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9. Combustion Air Inducer (B6)
All G50UH(X) units use a combustion air inducer to move
air through the burners and heat exchanger during heating
operation. The blower uses a 120VAC motor. The motor
operates during all heating operation and is controlled by
furnace control A92. The inducer also operates for 15 sec-
onds before burner ignition (pre-purge) and for 5 seconds
after the gas valve closes (post-purge).
A proving switch connected to the combustion air inducer ori-
fice plate is used to prove inducer operation. The combus-
tion air inducer orifice will be different for each model. See
table 9 for orifice sizes. The switch monitors air pressure in
the inducer housing. During normal operation, the pressure
in the housing is negative. If pressure becomes less negative
(signifying an obstruction) the proving switch opens. When
the proving switch opens, the furnace control (A92) immedi-
ately closes the gas valve to prevent burner operation.
TABLE 9
G50UH(X) Unit
C.A.I. Orifice Size
24A−045
1 1/4"
24A/36A−070
1 7/16"
48B−070
1 1/2"
36B, 48B−090
1 11/16"
48C, 60C−110 (−1, −2, −3 units)
1 7/8"
48C, 60C−110 (−4, −5 units)
2 5/32"
36C−110
2 5/32"
48C, 60D−135 (−6 and later)
(−1 to −5 units)
2 3/8"
(2 5/32")
60D−155
2.60"
Horizontal Applications
The G50UH(X) furnace can be installed in horizontal ap-
plications.
The combustion air inducer may be rotated clockwise or
counterclockwise by 90° to allow for vertical vent dis-
charge in a horizontal application. Remove the four mount-
ing screws, rotate the assembly (assembly consists of ori-
fice plate, proving switch, gasket and combustion air in-
ducer), then reinstall the mounting screws. See figure 13.
Use the provided wire tie to bundle the pressure switch
wires with the inducer motor power leads.
Route the wires
away from moving parts and the heat of the inducer
motor to prevent damage to the wires.
Use sheet metal
shears to remove the cut out from the side of the cabinet.
See figure 14. Use the two provided sheet metal screws to
install the cut out on the top cap to cover the original flue
outlet opening.
FIGURE 13
Combustion Air Inducer
(Upflow Position)
Mounting Screws
MOUNTING SCREWS
90°
90°
(Remove)
(Remove)
Power Leads
Flue Transition
(Do not remove
)
G50UH−15 and later assembly Shown
Flue Outlet Hole
(
Reattach
Cutout Here)
Supply Air
Opening
Top View of Furnace
Top Cap
Cut out
Optional
Flue Outlet
Optional Flue Outlet
(Horizontal Installation)
FIGURE 14
