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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
For units with electric heat, a one inch clearance is required around the duct extensions. The duct extensions must be constructed of
galvanized steel with a minimum thickness of .019” as per the NFPA standards 90A & 90B.
Figure 6 Air Conditioner Wall Mount Detail
3.8 Electrical Connections
WARNING ELECTRICAL SHOCK HAZARD
Failure to follow safety warnings exactly could result in serious injury, death, and/or
property damage.
Turn off electrical power at fuse box or service panel BEFORE making any electrical
connections and ensure a proper ground connection is made before connecting line
voltage.
Important
All electrical work must meet the requirements of local codes and ordinances.
Work should be
done
only
by qualified persons.
The units may incorporate an internal crankcase heater for compressor protection.
The crankcase
heater must be energized for at least 24 hours prior to starting the compressor.
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
