Lennox ML180UHA Installation Instructions Manual page 9

(Upflow Applications Only -- For use with A, B, C and D cabinets)
AIR FLOW
368 (14−1/2) A WIDTH (65W75)
446 (17−1/2) B WIDTH (50W89)
533 (21) C WIDTH (50W99)
622 (24−1/2) D WIDTH (51W00)
NOTE- Optional Side Return Air Filter Kits are not for use with Optional 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 850 L/s (1800 cfm) or more of air (W x H): 584 x 279
mm. (23 X 11 in.)
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 356 mm (14 in.)] is preferred.
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 9.
Optional Return Air Base
FURNACE
FRONT
IF BASE
IS USED
WITHOUT
INDOOR AIR
IAQ CABINET,
QUALITY
A SINGLE
CABINET
RETURN AIR
(PCO, FILTER
PLENUM
CABINET, ETC
MUST
COVER BOTH
UNIT AND
RETURN
AIR BASE
OPENINGS
OPTIONAL
RETURN
AIR BASE
83 (3−1/4)
184 (7−1/4)
FIGURE 8
Removing the Bottom Panel
Screw
Bottom Panel
Page 9
1
584 (26)
Overall
1
(Maximum)
Minimum
279 (11)
Maximum
2
1
Unit side return air
356 (14)
Opening
SIDE RETURN
143
AIR OPENINGS
(5−5/8)
(Either Side)
584
(23)
683
(26−7/8)
SIDE VIEW
Bottom Cap
FIGURE 9
1
570
(22)
Overall
(Maximum)
19
(3/4)