Cases of compressor damage summarized by some manufacturers, with solutions and precautions for use.

Case 1: Loose wiring leads to burning of compressor in open-phase operation.

Fault phenomenon: During the use of a top-blown 60kW modular cold and hot water unit in Sichuan, the air switch of one compressor could not be closed, and its terminal was burnt out.

Cause analysis: one of the three terminals of the compressor was burnt out, and the upper and lower connections were not conductive, and the cold-pressed terminal of the connection became dark black, which was obviously caused by loose connection head.

Solution: Replace the terminal and fasten all electrical wiring. After replacing the compressor, the fluorine system must be cleaned.

Precautions: All electrical wiring, especially the power cord and plug of compressor and electromechanical appliances, must be checked and fastened before unit commissioning.

Case 2: Hydraulic hammer of press caused by poor heat exchange and failure of insulation probe.

Fault phenomenon: When the ambient temperature of 12 fan units in a building is about 15℃, one compressor burns out, the return pipes of the other units freeze up thick ice and the evaporator of the indoor unit freezes.

Cause analysis: After dissection, the compressor was burnt down due to liquid impact. If the outdoor ambient temperature is not within the specified range, the refrigerant liquid will not completely evaporate in the evaporator after long-term use, and the liquid will enter the compressor to form a liquid hammer.

Under normal cooling conditions, when the indoor coil temperature is lower than -2℃ for 2 minutes, the indoor coil will be protected against freezing, and when it is higher than 6℃ or the compressor is shut down for 7 minutes, it will automatically restart. The evaporator of the indoor unit was frozen on site, but the unit was not protected. After careful inspection, it was found that the temperature sensor of the indoor coil was not placed in the right place, and it was not placed on the copper elbow that was most prone to frost, which caused the unit to fail to start the normal protection function.

Solution: Move the indoor coil temperature sensor to the elbow which is prone to frost, so that it can accurately detect the evaporation temperature of the evaporator and avoid severe frost or icing.

Case 3: The large drop without oil return bending causes the press to hold the shaft.

Fault phenomenon: A hospital installed a number of high static pressure air duct machines. After using them for one summer, the compressor of one unit made a low buzzing sound as soon as it started heating, and then it tripped, about 4 seconds. It is preliminarily judged that the compressor locks the shaft, causing excessive current and tripping.

Cause analysis: On-site inspection shows that the whole building is about 30 meters high, and all the units are installed on the roof. The faulty compressor unit is used on the first floor. Through the inspection of the connecting copper pipes of the internal and external units, it is found that the height difference between the internal and external units is 26 meters and there is no oil return bend on the connecting pipe, so other units can be equipped with oil return bends. When the removed compressor is poured out, only a small amount of compressor lubricating oil flows out, and the compressor is seriously short of oil.

Treatment: Install four oil return bends on the 26-meter connecting pipe. The standard is to install an oil return bend about 6 meters, and install a check ring at the indoor machine interface.

Case 4: The connecting pipe is too long and it is difficult to return oil, which causes the press to hold the shaft.

Fault phenomenon: A supermarket installed five W fans, and the cooling effect was acceptable after running for a period of time at first, but it didn't take long for users to feel that the indoor temperature couldn't drop and they couldn't feel the air conditioning under several tuyeres, so they reported for repair. Maintenance personnel rushed to the scene, opened the electric cabinet panels of five units, and found that only five compressors were working (10 compressors in total), and the thermal relays of the other five compressors were protected. After reset, four of them were turned on but the compressors made a "giggle" sound, and one compressor tripped as soon as it started, and the compressor was damaged.

Cause analysis: Due to the limitation of installation location, the length of the single copper pipe connecting the internal and external units of the burned compressor is about 75 meters, and the length of several other units is 60 meters. According to the product technical requirements, the length of a single connecting copper tube should not exceed 30 meters. Too long copper pipe connection will make it difficult for compressor to return oil.

When the removed compressor is poured out, no oil can be seen. However, when the two interfaces of the internal unit are loosened, a large amount of compressor oil is discharged, so it can be concluded that the compressor is short of oil and the shaft is damaged.

Treatment method: immediately move the external units of five air conditioning units to the specified range of the length of a single connecting copper tube and add a certain amount of refrigeration oil. An oil separator is added to each fluorine system.

Case 5: The compressor was damaged due to water ingress into the copper tube during installation.

