Johnson Controls YEWS Series, Installation, Operation And Maintanance Instructions

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6. Replace the water box gasket with a new gasket and
reassemble the water boxes onto the condenser.
Evaporator tubes
The standard evaporator tubes used in YORK YEWS-E
Chillers are internally enhanced copper tubes.
If the equipment is located in an unheated area
that is susceptible to freezing, the water must be
drained from the evaporator to prevent tube
damage from freezing.
Maintain evaporator water or brine flow rates through the
evaporator tubes that the chiller was designed for. Refer to
the engineering data on the sales order form for the
correct flow rates. Generally, the water or brine that is
circulated through the evaporator is part of closed loop
circuit that is treated with chemicals to prevent the
formation of scale and debris.
Evaporator
It is difficult to determine by a particular test whether
possible lack of performance of water evaporator is due to
fouled tubes alone or due to a combination of troubles.
Trouble which may be due to fouled tubes is indicated
when, over a period time, the cooling capacity decreases
and the split (temperature difference between the water
leaving the evaporator and the refrigerant temperature in
the evaporator) increases. A gradual drop off in cooling
capacity can also be caused by a gradual leak of
refrigerant from the system or by a combination of fouled
tubes and shortage of refrigerant charge. An excessive
quantity of oil in the evaporator can also contribute to
erractic performance.
If cleaning of the evaporator tubes is required, follow the
condenser cleaning procedure.
8.6 Checking System For Leaks
Leak Testing During Operation
The refrigerant side of evaporator is carefully pressure
test and evacuated at factory.
WARNING
After system is operated under load, the high pressure
components should be carefully leak test with a leak
detector to be sure all joins are tight.
If a leak exits, frequent purging will be required or
refrigerant will be lost.
If any leaks are indicated, they must be repaired
immediately. Usually, leak can be stopped by tightening
flare nuts or flange bolts. However, if it is necessary to
repaired a weld joins, the refrigerant charged muse be
removed. (See the
“
Handling Refrigerant for Disma-ntling
and Repair
”
Section of the Maintenance Section in this
manual).
Conducting R-134a Pressure Test
With the R-134a charge removed and all known leaks
repaired, the system should be charge with a small amount
of R-134a mixed with dry nitrogen so that a halide torch or
electronic leak detector can be used to detect any leaks too
small to be found by soap test.
To test with R-134a, proceed as follows:
1. With no pressure in the system, Charge R-134a gas and
dry nitrogen into the system through charge valve to a
pressure of 150PSI..
2. To be sure that the concentration of refrigerant has
reached all parts of the system, slightly open the oil
charging valve and test the presence of refrigerant with a
leak detector.
3. Test around each join and factory weld. It is important
that this test is thoroughly and carefully done, spending as
much time as necessary and using a good leak detector.
4. To check for refrigerant leaks in evaporator and
condenser, open the vents in the condenser and evaporator
heads and test for presence of refrigerant. If no refrigerant is
present, the tubes and tube sheets can be considered tight. If
refrigerant is detected at the vents, the head must be
removed, the located (by means of soap test or leak
detector)and repaired.
YEWS-E Water Cooling Screw Chiller/Heat Pump
60