SYSTEM OPERATION
29
Low Voltage Wiring - General Information
The Furnace functions with any thermostat that can be
configured to provide 24VAC on Y for cooling calls and 24VAC
on W for Heating calls. Based on these simple inputs, internal
algorithms will decide how to control two stages of furnace
heat in addition to any single or multi stage outdoor heating /
cooling operation (the algorithms will handle dual fuel multi-
stage systems as well). The thermostat must be setup to
provide only a Y call when cooling is required and only a W
call when heating is required. This is generally accomplished
by selecting single stage heat / single stage cool mode during
setup (if setup is required). Do not set thermostat to heat
pump operation as system will not operate properly.
Note: The only exception is if a single stage non-communicating
Heat Pump is connected to the furnace. Refer to Non-
Communicating Single Stage Heat Pump diagram for details.
Thermostat connections to the control board are R, C, G,
W, Y & Dehum. Provided the thermostat does not require a
common wire as few as two thermostat wires may be used
for heat only (R and W) or cool only (R and Y) systems. A
minimum three thermostat wires may be used for heating
and cooling systems (R, W and Y). Refer to thermostat wiring
diagrams below for your system configuration.
Low voltage connections can be made through either the right
or left side panel of the furnace. Thermostat wiring entrance
holes are located in the blower compartment.
Thermostat
Communica
�
ng Outdoor Unit
Condensate
Switch
Figure 35
Main Control Board
For gas heat only operations (no outdoor unit installed) the
thermostat must be setup to provide a single stage W call
when heating is required. See Gas Heat Only wiring diagram
for wiring instructions.
R
C
G
W
Y
Dehum
Optional
Optional
INDOOR
BOARD TERMINAL
CONNECTIONS
R
C
G
W
Y
Dehum
24 VAC
Thermostat
1
2
R
C
Gas Heat Only
Figure 36
Low Voltage Wiring - Communicating Outdoor
Unit
Internal logic will control staging of all multi stage equipment (2
stage AC/HP units and Inverter AC/HP units). The thermostat
is only required to provide a single stage heat / cool call and
fan or dehumidification call during operation.
Two wires are required between the indoor unit and outdoor
unit on the 1 and 2 terminals. It is recommended to install a
separate transformer with all 2 stage outdoor units to reduce
the power draw on the indoor transformer.
4 wires (R,C for power and 1, 2 for communications) can be
used for AC applications. See wiring images for details.
Do not connect R & C between the indoor unit and the
outdoor unit if there is already a transformer installed in
the outdoor unit providing 24VAC to the outdoor control. In
this case, just use 1 and 2 terminals for communications.
R
C
G
W
Y
Dehum
Optional
Optional
Optional if
feature
supported by
thermostat
L1
L2
INDOOR
BOARD TERMINAL
CONNECTIONS
OUTDOOR
BOARD TERMINAL
CONNECTIONS
OUTDOOR
TRANSFORMER
24VAC
240V
GROUND RECOMMENDED
(FIELD PROVIDED)
1
2
R
C
R
C
G
W
Y
Dehum
1
2
R
C
Note:
for 2 Stage Air Conditioners, R & C wires can
be used between the indoor and outdoor units provided
a transformer is not already installed in the outdoor unit.
For 2 stage heat pumps, a transformer is always required
in the outdoor unit (R & C connections cannot be used)
Figure 37
Communicating Two Stage Air Conditioner
or Heat Pump
