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approximately 20 psig. It is possible that the unit might experience a mild surge condition prior to cutout. If this
should occur, immediately shut off the compressor. Use a portable condensing unit to complete the pump down,
condense the refrigerant, and pump it into the condenser or pumpout vessel using approved procedures.
A pressure regulating valve must always be used on the drum being used to build the system pressure. Also, do not
exceed the test pressure given above. When the test pressure is reached disconnect the gas cylinder.
Pressure Testing
No pressure testing is necessary unless some damage was incurred during shipment. Damage can be determined
upon a visual inspection of the exterior piping, checking that no breakage occurred or fittings loosened. Service
gauges should show a positive pressure. If no pressure is evident on the gauges, a leak may have occurred,
discharging the entire refrigerant charge. In this case, the unit must be leak tested to determine the location of the
leak.
Leak Testing
In the case of loss of the entire refrigerant charge, the unit must be checked for leaks prior to charging the complete
system. This can be done by charging enough refrigerant into the system to build the pressure up to approximately
10 psig (69 kPa) and adding sufficient dry nitrogen to bring the pressure up to a maximum of 125 psig (860 kPa).
Leak test with an electronic leak detector. Halide leak detectors do not function with R-134a. Water flow through
the vessels must be maintained anytime refrigerant is added or removed from the system.
If any leaks are found in welded or brazed joints, or it is necessary to replace a gasket, relieve the test pressure in the
system before proceeding. Brazing is required for copper joints.
After making any necessary repair, the system must be evacuated as described in the following section.
Evacuation
After it has been determined that there are no refrigerant leaks, the system must be evacuated using a vacuum pump
with a capacity that will reduce the vacuum to at least 1000 microns of mercury.
A mercury manometer, or an electronic or other type of micron gauge, must be connected at the farthest point from
the vacuum pump. For readings below 1000 microns, an electronic or other micron gauge must be used.
The triple evacuation method is recommended and is particularly helpful if the vacuum pump is unable to obtain the
desired 1 millimeter of vacuum. The system is first evacuated to approximately 29 inches of mercury. Dry nitrogen
is then added to the system to bring the pressure up to zero pounds.
Then the system is once again evacuated to approximately 29 inches of mercury. This is repeated three times. The
first pulldown will remove about 90% of the noncondensables, the second about 90% of that remaining from the first
pulldown and, after the third, only 1/10-1% noncondensables will remain.
Charging the System
DWSC and DWDC water chillers are leak tested at the factory and shipped with the correct charge of refrigerant as
indicated on the unit nameplate. In the event the refrigerant charge was lost due to shipping damage, the system
should be charged as follows after first repairing the leaks and evacuating the system.
1.
Connect the refrigerant drum to the gauge port on the liquid line shutoff valve and purge the charging line
between the refrigerant cylinder and the valve. Then open the valve to the mid-position.
2.
Turn on both the cooling tower water pump and chilled water pump and allow water to circulate through the
condenser and the chiller. (It will be necessary to manually close the condenser pump starter.)
3.
If the system is under a vacuum, stand the refrigerant drum with the connection up, and open the drum and
break the vacuum with refrigerant gas to a saturated pressure above freezing.
4.
With a system gas pressure higher than the equivalent of a freezing temperature, invert the charging cylinder
and elevate the drum above the condenser. With the drum in this position, valves open, water pumps
D–EIMWC00808-16HU - 53/64
Do not use oxygen or a mixture of R-22 and air to build up pressure
as an explosion can occur causing serious personal injury.
WARNING
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