Common failures and causes analysis of refrigeration compressors
The refrigeration compressor is the heart of the entire refrigeration system and the most important in the refrigeration system. Its main function is to compress the low-temperature and low-pressure gas from the evaporator into high-temperature and high-pressure gas to provide source power for the entire refrigeration cycle.
There are mainly three types of compressors used in air conditioners: piston type, rolling rotor type, and scroll type.
Piston:
Rolling rotor type:
Scroll compressor:
Properly handle the compressor:
The sequence of pulling out the rubber plug: first exhaust pipe and then suction pipe. If the rubber plug of the suction pipe is pulled out first, the refrigerating oil collected on the filter screen of the reservoir will be sprayed out with nitrogen, so pull the rubber plug of the exhaust pipe first to reduce the nitrogen pressure in the compressor, and alleviate and eliminate the oil spray phenomenon
1. How to identify the 3 terminals on the casing of a hermetic compressor?
The resistance between running terminal (R), starting terminal (S), common terminal (C), RS is greater than the resistance between SC and RC. The resistance between RS is equal to the resistance between SC and the resistance between RC.
The above rules can be used to distinguish. It should be noted that the resistance value of the terminal temperature rise tester of the three-phase compressor is equal.
2. How to judge the compressor motor winding short circuit?
Use a multimeter to select the resistance gear, and after zero adjustment, measure the resistance value of the compressor motor winding C-R or C-S. If the resistance value of the measured winding is less than the normal value, it can be judged that the winding is short-circuited.
Three-phase compressor:
◆ The resistance value measured twice is infinite, indicating that one set of windings is open;
◆ All three tests are infinite, indicating that at least two sets of windings are open;
◆ In 2 of the 3 measurements, the measured resistance value was significantly lower than the other, indicating a short circuit.
3. How to judge that the compressor motor hits the shell and passes the ground?
Use the resistance file of the multimeter. Then put one pen tightly against the common point, and another test pen tighten the compressor process tube to expose the metal part, or take off 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 the internal wiring touches the shell through the ground.
4. How to judge that the compressor motor winding is open?
Adjust the multimeter to the resistance range, connect the test leads to the terminals of any two windings, and measure the resistance value. If the winding value is infinite, that is, there is no conduction between the terminals of the two windings, it can be judged that the winding is open.
5. What to check if the compressor does not start?
◆ Check whether the compressor is overloaded, the pressure switch, and the overcurrent protector are tripped or damaged.
◆ Check whether the indoor temperature sensor and tube temperature sensor are open or poorly connected, and whether they are short-circuited in the heating state.
◆ Check whether the relay is closed, whether the compressor is open or short-circuited, and the compressor capacitor is broken.
6. What are the reasons for the compressor to be overheated and stop soon after starting?
◆ The refrigerant is insufficient or excessive, the capillary assembly is blocked, and the inside of the four-way valve is leaking.
◆ The compressor itself is faulty, such as short circuit, open circuit, contact with the shell and ground.
◆ If the high pressure pressure is too high, the pressure relay will act.
◆ The condenser is poorly ventilated or the air flow is short-circuited, or the system is mixed with non-condensable gas.
◆ The ambient temperature of the outdoor unit is too high.
◆ Compressor jam or shaft holding.
7. The performance of low compressor efficiency
Generally, the discharge pressure drops, the suction pressure rises, and the temperature of the compressor cylinder head and suction and discharge chambers is too high.
8. Judgment of the compressor's inability to work
First test whether the suction port is inhaled, and then test whether the exhaust port is exhausted, and block the exhaust port with your hand. If you feel that the pressure is not very large, or even there is no exhaust, it can be considered that the compressor has lost its working ability.
9. Why is the compressor motor too current?
There is a short circuit between the compressor turns, but the fuse is not blown. The "secondary friction" of the compressor destroys the smoothness of the friction surface, causing the compressor's power and current to increase, but it has not reached the level of "holding shaft" or "cylinder jamming", preventing the compressor from rotating.
Use a multimeter to check the insulation resistance of the compressor to the ground. Normally, it should be above 2MΩ. If it becomes smaller or close to 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 a short circuit between turns, the operating current increases.
10. What are the reasons for the difficulty in starting the three-phase compressor motor?
◆ The power supply voltage is too low and the compressor motor winding is short-circuited.
11. How to troubleshoot the problems that the speed of the three-phase compressor motor slows down, the fuse of one phase is blown, and the current of one phase increases during operation?
◆ It is often caused by a phase of the compressor motor windings touching the ground. After removing the ground wire, use a test pencil to test whether the case is live. If the casing is live, rewind the compressor motor winding or replace the compressor.
12. How to eliminate the "whooping" sound from the three-phase compressor motor during operation?
◆ The three-phase compressor motor emits a "babble" during operation, which is caused by the serious imbalance of the three phases. One phase of the power supply is missing, and the three phases can be restored.
13. How to exclude the reverse rotation of the three-phase compressor motor?
◆ It is caused by a wiring error, just exchange two wires of the three-phase arbitrarily.
14. Compressor replacement sequence and points of attention
◆ R22 is a non-flammable gas, but if it comes into direct contact with a high-temperature flame, toxic gas will be generated. Therefore, before welding, release the refrigerant in the refrigeration system.
◆ R32 is a flammable and explosive refrigerant. Our Refrigeration Encyclopedia has repeatedly emphasized the characteristics of this refrigerant. Any R32 refrigeration equipment involved in the maintenance of the refrigeration system requires replacement of parts, it must be vacuumed before operation! Be careful not to introduce fire sources!
◆ R410A is low-toxic, non-flammable and non-explosive. To replace the compressor, you must use the R410A compressor, and absolutely cannot use the R22 compressor to install it. When replacing the valve, there is a special mark on the valve body of R410A
15. What are the types of compressor overload protectors for air conditioners?
◆ External overload protector; embedded overload protector.
16. What are the protections of compressors?
◆ Overload protector: Mainly used for overcurrent and overheat protection of compressor motors.
◆ Internal protector: It mainly protects the compressor motor from overcurrent.
◆ Thermal relay: Mainly used for line overcurrent protection of three-phase compressor motors.
◆ Reverse phase preventer: Mainly used for three-phase rotary compressors to prevent the compressor from reversing the direction of rotation or lacking phase energy.
17. What are the common reasons for overload protectors?
◆ The power supply voltage is too low and the symmetry of the three-phase voltage is poor.
◆ The compressor motor runs at low speed for extended time.
◆ The compressor motor runs at low voltage and load for a long time.
◆ The cooling medium path of the compressor motor is blocked.
◆ The operating environment temperature is too high.
18. What is the hydraulic shock of the compressor?
◆ The refrigerant does not completely evaporate in the evaporator, causing the refrigerant to be sucked back by the compressor in wet vapor or liquid form, causing liquid shock to the compressor.
◆ Liquid shock will cause damage to the valve disc, valve plate, and piston. In severe cases, the connecting rod may also be deformed, or even the compressor may be damaged.
