AAON CC-063 - Manual (Page 11)

11
Direct Expansion (DX) Condensing Units
Condensing units are factory assembled and
wired, including a holding charge of
refrigerant. Refrigeration systems include
factory provided liquid line filter driers and
fully hermetic scroll compressors with a
positive pressure forced lubrication system.
Never cut off the main power supply to the
unit, except for servicing, emergency, or
complete shutdown of the unit. When power
is cut off from the unit, compressors using
crankcase heaters cannot prevent refrigerant
migration. This means the compressor may
cool down and liquid refrigerant may
accumulate in the compressor. Since the
compressor is designed to pump refrigerant
gas, damage may occur when power is
restored.
If power to the unit must be off for more
than an hour, turn the thermostat system
switch to “Off”, or turn the unit off at the
control panel, and then cut off the main
power supply. Leave the unit off until the
main power supply has been turned on again
for at least 24 hours. This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run.
Always control the system from the
thermostat, or control panel, never at the
main power supply, except for servicing,
emergency, or complete shutdown of the
unit.
Note: Low Ambient Operation
Units without a low ambient option, such as
adjustable fan cycling or the 0°F low
ambient option, will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55°F. Low
ambient and/or air handling unit economizer
options are recommended if cooling
operation below 55°F is expected.
Note: Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode, cooling mode or off. Do not
leave part of the systems switched to the
opposite mode. Cooling only systems should
be switched off at the thermostat during the
heating season.
Wiring Diagrams
Unit specific wiring diagrams are laminated
in plastic and affixed inside the controls
compartment door.
CRANKCASE HEATER
OPERATION
Units are equipped with compressor
crankcase heaters, which should be
energized at least 24 hours prior to
cooling operation, to clear any liquid
refrigerant from the compressors.
CAUTION