The characteristic of the cold storage system is that the compressor of the refrigeration system is running normally, but the cooler unit is not frosted, the high-pressure exhaust pressure is lower than the normal value, and the low-pressure return air pressure is lower than the normal value or even negative. After the refrigeration system is dirty and blocked, the refrigerant cannot circulate, causing the low pressure protection of the high and low pressure relays to act, and the compressor shuts down. Manually turn on the condensing unit again, and the failure phenomenon remains, which is a typical dirty blockage failure.

The thermal expansion valve is often dirty and blocked, which is characterized by: when the inlet of the expansion valve is frosted (or the valve cover is also frosted), the temperature of the liquid inlet pipe is lower than the normal temperature, and even condensation occurs. The suction pressure of the compressor is lower than the corresponding normal pressure at the storage temperature, and the temperature in the cold storage decreases slowly or does not drop, which indicates that the thermal expansion valve is dirty and blocked.

The solution to the problem of dirty blockage in the thermal expansion valve is to close the shut-off valve from the liquid outlet valve of the refrigeration system to the cooler unit. Disassemble the liquid inlet of the expansion valve, take out the filter screen and clean it with kerosene and put it back in again. After replacing the desiccant in the drying filter, first open the stop valve of the liquid inlet of the drying filter, and loosen the liquid outlet of the thermal expansion valve. After the gas escapes, tighten it and then open the stop valve of the liquid outlet of the thermal expansion valve, which can eliminate the failure phenomenon and restore the normal operation of the refrigeration system.