AAON M2-036 - Manual (Page 71)

71
Checking Liquid Sub-Cooling
Measure the temperature of the liquid line as
it leaves the condenser.
Read the gauge pressure at the liquid line
close to the point where the temperature was
taken. Use liquid line pressure as it will vary
from discharge pressure due to condenser
pressure drop.
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart.
Subtract the measured liquid line
temperature from the saturated temperature
to determine the liquid sub-cooling.
Compare calculated sub-cooling to the table
below for the appropriate unit type and
options.
Checking Evaporator Superheat
Measure the temperature of the suction line
close to the compressor.
Read gauge pressure at the suction line close
to the compressor.
Convert the pressure obtained to a saturated
temperature using the appropriate refrigerant
temperature-pressure chart.
Subtract the saturated temperature from the
measured suction line temperature to
determine the evaporator superheat.
Compare calculated superheat to the table
below for the appropriate unit type and
options.
Table 12 - Acceptable Air-Cooled
Refrigeration Circuit Values
Air-Cooled
Condenser
Sub-Cooling 12-18°F
Sub-Cooling with
Hot Gas Reheat
15-22°F
Superheat 8-15°F
Table 13 - Acceptable Water-Cooled
Refrigeration Circuit Values
Water-Cooled
Condenser
Sub-Cooling 6-10°F
Sub-Cooling with
Hot Gas Reheat
8-12°F
Superheat 8-15°F
Adjusting Sub-Cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator superheat is within the
DO NOT OVERCHARGE!
Refrigerant overcharging leads to
excess refrigerant in the condenser
coils resulting in elevated compressor
discharge pressure.
CAUTION
Thermal expansion valve must be
adjust to approximately 8-15°F of
suction superheat. Failure to have
sufficient superheat will damage the
compressor and void the warranty.
CAUTION