27
Single stage furnaces are not supplied with a built-
in twinning capability. Other valuable features and
enhancements were made to the new control that made it
necessary to remove the twinning capability. For twinning
of single stage furnaces with PSC motors, a twinning kit
(920919) is available for purchase.
If both single stage furnaces are upgraded to the fixed
speed iSEER™ blower, the twin terminal on the blower
control boards (Figure 29) may be used to twin the single
stage furnaces only if the following criteria are met:
• Bothfurnacesandmotorsmustbethesamesize.
• Bothmotorsmustbeonthesamespeedforcooling
and heating.
• Bothfurnacesmusthaveacommonreturnductand
common supply plenum.
• Both furnacesmust be the same phase and on the
same leg of power.
For twinning of single stage furnaces equipped with fixed
speed iSEER™ blowers, refer to
Figure 29 (page 28) and
the following instructions:
Figure 27. Line Voltage Field Wiring
Field Supplied
Disconnect w/in
Sight of Furnace
Field Supplied
Panel Connector
Field Supplied
Fused Service
Panel
Black (Hot)
White (Neutral)
Green or Bare
(Ground)
Black
White
Black
White
Black
White
Field Line Voltage Wiring
Factory Line Voltage Wiring
Ground
Ground
Junction Box (may be int. or ext. to the furnace). These
connections can be made in the field supplied disconnect
at the furnace. NOTE: Connections made within the furnace
burner compartment do not require a junction box.
Ground
FURNACE
MODEL NUMBERS
FURNACE
INPUT
(BTUH)
CABINET
WIDTH
(IN.)
NOMINAL
ELECTRICAL
SUPPLY
MAXIMUM
OPERATING
VOLTAGE
MINIMUM
OPERATING
VOLTAGE
MAXIMUM
FURNACE
AMPERES
MAXIMUM
FUSE OR CIRCUIT
BREAKER AMPS*
(GUH92A & GDD92A)038A3XF 38,000 14 ¼ 115-60-1 127 103 6.6 15
(GUH95A & GDD95A)38B4XF 38,000 17 ½ 115-60-1 127 103 8.2 15
GUH95C054B3XE
54,000 17 ½ 115-60-1 127 103 11.6 15
(GUH92A, GUH95A, GDD92A, GDD95A)54B4XF 54,000 17 ½ 115-60-1 127 103 6.2 15
GUH95C072C5XE
72,000 17 ½ 115-60-1 127 103 11.6 15
(GUH92A & GDD92A)072B4XF 72,000 21 115-60-1 127 103 10.9 15
(GUH92A, GUH95A, GDD92A, GDD95A)072CXF 72,000 21 115-60-1 127 103 8.7 15
GUH95C090C5XE
90,000 21 115-60-1 127 103 15.3 20
(GUH92A, GUH95A, GDD92A, GDD95A)090CXF 90,000 21 115-60-1 127 103 8.7 15
GUH95C108D5XE
108,000 24 ½ 115-60-1 127 103 17.2 20
(GUH92A, GUH95A, GDD92A, GDD95A)108DXF 108,000 24 ½ 115-60-1 127 103 11.7 15
GDD95A118D5XF 118,000 24 ½ 115-60-1 127 103 17.2 20
GUH95C120D5XE
120,000 24 ½ 115-60-1 127 103 17.2 20
(GUH92A, GUH95A, GDD92A, GDD95A)120D5XF 120,000 24 ½ 115-60-1 127 103 11.7 15
THERMOSTAT WIRE GAUGE
RECOMMENDED THERMOSTAT WIRE LENGTH
2 - WIRE - HEATING 4 OR 5 WIRE - COOLING
24 55 ft. 25 ft.
22 90 ft. 45 ft.
20 140 ft. 70 ft.
18 225 ft. 110 ft.
* Time-delay fuses or circuit breakers are required.
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