The expansion valve is one of the four major components of the refrigeration system. It is an important device for regulating and controlling the flow and pressure of refrigerant into the evaporator. It is also the “demarcation line†on the high and low pressure sides. Its regulation is not only related to the normal operation of the entire refrigeration system, but also an important indicator to measure the technical level of the operator.
Today we will tell you about the troubleshooting of the thermal expansion valve, and how to adjust the opening of the thermal expansion valve, hot dry goods!
1. Failure of improper adjustment of thermal expansion valve
1, the opening degree is too small
If the opening degree of the thermal expansion valve is too small, the supply of the liquid will be insufficient, so that there is not enough freon to evaporate in the evaporator, and the refrigerant has evaporated in the middle of the flow in the evaporation tube, and there is no liquid in the evaporator tube after this. The refrigerant is available for evaporation and only the steam is superheated.
At the same time, the outlet pressure of the expansion valve is too low, and the corresponding evaporation pressure and temperature are too low. The evaporation rate is slowed down, the cooling capacity per unit volume (time) is reduced, and the cooling efficiency is lowered.
Therefore, a considerable part of the evaporator fails to fully exert its performance, resulting in insufficient cooling capacity and reducing the cooling effect of the air conditioner. Most of the compressors for the air conditioners in the engine room use the steam from the evaporator to cool the compressor. If the thermal expansion valve is not opened enough, the steam superheat will be too large, the cooling effect on the compressor will be reduced, and the exhaust temperature of the compressor will increase. The lubricating oil becomes thinner, the lubrication quality is lowered, and the working environment of the compressor is deteriorated, which seriously affects the working life of the compressor.
2, the opening degree is too large
If the thermal expansion valve is opened too much, the flow rate of the refrigerant will be much higher, that is, the supply of the thermal expansion valve to the evaporator is greater than the evaporator load, so that the liquid refrigerant evaporates excessively, which may cause some liquid refrigerant to evaporate in the evaporator. It is sucked into the compressor together with the gaseous refrigerant, causing the wet stroke (liquid blow) of the compressor, so that the compressor can not work normally, causing a series of bad working conditions, and even the accident of the cylinder damaging the compressor.
At the same time, the thermal expansion valve is opened too much, so that the corresponding evaporation pressure and temperature of the refrigerant entering the evaporator are too high, the cooling capacity is decreased, the power consumption of the compressor is increased, and the power consumption is increased.
Because the refrigeration power of the new compressor is not equipped with the system, the adjustment pressure of the expansion valve is always lower than normal, indicating that the compressor power is too large, resulting in large inspiratory capacity, too small evaporation area, contradictory reaction of operating conditions, and then open again. The expansion valve inhales the wet gas due to the inability of the liquid to boil and evaporate, causing the compressor to frost.
Second, the adjustment of the thermal expansion valve
1. Before adjusting the thermal expansion valve, it must be confirmed that the cooling abnormality is caused by the thermal expansion valve deviating from the optimal operating point, not because the system refrigerant charge is not suitable, the dry filter and the expansion valve filter are clogged, and the solenoid valve Causes of malfunction, poor cooling of the condenser fan, cooling power of the newly replaced compressor, and other reasons such as the system is not equipped.
At the same time, it is necessary to ensure the correctness of the sampling signal of the temperature sensing package. The installation position of the temperature sensing package must be correct. It must not be installed directly under the pipeline to prevent the temperature sensing of the temperature sensing package from affecting the temperature. In addition, if the thermal expansion valve that loses the adjustment function is replaced with a new expansion valve, the new product has been debugged and proofread at the factory, so it is no longer necessary to adjust the expansion valve and open it for direct installation.
2, stop. Insert the probe of the digital thermometer into the insulation of the evaporator return port (corresponding to the temperature sensor position). Connect the pressure gauge to the tee of the compressor's low pressure valve.
3. Turn on the machine and let the compressor run for more than 15 minutes to enter the stable running state, so that the pressure indication and temperature display reach a stable value.
Third, the thermal expansion valve adjustment steps
When adjusting, first unscrew the bonnet under the thermal expansion valve and rotate the valve stem clockwise to make the opening of the pinhole of the valve body small, that is, the flow rate of the liquid supply is reduced (simplified as a small opening); The hole opening is large, that is, the liquid supply flow rate is increased (abbreviated as reverse rotation).
The same method as adjusting the water valve to control the flow of water. The flow adjustment should be carried out during the normal operation of the refrigeration system, and it should be operated slowly and gradually adjusted. The basis for judging the size of the liquid supply flow is:
(1) It is judged whether the adjustment amount is appropriate by the shape change of the frost expansion of the thermal expansion valve.
