Lennox International Inc G50UH-36A-070 Optional Return Air Base, 27-5/8, Side View, Front View

Return Air -- Upflow Applications

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.

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) clean- able air filter. (Required to maintain proper air velocity.) See figure 7.

2 - Return air from single side with optional RAB Return Air Base. See figure 8.

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)

20" X 25" X 1"

(508mm X635mm X 25mm)

Cleanable Filter

_/

Return Air

Plenum

Transition

FIGURE 7

Optional Return Air Base

(Upflow Applications Only -- For use with B, C and D cabinets only)

J

I

©

r

14

41

(102)1"9_-

123(584)	fL_-
Overall	1 MinimuV_

				(Maximum)	11 (279)	1 22-7-16
					2 Maximurr
AIR FLOW							(570)
		L		1 Unit Openingsidereturn air	11_5.6) __ j	Overall
						Maximum)
		7-1/4 (184)		5 -5/8		_2
				(143)
		OPTIONAL RAB		.....................23 (584)	!	--	3/4
							(19)
17-1/2 (446) RAB-B	(98M60)	RETURN AIR BASE
21 (533) RAB-C	(98M58)	7/8	_1--	27-5/8 (702)
24-1/2 (622) RAB-D	(98M59)	(22)		SIDE VIEW

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.

FIGURE 8

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