Page 8
Optional Return Air Base
(Upflow Applications Only)
NOTE- Optional side return air filter kits are not for use with return air base.
1
Both the unit return air opening and the base return air opening must be covered by a single plenum or IAQ cabinet.
Minimum unit side return air opening dimensions for units requiring 1800 cfm or more of air (W x H): 23 x 11 in. (584 x 279 mm).
The opening can be cut as needed to accommodate plenum or IAQ cabinet while maintaining dimensions shown.
Side return air openings must be cut in the field. There are cutting guides stenciled on the cabinet for the side return air
opening. The size of the opening must not extend beyond the markings on the furnace cabinet.
2
To minimize pressure drop, the largest opening height possible (up to 14 inches) is preferred.
FRONT VIEW
1
Unit side return air
Opening
SIDE VIEW
3−1/4
(83)
1
23 (584)
Overall
(Maximum)
(584)
23
3/4
(19)
1
22−7/16
(570)
Overall
(Maximum)
SIDE RETURN
AIR OPENINGS
(Either Side)
5−5/8
(143)
1
Minimum
11 (279)
2
Maximum
14 (356)
(683)
26−7/8
7−1/4
(184)
FURNACE
FRONT
AIR FLOW
IF BASE
IS USED
WITHOUT
IAQ CABINET,
A SINGLE
RETURN AIR
PLENUM
MUST
COVER BOTH
UNIT AND
RETURN
AIR BASE
OPENINGS
INDOOR AIR
QUALITY
CABINET
(PCO, Filter
Cabinet, etc.)
AIR BASE
OPTIONAL
RETURN
CONDENSATE
TRAP
17−1/2 (446) B Width (50W98)
21 (533) C Width (50W99)
24−1/2 (622) D Width (51W00)
FIGURE 8
NOTE - Units with 1/2 hp blower motor are equipped
with three exible legs and one rigid leg. The rigid leg is
equipped with a shipping bolt and a at white plastic wash-
er (rather than the rubber mounting grommet used with
a exible mounting leg). See FIGURE 9. The bolt and
washer must be removed before the furnace is placed
into operation. After the bolt and washer have been re-
moved, the rigid leg will not touch the blower housing.
RIGID LEG
remove shipping bolt and washer
UNITS WITH 1/2 HP
BLOWER MOTOR
FIGURE 9
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or
alcove installations are shown in FIGURE 10 and FIGURE
11.
WARNING
The blower door must be securely in place when the
blower and burners are operating. Gas fumes, which
could contain carbon monoxide, can be drawn into the
living space resulting in personal injury or death.
WARNING
Improper installation of the furnace can result in personal
injury or death. Combustion and ue products must
never be allowed to enter the return air system or air in
the living space. Use sheet metal screws and joint tape
to seal return air system to furnace.
In platform installations with furnace return, the furnace
should be sealed airtight to the return air plenum. A door
must never be used as a portion of the return air duct
system. The base must provide a stable support and an
airtight seal to the furnace. Allow absolutely no sagging,
cracks, gaps, etc. For no reason should return and
supply air duct systems ever be connected to or from
other heating devices such as a replace or stove, etc.
Fire, explosion, carbon monoxide poisoning, personal
injury and/or property damage could result..
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