17
Marvair ModPac Installation & Operation Manual
11/2017 Rev.8
8. On the inside of the building, install the wall sleeves in the supply and return air openings. The
sleeves may be trimmed to fit flush with the inside wall. 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.
9. Check the fit of each sleeve to its mating flange for possible air leaks. Apply silicone sealer to
close any gaps. Install the air return and supply grilles.
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.
2.8 Electrical Connections
IMPORTANT!
All electrical work must meet the requirements of local codes and ordinances.
Work should be
done
only
by qualified persons.
CAUTION
These air conditioners incorporate an internal crankcase heater for compressor protection.
The crankcase heater must be energized for at least 24 hours prior to starting the compressor.
ModPac air conditioners may be ordered with a scroll 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 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.
Failure to ensure proper rotation will void the warranty of the compressor.
To change the rotation, turn off power to the unit and swap L1 and L2 at the disconnect or circuit breaker.
High Voltage Wiring
The power supply should have the proper voltage, phase, and ampacity for the selected model.