A. If the expansion valve body is completely frosted, it indicates that the flow rate is too small and should be adjusted;
B. If there is no change in the shape of the frost when the volume is increased, the expansion valve orifice may be partially blocked and cleaned;
C. If the expansion valve body only has frost on the outlet side, indicating that the flow rate is too large, it should be reduced;
D. If the outlet side and the lower part of the expansion valve body are frosted at 45 °C, the inlet side should not be frosted, indicating that the adjustment is accurate and appropriate;
E. If the expansion valve body only has frost on the inlet side, it indicates that the filter part at the inlet of the valve body is blocked and should be cleaned;
F. If the expansion valve body is completely frost-free, it indicates no flow, the refrigerant may leak or the shut-off valve in the pipeline is not opened or the expansion valve is sensitive. The capillary leaks or the expansion valve orifice is blocked or the inlet of the valve body is filtered. The part of the net is blocked and should be cleaned.
(2) It is also possible to judge whether the adjustment is appropriate by the shape change of the frost at the suction pipe of the compressor.
A. If the white frost is connected to the suction cut-off valve, it indicates that the flow rate is too large and should be adjusted small;
B. If the hoar frost does not reach the suction pipe, it indicates that the flow rate is too small and should be adjusted.
(3) In addition, it is judged whether the adjustment amount is appropriate by the magnitude of the pressure value on the low pressure side.
(4) The uniform and complete condition of the evaporator coil frosting to determine whether the adjustment is appropriate.
(5) Under normal circumstances, the expansion valve is very quiet when working. If a clear "filament" sound is emitted, the refrigerant in the system is insufficient.
(6) Using a thermometer to measure the difference between the temperature of the return pipe and the evaporating temperature (ie, the actual superheat) and the standard superheat (between 5-8 °C) to determine whether the adjustment is appropriate.
Using the suction pressure of the compressor as the saturation pressure in the evaporator, the table looks for an approximate evaporation temperature.
The temperature of the return pipe was measured with a thermometer, and compared with the evaporation temperature, it was between 5-8 ° C in the normal range. The inspiratory pressure value and the return air tube temperature must be read at the same time, otherwise the calculated actual superheat is not accurate.
Adjustment,
A. If the degree of superheat is too small, the adjusting screw can be rotated clockwise (ie, increase the spring force and reduce the opening degree of the thermal expansion valve) to reduce the flow rate;
B. Conversely, if the degree of superheat is too large, that is, the supply of liquid is insufficient, the adjustment screw can be rotated in the opposite direction (counterclockwise) to increase the flow rate. Because the thermal expansion valve temperature sensing system in the actual work has a certain thermal inertia, the signal transmission hysteresis is formed, and the operation is basically stable before the next adjustment can be made.
In the adjustment, you must not take the rapid adjustment of the ups and downs, so that the refrigeration system is unstable and can not control the effect.
The coarse expansion should be started first. (The thermal expansion valve of the air conditioner for the machine room generally adopts the pressure rod type and the scattered gear type. The loose gear type uses a small gear to drive a large gear. The number of adjustments is relatively large, and the general adjustment can be made. 2~4 laps; the number of adjustable laps is relatively small, 1/4 turn each time; the thermal expansion valve of air conditioner adopts the loose gear type), observe the change of the pressure value of the pressure gauge on the low pressure side, and the pressure value of the gauge is stable. After that, fine-tune it. Adjust 1/2, 1/3, and 1/4 turns each time.
The adjustment of the expansion valve must be carried out carefully and patiently. The adjustment pressure must be caused by the heat exchange boiling of the evaporator and the warehouse temperature (evaporation) and then passed through the pipeline into the compressor suction chamber to be reflected on the pressure gauge. It takes a time. Each time the expansion valve is mobilized, it usually takes 15-30 minutes to stabilize the adjustment pressure of the expansion valve on the suction pressure gauge. According to the observation of the change of the low pressure value, it is also necessary to observe the frosting at the expansion valve body, the evaporator coil and the compressor suction pipe to judge whether the adjustment is appropriate.
note:
1. When the system is pressed and leaked and the refrigerant is filled before the expansion valve is adjusted, it cannot be injected from the high pressure end. Otherwise, it is difficult to inject, and the pressure at the high and low pressure ends cannot be balanced. Because the expansion valve is the high and low pressure delimiter of the connection system, if the evaporator outlet pipe temperature of the expansion valve temperature sensor is not hot or superheated when the refrigeration system is not operating normally, the expansion valve outlet valve port can not be opened, the system The pipeline is cut off, and the high and low pressure sides are not connected, so the pressure at the high and low pressure ends cannot be balanced.
