What causes a high-pressure protection shutdown in an air-source heat pump water heater?

To resolve the issue of a high-pressure shutdown in an air-source heat pump water heater, it is essential to understand the exact cause of this malfunction. The operating principle of an air-source heat pump water heater is similar to that of an air conditioner. The process of pressurization and heating takes place entirely within the heat pump (typically reaching temperatures of 100 degrees Celsius). Once the heat enters the heat exchanger, it releases high-temperature heat to warm the water, while simultaneously cooling and converting into a liquid state. When it reaches the evaporator, the liquid rapidly absorbs heat, evaporates, and reverts to a gaseous state, with its temperature dropping to between -20 and -30 degrees Celsius. At this point, the air surrounding the evaporator continuously transfers low-temperature heat to the refrigerant. Through this continuous circulation, the refrigerant converts low-temperature heat from the air into high-temperature heat, thereby heating the cold water. A high-pressure alarm is triggered when the high-pressure sensor detects that the temperature of the high-pressure copper pipe has exceeded the normal range; generally, an alarm sounds when it exceeds 120°C. Abnormal high pressure is usually caused by a lack of water in the tank—commonly referred to as insufficient water volume—which prevents heat from dissipating, or by an excessively high set outlet temperature. As temperature increases, so does pressure; if heat cannot be dissipated, the system will activate high-pressure protection. If heat cannot be dissipated, check whether the refrigerant system piping is unobstructed and whether the three-way or four-way valves are functioning normally.

In addition to excessive temperature causing the air-source heat pump water heater to repeatedly shut down due to high pressure, overcharging with refrigerant can also lead to high-pressure faults. Other causes include poor condenser heat dissipation, obstructed exhaust airflow, high ambient temperatures, insufficient condenser surface area, a clogged refrigeration system throttle valve, or deformed copper tubing. High-pressure alarms are rarely caused by a single issue alone. Established in 2010, Sichuan Huigao Mechanical & Electrical Engineering Co., Ltd. is an integrated engineering firm specializing in mechanical and electrical equipment engineering, as well as the design, installation, and maintenance of intelligent systems. We provide clients with professional design, construction, and service management; deliver comprehensive solutions for creating comfortable living environments; and offer a technical platform to meet clients’ “one-stop” service needs. For inquiries, please contact Mr. Li at 18982050285.