Scroll compressor failure and replacement need to carry out a series of checks, and now the refrigeration encyclopedia public number to share the inspection and replacement process, I hope to be useful to you. If this article was helpful to you, please click "nice" in the bottom right corner of this article.

The first step: compressor electrical detection

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

Insulation resistance: compressor terminal resistance to the ground, generally can be used megohm meter or multimeter ohm file (40 megohm file) between the compressor terminal and the compressor copper tube test, generally above 40 megohm. If there is liquid refrigerant in the compressor or the air humidity is large, the insulation resistance value will be small

Step 2: Replace the faulty compressor

When welding system components, discharge refrigerant first, and discharge refrigerant from the high pressure side and the low pressure side at the same time. If done only from the high pressure side, the vortex seal will cause the refrigerant to remain on the low pressure side, and when the connection pipe is welded down, the mixture of refrigerant and oil will be ejected and ignited in the event of a flame.

If you need to replace the compressor, cut off the connecting tubes on both sides of the compressor before taking it out.

If the compressor is damaged because of the motor burning, the pollution degree of the lubricating oil should be checked. Before replacing the compressor, the gas-liquid separator and filter dryer should be replaced at the same time, and a filter dryer should be added on the suction side. After the system runs for a period of time, the pollution level of the filter core should be checked to determine whether the filter should continue to clean the system.

Step 3: Storage and handling of the new compressor

When the new compressor is being transported, the compressor should be kept vertical. Excessive tilt, horizontal lying and overturning of the compressor may cause a large amount of lubricating oil to enter the scroll disk, resulting in oil ejection or temporary non-start when the sealing plug is opened.

Step 4: Remove sealing plug and fix foot

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

Place the steel bushings in the fixing bolts respectively, then lift the compressor into the installation position, and gently tighten the nut with the belt washer. If the nut with the belt washer is tightened, the bushings will tilt or even break, which will cause vibration and noise.

Step 5: Compressor suction and exhaust pipe welding

Attention! Many compressor suction and exhaust pipe for copper-plated steel pipe, it is best to use silver containing at least 5% of the solder, such as the use of silver containing less than 2% of the solder, there should be very good skills to ensure that the solder does not enter the compressor to cause failure.

At the same time, a trace amount of nitrogen should be passed into the welding to prevent the production of oxides, which will fall into the compressor and cause failure, and do not overheat the pipe mouth. The welding time is 15-20 seconds.

Step 6: Vacuum

The existence of air, that is, non-condensable gas, has great harm to the refrigeration system, such as no vacuum, the refrigeration system is usually mainly manifested as: the condensation pressure of the system is increased, the condensation temperature is increased, the compressor exhaust temperature is increased, and the power consumption is increased. At the same time, because the exhaust temperature is too high, it may lead to the carbonization of lubricating oil, affect the lubrication effect, and burn the refrigeration compressor motor in serious cases.

The vacuum should be taken from the high pressure side and the low pressure side at the same time, and the vacuum degree should be read by a special vacuum gauge. The normal system vacuum degree should be below -756 MMHG. The vacuum time should be determined according to the size of the model refrigeration system and the size of the vacuum pump.

Step 7: Refrigerant charging

First, check whether the refrigerant model is consistent with the refrigerant marked on the external machine, and then charge the refrigerant from the high pressure side. If only the low pressure side is charged, the scroll disk may be axially sealed and temporarily unable to start.

If the required charge amount cannot be reached at one time, the total charge amount should be reached as far as 70% to 75% before the first start, and then the refrigerant system pressure, current, frost return, temperature, etc. should be closely observed at this time, and the situation should be decided whether to continue a small amount of filling to achieve the optimal efficiency. If the system has a nameplate number indicating the amount of refrigerant charged, it should be weighed and filled.

Step 8: Electrical connection

The electrical box cover on both sides of the clamp to the internal pressure, you can open the electrical box cover, three-phase scroll compressor wiring has 50% of the possibility of reversal, this time the high and low pressure of the system will not change, the suction is not cool, the exhaust is not hot. This fault can be eliminated by switching any two of the three phases. A short reversal is not a problem.

For the terminals connected with screws, be careful not to exert too much force to avoid damage to the internal thread of the terminals or screw breakage.

Generally, it is not necessary to add refrigerant oil when replacing the compressor, because the oil has been injected into the new compressor. In special cases, such as long pipe installation, refrigerant oil must be added. For example, if the refrigerant is R22, the refrigerant oil brand is 3GS.

Common faults and analysis of scroll compressor

Common fault 1: compressor oil shortage and compressor lubrication is insufficient, the reasons are as follows:

The compressor starts and stops frequently for a long time.

The system contains air or moisture.

System return or refrigerant migration to dilute lubricating oil.

Compressor reversal

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

There are other chemicals in the system that react with the lubricating oil to make the lubricating oil deteriorate.

Common fault 2: compressor liquid stroke, the reasons are as follows:

Excessive refrigerant is added to the system, resulting in a large amount of liquid return.

The inner fan does not rotate and the air volume is small, resulting in incomplete refrigerant evaporation.

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

Excessive oil addition, resulting in system oil shock (low pressure chamber compressor).

Common fault 3: compressor burned at high temperature, the reasons are as follows:

The system vacuum is insufficient.

Too little refrigerant is added or refrigerant leaks.

The air exhaust or top temperature is too high due to ice blockage of the system return pipe.

If the connecting pipe is too long or the pipe diameter is small, the system resistance increases, resulting in the increase of exhaust temperature and pressure.

Common failure 4: compressor motor damage, the reasons are as follows:

Contactor contact melting or abnormal, such as lack of phase, phase offset.

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

Insufficient motor cooling, a large amount of refrigerant leakage or evaporation pressure is too low will cause the mass flow rate of the system to decrease, so that the motor can not get good cooling.