
Factory Control Wires  
Field Wiring  
Thermostat, Cooling  
Thermostat, Heating  
Intermittent Pilots (48MA) — Pilot flame should be  
approximately 1 to 11⁄2 in. high.  
Fig. 30 — Humidistat Connections  
ADJUSTMENT  
1. Turn system switch to OFF position.  
2. If intending to adjust every zone, disconnect main gas  
valve wires from terminal W on pilot switches in each  
zone.  
LEGEND  
CCP  
DLT  
—
—
—
—
—
—
—
—
Capacity Control Pressure Switch  
Discharge Line Thermostat  
Fan Cycling Pressure Switch  
Fusible Plug  
LPS  
OFM  
TXV  
—
—
—
Low-Pressure Switch  
Outdoor (Condenser) Fan Motor  
Thermostatic Expansion Valve  
FCPS  
FP  
Hand Valve  
Auto. Valve  
Capilliary  
HGBP  
HPS  
IFM  
Hot Gas Bypass  
High-Pressure Switch  
Indoor (Evaporator) Fan Motor  
Liquid Line Solenoid  
LLS  
Fig. 31 — Refrigerant Piping Schematic (10-Zone Unit Shown — 8- and 12-Zone Units Similar)  
35  
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LEGEND  
GV  
—
—
—
—
Gas Valve (Zone Module)  
Main Burner  
Main Manual Gas Valve  
Pilot Burner  
NOTE: Unit is equipped with a forced-draft blower and the following safety de-  
vices: forced-draft airflow switch, flame roll-out protection switch, combustion  
chamber access door switch, heating limit switches, and spark-ignited auto-  
matic pilots. All of these switches are located in the heating section and must  
be in safe condition before the main burners can ignite.  
MB  
MGV  
PB  
Fig. 32 — Gas Piping Schematic (10-Zone 48MA Unit Shown — 8- and 12-Zone Units Similar)  
3. Turn system switch to ON position. Set each zone ther-  
mostat at setting to call for heat. Pilot will ignite.  
10. Remove burner access panel. Disconnect gage line con-  
nection on zone manifold. Replace plug in manifold pres-  
sure tap.  
NOTE: A time-delay relay will shut unit down in 180 sec-  
onds if main manual gas valve is not open.  
11. Repeat steps 3-10 for each heating module.  
12. Replace all unit panels. Turn control circuit service switch  
to ON position, and set zone thermostat as desired.  
4. Remove burner access panel.  
5. Remove screw-cap cover on zone gas valve to expose pi-  
lot adjusting screw. With a small screwdriver, turn ad-  
justing screw until flame is correct height. Replace screw-  
cap cover on gas valve.  
6. Turn system switch to OFF position.  
7. Reconnect main gas valve wires to W1 on pilot switches.  
8. Set system switch at ON position, and set zone thermo-  
stats as desired.  
9. Replace burner access panel.  
Main Burner Adjustment (48MA) — Flame should  
appear clear blue (almost transparent) in color with a well-  
defined inner cone. If there is insufficient primary air, flame  
will be yellow tipped. If there is too much primary air, flame  
will be well defined but have a tendency to lift or dance off  
ports. Allow unit to operate for at least 15 minutes before  
making final primary air adjustment.  
ORIFICE ALIGNMENT — The most likely cause of burner  
flame flashback is misalignment of the burner orifice. Be sure  
that orifice points straight down the burner.  
PRESSURE ADJUSTMENT (NATURAL GAS)  
1. Turn control circuit service switch to OFF position, and  
set thermostat at lowest setting.  
2. Remove the 2 heating control access panels and the burner  
access panel.  
PRIMARY AIR ADJUSTMENT — Observe flame charac-  
teristics through view ports in main burner access panel. Turn  
off main manual gas valves in burner control compartment.  
Then remove main burner access panel.  
If Flame Is Yellow (Insufficient Primary Air) — Turn spoiler  
screw counterclockwise about 4 turns for each1⁄4 in. of change  
in spoiler length. See Fig. 33 for spoiler screw location.  
