035-18550-001-A-0902
Unitary Products Group
9
COMPRESSORS
Units are shipped with compressor mountings factory-
adjusted and ready for operation.
COMPRESSOR CRANKCASE HEATER
The compressor is equipped with a crankcase heater
to prevent refrigerant from mixing with crankcase oil
during the “OFF” cycle. The heaters will be energized
when the compressor is not running providing the unit
disconnect switch is closed.
If a unit has just been installed or the unit disconnect
switch has been open for a long period of time, move
the system switch on the room thermostat to the “OFF”
position before closing the unit disconnect switch. Eight
hours of crankcase heat are required to drive the liquid
refrigerant out of the compressor before the compres-
sor can be started.
POWER AND CONTROL WIRING
Install electrical wiring in accordance with the latest
National Electrical Code (NFPA Standard No. 70) and/
or local regulations. The unit should be grounded in
accordance with these codes.
POWER WIRING
Check the voltage of the power supply against the data
on the unit nameplate. Check the size of the power
wire, the disconnect switch and the fuses against the
data on Table 3.
NOTE:
Copper conductors must be installed between
the disconnect switch and the unit.
Refer to Figure 4 for the location of the power wire
access opening through the front of the unit. This open-
ing will require a field-supplied conduit fitting.
The field-supplied disconnect switch must be suitable
for an outdoor location. Although it should be installed
near the unit, do NOT secure it to the unit cabinet.
Refer to Figure 5 for typical field wiring.
PHASING
Scroll compressors operate in one direction only, if a
three phase scroll compressor is experiencing:
• Low amperage draw
• Similar discharge and suction pressures
• Increased noise level
then the compressor is operating in reverse. To correct
this condition, switch any two (2) line voltage leads at
the contactor. Please note, single phase scroll com-
pressors will start and run in one direction only. The
reverse operation is not a concern.
CONTROL WIRING
Refer to Figure 5 for the location of the control wire
access opening through the front of the unit.
Route the necessary low voltage control wires (18 Awg
Min) from terminal block TB2 of the unit control box
through this access opening to the indoor unit and to
the room thermostat. Refer to Figure 5 for typical field
wiring.
The room thermostat should be mounted about 5 feet
above the floor and located where it will be exposed to
normal room air circulation. Do not locate it on an out-
side wall, near a supply air grill, or where it may be
affected by sunlight and/or drafts. Circulation of air to
the thermostat should not be blocked by curtains,
drapes, furniture, partitions, etc.
Some installations may require a locking cover to pro-
tect the thermostat from tampering and/or damage.
WIRE SIZING
Refer to the following chart to size the control wiring
properly. If the wiring is undersized, voltage drop could
become excessive and result in malfunctioning of the
unit controls.
Do Not loosen compressor mounting bolts.
Do not attempt to start the compressor without
at least eight hours of crankcase heat or com-
pressor damage will occur.
Units equipped with scroll compressors oper-
ate in one direction only.
Incorrect scroll compressor rotation can dam-
age or fail the compressor(s).
