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Marvair GAA A/C w/Gas Heat I&O Manual
06/2023 Rev.5
CAUTION
This system contains components that require phasing for correct rotation. Failure to observe rotation and
correct on start-up will cause damage not covered by the warranty.
ATTENTION
Ce système contient des composants qui nécessitent un phasage pour une rotation correcte. Il faut observer
le sens de rotation et le corriger tout de suite s’il y a lieu au démarrage, sous peine de dommages qui ne
seraient pas couverts par la garantie.
Scroll compressors, like several other types of compressors, will only compress in one rotational
direction. The direction of rotation is not an issue with single-phase compressors since they will
always start and run in the proper direction. However, three phase compressors will rotate in either
direction depending upon phasing of power. Since there is a 50-50 chance of connecting power in such
a way as to cause rotation in the reverse direction, it is imperative to confirm that the compressor is
rotating in the proper direction at the initial field start-up of the system. Verification of proper rotation
is made by observing
that the suction pressure drops and the discharge pressure rises when the compressor is energized. An
alternate method of verification for self contained system with small critical refrigerant charges, where
the installation of gauges may be objectionable, can be made by monitoring the temperature of the
refrigerant lines at the compressor. The temperature should rise on the discharge line while the suction
line temperature decreases. Reverse rotation also results in a substantially reduced current draw when
compared to tabulated values.
There is no negative impact on durability caused by operating three phase compressors in the reversed
direction for a short duration of time, usually defined as less than one hour. However, after several
minutes of operation the compressor’s internal protector will trip. The compressor will then cycle on
the protector until the phasing is corrected. Reverse operation for longer than one hour may have a
negative impact on the bearings.
3. Install the ground wire on the ground lug.
Low Voltage Wiring
1. Pull the low voltage wiring from the air conditioner to the thermostat / sub-base assembly.
2. Mount the sub-base on a level plane. Connect the thermostat wire to the unit terminal board and the
thermostat.
3. If applicable, attach the thermostat assembly to the sub-base. Check the stage two heat anticipator
setting. For units with electric heat and thermostats with an adjustable heat anticipator, energize the
electric heat and measure the current on the lead attached to the W2 terminal. Adjust / set the heat
anticipator per the instructions provided with the thermostat.
Terminals 8 & 10 on the Marvair
®
GAA unit with economizer can be connected to a normally closed smoke
alarm or fire stat to cause equipment shutdown when the circuit is opened. ( Remove factory jumper ).
THE INTERNAL TRANSFORMER IS NOT DESIGNED TO POWER OTHER EXTERNAL
DEVICES.