3. Remove plug from zone manifold pressure tap. Connect  
suitable gage. Route gage line through pilot switch grom-  
met so that burner access panel may be closed.  
If Flame Lifted Off Ports (Too Much Primary Air) — Turn  
spoiler screw clockwise about 4 turns for each1⁄4 in. of change  
in spoiler length. See Fig. 33 for spoiler screw location.  
Replace main burner access panel and turn on main manual  
gas valves. Observe flame characteristics. Repeat these pro-  
cedures as required until correct flame characteristics are  
achieved.  
4. Close burner access panel.  
5. Turn control circuit service switch to ON position. Set  
zone thermostat to call for heat. After pilot is proven,  
burner will operate.  
NOTE: A time-delay relay will shut unit down in  
180 seconds if main manual gas valve is not open.  
6. Remove screw cap from zone module gas valve pres-  
sure regulator to expose pressure adjustment screw.  
Outdoor-Air Thermostat Adjustment (50ME with  
Electric Heat) — The outdoor-air thermostat (OAT) is  
located in upper right-hand area of zone control board  
(Fig. 34 and 35), is factory set at 40 F, and is adjustable be-  
tween −10 F and 55 F.  
7. Turn pressure adjustment screw with a small screw-  
driver until 3.5 in. wg is achieved.  
8. Replace screw cap.  
9. Turn control circuit service switch to OFF position and  
set zone thermostat at lowest position.  
36  
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Fig. 33 — Spoiler Screw Location  
LEGEND  
COMPR  
COND  
—
—
Compressor  
Condensing  
*AFS1 deenergizes control circuit if loss of indoor air occurs.  
†Factory-supplied option.  
Fig. 34 — Major Component Identification (Typical 10-Zone Unit Shown; 8-Zone Units Similar)  
37  
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HTR  
—
Heater  
*AFS1 deenergizes control circuit if loss of outdoor air occurs.  
†Factory-supplied option.  
Fig. 35 — Major Component Identification (Typical 12-Zone Unit Shown).  
When OAT is open, final stage heating element in all zone  
modules is inactive. When OAT is closed, final stage heating  
element in a zone module may be energized whenever second-  
stage thermostat for that zone module calls for heat as  
follows:  
Be sure that temperature rise is within range shown on  
unit instruction plate and Table 1 (48MA only).  
Sequence of Operation — When unit power is on  
and no zone thermostat is calling for cooling or heating, the  
evaporator fan and crankcase heater(s) are on. The outdoor-  
air dampers are at the pre-set position.  
UNITS WITH 2-ELEMENT HEATERS  
First-Stage Heat — One element energized  
Second-Stage Heat  
OAT Open — One element energized  
OAT Closed — Two elements energized  
UNITS WITH 3-ELEMENT HEATERS  
First-Stage Heat — One element energized  
Second-Stage Heat  
OAT Open — Two elements energized  
OAT Closed — Three elements energized  
COOLING — On a call for cooling from a zone thermostat,  
compressor no. 1, with unloader(s), starts; the liquid line so-  
lenoid for that zone evaporator coil opens; and condenser-  
fan motor no. 1 starts. Compressor will load or unload in  
response to suction pressure as required. As additional cool-  
ing is required (i.e., more zones call for cooling), compres-  
sor no. 2 (no unloaders) will be energized (024-040 units  
only). If required, compressor no. 1 will unload when com-  
pressor no. 2 (024-040 units only) is energized. As cooling  
requirements decrease, capacity control pressurestats pre-  
vent compressor no. 1 from shutting down while compres-  
sor no. 2 (024-040 units only) is in operation. Compressor  
no. 1 will fully load up after compressor no. 2 (024-040 units  
only) shuts down as required to match heat load.  
If heat load is not sufficient to maintain operation of com-  
pressor no. 1 in an unloaded condition, hot gas bypass valve  
will meter hot gas to outdoor air evaporator coil to supply  
additional load. On 48MA and 50ME040, hot gas is intro-  
duced into evaporator whenever required to eliminate un-  
loader short-cycle operation.  
