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Marvair ComPac AVHDA I&O Manual 03/2019 Rev.3
2. Test for proper phasing as follows:
A. Power up the units.
B. Using an AC volt meter set to the 300 volt scale, measure voltage between terminal L1 on
the compressor contactor of unit #1 and terminal L1 on the compressor contactor of unit #2 If
voltage is present, units are wired out of phase and must be rewired.
C. If units are not in phase, turn off power and reverse the field power leads connected to the
internal circuit breaker on one of the units only.
D. Restore power and retest the phase (step B). When the voltage reads "0", the units are in phase.
E. Turn off power and proceed.
Low Voltage Wiring
IMPORTANT.
The following instructions are generic wiring instructions and may not be applicable
for air conditioners with various options. Always refer to the wiring diagram in the air conditioner for
the proper method to wire your unit.
1. On single units, pull the low voltage wiring (e.g., 18 gauge 4-conductor Class 2 thermostat wire)
from the air conditioners into the thermostat / subbase assembly. See Figure 4a for connections to
various thermostats.
2. Mount the thermostat on the wall of the shelter. The thermostat should be located so that the supply
air from the unit does NOT blow directly on to the thermostat. Connect the thermostat to the terminal
block in the air conditioner as shown in Figure 6a.
3. On dual units, refer to either the CommStat Touch or CommStat 4
Controller Specification sheet.
Wire the two air conditioners to the Lead/Lag Controller, according to the wiring diagram on the
specification sheet.
Remote Signalling:
Terminals 5 & 7(N.O.) and 6 & 7 (N.C.) on the air conditioners terminal board are dry
contacts which can be used for remote signalling in the event of a/c cutoff on low or high pressure limit.
Continuous fan operation:
For continuous indoor fan operation on single units, install a jumper between
terminals 8 and 3.
CommStat Touch and CommStat 4 Lead /Lag Controller
Please refer to the Product Data sheet for the CommStat Touch or CommStat 4 controller for complete
instructions on installing and programming this controller.
