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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 or R-513A. 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.
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Unit Startup and Maintenance
Charging the System
WSC 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.
NOTE: At this point, the charging procedure should be
interrupted and pre-start 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.
Oil Analysis
Interpreting Oil Analysis Data
Oil wear metals analysis has long been recognized as a useful
tool for indicating the internal condition of rotating machinery
and continues to be a preferred method for Daikin Applied
centrifugal chillers. Daikin Applied service or a number of
laboratories specializing in oil testing can do the test. To
accurately estimate the internal condition it is essential to
properly interpret the oil wear test results.
Numerous test results from various testing laboratories have
recommended action that has prompted unnecessary concern
by customers. Polyolester oils are excellent solvents and can
readily dissolve trace elements and contaminants. Most of
these elements and contaminates eventually end up in the oil.
Also, the polyolester oils used in R-134a and R-513A chillers
67
IOM 1274-3 • CENTRIFUGAL WATER CHILLERS
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