Scroll compressor failure and replacement require a series of inspections. Now the public account of Refrigeration Encyclopedia shares the inspection and replacement process, I hope it will be useful to everyone. If this article is helpful to you, please click on the bottom right corner of this article“good looking”。

Voltage and current measurement: The output terminal of the compressor AC contactor is used to determine whether the compressor's power supply voltage and starting voltage are within the normal range.

Insulation resistance: the resistance of the compressor terminal to the ground. Generally, a megger or multimeter can be used to test the resistance between the compressor terminal and the copper pipe on the compressor. It is generally above 40 megohm. If there is liquid refrigerant in the compressor or the air humidity is high, the insulation resistance value will be too small

When welding the system components, the refrigerant should be discharged first,and the refrigerant should be discharged from the high-pressure side and the low-pressure side at the same time. If only from the high-pressure side, the scroll seal will cause the refrigerant to remain on the low-pressure side. When the connecting pipe is welded, the mixture of refrigerant and oil will spray out and be ignited when it encounters a flame.

If the compressor needs to be replaced, the connecting pipes on both sides of the compressor must be cut off before taking the compressor out.

If the compressor is damaged due to the burning of the motor, check the pollution degree of the lubricating oil.The degree of contamination of the lubricating oil should be checked.Before replacing the compressor, the gas-liquid separator and filter drier should be replaced at the same time, and a filter drier should be added on the suction side. After letting the system run for a period of time, check the pollution degree of the filter core to determine whether a filter is needed. Continue to clean the system.

When the new compressor is being transported, the compressor should be kept vertical.Excessive tilting of the compressor, lying and knocking over will cause a large amount of lubricating oil to enter the scroll,which may cause oil to spray out or temporarily fail to start when the sealing plug is opened.

The compressor has been filled with a certain pressure of dry air before leaving the factory, and then sealed with a sealing rubber plug. The purpose is to ensure cleanness and dryness. Since the suction pipe port is close to the oil level, the exhaust plug should be pulled out before installation , Then pull out the suction plug, clean the inner ring of the suction pipe mouth with a cloth, and wipe off the oil film to facilitate welding.

Put the steel sleeves into the fixing bolts, and then hoist the compressor into the installation position, and then gently tighten the nuts with washers. When tightening the nuts with washers,if the sleeves are tilted or even broken with force, this will cause vibration and noise.

note! Many compressor suction and exhaust pipes are copper-plated steel pipes. It is best to use solder containing at least 5% silver. If you use solder containing less than 2% silver, you should have very good techniques to ensure that the solder does not enter the compressor and cause malfunctions. .

A trace amount of nitrogen should be introduced during welding to prevent oxides from being generated and falling into the compressor to cause malfunctions.Do not overheat the nozzle.The welding time is 15-20 seconds.

Step 6: Vacuum

The existence of air, which is non-condensable gas, is very harmful to the refrigeration system. If it is not vacuumed, the refrigeration system usually mainly manifests as: system condensation pressure rises, condensation temperature rises, compressor discharge temperature rises, and power consumption The amount increases.At the same time, the excessively high exhaust temperature may cause the carbonization of the lubricating oil, which affects the lubrication effect, and burns the refrigeration compressor motor in severe cases.

The vacuum should be carried out from the high-pressure side and the low-pressure side at the same time. The vacuum degree should be read by a dedicated vacuum gauge. The normal system vacuum degree should be below -756mmHg. The vacuuming time should be determined according to the size of the refrigeration system of the model and the size of the vacuum pump.

First of all, confirm whether the refrigerant model matches the refrigerant marked on the external machine, and then charge from the high-pressure side. If only filling from the low pressure side, it may cause the scroll to be sealed in the axial direction, temporarily unable to start.

If the required charge volume cannot be reached at one time, the total charge volume should be 70%~75% before the first start, and then charge at startup. At this time, pay close attention to the refrigerant system pressure and current. Re-frost, temperature, etc., depending on the situation to decide whether to continue to fill a small amount to achieve the best efficiency. If the system has a nameplate number indicating the refrigerant charge, it should be weighed and filled.

Press the hooks on both sides of the electrical box cover inward to open the electrical box cover. The wiring of the three-phase scroll compressor may bereversed by 50%.At this time, the high and low pressure of the system will not change, and the suction will not be cold. The exhaust is not hot.This fault can be eliminated as long as the wiring of any two of the three phases is reversed. Reversing for a short time will not cause problems.

For the terminals connected by screws, be careful not to use excessive force to avoid damage to the internal threads of the terminals or breakage of the screws.

Generally, there is no need to increase the refrigerating oil when replacing the compressor, because the new compressor has already been filled with oil. In case of special circumstances, such as installation of long connecting pipes, when refrigerating oil must be added, for example, when the refrigerant is R22, the brand of refrigerating oil is 3GS.

Common fault 1: Compressor lack of oil and compressor lubrication, the reasons are as follows:

• The compressor frequently starts and stops for a long time.

• The system contains air or moisture.

• System liquid return or refrigerant migration dilute lubricating oil.

• Compressor reversal (such as wrong phase sequence)

• The system refrigerant leakage makes the compressor lubricating oil less.

• There are other chemical substances in the system, which cause the lubricating oil to deteriorate after chemical reaction with lubricating oil.

Common fault 2: Compressor liquid shock, the reasons are as follows:

• Too much refrigerant is added, causing a large amount of liquid back in the system.

• The internal fan does not rotate, the air volume is small, etc., resulting in incomplete evaporation of the refrigerant.

• When the power is off, the solenoid valve still maintains a certain degree of opening, causing a large amount of liquid back in the system.

• Too much oil is added, causing system oil shock (low pressure chamber compressor).

Common fault 3: Compressor burns at high temperature, the reasons are as follows:

• The system vacuum is not enough.

• Too little refrigerant is added or refrigerant leaks.

• The system's return pipe is blocked by ice causing the exhaust gas or the top temperature to be too high.

• If the connecting piping is too long or the pipe diameter is small, the resistance of the system will increase, causing the exhaust temperature and pressure to rise.

Common failure 4: The compressor motor is damaged, the reasons are as follows:

• Melting or abnormality of contactor contacts, such as phase loss or phase deviation.

• The rated voltage of the power supply cannot exceed ±10%; the unbalance rate of the three-phase voltage cannot exceed 3%.

• Insufficient cooling of the motor, a large amount of refrigerant leakage or low evaporation pressure will cause the system mass flow to decrease, making the motor unable to get good cooling.