2. The refrigeration system consisting of a thermal expansion valve and a single-phase fully enclosed compressor may be difficult to start the compressor. The reason is the same as above
Today we will tell you about the troubleshooting of the thermal expansion valve, and how to adjust the opening of the thermal expansion valve, hot dry goods!
1. Failure of improper adjustment of thermal expansion valve
1, the opening degree is too small
If the opening degree of the thermal expansion valve is too small, the supply of the liquid will be insufficient, so that there is not enough freon to evaporate in the evaporator, and the refrigerant has evaporated in the middle of the flow in the evaporation tube, and there is no liquid in the evaporator tube after this. The refrigerant is available for evaporation and only the steam is superheated.
At the same time, the outlet pressure of the expansion valve is too low, and the corresponding evaporation pressure and temperature are too low. The evaporation rate is slowed down, the cooling capacity per unit volume (time) is reduced, and the cooling efficiency is lowered.
Therefore, a considerable part of the evaporator fails to fully exert its performance, resulting in insufficient cooling capacity and reducing the cooling effect of the air conditioner. Most of the compressors for the air conditioners in the engine room use the steam from the evaporator to cool the compressor. If the thermal expansion valve is not opened enough, the steam superheat will be too large, the cooling effect on the compressor will be reduced, and the exhaust temperature of the compressor will increase. The lubricating oil becomes thinner, the lubrication quality is lowered, and the working environment of the compressor is deteriorated, which seriously affects the working life of the compressor.
2, the opening degree is too large
If the thermal expansion valve is opened too much, the flow rate of the refrigerant will be much higher, that is, the supply of the thermal expansion valve to the evaporator is greater than the evaporator load, so that the liquid refrigerant evaporates excessively, which may cause some liquid refrigerant to evaporate in the evaporator. It is sucked into the compressor together with the gaseous refrigerant, causing the wet stroke (liquid blow) of the compressor, so that the compressor can not work normally, causing a series of bad working conditions, and even the accident of the cylinder damaging the compressor.
At the same time, the thermal expansion valve is opened too much, so that the corresponding evaporation pressure and temperature of the refrigerant entering the evaporator are too high, the cooling capacity is decreased, the power consumption of the compressor is increased, and the power consumption is increased.
Because the refrigeration power of the new compressor is not equipped with the system, the adjustment pressure of the expansion valve is always lower than normal, indicating that the compressor power is too large, resulting in large inspiratory capacity, too small evaporation area, contradictory reaction of operating conditions, and then open again. The expansion valve inhales the wet gas due to the inability of the liquid to boil and evaporate, causing the compressor to frost.
Second, the adjustment of the thermal expansion valve
1. Before adjusting the thermal expansion valve, it must be confirmed that the cooling abnormality is caused by the thermal expansion valve deviating from the optimal operating point, not because the system refrigerant charge is not suitable, the dry filter and the expansion valve filter are clogged, and the solenoid valve Causes of malfunction, poor cooling of the condenser fan, cooling power of the newly replaced compressor, and other reasons such as the system is not equipped.
At the same time, it is necessary to ensure the correctness of the sampling signal of the temperature sensing package. The installation position of the temperature sensing package must be correct. It must not be installed directly under the pipeline to prevent the temperature sensing of the temperature sensing package from affecting the temperature. In addition, if the thermal expansion valve that loses the adjustment function is replaced with a new expansion valve, the new product has been debugged and proofread at the factory, so it is no longer necessary to adjust the expansion valve and open it for direct installation.
2, stop. Insert the probe of the digital thermometer into the insulation of the evaporator return port (corresponding to the temperature sensor position). Connect the pressure gauge to the tee of the compressor's low pressure valve.
3. Turn on the machine and let the compressor run for more than 15 minutes to enter the stable running state, so that the pressure indication and temperature display reach a stable value.
Third, the thermal expansion valve adjustment steps
When adjusting, first unscrew the bonnet under the thermal expansion valve and rotate the valve stem clockwise to make the opening of the pinhole of the valve body small, that is, the flow rate of the liquid supply is reduced (simplified as a small opening); The hole opening is large, that is, the liquid supply flow rate is increased (abbreviated as reverse rotation).
The same method as adjusting the water valve to control the flow of water. The flow adjustment should be carried out during the normal operation of the refrigeration system, and it should be operated slowly and gradually adjusted. The basis for judging the size of the liquid supply flow is:
(1) It is judged whether the adjustment amount is appropriate by the shape change of the frost expansion of the thermal expansion valve.
