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If this unit is being installed in an application with
combustion air coming in from a space serviced by an
exhaust fan, power exhaust fan, or other device which
may create a negative pressure in the space, take care
when sizing the inlet air opening. The inlet air opening
must be sized to accommodate the maximum volume
of exhaust air as well as the maximum volume of
combustion air required for all gas appliances serviced
by this space.
Roof Terminated
Exhaust Pipe
* See Maximum Vent Lengths table
NOTE-The inlet and outlet air openings shall each have a
free area of at least one square inch per 4,000 Btu (645mm
per 1.17kW) per hour of the total input rating of all equipment
in the enclosure.
Figure 9. Equipment in Confined Space
(Inlet Air from Ventilated Attic and Outlet Air to
Roof Terminated
Exhaust Pipe
Ventilation
Furnace
Louvers
(Crawl Space)
Coupling or
3 in. to 2 in.
Transition
(Field Provided)
* See Maximum Vent Lengths table
NOTE-The inlet and outlet air openings shall each have a
free area of at least one square inch per 4,000 Btu (645mm
per 1.17kW) per hour of the total input rating of all equipment
in the enclosure.
Figure 10. Equipment in Confined Space
(Inlet Air from Ventilated Crawl Space and Outlet Air
to Outside)
507768-05G / 31-5000655
WARNING
Ventilation Louvers
Inlet Air
(Minimum 12 in.
(305mm) above
Attic Floor)
*Intake Debris
Screen
(Provided)
Furnace
Outside)
Inlet Air
Minimum
12 in. (305mm)
above Crawl
Space Floor
*Intake Debris Screen Provided
Shipping Bolt Removal
Units with 1/2 hp & 3/4 hp blower motor are equipped
with three flexible legs and one rigid leg. The rigid leg
is equipped with a shipping bolt and a flat white plastic
washer (rather than the rubber mounting grommet used
with a flexible mounting leg). See Figure 11. The bolt and
washer must be removed before the furnace is placed into
operation. After the bolt and washer have been removed,
the rigid leg will not touch the blower housing.
Installation
2
Setting Equipment
Do not connect the return air ducts to the back of the
furnace. Doing so will adversely affect the operation of
the safety control devices, which could result in personal
injury or death.
Blower access panel must be securely in place when
blower and burners are operating. Gas fumes, which
could contain carbon monoxide, can be drawn into
living space resulting in personal injury or death.
Upflow Applications
The gas furnaces can be installed as shipped in the upflow
position. Refer to Figure 13 for clearances. Select a location
that allows for the required clearances that are listed on
the unit nameplate. Also consider gas supply connections,
electrical supply, vent connection, condensate trap and
drain connections, and installation and service clearances
2
[24 inches (610 mm) at unit front]. The unit must be level
from side to side. Tilt the unit slightly (maximum 1/2 in.
from level) from back to front to aid in the draining of the
heat exchanger. See Figure 12.
Allow for clearances to combustible materials as indicated
on the unit nameplate.
Issue 2223
Units with 1/2 HP & 3/4 HP
Blower Motor
Figure 11.
WARNING
WARNING
Page 9 of 56
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