AAON H3 Series, Установка, эксплуатация и обслуживание

Страница: 38 / 80

38
Direct Expansion (DX) Systems
All DX refrigerant coils are factory charged
with a nitrogen holding charge. All DX
systems include evaporator coils and thermal
expansion valves (TXV).
Never turn 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, crankcase heaters
cannot prevent refrigerant migration into the
split system condensing unit compressors.
This means the compressor may cool down
and liquid refrigerant may accumulate in the
compressor. The compressor is designed to
pump refrigerant gas and 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 leave the unit off until the main
power switch has been turned on again for at
least 24 hours for units with compressor
crankcase heaters. This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is started.
Always control the unit from the thermostat,
or control panel, never at the main power
supply, except for emergency or complete
shutdown of the unit.
During the cooling season, if the air flow is
reduced due to dirty air filters or any other
reason, the cooling coils can get too cold
which will cause excessive liquid to return to
the compressor. As the liquid concentration
builds up, oil is washed out of the
compressor, leaving it starved for lubrication.
The compressor life will be seriously
shortened by reduced lubrication and the
pumping of excessive amounts of liquid oil
and refrigerant.
Piping shall be in accordance with
national and local codes. Pressure
limiting devices, backflow preventers
and all other safety requirements are
the sole responsibility of the installing
contractor.
WARNING
Ensure water piping entries into the
unit are properly sealed. Failure to
seal the entries may result in damage
to the unit and property.
CAUTION
CRANKCASE HEATER
OPERATION
Some units are equipped with
compressor crankcase heaters, which
must be energized at least 24 hours
prior to cooling operation, to clear any
liquid
refrigerant from the
compressors.
CAUTION