Carrier WeatherMaker 48A020 Installation Instructions Manual page 34

Step 14 — Perform Field Modifications
DUCTWORK
Bottom Return Units (48A2,A3,A6,A7) Field-Modified for
Side Return
The 48A2,A3,A6,A7 units with bottom return air connec-
tions may be field-modified to accommodate side return air
connections.
IMPORTANT: The following section is a guideline and not a
comprehensive procedure to field-modify the units. The
installing contractor must provide some design initiative. Field
conversion is complex and is not recommended.
Conversion to horizontal return requires that the bottom return
openings of the unit must be sealed with airtight panels capable of
supporting the weight of a person. The return ductwork connec-
tion locations on the side of the unit are higher than normal (31 in.
high). Unit-mounted power exhaust or barometric relief cannot be
used because return air ductwork will cover the power exhaust or
barometric relief installation locations. Power exhaust or baromet-
ric relief may be installed in the return air ductwork.
To convert the unit, perform the following:
1. Seal the bottom return openings of the unit with airtight
panels capable of supporting the weight of a person.
RA
97.78" (027-050), 150.47" (060)
INSIDE DIMENSION
Fig. 46 — Side Return Air Conversion
2. Remove the panels located below the economizer outdoor-air
dampers. These openings will be used for the return-air
ductwork. There are 2 panels on 48A2,A3,A6,A7020-050
units. There are 3 panels on 48A2,A3,A6,A7060 units. These
openings are normally used for power exhaust or barometric
relief.
3. Run the return air ductwork up to the openings. One single
duct is recommended to connect to the unit over the return air
openings. See Fig. 46. The return duct must incorporate a
minimum / -in. flange for connection to the unit cabinet. The
3
4
unit does not have duct flanges for this conversion.
Side Supply and Return Units (48A4,A5,A8,A9) with Field-
Installed Power Exhaust in Return Duct
Space must be available in the return duct to mount the power ex-
haust fan (gravity relief) modules. Dimensions and suggested lo-
cations are shown in Fig. 46. These instructions are a guideline
and not a comprehensive procedure. The design contractor must
provide some design initiative.
The wiring harness that is provided with the power exhaust acces-
sory is not long enough for the fan modules to be mounted in the
return air duct. Field-supplied wiring must be spliced into the har-
ness. Use a junction box at each splice. The wiring may be run in
the return duct, or externally in conduit. A service access panel
will be needed near each power exhaust fan.
31.25"
INSIDE
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