AAON CN-140 - Manual (Page 32)

32
The system is undercharged if the superheat
is too high and the sub-cooling is too low.
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling.
If the sub-cooling is correct and the
superheat is too high, the expansion valve
may need adjustment to correct the
superheat.
Special Low Ambient Option Charging
Instructions
For units equipped with low ambient
refrigerant flood back option being charged
in
the summer when the ambient
temperature is warm:
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
must be added. Add approximately 80% of
the receiver tank volume to the charge to
help fill the receiver tank. The additional
charge is required for the system when
running in cold ambient conditions.
For units equipped with low ambient
refrigerant flood back option being charged
in
the summer when the ambient
temperature is cold:
Once enough charge has been added to get
the evaporator superheat and sub-cooling
values to the correct setting more charge
may need to be added. If the ambient
temperature is 0°F no more charge is
required. If the ambient temperature is
around 40°F add approximately 40% of the
receiver tank volume.
The unit will have to be checked for proper
operation once the ambient temperature is
above 80°F.
DO NOT OVERCHARGE!
Refrigerant overcharging leads to
excess refrigerant in the condenser
coils resulting in elevated compressor
discharge pressure.
CAUTION
DO NOT OVERCHARGE!
Refrigerant overcharging leads to
excess refrigerant in the condenser
coils resulting in elevated compressor
discharge pressure.
CAUTION