Trane RAUC-IOM-15, Installation & Maintenance Instructions Manual

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36
Installation (Continued)
Variable Air Volume Control
(Honeywell W7100A)
In a variable air volume system, the desired space tempera-
ture is maintained by varying the amount of conditioned air
being delivered to the space. As the cooling requirements of
the space decreases, less air is delivered to the zone; con-
versely, as the cooling requirements of the space increases,
a greater volume of air is delivered to the zone.
The descriptions of the following basic input devices used
with the Honeywell W7100A discharge air controller are to
acquaint the operator with their function as they interface
with the controller. Refer to the field connection diagram in
Figure 3-13 for the specific component connections at the
unit control panel.
For discussion of evaporator fan interlock, hot gas bypass,
and economizer connections, refer to the “Controls Using
115 VAC” section. Refer to Figure 3-12 for the specific com-
ponent connections.
Discharge Air Sensor
(Honeywell 8RT3)
Each unit ordered with variable air volume controls (digit 9
in the model number) is shipped with a Honeywell 8RT3
discharge air sensor.
The sensor should be installed in a turbulent free area of
the discharge air duct at a location that will provide accurate
supply air sensing. Refer to the illustration in Figure 3-12 for
installation and sensor dimensional information.
The sensor serves two functions;
1. It sends the supply air temperature data to the Discharge
Air Controller, in the form of an analog input, to control
the economizer (if applicable) and the cycling of the com-
pressors.
2. It serves as a low limit sensor for the system when the
supply air temperature reaches too high a delta tee be-
tween the actual supply air temperature and the supply
air temperature setpoint.
Before installing any connecting wiring, refer to Figure 3-2
for the electrical access locations provided on the unit. Wire
the sensor in accordance with the field connection diagram
in Figure 3-13. Shielded cable (Belden 8760 or equivalent)
must be used when wiring the sensor to the terminal board
inside the unit’s control panel.
Connect the shielded cable to the appropriate terminals on
the terminal board (7TB7), in the unit’s control panel.
Ground the shield (at the unit only) using the ground screw
in the “customer 24 volt connection area as shown in the
field connection diagram.
Suction Line Thermostat
Each unit ordered with variable air volume controls (digit 9
in the model number) is shipped with a suction line thermo-
stat (6S63) that must be field installed.
Locate the thermostat close to the expansion valve bulb on
a slightly flattened portion of the suction line. The thermo-
stat must be securely fastened to the suction line and a field
provided thermoconductive grease must be applied
to the area to ensure good heat transfer.
Before installing any connecting wiring, refer to Figure 3-2
for the electrical access locations provided on the unit. Wire
the suction line thermostat in accordance with the field con-
nection diagram in Figure 3-13. Refer to Table 3-6 (AC Con-
ductors) for wiring specifications.
Insulate the suction line, where the thermostat is mounted,
to isolate it from the surrounding air.
Night Setback
If night setback operation is desired, connect a set of nor-
mally open contacts (field provided) to the appropriate ter-
minals on the terminal board (7TB7), in the unit’s control
panel. Remove the factory installed jumper at the terminal
board when making the final wiring termination. Refer to the
field connection diagram in Figure 3-13 for details.
Figure 3-12
8RT3 Discharge Air Sensor Assembly