Marvair MAA/MGA Wall Mount AC Installation & Operation Manual
05/2023 Rev.21
41
CAUTION
Note: Power supply service must be within allowable range (+10% - 5%) of rated
voltage stamped on the unit rating plate. To operate nominal 230/208V unit at 208V,
change the transformer line tap from 240V to 208V following the instruction on
wiring label in unit.
2. Connect the wires to the input side of the internal breaker or terminal block (L1 & L2 for single-
phase units; L1, L2, & L3 for three-phase models).
3. Install the ground wire on the ground lug.
4. For units designed for operation on 208/230V, 60Hz power supply, the transformer is factory wired
for a 230V power supply. For a 208V power supply, remove the orange lead from the transformer
and connect the red lead. Insulate the orange lead.
5. 460V units have a step down transformer for 230V motors.
CAUTION
The external breaker(s) that provide power to the air conditioner must be sized per
the maximum Fuse Size (MFS) shown on the Unit's data label.
Dual Unit Phasing
For applications where one controller operates two units, e.g., the CommStat 4 or CommStat Touch
HVAC controller.
Newer HVAC controllers sunch as the CommStat do not require unit phasing. However, if other devices
are connected to the control system, phasing of the air conditioner is required. Earlier models; i.e.,
LL357, LL357A, LL357D2 require the unit to be properly phased.
1. Wire each unit as described in steps 1 through 4 above.
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 unit into the thermostat / subbase assembly. See Figure 13b 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 13b.
3. On dual units, refer to the
CommStat 4 or CommStat 3 HVAC Controller Specification sheet.
Level
and install the controller subbase. Wire the two A/C
units to the Lead/Lag Controller, according to
the wiring diagram on the specification sheet and as shown in Figure 13c for the CommStat 3 and
Figure 13d for the CommStat 4 (note: the diagram also appears on the back cover of the controller).
Remote Signalling:
Terminals 5 & 7(N.O.) and 6 & 7 (N.C.) on the terminal board are dry contacts which
