Return Air Opening Guidelines
NOTE − Do not bring in air from the back of the unit. Return air can be brought in from the sides or bottom only.
Bottom Return
If the air handler is installed on a platform with bottom re- turn, make an airtight seal between the bottom of the air handler and the platform to ensure that the air handler op- erates properly and safely. Use aluminum tape or mastic between the plenum and the air handler cabinet to ensure a tight seal. The air handler is equipped with a removable bottom panel to facilitate installation.
Side Return
For side return air applications, cut the air handler cabinet at the maximum return air dimensions shown on page 2. See figure 3 for a typical side inlet arrangement with a tran- sition and filter.
NOTE − Single side inlet applications result in approxi- mately a 4 percent reduction of CFM on B−size units and approximately a 5 percent reduction of CFM on C−size units:
Side Return Air With Transition And Filter
20" X 25" X 1"
(508MM X 635MM X 25MM)
CLEANABLE FILTER
RETURN AIR
PLENUM
TRANSITION
Figure 3
Return Air Base
For return air with the optional return air base (RAB), see figure 4 (and refer to installation instructions provided with Return Air Base kit).
*NOTE − Both unit and return air base openings must be connected to and entirely covered by a single plenum or IAQ accessory opening. Optional side return air filter kits cannot be used with RAB Return Air Base.
Optional Return Air Base and Unit Dimensions − Inches (mm)
AIR FLOW
RETURN
AIR BASE
17 (432) RAB−B (98M60)
21 (533) RAB−C (98M58)
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| *23 (584) Overall (Max.) |
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NOTE − IN SIDE RETURN |
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APPLICATIONS, THE RAB |
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IS REQUIRED FOR 100% |
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| 11 (279) |
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CFM CAPACITY. |
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| 14 (356) |
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| *Unit |
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| Side Return |
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7−1/4 |
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(184) |
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| Opening | (143) |
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| 23 (584) |
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7/8 (22) |
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| 27−5/8 (702) |
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*Height varies with plenum or IAQ accessory height.
3/4
(19)
FRONT VIEW | SIDE VIEW |
Figure 4
Page 6
505047 09/06
