Troubleshooting
The following tables include the most common problems. For detailed troubleshooting of the
refrigeration plant, refer to the manual of the plant or common refrigeration literature.
Refrigeration plant, general issues
Table 20: Refrigeration plant, general issues
Symptom
Probable cause
Solution
Refrigeration load lower than
compressor capacity
Reduce compressor capacity
High suction line loss
Check valves, strainers, and
similar
Suction pressure
(excessively low)
Malfunction of evaporator
Check the evaporator for
issues, such as, fouling, and
accumulated oil. Check the
liquid expansion valve system,
the filter in liquid line, and
refrigerant charge (insufficient)
Safety cut-out set too low
Check the settings of alarms
and warnings (control system)
and the separate safety
pressure cut-out
High discharge line loss
Check the valves and check
valve
Malfunctioning of condenser
Check the condenser, the liquid
drain from the condenser,
the refrigerant charge (too
much), the water and air inlet
temperature (too high), and the
water and air flow (too low)
Discharge pressure
(excessively high)
Air or non-condensable gasses
in the system
Purge the air from the
condenser side
Compressor unit, general issues
Table 21: Compressor unit, general issues
Symptom
Probable cause
Solution
Electrical supply
Check the main switch and
fuses. Reset the emergency
stop switch.
Alarm in control system
Register the alarm, correct if
necessary, and reset. Refer to
the Control manual
Compressor cannot start
Oil level too low
Charge oil
Compressor starts but
immediately stops
Oil system failure (temperature,
pressure, level)
Check oil level and check the
valve positions
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SAB 283-355 A-Frame OHU 6042 and OHU 7650 (including ATEX) Screw Compressor Unit
