ST-SP Pag. 59 Rev 02 05/13
UK
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POSSIBLE CAUSES SOLUTIONS
A
The compressor does not start and does not release a humming sound
1 Lack of voltage. Start-up relay with open contacts.
2 Thermal cut-off intervenes.
3 Loose electrical connections or incorrect electrical connections.
1 Check the line or replace the relay.
2 Re-check the electrical connections.
3 Tighten or re-do the connections in accordance to the
wiring diagram.
B
The compressor does not start (releases humming sound) and the
thermal cut-off intervenes
1 Incorrect electrical connections.
2 Low voltage supply to the compressor.
3 Defective start-up of the condenser.
4 Relay does not close.
5 Winding of the electrical motor interrupted or in short-circuit.
1 Re-do the connections.
2 Identify the cause and eliminate it .
3 Identify the cause and replace the condenser.
4 Identify the cause and replace the relay if necessary.
5 Replace the compressor.
C
The compressor starts but the relay does not open
1 Incorrect electrical connections.
2 Low voltage supply to the compressor.
3 Relay blocked in closed position.
4 Excessive discharge pressure.
5 Winding of the electrical motor interrupted or in short-circuit.
1 Check the electrical circuit.
2 Identify the cause and eliminate it.
3 Identify the cause and eliminate it .
4 Identify the cause and replace the relay if necessary.
5 Replace the compressor.
D
Intervention of the thermal cut-off
1 Low voltage supply to the compressor (imbalanced phases on tri-
phase motors).
2 Defective thermal cut-off.
3 Defective running condenser.
4 Excessive discharge pressure.
5 Suction pressure too high.
6 Compressor overheated, hot return gas.
7 Winding of the compressor motor in short-circuit.
1 Identify the cause and eliminate it.
2 Check its characteristics and replace it if necessary.
3 Identify the cause and eliminate it .
4 Check the ventilation and any possible restrictions or
obstructions in the system circuit.
5 Check the sizing of the system. Replace the condensing
unit with a more powerful one, if necessary.
6 Check the refrigerant load; repair the potential loss and
add gas if necessary.
If the semi-machine does not have a safety valve, the load of
refrigerant gas must be lower than 10 kg.
7 Replace the compressor.
E
The compressor starts and circulates, with short-spanned function cycles
1 Thermal cut-off.
2 Thermostat.
3 Intervention of the high pressure meter, due to the insufficient
cooling of the condenser.
4 Intervention of the high pressure meter, due to the excessive load
of refrigerant gas.
5 Intervention of the low pressure meter, due to the scarce load of
refrigerant gas.
6 Intervention of the low pressure meter, due to the restriction or
clogging of the expansion valve.
1 See previous point (thermal cut-off intervention).
2 Small differential; correct adjustment .
3 Check that the motorized ventilator functions correctly or
clean the condenser.
4 Reduce the refrigerant load.
5 Repair the loss and add refrigerant gas.
If the
PARTLY COMPLETED MACHINERY does not have a safety valve, the
load of refrigerant gas must be lower than 10 kg.
6 Replace the expansion valve.
F
The compressor functions uninterruptedly or for long periods
1 Poor load of refrigerant gas.
2 Thermostat contacts blocked in closed position.
3 System insufficiently sized in function of the load.
4 Excessive load to cool or insufficient insulation.
5 Evaporator covered with ice.
6 Restriction in the system circuit.
7 Condenser clogged.
1 Repair the loss and add refrigerant gas.
If the
PARTLY COMPLETED MACHINERY does not have a safety valve, the
load of refrigerant gas must be lower than 10 kg.
2 Replace the thermostat.
3 Replace the system with a more powerful one.
4 Reduce the load and improve insulation, if possible.
5 Defrost.
6 Identify the resistance and eliminate it .
7 Clean the condenser.
G
Running condenser damaged, interrupted, or in short-circuit
1 Incorrect running condenser.
1 Replace the condenser with the correct type.
H
Start-up relay defective or burnt out
1 Incorrect relay.
2 Relay assembled incorrectly .
3 Incorrect running condenser.
1 Replace with the correct relay.
2 Reassemble the relay in the correct position.
3 Replace the condenser with the correct type.
I
Compartment temperature too high
1 Thermostat regulated too high.
2 Expansion valve under-sized.
3 Evaporator under-sized.
4 Insufficient air circulation.
1 Regulate correctly.
2 Replace the expansion valve with a suitable one.
3 Replace it increasing the surface of the evaporator.
4 Improve air circulation.
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