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NOTE: Furnace combustion-air and vent pipe connections are sized for 2-in. pipe. Any pipe size change should be made outside furnace casing
in vertical pipe. (See Fig. 35.) This allows proper drainage of vent condensate.
Combustion-air and vent pipes must terminate together in same atmosphere pressure zone, either through roof or sidewall (roof termination
preferred), using accessory termination kit. See Table 5 for required clearances.
Furnace combustion-air and vent pipe connections must be attached as shown in Fig. 37. Combustion-air intake plug fitting and inducer housing
alternate vent cap may need to be relocated in some applications.
NOTE: Slope combustion-air and vent pipes a minimum of 1/4 in. per linear ft with no sags between hangers.
CAUTION: When combustion-air pipe is installed above a suspended ceiling, pipe must be insulated with 3/8-in. thick
Armaflex-type insulation. Combustion-air pipe should also be insulated when it passes through warm, humid space.
An abandoned masonry chimney may be used as a raceway for properly insulated and supported combustion-air and vent pipes. Each furnace must
have its own set of combustion-air and vent pipes and be terminated individually, as shown in Fig. 39, 40, 44 and 45.
Fig. 33—355MAV Variable Speed Furnace Control
A99098
SEC-2
SEC-1
DE
W2 Com
24V
W/W1 Y/Y2 HUMRG
DEHUM
DE CONNECTION
DE CONNECTION
LOCATION
Fig. 34—Thermidistat Connection
A98295
24 VAC HOT
DEHUMIDIFY
24 VAC COMM
RR
Com
DHUM
DEHUM
C
DE
NOTE 1
THERMIDISTAT
VARIABLE-SPEED
CONDENSING
FURNACE
NOTE 1 - Remove DE Connection
To Enable DEHUM Input
—30—