4. Attach twinning reference label 327956-101 on the outside of blower access door of RH furnace
5. Manually close the blower switch.
6. Turn on power and gas to furnaces.
7. Using appropriate section below, operate furnaces through 2 cycles in each mode to confirm correct operation by operating only the
thermostat.
a. Single- or 2-stage gas heating thermostat R-to-W/W1 for low-gas heat. Single-stage thermostat with adaptive heating mode causes
furnace to operate in low-gas-heat mode for up to 16 minutes, and then furnace automatically switches to high-gas heat. First stage of
a 2-stage thermostat without adaptive heating mode causes furnace to operate in low-gas-heat mode indefinitely.
b. First and second-stage of 2-stage heating thermostat R-to-W/W1-and-W2 for high-gas-heat.
c. Thermostat R-to-G for continuous fan or 2-stage cooling low-cool blower.
d. Cooling thermostat R-to-G-and-Y/Y2 for single-speed cooling blower or for 2-stage cooling high-cool blower.
8. Reinstall control doors on both furnaces.
9. Instruct user in operation of furnaces and thermostat.
PROCEDURE 9—SEQUENCE OF OPERATION
See Fig. 13, 14, or 15 and 37 or 38 for condensing furnace twinning connection and schematic wiring diagrams while reviewing sequence of
operation.
Twinning operation is controlled by LH or MAIN furnace. The TEST/TWIN connection wire ensures the 2 furnaces coordinate their blower
operation. When either furnace requires blower operation, both furnace blowers operate at same speed. Both furnaces operate simultaneously in
the same mode: heat, cool, or continuous fan. Exceptions can occur if a safety switch on either furnace is opened by a problem (such as pressure
switch, flame roll-out switch, main limit switch, twinning kit auxiliary limit switch, or flame-proving sensor). In such a case, the other furnace
continues to operate unless open switch is the flame roll-out, main limit, or twinning kit auxiliary limit switch, in which case both furnaces respond.
Before performing component test, disconnect TKR yellow wire labeled TEST from LH furnace control center TEST/TWIN terminal. After
removing yellow wire, component test can be initiated on each furnace individually as stated in Installation, Start-Up, and Operating Instructions.
A.
Fixed Capacity Furnaces
SINGLE-STAGE HEAT, SINGLE STAGE FURNACES WITH SINGLE-STAGE GAS-HEAT THERMOSTAT
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 the sequence of operation.
TWO-STAGE HEAT, SINGLE STAGE FURNACES WITH 2-STAGE GAS-HEAT THERMOSTAT
1. The two-stage thermostat determines if furnaces are operating in first-stage heat (LH furnace operates in heat while RH furnace blower
operates but RH furnace is not heating) or if furnaces are operating in second-stage heat (both furnaces operate in heat), depending on how
many thermostat stages are calling for heat. If two-stage cooling is used, Y1 from the thermostat will initiate both furnace blowers to the
cooling speed and the first A/C unit. Y2 from the thermostat will go directly to the outdoor unit and initiate the second A/C unit.
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 SINGLE-STAGE GAS-HEAT THERMOSTAT
NOTE:
See Section 2, Procedure 2 - Electrical Connections, Step 3 for control board wiring and LHT switch setup.
1. LH furnace control determines whether furnaces are both operating in low-gas heat or high-gas heat, depending on the control’s adaptive
gas heating mode when the R-to-W/W1 circuit is closed in LH furnace.
Fig. 36—Sidewall Termination of More Than 12 in. (Dimension “A” is Touching or 2-in. Maximum Separation)
A96130
COMBUSTION AIR
COMBUSTION AIR
VENT
A
—36—
