Analysis of Common Faults of Fully Enclosed Refrigeration Compressor

Date:May 04, 2020

01.how to identify the 3 terminals on the fully enclosed compressor casing?

[China Refrigeration Network] The resistance between the operating terminal (R), the starting terminal (S), the common terminal (C) and RS is greater than that between SC and RC.  The resistance between RS is equal to the resistance between SC and RC.

The above rules can be used to distinguish.  It should be noted that the resistance values of the terminal temperature rise testing machine of the three-phase compressor are equal.

02.How to judge the compressor motor winding short circuit?

Use multimeter to select resistance gear, and measure the resistance value of compressor motor winding C-R or C-S after zero adjustment.  If the resistance value of the measured winding is less than the normal value, the winding can be judged to be short-circuited.

Three-phase compressor:

The resistance measured twice is infinite, indicating that a group of windings is open circuit.

All three tests are infinite, indicating that at least two groups of windings are open circuit.

The resistance measured in 2 of the 3 measurements is obviously smaller than that measured in the other, indicating a short circuit.

03.How to judge the compressor motor touching the ground?

Use the resistance of the multimeter.  Then, tightly fasten one pen to the common point, fasten the other pen to the exposed metal part of the compressor process pipe, or support a small piece of paint on the shell plate for measurement.  If the resistance value is very small, it can be judged that the winding or internal wiring touches the ground.

04.How to Judge Open Circuit of Compressor Motor Winding?

Adjust the multimeter to the resistance position, connect the probe to the terminals of any two windings, and measure the resistance value.  If the winding value is infinite, i.e. there is no conduction between the terminals of the two windings, the open circuit of this winding can be judged.

05.compressor does not start check what?

Check whether compressor overload, pressure switch and overcurrent protector are tripped or damaged.

Check the indoor temperature sensor and tube temperature sensor for open circuit or poor contact and short circuit.

Check whether the relay is engaged, whether the compressor is open or short-circuited, and whether the compressor capacitance is bad.

06.What are the reasons why the compressor is overheated and shut down soon after starting?

Insufficient or excessive refrigerant, blocked capillary assembly, and air leakage inside the four-way valve.

Faults of the compressor itself, such as short circuit, open circuit, touching the shell to the ground, etc.

If the high pressure is too high, the pressure relay will act.

The condenser has poor ventilation or short circuit, or the system is mixed with non-condensable gas.

Ambient temperature of outdoor unit is too high.

The compressor is stuck with cylinder or shaft.

07.compressor performance of low efficiency

Generally speaking, the exhaust pressure drops, the suction pressure rises, and the temperature of the compressor cylinder head and suction and exhaust chambers is too high.



08.Judgment of compressor loss of working capacity

First, try whether the suction port has suction or not, then try whether the exhaust port has exhaust, and plug the exhaust port with your hands. If you feel that the pressure is not very high or even there is no exhaust, you can think that the compressor has lost its working capacity.

09.Why is the current of compressor motor too large?

The compressor has a short circuit between turns, but it has not reached the level of blowing fuse.  The "secondary friction" of the compressor has damaged the smoothness of the friction surface, resulting in an increase in the power and current of the compressor, but it has not yet reached the level of "locking the shaft" or "blocking the cylinder", which prevents the compressor from rotating.

Check the insulation resistance of the compressor to ground with a multimeter. Under normal circumstances, it should be more than 2MΩ. If it becomes smaller or approaches zero, it indicates a short circuit.  If the insulation resistance to ground is normal, check the resistance value of the starting and running windings.  If there is an interturn short circuit, the operating current will increase.

10.Why is it difficult to start the motor of 3-phase compressor?

The power supply voltage is too low and the compressor motor winding is short-circuited.

11. How to eliminate the faults of three-phase compressor motor such as slow speed, one-phase fuse blowing and one-phase current increasing during operation?

It is often caused by the compressor motor winding colliding with the casing.  After removing the grounding wire, electroprobe can be used to test whether the casing is charged.  If the casing is charged, rewind the compressor motor winding or replace the compressor.

12.How to eliminate the "utter" sound from the three-phase compressor motor during operation?

The motor of the three-phase compressor emits "noise" during operation, which is caused by serious unbalance of the three phases. If one phase of power supply is out of phase, the three phases can be restored.

13. How to Eliminate Reversal of Three-phase Compressor Motor?

It is caused by wrong wiring and can be replaced by two lines in three phases.

14.compressor replacement sequence and points for attention

R22 is a non-combustible gas, but if it comes into direct contact with high-temperature flame, toxic gas will be generated. Therefore, the refrigerant in the refrigeration system will be discharged before welding operation.

R32 is flammable and explosive refrigerant, and our refrigeration encyclopedia has repeatedly emphasized the characteristics of this refrigerant.  If the R32 refrigeration equipment needs to be replaced for maintenance of the refrigeration system, it must be vacuumized before operation!  Be careful not to introduce fire!

R410A is low toxic, non-flammable and non-explosive. Replace the compressor, make sure to use the compressor of R410A, and never use R22 compressor to install it.  When replacing the valve member, the valve body of R410A is specially marked.

15.What are the types of overload protectors for air conditioner compressors?

External overload protector;  Buried overload protector.

16.What is the protection of the compressor?

Overload protector: mainly used for overcurrent and overheat protection of compressor motor.

Internal protector: mainly protects the compressor motor from overcurrent.

Thermal relay: mainly used for line overcurrent protection of three-phase compressor motor.

Inversion preventer: mainly used in three-phase rotary compressor to prevent the compressor from inverting or lacking phase energy in the rotation direction.

17.What are the common causes of 17 overload protectors?

The power supply voltage is too low and the symmetry of the three-phase voltage is poor.

Compressor motor runs at low speed for extended time.

The compressor motor operates under low voltage and load for a long time.

The cooling medium passage of compressor motor is blocked.

The operating environment temperature is too high.

18.What is the liquid impact of the compressor?

The refrigerant is not completely evaporated in the evaporator, causing the refrigerant to be sucked back by the compressor in wet vapor or liquid state, resulting in liquid impact of the compressor.

Liquid percussion will cause valve plates, valve plates and pistons to be damaged and damaged. In serious cases, the connecting rod may deform and even the compressor may be damaged.

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