Optional Glycol Heating Coils — Start up glycol  
solution supply system in accordance with equipment manu-  
facturer’s instructions. Solution supply temperature must not  
exceed 200 F. Maximum solution flow through each zone  
module heating coil is 6 gpm.  
Zone Airflow Adjustment — Adjust each zone duct  
balancing damper to provide required airflow to each zone.  
Increasing or decreasing airflow to one zone may cause a  
change in the airflow to other zones. After initial damper  
settings have been made, repeat the adjustment procedure,  
as required, to be sure final desired airflows are achieved.  
Do not go below 600 cfm or above 1200 cfm per zone  
module.  
The Motormaster௡ head pressure control device will vary  
speed of condenser-fan motor no. 1 to regulate airflow across  
condenser coil. As required, condenser-fan motor no. 2  
(no. 2 and 3 on 3-fan units) will cycle on and off in response  
to head pressure via a cycling pressurestat. See Head Pres-  
sure Control section on page 40.  
38  
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HEATING (48MA) — On call for heating from a zone, the  
forced draft blower will start and the pilot will light. The  
zone burner will ignite after the pilot has been proven. (Ap-  
proximately 60 seconds.)  
NOTE: A time-delay relay will shut unit down in 180 sec-  
onds if the unit main gas valve is not open.  
OUTDOOR-AIR INLET SCREENS — Clean with steam or  
hot water and mild detergent.  
GAS HEATING SECTION — Inspect burners and heat ex-  
changers before each heating season. Remove exhaust grilles  
to inspect heat exchangers. Clean with wire brush if there is  
any accumulation of debris. The main burners should also  
be cleaned if there is any accumulation of debris. Fire each  
zone to be assured of proper operation. Correct pilot height  
is 1 to 11⁄2 inches.  
HEATING (50ME WITH ELECTRIC HEAT) — On a call  
for heating from a zone, the first-stage heating relay, con-  
tactor, and heating element are energized. Upon additional  
calls for heating from that zone, stage 2 is energized in a  
similar manner. However, second element on 2-element heater  
assemblies and second and third heating elements on 3-element  
heater assemblies are energized as described in Outdoor Air  
Thermostat Adjustment section on page 36.  
COMBUSTION AIR FAN — Inspect blower wheel for dirt,  
and remove and clean if necessary.  
Airflow Switches  
INDOOR AIRFLOW SWITCH (AFS1) — This switch is  
located in evaporator fan inlet venturi. This switch will shut  
down unit if airflow through zone modules is insufficient.  
COMBUSTIONAIRFLOW SWITCH (AFS2) — This switch  
(48MAonly) is located in combustion air plenum. This switch  
will shut down unit heating mode if combustion air is in-  
sufficient. See Forced-Draft Blower (48MA) section on  
page 42 for details on combustion air shutter adjustment.  
Heating Lockout (50ME with Electric Heat) — If any zone  
module is operating on mechanical cooling (Compressor[s]  
is operating), one heating element in each zone module is  
locked out and zone module cannot be energized. Operation  
of lockout circuit is independent of outdoor-air thermostat  
operation.  
HEATING (50ME WITH GLYCOL HEATING COILS) —  
On a call for heating from a zone, the heating relay and heat-  
ing coil solenoid valve for that zone are energized. If 2 or  
more unit zone modules are joined to serve a common zone,  
stage 2 of heating thermostat operates remaining heating  
relays and solenoid valves depending on connection  
arrangement.  
OUTDOOR-AIR DAMPER — This control regulates the  
amount of outdoor air that passes through the outdoor air  
evaporator coil and enters the return air-stream (Fig. 34 and  
35). A knob in the zone control and thermostat panel acti-  
vates the damper control motor (damper operator). Damper  
may be fully closed, fully open, or set at any intermediate  
position by setting the knob as desired. In the fully open po-  
sition, the damper will permit 25% outdoor air and 75% re-  
turn air into the unit.  
