Lennox International Inc EL280UH installation instructions Return Air

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 − 60C and 60D units that require air volumes over 1800 cfm (850 L/s) must have one of the following:

1 − Single side return air with transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter. (Re- quired to maintain proper air velocity.) See figure 9.

2 − Single side return air with optional return airbase. See fig- ure 10.

3 − Bottom return air.

4 − Return air from both sides.

5 − Bottom and one side return air.

Refer to Engineering Handbook for additional information.

Single Side Return Air

(with transition and filter)

20” X 25” X 1”

(508mm X 635mm X 25mm)

Cleanable Filter

Return Air

Plenum

AIR FLOW

Transition

FIGURE 9

Optional Return Air Base

(Upflow Applications Only −− For use with A, B, C and D cabinets)

	FURNACE
	FRONT
		IF BASE	3−1/4
		IS USED
		WITHOUT	(83)
	INDOOR AIR	IAQ CABINET,
		A SINGLE
		RETURN AIR
		PLENUM
AIR FLOW		MUST
		COVER BOTH
		UNIT AND
		RETURN
		AIR BASE	7−1/4
		OPENINGS	(184)
14−1/2” (368) A Width (65W75)	OPTIONAL
17−1/2” (446) B Width (50W98)	RETURN AIR BASE

21”− (533) C Width (50W99)

24−1/2”− (622) D Width (51W00)

123 (584)

	Overall
		1 Minimum
(Maximum)
		11 (279)
1 Unit side return air		2 Maximum
		14 (356)
Opening

5−5/8	SIDE RETURN
	AIR OPENINGS
(143)
	(Either Side)

23

(584)

26−7/8

(683)

SIDE VIEW

122−7/16

(570)

Overall

(Maximum)

3/4

(19)

NOTE− Optional Side Return Air Filter Kits are not for use with Optional Return Air Base.

1Both 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.

2To minimize pressure drop, the largest opening height possible (up to 14 inches) is preferred.

FIGURE 10

Page 10