Water/Glycol Cooled Systems; Water/Glycol Cooled Systems Charging - DA Data Cool Series Installation, Operation And Maintanance Manual

5.3 Water/Glycol Cooled Split Systems
5.3.1. Water/Glycol Cooled Split Systems Charging
All water/glycol Data Cool units are split systems requiring field charge. After the refrigerant piping and
water line piping is properly completed, connect the refrigerant drum to the low side and charge with
vapor. Charge with approximately three lbs. per nominal ton.
For example, a model DACU 0334-AO is a nominal 3 ton unit. Charge with about 9 lbs. of refrigerant to
begin. It is likely that more refrigerant will be required to complete the charging procedure. Make sure
all hoses are properly purged.
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.
Start the evaporator fan and compressor. Check the liquid line sight glass to get a feel for the approximate
charge. Bubbles in the sight glass are not unusual at this point and can be caused by flashing from liquid
line pressure drop, low sub-cooling or low charge. It is likely that more refrigerant will be required to
complete the charging procedure.
Adjust the refrigerant charge until the sight glass clears or has only 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 a head pressure of 225 to 275 psi.
Suction pressure should be 58 psi or greater. The superheat at the compressor suction line at least 6
inches away from the compressor should be 8-15°.
Note: Charging to a full liquid line sight glass should never be the sole means of determining
the correct refrigerant charge. Other parameters such as superheat, suction pressure, head
pressure, sub-cooling and ambient temperature are also important parameters. A system
charged to a clear sight glass is often overcharged.
The water regulating valve should be adjusted to maintain 230 to 260 psi head pressure. Suction
pressure should be 58 psi or greater. The superheat at the compressor suction line at least 6 inches
away from the compressor should be 8-15°.
It is necessary to measure and note proper unit operation including superheat, head and suction pressure.
Some adjustment to charge may be required.
Adjust the refrigerant charge again until the sight glass clears or has only sparse bubbles. The unit
should be allowed to stabilize for several minutes before meaningful measurements can be taken.
All water/glycol cooled units have a water regulating valve. A head pressure sensing transducer is
connected to a shrader fitting on the discharge line and water is regulated into the condenser coil.
Condenser coils may be plate fin or coaxial type.
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