Service Switch — A control circuit service switch is  
located in the power and condensing control box (Fig. 34  
and 35). Shut down unit (compressors, fans, and control cir-  
cuits) at this switch.  
Do not use compressor circuit breakers to start and stop  
compressors except in emergency.  
Time Guardா Control Circuit — Each compressor  
circuit has a 5-minute delay before restarting compressor af-  
ter shutdown for any reason. On starting, Time Guard device  
timer causes a delay of 15 seconds after thermostat closes  
before compressor starts. On compressor shutdown, timer re-  
cycles for 4 minutes, 45 seconds. During this time, compres-  
sor cannot restart.  
On 2-compressor units, no. 2 compressor will not start for  
at least 21⁄2 minutes after no. 1 compressor starts. See  
Capacity Control Pressure Switches section below.  
SERVICE  
Cabinet Panels and Grilles  
Capacity Control Pressure Switches (CCP)  
SIDE PANELS — To remove a panel, remove lower screw  
on T-fastener. Loosen T-fastener pivot screw. Swing aside  
T-fastener. Pull bottom of panel out and down.  
TOP PANELS — Remove end caps from each end of rain  
covers. Remove panel screws and lift off panels as required.  
Save end caps and screws for reinstallation.  
(2-Compressor Units Only) — These switches are  
connected to the suction side of the system on compressor  
no. 2. Approximately 21⁄2 minutes after compressor no. 2 starts,  
the timer makes the circuit to CCP1 and CCP2 to operate  
compressor no. 2 as follows:  
1. CCP1 is open (opens at 63 psig; closes at 83 psig). This  
prevents cycling of compressor no. 2 at start-up.  
HEATERACCESS PANELS — See Side Panels section above.  
2. CCP2 is closed (opens at 54 psig; closes at 78 psig).  
3. Holding relay no. 2 (HR2) is deenergized.  
When the suction pressure reaches 83 psig, CCP1 closes  
to energize HR2 and compressor no. 2. Compressor no. 2  
will then be operated by CCP2.  
Cleaning — Inspect unit interior at the beginning of each  
heating and cooling season and during each season as op-  
erating conditions require. Remove unit side panels and top  
panels to expose unit interior as required.  
EVAPORATOR COILS (ZONE COOLING COILS) AND  
GLYCOL HEATING COILS — Clean with a stiff brush,  
vacuum cleaner, or compressed air.  
CONDENSER AND OUTDOOR-AIR COOLING COILS  
— Clean with a stiff brush or vacuum cleaner. If cleaning  
with compressed air or low-pressure water or steam, guard  
against damaging compressor, wiring, and nearby controls.  
CONDENSATE DRAINS — Check and clean annually at  
start of cooling season.  
INDOOR-AIR FILTERS — Clean or replace filters at start  
of each heating and cooling season and as often as necessary  
during each season, depending on operating conditions. Re-  
fer to Table 1 for type and size of filters used. Filter section  
is shown in Fig. 34 and 35. Indoor-air filter tracks will ac-  
cept 2 layers of one-in. thick filters.  
Compressor Oil — Compressors have their own oil sup-  
ply. Compressor crankcases on 2-compressor units are in-  
terconnected. Loss of oil due to a leak in the system should  
be the only reason for adding oil after unit has been in op-  
eration. A sight glass is provided in the crankcase intercon-  
nection line or on the compressor crankcase. Remove end  
panels to gain access to compressors. Sight glass on 06D  
1
2
compressor should be about ⁄3 to ⁄3 full of oil. Sight glass  
1
1
on 06E compressor should be about ⁄8 to ⁄2 full of oil.  
Compressor data is shown in Table 1 and on dataplate at-  
tached to compressor body. Refer to 06D or 06E Compres-  
sor Service Manual for additional compressor service  
information.  
39  
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TO ADD OR REMOVE OIL  
1. Close liquid line and hot gas bypass shutoff valves. See  
Fig. 31.  
