2. Operation in all modes (sequence of operation) is the same for twinned furnaces as for an individual furnace. See furnace Installation,
Start-Up, and Operating Instructions for more information on sequence of operation.
TWO-STAGE HEAT, TWO STAGE FURNACES WITH 2-STAGE GAS-HEAT THERMOSTAT
NOTE: See Section 2, Procedure 2 - Electrical Connections, Step 3 for control board wiring and LHT switch setup.
1. The 2-stage thermostat (NOT furnace control’s adaptive gas heating mode) determines whether furnaces are both operating in low-gas heat
or high-gas heat, depending on whether 1 or both thermostat stages (W/W1 or W/W1-and-W2) are calling for heat.
2. Operation in all modes (sequence of operation) is the same for twinned furnaces as for an individual furnace. See furnace Installation,
Start-Up, and Operating Instructions for more information on sequence of operation.
Table 5a—Single Stage Heating with Single Stage Thermostat Using 2 Single Stage Furnaces
THERMOSTAT CONNECTIONS CONTROL BOARD CONNECTION ACTION
R R Power from control board to thermostat
W W Starts L/H and R/H furnaces for heating
Table 5b—Single Stage Cooling with Single Stage Thermostat Using 2 Single Stage A/C units
THERMOSTAT CONNECTIONS CONTROL BOARD CONNECTION ACTION
R R Power from control board to thermostat
Y Y/Y2 (Y on standard control board)
Energizes accessory cooling relay(s) to start L/H and R/H A/C
for cooling
G G Starts both indoor fans on cooling speed (With Y/Y2 energized)
Dehum* Dehum*
Reduces airflow in cooling mode from cooling speed to heating
speed when Dehum input is removed
* Dehum is not available on all thermostats or control boards
Table 6a—Two Stage Heating with Two Stage Thermostat Using 2 Single Stage Furnaces
THERMOSTAT CONNECTIONS CONTROL BOARD CONNECTION ACTION
R R Power from control board to thermostat
W1 W Starts L/H furnace for first stage heating
W2 None
Thermostat W2 wired directly to R/H accessory relay to start
R/H Furnace for second stage heating
Table 6b—Two Stage Cooling with Two Stage Thermostat Using 2 Single Stage A/C units
THERMOSTAT CONNECTIONS CONTROL BOARD CONNECTION ACTION
R R Power from control board to thermostat
Y1 Y/Y2 (Y on standard control board)
Energizes accessory cooling relay to start L/H and A/C for first
stage cooling and cooling speed blower
Y2 None
Thermostat Y2 wired directly to R/H accessory relay to start R/H
A/C
G G Starts both indoor fans on cooling speed (With Y/Y2 energized)
Dehum* Dehum*
Reduces airflow in cooling mode from cooling speed to heating
speed when Dehum input is removed
* Dehum is not available on all thermostats or control boards
Table 6c—Continuous Fan Operation
THERMOSTAT CONNECTIONS CONTROL BOARD CONNECTION ACTION
R R Power from control board to thermostat
G G Starts both fans in heating speed*
* Staged Continuous Fan operation is not available
—39—
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