PROCEDURE 4—VENTING
Refer to Installation, Start-Up, and Operating Instructions supplied with each furnace for venting information. Each furnace must always be
individually vented. Do not common-vent or breach-vent condensing furnaces. For direct-vent installations, refer to Fig. 32, 33, 34, 35, or 36 for
proper termination. It is important that vent terminations be made as shown to avoid recirculation of flue gases.
PROCEDURE 5—GAS SUPPLY PIPING
NOTE:
All gas connections must be made through exposed outer side of each furnace. Do not common connect any connection other than supply-
and return-air ducts.
Furnaces are recommended to be provided with a single shutoff valve. However, individual shutoff valves may be required by local codes or
jurisdictions. Refer to Installation, Start-Up, and Operating Instructions provided with each furnace for additional gas supply information.
PROCEDURE 6—CONDENSATE DRAIN CONNECTIONS
The condensate trap is factory installed in blower shelf and factory connected for UPFLOW applications. Install condensate trap extension drain
such that field drain connections are on the left side for LH (MAIN) furnace and on right side for RH (SECONDARY) furnace. (See Fig. 29.)
The condensate trap must be relocated for downflow and horizontal applications.
See furnace Installation, Start-Up, and Operating Instructions for details on attaching field drain for downflow and horizontal applications.
PROCEDURE 7—ELECTRICAL SUPPLY CONNECTIONS
NOTE:
All electrical power connections must be made through exposed outer side of each furnace. Do not common connect any connection other
than supply- and return-air ducts.
1. Each furnace shall be connected to its own 115-vac power supply. The twinning kit installation interconnects the furnaces, allowing them
to operate as a single furnace. The L1 (black) connection to each furnace must be connected to circuit breakers connected to the same service
panel 115-vac phase leg.
On single-phase
(residential) systems, each furnace circuit breaker should be located directly across from each other in service panel, or
each furnace circuit breaker should be located on the same side of service panel, but must skip 1 space to be connected to the same leg of
the 1-phase power supply.
On 3-phase
(commercial) systems, each furnace circuit breaker should be located directly across from each other in service panel, or each
furnace circuit breaker should be located on the same side of service panel, but must skip 2 spaces to be connected to the same leg of the
3-phase power supply.
The proper 115-vac phasing of furnace connections permits 24-vac transformer phasing as described below.
2. Phasing of the connected 24-vac transformer secondary circuits can be determined with the LED status of both furnaces. See furnace
Installation, Start-Up, and Operating Instructions and status code label on blower access panel or main furnace door. The furnaces’
transformers’ black leads should be connected to PR1 connectors and white leads to PR2 connectors on controls. If 1 or both LEDs are
rapidly flashing, disconnect lead at TEST/TWIN terminal of LH furnace and observe LED at each furnace.
IF:
a. Both LEDs are on continuously:
System phasing is okay.
b. One or both LEDs are rapidly flashing:
(1.) Line voltage polarity is reversed.
(2.) Reverse SEC-1 and SEC-2 in furnace with rapid flashing LED.
c. One LED is off, 1 LED is on continuously:
(1.) The 24-vac circuit is inoperative on furnace with LED light off.
(2.) Check transformers, auxiliary limits, and door switches in both furnaces and correct problem.
3. Reconnect lead at TWIN/TEST terminal of LH furnace and observe LED at each furnace. The LEDs will glow steady for proper phasing.
PROCEDURE 8—START-UP AND ADJUSTMENT
NOTE:
Refer to Installation, Start-Up, and Operating Instructions supplied with furnace for detailed information.
1. Shut off all power and gas to both furnaces.
Fig. 32—Rooftop Termination (Dimension “A” is Touching or 2-in. Maximum Separation)
A96128
A
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