Page 10
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.
NOTE − When air volumes over 1800 cfm (850 L/s) are
required with 60C or 60D models in an upflow applica-
tion, the following return air options are available:
1 − Return air from single side with transition which will
accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter.
(Required to maintain proper air velocity.) See figure 9.
2 − Return air from single side with optional RAB Return
Air Base. See figure 10.
3 − Return air from bottom.
4 − Return air from both sides.
5 − Return air from bottom and
one side.
Refer to Engineering Handbook for additional information.
G43UF applications which include side return air and a
condensate trap installed on the same side of the cabi-
net require either a return air base or field−fabricated
transition to accommodate an optional IAQ accessory
taller than 14−1/2".
Side Return Air
(with transition and filter)
FIGURE 9
Return Air
Plenum
Transition
20" X 25" X 1"
(508mm X635mm X 25mm)
Air Filter
FIGURE 10
Optional Return Air Base
NOTE− Optional Side Return Air Filter Kits are not for use with RAB 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.
NOTE− Optional Side Return Air Filter Kits are not for use with RAB Return Air Base.
1
Unit side return air
Opening
FRONT VIEW
SIDE VIEW
27−5/8 (702)
4
(102)
1
23 (584)
Overall
(Maximum)
OPTIONAL RAB
RETURN AIR BASE
23 (584)
7−1/4 (184)
7/8
(22)
3/4
(19)
1
22−7−16
(570)
Overall
(Maximum)
SIDE RETURN
AIR OPENINGS
(Either Side)
FURNACE
FRONT
14
(356)
AIR FLOW
5−5/8
(143)
1
Minimum
11 (279)
2
Maximum
14 (356)
21 (533) RAB−C (98M58)
24−1/2 (622) RAB−D (98M59)
17−1/2 (446) RAB−B (98M60)
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