GEA Grasso - Guide to Disturbances, Their Causes and Remedies

OPERATING INSTRUCTIONS
CO
2
/NH
3
CASCADE UNIT
250 - 1000 KW
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4.9 Guide to disturbances, their causes and remedies
The units/ CO
2
/NH
3
-cascade units manufactured by Grasso GmbH Refrigeration Technology are highly advanced,
automatic and extremely efficient systems. It is, however, possible that disturbances may occur, making it difficult
to maintain continuous operation or causing part or the whole of the system to break down.
Table of disturbances
Failure Cause Remedy
Slow loss of refrigerant through
leaks in the refrigerant circuit.
Check the entire system for leaks.
Repair where found and top up the
refrigerant if necessary.
Pressure gauge defective. Replace manometer.
Defective capacity control devices in
the compressors
Check capacity control devices,
connections for solenoid valves.
The suction pressure is too low,
performance reduced and the
system overheats.
The suction filters in the chiller are
clogged.
Remove suction filter elements, clean
or replace.
The suction pressure increases and
the compressors become covered
with a thick layer of hair frost or
makes noises which indicate the
presence of liquid (refrigerant) in the
compressors.
The compressors are sucking in wet
steam or liquid when it is started up.
The safety device to prevent a too
high liquid level is not responding.
Check liquid levels, drain some
refrigerant if necessary. Repair safety
device. Check superheat.
The condensation pressure is too
high.
There is air or other non-
condensable gases in the refrigerant
circuit.
The refrigerant circuit should be
vented.
The electrical circuit is interrupted by
a pressure switch in the safety chain.
Switch on the power supply, check
the pressure switch and replace or
set properly as appropriate.
The compressors do not start up
after the system is switched on or
turns itself off again.
No oil pressure is building up in the
unit/ cascade. The oil circuit is
disturbed by clogged oil filters or
leaks.
Replace or clean the oil filters, seal
the leaks and top up with oil.
The compressors do not adjust to
the required capacity.
The capacity control device is
malfunctioning due to disturbances
in the oil circuit or mechanical
influences.
Check the oil circuit. The
compressors should only be repaired
by experts. Check the position
detector of the compressor control
slide.
The condensation pressure is too
high.
See above. The compressors are shut off very
often by the maximum pressure
governor.
The maximum pressure governor is
defective or set wrongly.
Remove the maximum pressure
governor, repair it, set it correctly or
replace it.