2. Pump down compressor and close suction and discharge  
service valves. Recover remaining refrigerant in  
compressor.  
If unit power is shut off for longer than a few hours, make  
sure power is on and that crankcase heater(s) has been on for  
at least 24 hours prior to start-up. This will ensure that re-  
frigerant has been driven out of compressor crankcase(s). To  
prevent start-up during this warm-up period, set control cir-  
cuit service switch at OFF position.  
Refrigerant Charge — Quantity and type of refriger-  
ant is shown on unit nameplate and in Table 1. Add refrig-  
erant as follows:  
NO CHARGE — Evacuate refrigerant system and add re-  
frigerant quantity specified or add 15 lb of refrigerant vapor  
to system and then refer to Low Charge section below.  
3. Add oil through oil filler plug.  
4. To remove oil, remove crankcase oil drain plug, and drain  
only as much oil as is required.  
Compressor Capacity Control Unloader(s)  
(Fig. 36) — Unloader(s) on compressor no. 1 are suction-  
pressure actuated to load or unload compressor at factory  
settings indicated in Table 1. If necessary, unloader(s) may  
be field adjusted or reset as follows:  
CONTROL SET POINT (Cylinder Load Point) — This un-  
loader set point is adjustable from 0 to 85 psig. To adjust,  
turn control set point adjustment nut clockwise to its bottom  
stop. In this position, load point is 85 psig. Turn adjustment  
nut counterclockwise to desired load point. Each full turn  
counterclockwise decreases load point by 7.5 psig.  
LOW CHARGE  
1. Set control circuit service switch at OFF position.  
2. Disconnect evaporator-fan contactor.  
3. Manually close airflow switch (AFS1) on evaporator fan  
housing (Fig. 34 and 35) with a piece of tape.  
4. Remove MH jumper (or master heating relay, MHR, if  
remote control panel accessory is used) from zone con-  
trol board to lock out heating.  
PRESSURE DIFFERENTIAL (Difference Between Cylin-  
der Load and Unload Points) — This unloader set point is  
adjustable from 6 to 22 psig. To adjust, remove differential  
adjustment screw sealing cap to expose pressure differential  
adjustment screw. Turn adjustment screw counterclockwise  
to its backstop position. In this position pressure differential  
is 6 psig. Turn adjustment clockwise to desired pressure dif-  
ferential. Each full turn clockwise increases differential by  
1.5 psig.  
5. Remove all cooling relays (CR) except CR8, from zone  
control board.  
6. Add jumper on terminals R-Y on module 8.  
7. Reset control circuit service switch to ON position.  
8. Operate unit for about 5 minutes.  
9. Add refrigerant vapor at no. 1 compressor suction serv-  
ice valve fitting at a rate of one lb per minute.  
10. Check liquid level in accumulator sight glass. Use ac-  
cumulator no. 1 on 040 units (adjacent to compressor  
no. 1). Add refrigerant until sight glass is 1⁄2 full. If sight  
glass appears clear (no bubbles) but a film of refrigerant  
shows at bottom of sight glass, refrigerant level is be-  
low sight glass. Continue adding refrigerant until sight  
glass is 1⁄2 full. If sight glass appears clear, but bubbles  
can be seen, refrigerant level is above top of glass. Re-  
frigerant system is overcharged. Recover refrigerant un-  
1
til sight glass is ⁄2 full.  
11. When correct refrigerant charge has been achieved, re-  
store unit to normal operation (reverse Steps 2-7).  
12. Be sure airflow switch (AFS1) functions normally and  
control circuit service is set at ON position.  
Head Pressure Control  
MOTORMASTER௡ HEAD PRESSURE CONTROL  
DEVICE — Outdoor (condenser) fan motor no. 1 (OFM1)  
is a 208/230-v motor operated by a Motormaster device ther-  
mistor (a thermally sensitive resistor) located on the con-  
denser coil as shown in Fig. 37. The function of this control  
is to maintain proper saturated condensing temperature at  
low outdoor ambient temperatures. The control does this by  
modulating OFM1 speed in response to the saturated con-  
densing temperature sensed by the thermistor. Control is fac-  
tory set and cannot be adjusted or serviced. However, ther-  
mistor or control may be replaced if necessary.  
