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Compressor overheating protection is designed to prevent the motor from being damaged due to high temperature, and when the internal temperature of the motor or compressor exceeds the standard, the working power supply is cut off through internal or external protection equipment to ensure the safety of the compressor. The refrigeration compressor inhales the low-temperature and low-pressure refrigerant gaseous substances in the system, which first cools the motor through the refrigerant and then compresses it. Therefore, the amount of superheat of the inhaled refrigerant vapor directly affects whether the compressor has a risk of overheating. This article will analyze this issue in order to provide you with useful references.
First, the refrigerant is insufficient
The lack of refrigerant will reduce the amount of refrigerant supplied to the evaporator, causing the evaporation temperature to rise, causing the compressor to draw in high-temperature refrigerant vapor, i.e., the superheat increases, which in turn causes the motor coil to overheat, triggering overheating protection. Especially in the hot summer, when the ambient temperature is high, if the refrigerant of the system is only slightly insufficient, it is difficult to judge only by the compressor current and system pressure, but it is easy to lead to overcharging. In this case, this can be evaluated by measuring the compressor exhaust pipe temperature: under normal conditions, this temperature should be about 20 °C higher than the saturation temperature at the corresponding discharge pressure. Below this value may have too much refrigerant, and above this value may not have enough refrigerant.
At the same time, the temperature of the suction tube can also be measured, which should normally be about 7°C higher than the saturation temperature at the corresponding suction pressure. If the actual pressure of the high pressure is measured to be 1.83MPa and the exhaust temperature is 85°C, the system refrigerant is insufficient by referring to the R22 refrigerant system temperature and pressure comparison table.
2. Excess refrigerant
Too much refrigerant leads to an increase in evaporation pressure and evaporation temperature, an increase in the overall pressure, an increase in the load of the compressor, and a difficult heat dissipation in a high-temperature environment, an increase in current, which is easy to cause overheating protection. Typical symptoms include: high air outlet temperature of the outdoor unit, uniform condensation but insufficient cold sensation of the indoor unit, no cold sensation of the thin pipe valve, slight cold of the coarse pipe valve, normal operation in the morning and evening, heat protection is easy to occur at noon, normal voltage, clean filter and external heat exchanger. Blindly applying fluorination to the rated or empirical current can lead to an excess of refrigerant.
3. The evaporator/condenser is dirty
The seriously dirty evaporator is equivalent to the internal fan stopping, resulting in the extremely poor evaporation effect of the refrigerant, and the compressor sucks in the gas-liquid mixed refrigerant, resulting in the frosting phenomenon of return gas, so it cannot be used as the cause of compressor overheating. However, when the evaporator heat dissipation is poor, the compressor sucks insufficient refrigerant dose, which causes insufficient refrigerant circulation, which can indeed lead to overheating protection. Similarly, the condenser dissipates heat poorly, the pressure increases, the current increases, and finally thermal protection is triggered. For example, the outdoor unit of the air conditioner in a high-rise apartment is placed in a narrow air-conditioning niche, and the heat dissipation is affected by the blinds, and the overheating problem is solved after removing the blinds and introducing condensate from the indoor unit to assist in heat dissipation.
Fourth, the throttling mechanism or system is blocked
For example, capillary micro-blockage is similar to capillary lengthening, and excessive throttling leads to an increase in high pressure and a decrease in low pressure. The air scalding of the external fan and the incomplete condensation of the evaporator confirm that the high pressure is too high and the evaporation pressure is too low. Typical manifestations include: poor refrigeration effect, incomplete condensation of the evaporator, hot air outlet of the external heat exchanger, reluctant operation of the original machine, and complete failure of the press after adding refrigerant.
Fifth, the voltage is too low
The experiment proves that when the power supply voltage drops below 190V, the system cannot go up at high pressure and low pressure, which is equivalent to compressor blow-by, which increases the specific volume of refrigerant gas sucked by the compressor, causes the superheat of the return gas to rise, and triggers thermal protection. For example, in the thermal protection of multiple air conditioners in a certain area, the voltage seems to be normal (210V) when turned on, but the voltage plummets below 190V after turning on other electrical appliances, resulting in the air conditioner cannot operate normally, and the press cannot be started and the damage is serious.
Sixth, the compressor itself problems
- Four-way valve string: The compressor relies on low-temperature return air cooling, and the four-way valve string will make the compressor inhale hot air instead of cold air, which not only loses cooling, but aggravates the heating up, which will inevitably lead to thermal protection.
- Lack of oil: The lack of oil in the compressor leads to poor lubrication of mechanical parts, which is easy to cause thermal protection.