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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.
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 operating, liquid refrigerant will flow into the condenser.
Approximately 75% of the total requirement estimated for the unit can be charged in this
manner.
5.
After 75% of the required charge has entered the condenser, reconnect the refrigerant drum
and charging line to the service valve on the bottom of the evaporator. Again purge the
connecting line, stand the drum with the connection up, and place the service valve in the
open position.
IMPORTANT: At this point, the charging procedure should be interrupted and prestart
checks made before attempting to complete refrigerant charge. The compressor must
not be started at this time. (Preliminary check must first be completed.)
NOTE: It is of utmost importance that all local, national, and international regulations
concerning the handling and emission of refrigerants are observed.
52
Centrifugal Chillers
The system is first evacuated to
D-EIMWC00804-14EN
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