FAN CYCLING PRESSURESTAT — Outdoor (condenser)  
fan motor no. 2 (OFM2), and no. 3 on 3-fan units (OFM3)  
is controlled by a nonadjustable pressurestat connected to  
compressor no. 1.  
Fan(s) shuts off at 86 F saturated condensing temperature  
(160 psig), restarts at 118 F (approximately 255 psig).  
Fig. 36 — Compressor Capacity Control  
Unloader  
Crankcase Heater(s) — One heater for each compres-  
sor keeps oil free of refrigerant while compressor is off. Crank-  
case heater(s) is automatically deenergized when the com-  
pressor(s) is in operation.  
40  
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LUBRICATION — Condenser-fan motors have factory-  
lubricated bearings. No relubrication is necessary for the first  
3 to 5 years of continuous operation except in excessively  
dirty outdoor-air applications. After the first relubrication bear-  
ings must be opened, cleaned, and repacked annually with  
light- to medium-duty multi-purpose grease.  
Evaporator Fans and Motor  
Shut off service switch to deenergize evaporator-fan  
motor.  
MOTOR REMOVAL — Disconnect motor power wires at  
conduit connection on unit junction box. Then remove mo-  
tor and conduit assembly from unit.  
FAN SHAFT BEARING REMOVAL  
1. Remove fan motor and belts.  
2. Loosen the locknut on each shaft bearing collar and re-  
move the fan drive pulley.  
3. Loosen the fan wheel locknuts and slide out fan shaft.  
4. Remove the 2 bearings.  
Reverse steps 1-4 to reassemble.  
FAN SPEED ADJUSTMENT — Pulley listed in Table 1 is  
factory installed in the unit.  
If the factory-supplied pulley is not suitable, provide a field-  
supplied pulley of the correct size as required. Refer to  
Table 1 for additional fan data.  
IMPORTANT: Increasing fan speed increases load on  
motor. Do not exceed maximum fan motor full load  
amperage (Tables 2 and 3).  
Fig. 37 — Motormasterா Thermistor  
Locations on Condenser Coil  
Condenser Fans  
Fig. 38 — Condenser-Fan Adjustment  
Shut off service switch to deenergize condenser-fan  
motors.  
ADJUSTMENT — Remove fan guard from top of unit. Re-  
move rubber hubcap from fan hub and loosen fan hub set-  
screws. Adjust fan height using a straight edge laid across  
fan deck venturi (Fig. 38). Tighten setscrews and replace rub-  
ber hubcap to prevent hub from rusting to motor shaft. Fill  
hub recess with Permagum (or similar adhesive) if rubber  
hubcap is missing.  
FAN MOTOR REMOVAL — Disconnect motor electrical  
leads at motor control box. Loosen fan hub setscrews and  
remove fan. Loosen motor mounting band and lift out  
motor.  
Reverse this procedure for reassembly.  
41  
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PULLEY REMOVAL  
1. Shut off unit power.  
2. Loosen fan motor mounting plate and remove belt.  
3. Loosen pulley setscrew.  
4. Slide pulley off shaft.  
Reverse steps 1-4 to install new pulley.  
PULLEYALIGNMENT — Loosen fan pulley setscrews and  
slide fan pulley along fan shaft for parallel alignment. Make  
angular alignment by loosening motor from mounting plate.  
BELT TENSION ADJUSTMENT — Loosen fan motor pivot  
bolts. Pull back motor mounting plate to proper belt tension  
(approximately 3⁄4-in. deflection with one finger) and tighten  
motor pivot bolts.  
LUBRICATION — Evaporator-fan shaft and motor bear-  
ings require annual lubrication after 3 to 5 years of continu-  
ous operation as follows:  
48MA016 AND 024  
48MA028-040  
Fig. 39 — Forced-Draft Blower  
Shutter Position  
DAMPER POSITION — When outdoor-air damper is fully  
open, the return-air damper will be fully closed and vice versa.  