A. If the expansion valve body is completely frosted, it indicates that the flow rate is too small and should be adjusted;
B. If there is no change in the shape of the frost when the volume is increased, the expansion valve orifice may be partially blocked and cleaned;
C. If the expansion valve body only has frost on the outlet side, indicating that the flow rate is too large, it should be reduced;
D. If the outlet side and the lower part of the expansion valve body are frosted at 45 °C, the inlet side should not be frosted, indicating that the adjustment is accurate and appropriate;
E. If the expansion valve body only has frost on the inlet side, it indicates that the filter part at the inlet of the valve body is blocked and should be cleaned;
F. If the expansion valve body is completely frost-free, it indicates no flow, the refrigerant may leak or the shut-off valve in the pipeline is not opened or the expansion valve is sensitive. The capillary leaks or the expansion valve orifice is blocked or the inlet of the valve body is filtered. The part of the net is blocked and should be cleaned.
(2) It is also possible to judge whether the adjustment is appropriate by the shape change of the frost at the suction pipe of the compressor.
A. If the white frost is connected to the suction cut-off valve, it indicates that the flow rate is too large and should be adjusted small;
B. If the hoar frost does not reach the suction pipe, it indicates that the flow rate is too small and should be adjusted.
(3) In addition, it is judged whether the adjustment amount is appropriate by the magnitude of the pressure value on the low pressure side.
(4) The uniform and complete condition of the evaporator coil frosting to determine whether the adjustment is appropriate.
(5) Under normal circumstances, the expansion valve is very quiet when working. If a clear "filament" sound is emitted, the refrigerant in the system is insufficient.
(6) Using a thermometer to measure the difference between the temperature of the return pipe and the evaporating temperature (ie, the actual superheat) and the standard superheat (between 5-8 °C) to determine whether the adjustment is appropriate.
Using the suction pressure of the compressor as the saturation pressure in the evaporator, the table looks for an approximate evaporation temperature.
The temperature of the return pipe was measured with a thermometer, and compared with the evaporation temperature, it was between 5-8 ° C in the normal range. The inspiratory pressure value and the return air tube temperature must be read at the same time, otherwise the calculated actual superheat is not accurate.
Adjustment,
A. If the degree of superheat is too small, the adjusting screw can be rotated clockwise (ie, increase the spring force and reduce the opening degree of the thermal expansion valve) to reduce the flow rate;
B. Conversely, if the degree of superheat is too large, that is, the supply of liquid is insufficient, the adjustment screw can be rotated in the opposite direction (counterclockwise) to increase the flow rate. Because the thermal expansion valve temperature sensing system in the actual work has a certain thermal inertia, the signal transmission hysteresis is formed, and the operation is basically stable before the next adjustment can be made.
In the adjustment, you must not take the rapid adjustment of the ups and downs, so that the refrigeration system is unstable and can not control the effect.
The coarse expansion should be started first. (The thermal expansion valve of the air conditioner for the machine room generally adopts the pressure rod type and the scattered gear type. The loose gear type uses a small gear to drive a large gear. The number of adjustments is relatively large, and the general adjustment can be made. 2~4 laps; the number of adjustable laps is relatively small, 1/4 turn each time; the thermal expansion valve of air conditioner adopts the loose gear type), observe the change of the pressure value of the pressure gauge on the low pressure side, and the pressure value of the gauge is stable. After that, fine-tune it. Adjust 1/2, 1/3, and 1/4 turns each time.
The adjustment of the expansion valve must be carried out carefully and patiently. The adjustment pressure must be caused by the heat exchange boiling of the evaporator and the warehouse temperature (evaporation) and then passed through the pipeline into the compressor suction chamber to be reflected on the pressure gauge. It takes a time. Each time the expansion valve is mobilized, it usually takes 15-30 minutes to stabilize the adjustment pressure of the expansion valve on the suction pressure gauge. According to the observation of the change of the low pressure value, it is also necessary to observe the frosting at the expansion valve body, the evaporator coil and the compressor suction pipe to judge whether the adjustment is appropriate.
note:
1. When the system is pressed and leaked and the refrigerant is filled before the expansion valve is adjusted, it cannot be injected from the high pressure end. Otherwise, it is difficult to inject, and the pressure at the high and low pressure ends cannot be balanced. Because the expansion valve is the high and low pressure delimiter of the connection system, if the evaporator outlet pipe temperature of the expansion valve temperature sensor is not hot or superheated when the refrigeration system is not operating normally, the expansion valve outlet valve port can not be opened, the system The pipeline is cut off, and the high and low pressure sides are not connected, so the pressure at the high and low pressure ends cannot be balanced.
2. The refrigeration system consisting of a thermal expansion valve and a single-phase fully enclosed compressor may be difficult to start the compressor. The reason is the same as above
Perimeter LED Display,LED Perimeter Boards,Stadium Perimeter LED Display,LED Perimeter Advertising Systems
ShenZhen UHLED Technology Co., LTD. , https://www.uhled.com