20/21
TROUBLESHOOTING
Examples of faults and solutions
FAULT
PROBABLE CAUSE
ACTION REQUIRED
1. Suction
Temperature too
high
Too much suction gas superheat
(above 20K)
Examine and adjust the thermostatic expansion
valves in the evaporators.
2. Suction
Temperature too
low
Liquid in the suction line.
Adjust thermostatic expansion valves.
Sensor bulb is loose or incorrectly positioned.
Check if the bulb is in contact with the suction line
and replace if necessary
3. Suction
Pressure too low
Too much oil in evaporators.
Drain oil from evaporators.
Filter in the liquid line clogged.
Examine and clean filters in liquid line.
Suction filter blocked.
Check suction filter.
Too much superheat of suction gas.
Adjust thermostatic expansion valves.
Thermostatic expansion valve blocked when in
closed position.
De-ice thermostatic expansion valve using warm
rags. If no improvement, change the thermostatic
expansion valve.
Problem with solenoid valve in the liquid line.
Check wiring and coil – replace if necessary
Installation insufficiently charged.
Charge the installation with refrigerant.
4. Compressor cuts
in and out too
often on LP safety
switch
See point 3
Low pressure safety switch set too high.
Adjust pressure safety switch.
5. Suction
Pressure too high
Restart after defrost.
Wait for confirmation
Compression problems
Change compressor
6. Condenser
Pressure too high
Insufficient flow of air in to the condenser
Clean the condenser. Check motor fans
Fan cut in not adjusted correctly
Adjust
High pressure safety valve set too low
Set pressure valve at maximum 0.9xPS, but take
into account the compressor limit.
Installation flooded
Drain liquid into receiver
Air or non-condensable gas in the HP circuit
Let air out at highest point.
7. Condenser
pressure too low
Fan cut-in incorrectly set.
Adjust pressure switch
8. Discharge
Temperature too
high
Too much superheat on suction.
Adjust thermostatic expansion valves.
9. Oil temperature
too high
Superheat on suction too great.
Check and adjust thermostatic expansion valves
Valve problems.
Check pressures. If necessary, adjust valves and
gaskets.
10. Oil
temperature too
low
Crankcase heater out of order.
Replace heater
Oil return saturated in liquid refrigerant
Adjust thermostatic expansion valve
11. Capacity too
great
Problem with control system or other automatic
devices.
Replace, repair or re-set
12. Insufficient
Capacity
Problem with control system or other automatic
devices
Replace, repair or re-set.
13. Oil foams
heavily after
stoppage
Thermostatic expansion valve (fluid in suction
line).
Check thermostatic expansion valve.
Bulb loose or incorrectly positioned
Check bulb position
Crankcase heater out of order
Replace heater