OPERATION  
Heating or Compressor Cooling — Dampers will assume the  
ventilation position indicated by the ventilation control knob.  
If a remote control center is used, DAY/NIGHT switch must  
be at the DAY position.  
Fan Shaft Bearings — Automotive-type grease fittings are  
factory supplied. Apply a medium-duty, lithium-based grease  
to fittings while rotating shaft.  
Fan Motor Bearings — Remove plugs and install automotive-  
type grease fittings. Use a suitable motor bearing grease per  
motor manufacturer’s recommendations.  
If terminals in unit control box labeled SHORT TO CLOSE  
DAMPERS are shorted or if DAY/NIGHT switch is set at  
NIGHT position, outdoor-air damper will close.  
Intermediate Season (Free Cooling Using Optional Econo-  
mizer) — If outdoor-air temperature drops below econo-  
mizer outdoor-air thermostat (ECT) setting, the compressor(s)  
will remain off. The dampers will modulate to maintain the  
mixed-air thermostat (MAT) setting. If the outdoor air tem-  
perature rises above the ECT setting, the unit will operate as  
described in Heating or Compressor Cooling section above.  
Forced-Draft Blower (48MA)  
LUBRICATION — Add 2 or 3 drops of a good grade of  
no. 20 SAE (Society of Automotive Engineers) motor oil at  
each oil cup on the motor once a year.  
AIR SHUTTER ADJUSTMENT — The air shutter is held  
in position on the blower inlet by a wing nut. Loosen wing  
nut and reposition shutter until correct pressure is achieved.  
Combustion chamber air pressure is to be measured through  
drain connection below heat exchangers. Correct pressures  
are 0.10 ± 0.01 in. wg for units 48MA016,024,034, and 040;  
0.14 ± 0.01 for units 48MA028 and 030. Figure 39 shows  
correct shutter position. Note pivot hole location.  
Optional Exhaust Damper — See Fig. 34 and 35.  
When unit is on economizer cycle (free cooling) and an ex-  
haust damper is part of the unit, the exhaust relay is ener-  
gized. The fan motor controls the Motormaster௡ head pres-  
sure control and the fan cycling pressure switches are bypassed  
so that condenser fans operate at full speed as follows:  
Zone Module Transformers — When replacing these  
transformers, be sure to connect wires on correct terminals  
to maintain correct polarity. See base unit label diagram on  
the unit for connections.  
• Fan no. 1 and 2 on units 48MA/50ME016-030  
• Fan no. 2 and 3 on units 48MA/50ME034,040  
When the return air damper is 25% closed, the exhaust  
damper begins to open. The condenser fans pull indoor re-  
turn air through the open exhaust damper and discharge it to  
the outdoors.  
Optional Economizer — See Fig. 40.  
THERMOSTAT SETTINGS — Set economizer outdoor air  
thermostat (ECT) at a temperature which will provide cool-  
ing with outdoor air only. This setting, when achieved, will  
lock out the compressor(s). A 45 F setting is suggested.  
Replacement Parts — A complete list of replacement  
parts may be obtained from any Carrier distributor upon  
request.  
Set mixed-air thermostat (MAT) as desired to provide mixed  
air of the correct temperature. This setting cannot be lower  
than the ECT setting. A 58 F setting is suggested.  
42  
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LEGEND  
1
2
—
—
—
—
—
—
—
—
—
—
Bearing Liner  
Speed Nut (5⁄16 in.)  
Washer  
3
4
Rivet  
5
Speed Nut (7⁄16 in.)  
Speed Nut (1⁄4 in.)  
Damper Lever  
Linkage Bar  
6
7
8
9
Linkage Rod (15 in.)  
Linkage Rod (22 in.)  
