Do you know the answers to frequently asked questions about refrigeration compressors?

Date:Apr 30, 2020

1. Why should the impurity content and moisture content of compressor and air conditioning system be controlled?

[China Refrigeration Network] Impurities entering the friction surface of moving parts in the compressor pump body will cause abnormal scratches and wear. Impurities entering the electromagnetic valve, expansion valve, control valve, capillary tube and stop valve in the refrigerator system will block the valve hole or make the valve close loosely and fail.

Compressor moisture will mainly have adverse effects in several aspects:

Capillary and expansion valve will produce ice jam, and evaporator cooling pipe will freeze.

Metal materials are corroded to form deposits;

The valve core is corroded and closed loosely.

The phenomenon of "copper plating" occurs on the surface of compressor pump body parts.

Accelerating the deterioration of insulating materials, refrigerants, refrigerating machine oil and other materials.

2. What effect will low voltage have on the air conditioning system?

If the voltage is too low, which is much lower than the operating voltage range specified by the compressor, the locked-rotor current value may not reach the operating current specification of the protector, which will cause the protector to fail to operate in time, resulting in overheating or even burning of the compressor motor.

3. What is the function and principle of the protector of the compressor?

The function of the compressor protector is mainly to protect the compressor from accidents such as motor burning when it is under abnormal conditions.

The main principle is to rely on the internal heating wire of the protector and the internal resistance of the bimetal to make the bimetal act through the combined action of current heating and external conduction heat, thus cutting off the circuit and protecting the compressor from damage.

4. How to make basic judgment and treatment after compressor failure?

Non-suction and exhaust pressure: firstly, check the compressor wiring and pipeline connection, check the impedance of main and auxiliary coils, insulation and pressure resistance of the compressor and other basic items.  If everything is normal, it is recommended to remove the compressor for idling detection for suction and exhaust.

The suction and exhaust method is: when the compressor is running, press your finger against the exhaust port for a few seconds, then release it, and observe whether there is any gas ejection, of which a small amount of oil is normal.  If there is suction and discharge, the discharge pressure is high, indicating that the compressor can work normally, otherwise the compressor is not normal.

5. Why should liquid refrigerant be prohibited from flowing back into the suction chamber of the compressor?

If the liquid refrigerant directly enters the suction chamber of the compressor, the volume of the compressor becomes smaller and smaller and the pressure rises sharply during the rotation of the crankshaft, resulting in abnormal stress on the pump body parts and valve plates and even damage.  Liquid percussion will also cause abnormal vibration and noise of the compressor.

6. Why should the refrigerant recovery time of air conditioner not be too long?

The cooling medium recovery room of air conditioner should not be too long.  Because the refrigerant recovery time is too long, the exhaust temperature will be very high due to the extremely thin refrigerant gas sucked, causing the temperature of the pump body parts of the compressor to rise rapidly.  Excessive temperature will make the expansion degree of each part differ too much, which will cause the fit clearance of some parts to become smaller or even disappear, resulting in abnormal scratches or wear.


7. What is the impact of the wrong connection of the compressor?  Why can't protectors protect?

Incorrect connection of the compressor will make it unable to work normally. According to different connection error modes, there will be phenomena such as locked rotation, reverse rotation, stop after starting and so on, which will most likely lead to direct burning of the compressor motor.

As the protector of the compressor is selected according to the working characteristics of the protector under abnormal working conditions when the compressor is correctly wired, it is impossible to ensure the protection of the compressor when the compressor is miswired.  In the case of wrong wiring, it is difficult to protect the motor through the protector.

8. Do you need to adjust the same system for compressors from different manufacturers?

Because the performance characteristics of compressors produced by different companies are different, for a specific compressor, the best performance can only be shown under specific refrigerant flow, suction and discharge pressure, temperature and other conditions.

Therefore, on the same refrigerator system, it is better to adjust the system separately when using different compressors to ensure that the compressors used work normally under appropriate refrigerant flow rate, suction and discharge pressure and temperature conditions, so as to effectively prolong the service life of the compressors and achieve the best use effect.

9. Why is there a requirement for compressor motor coil temperature during operation?

The insulation grade (insulation grade: A (105 C), E (120 C), B (130 C), F (155 C), H (175 C)) and heat resistance of the insulation material used for the compressor motor are determined.  For motor enameled wires, too high a temperature will lead to a decrease in cocoon weight, a decrease in friction resistance K, easy peeling, a decrease in insulation breakdown voltage and insulation impedance K, etc., thus greatly reducing the service life.

In addition, too high a temperature of the motor may cause too much polymer in the insulation material to be dissolved out, which will precipitate and accumulate somewhere in the system or at the exhaust port of the compressor, thus affecting the performance of the compressor and the system.  In addition, too high a coil temperature will reduce the efficiency of the compressor motor.

10. Why can the compressor be restarted after shutdown for at least 3 minutes?

When the compressor is started, there will be more refrigerating machine oil circulating into the air conditioner system with refrigerant. If there is not enough running time, [source: Public Number of Refrigeration Encyclopedia], the refrigerating machine oil will not be able to return to the compressor cavity in time, and frequent shutdown soon after starting will lead to low internal oil level of the compressor, which will easily lead to poor lubrication of mechanical moving parts of the compressor.  In addition, the shutdown time of more than 3 minutes is mainly to give the system enough pressure balance time, otherwise due to the existence of high and low pressures, the compressor cannot be started normally.

11. Why can't the compressor operate under "vacuum conditions"?

The so-called "vacuum condition" is not an absolute vacuum state, but an extremely low pressure state, where ionization of gas molecules occurs.

According to the actual experimental results, the breakdown voltage of the compressor terminal is the lowest at the compressor internal pressure of 3.5mmHg, which is easy to cause breakdown and internal carbon deposition when electrifying, thus damaging the insulation of the sealing terminal. When the cocoon is tightened, the sealing terminal will burn out and fly out during the operation of the compressor.  Therefore, it should be avoided to electrify the compressor when it is vacuumized.

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