Carrier 48AJ installation instructions Field Modifications, Pressure Transducer Locations

building, route the high tap to atmosphere and the low tap to building air.

Step 12 — Install All Accessories — After all the factory-installed options have been adjusted, install all field- installed accessories. Refer to the accessory installation instruc- tions included with each accessory.

The 48A Series units have a large number of factory- installed options which were previously available only as accessories. Some of the available options can also be installed in the field if needed. In most cases the units have been pre-wired so that the accessories can be easily installed. Instructions are shipped with each accessory. Configuration of the controls for these accessories as well as the factory-installed options can be found in the Controls, Start-Up, Operation, Service and Troubleshooting Book. The following is a list of some of the common accessories:

•Thermostats and space temperature sensors

•LP (liquid propane) conversion kit

•Accessory barometric relief damper

•Accessory power exhaust

•Non-modulating to modulating power exhaust

•Condenser coil hail guards

•Outdoor humidity sensor (used for economizer enthalpy changeover)

•Return air humidity sensors (used for economizer differential enthalpy changeover)

•Return air smoke detector

•Controls expansion module (used for interface to build- ing management systems, not typically needed on system with the Carrier Comfort Network® [CCN] sys- tem)

•Plugged filter sensor

•Motormaster® V low ambient head pressure control

IMPORTANT: Carrier recommends the installation of field-fabricated wind baffles on all vertically oriented condenser coils when operating in environments with prevailing winds of more than 5 MPH and where tem- peratures drop below 32 F. See the Motormaster accessory installation guide for instructions.

Step 13 — Field Modifications

DUCTWORK

Bottom Return Units (48AJ and AK) Field-Modified for Side Return — The 48AJ 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 return openings of the unit must be sealed with airtight panels

capable of supporting the weight of a person. The return ductwork 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 48AJ,AK020- 050 units. There are 3 panels on 48AJ,AK051 and 060 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. 34. The return duct must incorporate a minimum 3/4-in. flange for connection to the unit cabinet. The unit does not have duct flanges for this conversion.

Side Supply and Return Units (48AW,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. 34. 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, or externally in conduit. A ser- vice access panel will be needed near each power exhaust fan.

AUXILIARY	PRESSURE TRANSDUCERS	a48-6976
CONTROL BOX	(INSIDE OF PANEL)

Fig. 33 — Pressure Transducer Locations

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