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2.
Stand the refrigerant cylinder with the connection up. In order to avoid possibility of freezing the
liquid within the evaporator tubes when charging an evacuated system, only refrigerant vapor
from the top of the refrigerant cylinder must be admitted first.
3.
Just before connecting the charging line to the service valve on top of the evaporator, open the
valve on the cylinder and purge any air in the charging line.
4.
After purging the charging connection and connecting the line to the evaporator, keep the
evaporator service valve closed while the cylinder valve is open. The charging line should be
filled with refrigerant and with very little or no air at this point.
5.
Turn on both the cooling tower water pump and chilled water pump and allow water to circulate
through the chiller. In order to lower the chiller system pressure, low water temperature is
recommended to accelerate the charging. Chiller system pressure as well as refrigerant cylinder
pressure should be monitored during charging process. Make sure the cylinder pressure is always
higher than the chiller system pressure in order to maintain refrigerant flow by pressure
differential.
6.
If there is oil in the oil sump, then energize the oil heater before charging with any refrigerant.
This will keep the oil hot and prevent any refrigerant concentration in the oil by boiling of the
refrigerant from the oil.
7.
Then open the service valve on top of the evaporator to the mid-position and break the vacuum
with refrigerant gas to a saturated pressure above the point corresponding to the freezing point of
the liquid to avoid the possibility of freezing liquid within the evaporator tubes. If the liquid is
water, then the system pressure corresponding to the freezing point would be 28 psig ( 0.19
MPaG ) for R-134a ( at sea level ). Therefore, keep charging with refrigerant vapor until the
chiller pressure is well above 28 psig.
8.
After the chiller pressure is above 28 psig by gas charging, the rest of the charge could be put
into the system by refrigerant liquid form and without water circulation even though running
water pumps until the end of charging process is strongly recommended.
9.
Reconnect the refrigerant cylinder and charging line to the service valve on the bottom of the
evaporator. Again purge the connecting line, stand the cylinder with the connection up, and place
the service valve in the open position.
10. At some point both the chiller and cylinder pressures might equalize with each other during the
charging process and in return that might slow or stop the process. However, there a few ways to
prevent situations like this (see #11 – 14 below).
11. Circulate cold water through the evaporator and condenser tubes to keep the chiller system
pressure lower.
12. If there is a crane in the facility, invert the charging cylinder and elevate the cylinder above the
evaporator. With the cylinder in this position, valves open, water pumps operating, liquid
refrigerant will flow into the evaporator by gravitational force.
13. If there is no crane capability in the facility, heat lamps are recommended to heat the cylinder to
raise the pressure. A recovery unit can be used to create a pressure difference.
14. If there are no crane or heat lamps available, then start the chiller and run at part load and low
condenser water temperature. Low evaporator pressure will improve and accelerate the rest of
the charging rapidly.
If charge needs to be added to improve performance, repeat Step 8 above while the chiller is running
at full load capacity and check the refrigerant charge level through sight glasses. The level on the
OMM WCT
While charging, every precaution must be taken to prevent moisture laden air from
entering the system.
Centrifugal Chillers
NOTE
!
D-EOMWC01302-16EN - 75/84
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