Fault phenomenon: 10 low static pressure air duct machines were newly installed in a bar. Not long after commissioning, two compression coils were burned and jacked.

Cause analysis: water flowed out when the low pressure port of the compressor was cut on site. It can be judged that water enters the compressor and damages the insulation of the enameled wire of the winding to damage the compressor. After asking the installation company, I learned that the installation company could not finish the welding in time, the two ends of the copper tube were not sealed, and it rained again in those days, which caused the system to enter the water.

Treatment method: The fluorine system is relatively small, so it can be repeatedly dried with dry nitrogen until the white paper placed at the outlet of the system is free of oil and water stains, and the system is vacuum dried.

Case 6. Short-circuiting the target flow switch causes the heat exchanger to freeze and crack.

Fault phenomenon: a set of water machine in a user's home has low voltage protection after starting, and after resetting, it is turned on again, and the low voltage protection alarm still appears. After testing the system pressure, it was found that the static pressure of the refrigerant was about 3kg, and the pressure was low, so it was determined that the refrigeration system was leaking fluorine. Further observation of the makeup water tank found that there was oil stain on the water surface, and it was confirmed that the plate heat exchanger was frozen.

Cause analysis: After careful inspection, it was found that there was no water flow in the water system due to the failure of the water pump, and the target flow switch was temporarily shorted by the maintenance personnel because it was damaged during the unit debugging, and then forgot to replace this accessory. Therefore, at this time, the target flow switch failed to play a protective role, which led to the freezing crack of the plate replacement.

Treatment method: replace the target flow switch, water pump and plate heat exchanger.

Case 7: Excessive fluorine addition leads to liquid hammer damage of compressor.

Fault phenomenon: the compressor shell of a Daikin unit in a coffee shop in Wuhan was damaged.

Cause analysis: after dissecting the compressor, it was found that the scroll of the scroll compressor had become a fragment. When asked about the fluorine supply during installation, the installation company replied that fluorine was supplied and liquid was added until the low pressure value was above 4.5 kg. At that time, the outdoor temperature was about 22℃, and the compressor current value was not measured. Therefore, it was judged that the compressor was damaged by liquid hammer due to excessive refrigerant filling.

Treatment method: replace the compressor and re-vacuumize the system and add fluorine.

Precautions: In order to prevent the unit from hydraulic impact caused by excessive fluoride addition, care should be taken when adding refrigerant, and various changes during the operation of the unit should be carefully observed to correctly grasp.

Liquid refrigerant should be charged at the high-pressure end when the compressor is turned off, and at the low-pressure end when the unit is turned on. Care must be taken to prevent liquid hammer when adding liquid.

Case 8, Three-phase compressor reverse shaft damage.

Fault phenomenon: A hotel installed a 5×20 cold-ton air-cooled heat pump module unit. Due to the power shortage, the user installed a high-power generator unit by himself, and turned on the air conditioning power supply. After starting up, the compressor sounded like the roar of a tractor, and the water temperature did not change significantly. After half an hour, the maintenance personnel arrived at the scene and found that the compressor was completely reversed, and immediately stopped. Upon inspection, one compressor has been damaged.

Cause analysis: the power supply lack and reverse phase protector was shorted by the debugging personnel during the no-load test run of the unit, and it was not restored after the debugging, so the unit failed to protect normally when the power supply went wrong. At the same time, the internal metal structure of the target flow switch is blocked by rust, and the mechanical part of the flow switch is stuck, so the pump inversion cannot be detected.

Treatment method: the protector of power shortage and reverse term shall be correctly wired. Replace the target flow switch and re-debug.

Case 9: The compressor was damaged due to water inflow in the plate leakage changing system.

Fault phenomenon: A 28KW household hot and cold water unit in a bath center leaked after running for one week. The maintenance personnel replaced the plate replacement, and the refrigeration system was simply cleaned before starting. The unit tripped after running for one hour, and the compressor was grounded.

Cause analysis: The cleaning and drying of the refrigeration system were not thoroughly handled when replacing the plate for the first time, resulting in a large amount of water in the refrigeration system, which entered the compressor and damaged the insulation of the enameled wire of the winding.

Treatment: When the refrigeration system has been flooded, the gas-liquid separator, liquid storage tank, drying filter and other accessories should be replaced, and the whole refrigeration system should be cleaned and dried as necessary.