Lennox G51MP SERIES Installation Instructions Manual page 11

Removing the Bottom Panel
Screw
Bottom Panel
FIGURE 10
(Upflow Applications Only −− For use with B, C and D cabinets only)
AIR FLOW
17−1/2 (446) RAB−B (98M60)
21 (533) RAB−C (98M58)
24−1/2 (622) RAB−D (98M59)
FRONT VIEW
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.
Bottom Cap
Optional Return Air Base
14
(356)
FURNACE
FRONT
7−1/4 (184)
OPTIONAL RAB
RETURN AIR BASE
7/8
(22)
FIGURE 11
Page 11
Setting an Upflow Unit
When the side return air inlets are used in an upflow ap-
plication, it may be necessary to install leveling bolts on the
bottom of the furnace. Use field−supplied corrosion−resist-
ant 5/16 inch machine bolts (4) and nuts (8). See figure 12.
NOTE − The maximum length of the bolt is 1−1/2 inches.
1 − Lie the furnace on its back and drill a 5/16 inch diame-
ter hole in each corner of the furnace's bottom. See fig-
ure 12 for the correct location of the holes. Drill through
the bottom panel and the bottom flange of the cabinet.
2 − Install one bolt and two nuts into each hole. Screw the
first nut onto a bolt and then insert the bolt into a hole. A
flat washer may be added between the nut and the bot-
tom of the unit.
3 − Screw another nut onto the bolt on the inside of the fur-
nace base. A flat washer may be added between the
nut and the bottom of the unit.
1
23 (584)
4
Overall
(102)
(Maximum)
1
Unit side return air
Opening
SIDE RETURN
5−5/8
AIR OPENINGS
(143)
(Either Side)
23 (584)
27−5/8 (702)
SIDE VIEW
1
Minimum
11 (279)
1
2 22−7−16
Maximum
(570)
14 (356)
Overall
(Maximum)
3/4
(19)