AAON RQ SERIES, Installation Operation & Maintenance, Page: 39 / 100

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Variable Speed Compressors
Variable speed compressors with an inverter
drive are available on 2-6 ton units. Variable
speed compressors should not be operated
outside the factory determined frequency
range. The factory determined compressor
frequency range is given below in Table 4.
For more information on the variable speed
compressor, reference the RQ Series
Variable Speed Compressor Supplement
(V83980).
Table 4 - Single Circuited Variable Speed
Compressor Frequency Range
Model (RQ)
Compressor Range
(rpm)
A, B
900-5000 rpm
Thermostat Control Wiring
If a thermostat is used for unit control,
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts, sun exposure, or
heat from electrical fixtures of appliances.
Control wiring must deliver adequate
voltage to components to assure proper
operation. Control voltage returning from
controller circuit must be a minimum of 21
VAC. To assure proper wiring use the
following chart to determine the allowable
wiring distances.
Table 5 - Control Wiring
Wire Size (Stranded)
- Copper Conductors
Only
Total Wire Distance
Allowable
20 AWG 200 ft
18 AWG 350 ft
16 AWG 500 ft
14 AWG 750 ft
12 AWG 1250 ft
Take the total wire distance allowable and
divide by the number of wires to be
connected. This indicates the distance
allowable for that size wire. The wiring to
the unit must not exceed the total wire
distance allowable. If the voltage at the
connectors is less than 21 VAC, isolation
relays must be installed. If under external
control 21 VAC must be field verified.
All external devices must be powered via a
separate external power supply.
Example:
A total of 8 wires must be pulled 75ft to
control the unit. What size wire should be
used?
According to the Table 4, 16 AWG allows
for 63ft (500 ft/8 wires) and 14 AWG allows
for 94ft (750 ft/8 wires). Thus, 14 AWG
should be used.
Scroll compressors are directional
and will be damaged by operation in
the wrong direction. Low pressure
switches on compressors have been
disconnected after factory testing.
Rotation should be checked by a
qualified service technician at startup
using suction and discharge pressure
gauges and any wiring alteration
should only be made at the unit
power connection.
CAUTION