SYSTEM OPERATION
13
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 communcations
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
1
2
R
C
R
C
G
W
Y
Dehum
Optional
Optional
Optional if
feature
supported by
thermostat
INDOOR
BOARD TERMINAL
CONNECTIONS
OUTDOOR
BOARD TERMINAL
CONNECTIONS
1
2
R
C
R
C
G
W
Y
Dehum
24 VAC
Thermostat
Figure 38
Communicating Inverter
Air Conditioner or Heat Pump
Low Voltage Wiring - Non-Communicating
Outdoor Unit
When using the furnace with a single stage non-communicating
air conditioner or heat pump use the wiring methods shown.
When using a single stage air conditioner, the thermostat must
be setup for single stage heating and single stage cooling
mode. When using a single stage heat pump, the thermostat
must be setup for dual fuel operation where the reversing
valve is energized in cooling mode (see Non-Communicating
Single Stage Heat Pump wiring diagram). In both cases
airflow must be selected using the tonnage menu where
Airflow = (400 CFM) x (Selected Tonnage). Tonnage values
range from 1 to 6 in 0.1 increments.
