Step 13 - Perform Field Modifications; Bacnet Communication Option Wiring - Carrier WEATHERMAKER 48A2 Installation Instructions Manual

NOTES:
1. Unless otherwise specified, all dimensions are to outside of part.
2. Dimensions are in inches.
3. On 48A4,A5 units, accessory barometric relief or power exhaust must be mounted in the field-supplied return ductwork.
Fig. 32 — Barometric Relief Damper and Power Exhaust Mounting Details
PRESSURE TRANSDUCERS
AUXILIARY
(INSIDE OF PANEL)
CONTROL BOX
Fig. 33 — Pressure Transducer Locations
Step 13 — Perform Field Modifications
DUCTWORK
Bottom Return Units (48A2 and A3) Field-Modified for
Side Return — The 48A2 and A3 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.
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 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.
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 48A2,A3020-
050 units. There are 3 panels on 48A2,A3060 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. 34. The return duct must
a48-6976
incorporate a minimum
the unit cabinet. The unit does not have duct flanges for
this conversion.
Side Supply and Return Units (48A4,A5) 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. 34. These instructions are a guideline and not a compre-
hensive procedure. The design contractor must provide 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, or externally in conduit. A ser-
vice access panel will be needed near each power exhaust fan.

BACnet Communication Option Wiring

WIRING THE UPC OPEN TO THE MS/TP NET-
WORK — The UPC Open controller communicates using
BACnet* on an MS/TP network segment communications at
9600 bps, 19.2 kbps, 38.4 kbps, or 76.8 kbps.
*Sponsored by ASHRAE (American Society of Heating, Refrigerating,
and Air Conditioning Engineers).
33
a48-3808
3
/ -in. flange for connection to
4