10  
Airflow Direction  
Fig. 40 — Economizer and Exhaust Damper Assemblies, Exploded View  
43  
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PACKAGED SERVICE TRAINING  
Our packaged service training programs provide an excellent way to increase your knowledge of the  
equipment discussed in this manual. Product programs cover:  
• Unit Familiarization  
• Installation Overview  
• Maintenance  
• Operating Sequence  
A large selection of product, theory, and skills programs is available. All programs include a video  
cassette and/or slides and a companion booklet. Use these for self teaching or to conduct full training  
sessions.  
For a free Service Training Material Catalog (STM), call 1-800-962-9212. Ordering instructions are  
included.  
Copyright 1996 Carrier Corporation  
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.  
Book 1 PC 111 Catalog No. 564-840 Printed in U.S.A. Form 48MA/50ME-3SI Pg 46 4-96 Replaces: 48MA/50ME-1SI  
Tab 1c 1d  
1
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START-UP CHECKLIST  
MODEL NO.:  
DATE:  
SERIAL NO.:  
TECHNICIAN:  
PRE-START-UP:  
Ⅺ VERIFY THAT ALL PACKING MATERIALS HAVE BEEN REMOVED FROM UNIT  
Ⅺ REMOVE ALL SHIPPING HOLDDOWN BOLTS AND BRACKETS PER INSTRUCTIONS  
Ⅺ VERIFY INSTALLATION OF ECONOMIZER HOOD  
Ⅺ VERIFY THAT CONDENSATE CONNECTION IS INSTALLED PER INSTRUCTIONS  
Ⅺ VERIFY THAT ALL ELECTRICAL CONNECTIONS AND TERMINALS ARE TIGHT  
Ⅺ CHECK GAS PIPING FOR LEAKS (48MA)  
Ⅺ CHECK THAT INDOOR-AIR FILTER IS CLEAN AND IN PLACE  
Ⅺ VERIFY THAT UNIT IS LEVEL  
Ⅺ CHECK FAN WHEEL AND PROPELLER FOR LOCATION IN HOUSING/ORIFICE, AND VERIFY SET SCREW  
IS TIGHT  
Ⅺ VERIFY THAT FAN SHEAVES ARE ALIGNED AND BELTS ARE PROPERLY TENSIONED  
START-UP  
ELECTRICAL  
SUPPLY VOLTAGE L1-L2  
L2-L3  
L3-L1  
COMPRESSOR AMPS — COMPRESSOR NO. 1 L1  
— COMPRESSOR NO. 2 L1  
L2  
L2  
L3  
L3  
SUPPLY FAN AMPS  
EXHAUST FAN AMPS  
ELECTRIC HEAT AMPS (50ME, IF APPLICABLE) L1  
L2  
L3  
TEMPERATURES  
OUTDOOR-AIR TEMPERATURE  
RETURN-AIR TEMPERATURE  
COOLING SUPPLY AIR  
F
F
F
F
DB (Dry-Bulb)  
DB  
F
WB (Wet-Bulb)  
GAS HEAT SUPPLY AIR (48MA)  
ELECTRIC HEAT SUPPLY AIR (50ME, IF APPLICABLE)  
F
PRESSURES  
GAS INLET PRESSURE (48MA)  
IN. WG  
STAGE NO. 1  
STAGE NO. 2  
GAS MANIFOLD PRESSURE (48MA)  
IN. WG  
IN. WG  
REFRIGERANT SUCTION  
CIRCUIT NO. 1  
PSIG  
PSIG  
CIRCUIT NO. 2  
CIRCUIT NO. 2  
PSIG  
PSIG  
REFRIGERANT DISCHARGE CIRCUIT NO. 1  
Ⅺ VERIFY REFRIGERANT CHARGE  
GENERAL  
Ⅺ ECONOMIZER MINIMUM VENT AND CHANGEOVER SETTINGS TO JOB REQUIREMENTS  
Copyright 1996 Carrier Corporation  
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.  
Book 1 PC 111 Catalog No. 564-840 Printed in U.S.A. Form 48MA/50ME-3SI Pg CL-1 4-96 Replaces: 48MA/50ME-1SI  
Tab 1c 1d  
1
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