Step 11 - Field Modifications - Carrier 50AJ/AK/AM020 Installation Instructions Manual

• Outdoor Humidity Sensor (used for Economizer Enthalpy
Changeover
• Return Air Humidity Sensors (used for Economizer Differ-
ential Enthalpy Changeover)
• Return Air Smoke Detector
• Controls Expansion Module (used for interface to Building
Management Systems, not typically needed on system with
the Carrier Comfort Network [CNN])
• Plugged Filter Sensor
Step 11 — Field Modifications
DUCTWORK
Bottom Return Units (50AJ and AK) Field-Modified for
Side Return — The 50AJ and AK units with bottom return air
connections 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.
Units with electric heat must not be converted because of
potential heating mode operating problems.
Conversion to horizontal return requires that the bottom re-
turn openings of the unit must be sealed with airtight panels ca-
pable of supporting the weight of a person. The return duct-
work connection 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 of return air ductwork
will cover the power exhaust or barometric relief installation
locations. Power exhaust or barometric relief may be installed
in the return air ductwork.
RA
97.78" (020-050), 150.47" (060)
INSIDE DIMENSION
31.25"
INSIDE
Fig. 39 — Side Return Air Conversion
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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.
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 50AJ,AK020-
050 units. There are 3 panels on 50AJ,AK060 and 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. 39. The return duct must
incorporate a minimum
the unit cabinet. The unit does not have duct flanges for
this conversion.
Side Supply and Return Units (50AW,AY) With Field-
Installed Power Exhaust in Return Duct — Space must be
available in the return duct to mount the power exhaust fan
(gravity relief) modules. Dimensions and suggested locations
are shown in Fig. 36. These instructions are a guideline and not
a comprehensive procedure. The design contractor must pro-
vide some design initiative.
The wiring harness that is provided with the power exhaust
accessory is not long enough for the fan modules to be mount-
ed in the return air duct. Field-supplied wiring must be spliced
into the harness. Use a junction box at each splice. The wiring
may be run in the return duct as shown in Fig. 36, or externally
in conduit. A service access panel will be needed near each
power exhaust fan.
3
/ -in. flange for connection to
4