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unit in reheat (dehumidification) mode to
check for correct operation.
Units equipped with heat pump options must
be charged in heating mode to get the proper
charge. After charging, operate the unit in
cooling mode to check for correct charge.
Charge may need to be adjusted for cooling
mode. If adjustments are made in the cooling
mode heating mode must be rerun to verify
proper operation.
After adding or removing charge the system
must be allowed to stabilize, typically 10-15
minutes, before making any other
adjustments.
The type of unit and options determine the
ranges for liquid sub-cooling and evaporator
superheat. Refer to the table below when
determining the proper sub-cooling.
Checking Liquid Sub-Cooling
Measure the temperature of the liquid line as
it leaves the condenser coil.
Read the gauge pressure at the liquid line
close to the point where the temperature was
taken. You must use liquid line pressure as it
will vary from discharge pressure due to
condenser coil 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 tables
below for the appropriate coil and system
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 tables
below for the appropriate coil and system
type and options.
Table 15 - Acceptable Fin & Tube Air-
Cooled Condenser Coil Refrigeration Circuit
Values
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