Abstract: A specific model of air source heat pump air conditioner, after operating in low ambient temperatures from 0℃ to -20℃ in the north for 2 to 5 heating seasons, test shows there is a problem of condenser branch pipe leakage. After investigation, it was found that the contact between the condenser branch pipe and the condenser tube plate was worn, resulting in refrigerant leakage. Siemens vibration testing equipment was used to collect vibration data of heat pump air conditioners with refrigerant leakage. Combined with finite element analysis, it was found that the cause of condenser branch pipe wear and leakage was the vibration impact generated during the four-way valve switching under the defrosting condition of the heat pump air conditioner. It was transmitted to the condenser branch pipe through the copper pipe, and relative vibration was generated at the interference fit of the flipping hole between the condenser branch pipe and the condenser tube plate. In cold winter conditions, the rate of frost formation in the condenser is fast, and the heat pump air conditioning frequently enters the defrosting condition. The frequent switching of the four-way valve accelerates the wear of the condenser branch pipe, ultimately leading to leakage. A new vibration damping rubber block was designed to address this issue. The rubber block was installed at the position where the amplitude of the gas collection pipe and condenser branch pipe was the highest, reducing the vibration caused by the impact of the four-way valve on the branch pipe. After experimental testing, the amplitude was reduced by more than 50%. Before the rectification, there were 767 after-sales cases caused by condenser branch pipe leakage in the previous heating season, with a direct loss of 900500 yuan. After the rectification the following year, there were 58 after-sales cases caused by condenser branch pipe leakage in the same heating season, the direct loss amount is 66400 yuan, and the reduction in after-sales cases after rectification is about 92%.

Key words: Heat pump air conditioning, Condenser branch pipe, Pipeline vibration, Four way valve, Defrosting conditions