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An air cooled package unit may require fi eld charging if a compressor is changed, if a leak devel-
ops or if non-condensable are in the system. Field charging should be done by referring to the unit
electrical nameplate for the factory charge.
Although this value represents the original factory charge, it is still necessary to measure and note
proper unit operation including superheat, sub-cooling, head and suction pressure. Some adjust-
ment to charge may be required.
WARNING: Before starting a compressor, the crankcase heater should be energized for
a minimum of 12 hours to reduce the possibility of liquid slugging on start-up. Failure to
energize the crankcase heater could result in compressor damage.
5.2.2 Split Indoor Air Cooled Systems Charging (Units with Indoor Condenser)
After refrigerant piping is properly completed, connect the refrigerant drum to the low side and
charge with vapor. For systems with R-407C, charge with approximately 2.55 lbs. per nominal ton.
Systems with R-410A require 3 lbs. per nominal ton.
For example, a model DAMA-0212 is a nominal 2 ton unit. Charge with about 5.10 lbs. of refrigerant
if R-407C. 6 lbs. if R-410A. It is likely that more refrigerant will be required to complete the charging
procedure for additional piping between the evaporator and the condenser. Make sure all hoses are
properly purged.
WARNING: Before starting a compressor, the crankcase heater should be energized
for a minimum of 12 hours to reduce the possibility of liquid slugging on start-up. Fail-
ure to energize the crankcase heater could result in compressor damage. If the system
is charged from a vacuum, the pre-heating of the compressor is not necessary.
Start the evaporator fan and compressor. Check the liquid line sight-glass to get a feel for the ap-
proximate charge. Bubbles in the sight-glass are not unusual at this point and can be caused by
fl ashing from liquid line pressure drop, low sub-cooling or low charge. It is likely more refrigerant
will be required to complete the charging procedure.
Adjust the refrigerant charge until the sight-glass clears or has sparse bubbles. The unit should be
allowed to stabilize for several minutes before meaningful measurements can be taken.
A properly charged system operating at typical parameters will have the following pressures:
Units with R-407C Head pressure 240 – 295 PSIG
Suction Pressure 58 PSIG or greater
Units with R-410A Head pressure 340 – 415 PSIG
Suction pressure 104 – 121 PSIG
The superheat at the compressor suction line should be 8 – 15 degrees. Sub-cooling should be
8 – 10 degrees.
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