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Thermostat Control Wiring
If a thermostat is used for unit control,
locate thermostat 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 or 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
- Copper Conductors
Allowable
Total Wire Distance Allowable =
(Quantity of Control Wires) x
(Control Wire Distance)
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 5 wires must be pulled 75ft to a
control the unit. What size wire must be
used?
According to Table 5, 18 AWG allows for
70ft (350 ft. /5 wires) and 16 AWG allows
for 100ft (500 ft. /5 wires). Thus, 16 AWG
must be used.
Figure 19 - Filter access Doors
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