High Exhaust Gas Temperature in Air Source Heat Pump Compressor

The protection of high exhaust gas temperature is one of the protection measures of air source heat pump. In the operation of a heat pump unit, due to some reasons, the outlet gas temperature of compressor will exceed the normal value, which will not only increase the power consumption of the compressor, but also make the lubricating oil coke with worse performance, affecting the normal operation of the compressor.

When the exhaust gas temperature of SPRSUN air source heat pump compressor is too high, error code Er05 will appear on the control panel to remind the user that the system is abnormal and needs to be handled in time.

Cases of High Exhaust Gas Temperature

High exhaust gas temperature mainly includes the following cases: high return air temperature, large heating capacity of motor, high compression ratio, high condensation pressure, and improper selection of refrigerant.

High Return Gas Temperature

The return gas temperature is relative to the evaporation temperature. In order to prevent liquid return, the return gas pipeline generally requires a superheat of 20℃. If the thermal insulation of the return pipeline is not good, the superheat will be far more than 20℃. The higher the return gas temperature, the higher the cylinder suction temperature and exhaust temperature. When the return gas temperature increases by 1℃, the exhaust gas temperature will increase by 1~1.3℃.

Motor Heating

For the return air cooled compressor, the refrigerant vapor is heated by the motor when it flows through the motor cavity, and the cylinder suction temperature is increased again. The heat generating capacity of the motor is affected by power and efficiency, while the power consumption is closely related to the output volume, volumetric efficiency, working condition and friction resistance.

Compression Ratio Too High

The higher the compression ratio, the higher the exhaust gas temperature. Reducing the compression ratio can significantly lower the exhaust temperature, including increasing the suction pressure and reducing the exhaust pressure. The suction pressure is determined by evaporation pressure and suction line resistance. By increasing the evaporation temperature, the suction pressure can be increased effectively, and the compression ratio will be reduced rapidly, thus lowering the outlet gas temperature. Other reasons include reverse expansion, gas mixing, compressor temperature rise, refrigerant type and so on.

Hidden Dangers of High Exhaust Gas Temperature

Influence of High Exhaust Temperature on Lubricating Oil

Generally, when the temperature of refrigeration oil reaches 177 ℃, fission and carbonization will occur. However, the temperature at the outlet of compressor exhaust valve is 28-42℃ higher than that at the exhaust pipe. Therefore, the exhaust gas temperature should be controlled below 135℃. If the exhaust gas temperature is too high, the lubricating oil may be carbonized and deteriorated and the lubricating performance will be reduced. The exhaust gas temperature also affects the viscosity of the lubricant. If the exhaust temperature is too high, the viscosity of lubricating oil will be reduced, and it is not easy to form a strong enough oil film, resulting in poor lubrication, accelerating wear and increasing power consumption. In addition, the thin oil film will reduce the internal sealing effect of the compressor.

Influence of High Exhaust Temperature on Motor

For the high pressure chamber compressor, the exhaust has the function of cooling the motor. The high exhaust gas temperature may be due to the higher operating frequency of the compressor and more power consumption, or the smaller refrigerant flow and poor cooling effect of the motor. In addition, the unprofitable power consumption caused by poor lubrication at high temperature will also increase, the heat production will improve, and the heat dissipation will decrease. In such a vicious cycle, the motor winding temperature will continue to rise, and it is easy to damage the motor by built-in protection or even damage the enameled wire insulation layer.

Influence of High Exhaust Gas Temperature on Compressor

If the temperature reaches the melting point of the sealing material, it will cause permanent damage to the compressor scroll, drive bearing and internal seal.

Causes of High Exhaust Gas Temperature in Compressor

Below is a list of reasons for high exhaust gas temperature in the air source heat pump compressor. Hopefully it is of help to you.

1. There is less refrigerant.

2. The opening of the expansion valve is small, and the expansion valve is broken.

3. The drying filter of the refrigerant system is blocked.

4. The evaporation temperature is too low.

5. The refrigerant quality is not good, mixed with air or water; if there is water, the expansion valve ice blockage will also cause high return gas temperature.

6. The condensation effect is not good and a large number of gaseous refrigerant returns to the expansion valve, which will also cause high return gas temperature.

7. Compressor bearing damage, resulting in mechanical friction, high suction temperature, motor overheating and thus high exhaust gas temperature.