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 − 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 8.
2 − Return air from single side with optional RAB Return Air Base. See figure 9.
3 − Return air from bottom and one side.
4 − Return air from both sides.
5 − Return air from bottom.
Refer to Engineering Handbook for additional information.
Single Side Return Air |
(with transition and filter) |
20” X 25” X 1” |
(508mm X635mm X 25mm) |
Cleanable Filter |
Return Air |
Plenum |
AIR FLOW |
Transition |
FIGURE 8
Optional Return Air Base
(Upflow Applications Only −− For use with A, B, C and D cabinets)
| FURNACE |
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| FRONT |
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| IF BASE | 3−1/4 |
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| IS USED | |
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| WITHOUT | (83) |
| INDOOR AIR | IAQ CABINET, |
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| A SINGLE |
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| RETURN AIR |
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| PLENUM |
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AIR FLOW |
| MUST |
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| COVER BOTH |
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| UNIT AND |
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| RETURN |
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| AIR BASE | 7−1/4 |
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| OPENINGS | (184) |
14−1/2” (368) A Width (65W75) | OPTIONAL |
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17−1/2” (446) B Width (50W98) | RETURN AIR BASE |
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21”− (533) C Width (50W99)
24−1/2”− (622) D Width (51W00)
1 23 (584) |
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| Overall |
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(Maximum) | 1 Minimum | ||||
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| 11 (279) |
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1 Unit side return air | 2 Maximum | ||||
14 (356) |
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Opening |
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| 5−5/8 | SIDE RETURN |
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| AIR OPENINGS |
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(143) |
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(Either Side) |
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| 23 |
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| (584) |
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| 26−7/8 |
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| (683) |
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| SIDE VIEW |
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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 9
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