Page 8
2 − Return air from single side with optional RAB Return
Air Base. See figure 7.
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.
Side Return Air
(with transition and filter)
FIGURE 5
Return
Air
Plenum
Transition
20" X 25" X 1"
(508mm X635mm X 25mm)
Air Filter
G71MPP applications which include side return air and
a condensate trap installed on the same side of the
cabinet require either a return air base or field−fabri-
cated transition to accommodate an optional IAQ ac-
cessory taller than 14.5".
Removing the Bottom Panel
Remove the two screws that secure the bottom cap to the
furnace. Pivot the bottom cap down to release the bottom
panel. Once the bottom panel has been removed, reinstall
the bottom cap. See figure 6.
Removing the Bottom Panel
FIGURE 6
Screw
Bottom Panel
Bottom Cap
Optional Return Air Base
(Upflow Applications Only −− For use with B, C and D cabinets only)
FIGURE 7
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
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)
14
(356)
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