Operating manual – DualPAC with reciprocating compressors
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5.6
Shutdown and alarms
5.6.1
Operating state
Experience has shown that variations in pressures and temperatures within the cooling cycle can
provide information about the operating state of a DualPAC.
In particular, suction and condensing pressures, as well as the temperatures of suction and pres-
sure gas, can provide important information.
Often, small changes in the variable pressures and temperatures are sufficient to create consider-
able changes in the operating conditions.
It is therefore very important to use the already mentioned logbook. If a DualPAC is not operating
in optimal conditions, the economy of the plant will not be optimal either.
Irregularities in the plant will often cause changes in the operating conditions but not make the
plant stop. Consequently, the operating state of a refrigeration plant must be checked at regular
intervals.
5.6.2
Troubleshooting
Too high condensing pressure
Cause
Solution
Insufficient water flow through the
condenser
Adjust water supply, or clean the condenser.
Fouling in the condenser
Clean the condenser.
Too high hot water temperature
Check hot water system, or reduce compressor
capacity.
Air or non-condensable gases in the
system
Remove air from the condenser.
A 1°K lower condensing temperature results in a 1% higher cooling performance and 3% lower
power consumption.
Too low evaporating temperature
Cause
Solution
Fouling in the evaporator
Clean the evaporator.
Oil in the evaporator
Inspect the oil recovery system.
Insufficient R717 charge
Check liquid level in evaporator.
Charge more R717 to the plant.
Suction gas superheat should be approx. 1.5 to 4°K.
A 1°K higher evaporating temperature results in a 4% higher cooling performance.
Missing oil
During the first 50 hours of operation, the compressor will lose oil. A few litres of oil will accumu-
late at the bottom of the oil separator, condenser and evaporator and never return to the com-
pressor. It is therefore not unusual that the compressor needs to be recharged with oil.
