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Improper installation of the furnace can result in
personal injury or death. Combustion and flue 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 fireplace or stove, etc. Fire, explosion, carbon
monoxide poisoning, personal injury and/or property
damage could result.
CONDENSATE
TRAP
AIR FLOW
17−1/2 (446) B Width (68W62)
21 (533) C Width (68W63)
24−1/2 (622) D Width (68W64)
FRONT VIEW
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.
508404-01
WARNING
FURNACE
FRONT
INDOOR AIR
QUALITY
CABINET
(PCO, Filter
Cabinet, etc.)
OPTIONAL
RETURN
AIR BASE
Figure 14. Optional Return Air Base
(Upflow Applications Only)
Return Air Guidelines
Return air can be brought in through the bottom or either
side of the furnace installed in an upflow application. If the
furnace is installed on a platform with bottom return, make
an airtight seal between the bottom of the furnace and the
platform to ensure that the furnace operates properly and
safely. The furnace is equipped with a removable bottom
panel to facilitate installation.
Markings are provided on both sides of the furnace cabinet
for installations that require side return air. Cut the furnace
cabinet at the maximum dimensions shown on Page 2.
Furnace applications which include side return air and a
condensate trap installed on the same side of the cabinet
(trap can be installed remotely within 5 ft.) require either a
return air base or field-fabricated transition to accommodate
an optional IAQ accessory taller than 14.5". See Figure 14.
3−1/4
IF BASE
(83)
IS USED
WITHOUT
IAQ CABINET,
A SINGLE
RETURN AIR
PLENUM
MUST
COVER BOTH
UNIT AND
RETURN
7−1/4
AIR BASE
(184)
OPENINGS
Issue 2332
1
23 (584)
Overall
1
(Maximum)
Minimum
11 (279)
Maximum
2
1
Unit side return air
14 (356)
Opening
SIDE RETURN
5−5/8
AIR OPENINGS
(143)
(Either Side)
23
(584)
26−7/8
(683)
SIDE VIEW
1
22−7/16
(570)
Overall
(Maximum)
3/4
(19)
Page 11 of 60
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