The invention relates to a control method for preventing failure caused by
water flow loss during
defrosting of a
heat pump unit. The
heat pump unit comprises a shell, a compressor, a four-way valve, a water side
heat exchanger, an air side
heat exchanger, a water outlet temperature sensor, a low-pressure
pressure sensor and a
refrigerant pipeline, wherein the compressor, the four-way valve, the water side
heat exchanger and the air side heat exchanger are arranged in the shell, and the
refrigerant pipeline communicates with the compressor, the four-way valve, the water side heat exchanger and the air side heat exchanger. The water outlet temperature sensor is arranged at the water drainage end of the water side heat exchanger. The low-pressure
pressure sensor is arranged at the air return end of the compressor. The method comprises the following steps that after a
defrosting mode is started, the outlet
water temperature is obtained through the outlet
water temperature sensor, and the low-pressure value is obtained through the low-
pressure sensor; and if the outlet
water temperature is larger than or equal to the preset temperature threshold value, and within the set first
time range, the outlet water temperature is not in the decreasing trend, and the low-pressure value is in the decreasing trend, the
defrosting mode is quitted. According to the method, the running reliability of the unit is enhanced, and the safety of the unit during defrosting is improved.