Product manual
24
ComPac 6/09-18
2.8 eleCTriCal ConneCTions
Important
All electrical work must meet the requirements of local codes and ordinances. Work should be
done only by qualied persons.
The ComPac
®
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 conrm that the compressor is rotating in the proper
direction at the initial eld start-up of the system. Verication 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 verication 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.
Marvair units have either a reciprocating or scroll compressor. A reciprocation compressor is standard
on the AVP24, 30 & 36 units. However, a scroll compressor is an option on these ComPac
®
I and
ComPac
®
II air conditioners. Units with scroll compressors have a "U" in the model number. The scroll
compressor is standard on all AVP42, 48, 60 & 72 units.
There is no negative impact on durability caused by operating three phase compressors in the reversed
direction for a short duration of time, usually dened 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.
High Voltage Wiring - (Single Units)
The power supply should have the proper voltage, phase, and ampacity for the selected model.
1. Size the incoming power supply lines according to Code requirements. Run the power conductors
through the knockouts on the wall side of the unit, or to those adjacent to the electrical control box.
Use appropriate conduit and strain reliefs.
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.
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.