Problems and case analysis of electronic expansion valve and four-way valve

Problems and case analysis of electronic expansion valve and four-way valve 1. The problem of electronic expansion valve

Judge the quality of electronic expansion valve:

Step one (see): Whether the wiring is in place and whether the wiring is damaged.

Step two (listening): After power-on, there is a "click" normally, check whether the coil is in place; Step three (measurement): Measure the coil resistance, insulation resistance and the voltage of the main board when the power is turned on. The winding between the common terminal COM (usually gray/blue wire) and other wires is generally more than 40 ohms, and the coil power supply voltage is usually 12V square wave pulse.

Step 4 (Valve body): If there is no abnormality in the above inspection and the valve body is frosted or blocked, tap the valve body to see if it can be recovered. If it cannot be recovered, replace the valve body.

Case number one

Phenomenon: The customer reported that the indoor unit of the air conditioner works normally, but does not refrigerate and occasionally refrigerates. After the master came to check the indoor and outdoor units of the air conditioner, he heard a "click, click" sound, and judged that there might be a problem with the electronic expansion valve.

Check: According to the air conditioner pressure from high pressure to negative pressure, it may be blocked somewhere in the system, and you cannot hear the "click, click" sound of the electronic expansion valve when it is turned on, and then the capillary flow is controlled by the electronic valve, and the machine can sometimes work normally , Judge the failure of the electronic expansion valve.

Treatment: The outlet master came to test the machine and found that the fans of the internal and external machines were rotating. When the working current of the external machine was measured, 4A, the compressor was normal, and the low pressure stress was measured 1Kg, and it was still falling, and the current was slowly rising. Turn on the power supply of the air conditioner, and the pressure slowly changes from negative pressure to about 17Kg. It is preliminarily judged that the system is blocked, and the resistance valve coil is measured. The voltage and resistance are normal. When the power is turned on, the electronic expansion valve cannot be heard. Remove the electronic valve coil and use Tap the screwdriver handle lightly, the pressure rises slightly, the electronic valve coil is installed dead, and the machine is turned on again. The air conditioner works normally, and the electronic expansion valve is damaged. After replacement, the machine is tested normally.

2. Common problems of four-way valve

Step one (listening): There is a sound of closing when switching, if not, go to the next step.

Step 2 (Measurement): The power supply voltage of the solenoid coil of the four-way valve is usually AC 220V. You can first measure whether the voltage at both ends of the coil is normal, and then use a multimeter to check whether the resistance of the solenoid coil is normal, usually between 0.5 and 2KΩ.

Step three (valve body inspection): tap the valve body lightly with a small wooden stick to observe whether the reversal can be restored. If it still fails to change direction, the four-way valve/pilot valve is stuck.

Step 4 (Check for air leakage): Use a temperature tester to measure the temperature difference between suction (5~15℃ in rated cooling mode) and exhaust (60~90℃ in rated cooling mode). Case two

Phenomenon: KTV users complained that the cooling effect of air conditioning was not good.

Check: There is no problem with the user's use area and the air conditioner, and this room is a box with good heat insulation. Check that the low pressure pressure of the air conditioner is 0.65Mpa, which is obviously high. When the refrigerant is put to 0.55Mpa, the air-conditioning at the air outlet of the indoor unit is still very small. Measure the working current of 7.3A, and touch the high and low pressure copper pipes normally. Less, prove that the compressor is fault-free. ③Touch the four copper pipes of the four-way valve with your hands. One of the exhaust pipes connected to the compressor has a higher temperature, and the other three have a thermal sense. At this time, the pressure is 3.06Mpa. When the air conditioner is adjusted to the heating state, the sound of the four-way valve is not very strong, and the heating effect is not very good, so it can be judged as the four-way valve blow-by failure.

Treatment: Replace the four-way valve, re-evacuate for leak detection, add refrigerant, and the user is satisfied with the test results.