Working principle, common faults, and maintenance points of air-cooled heat pumps

1. Cooling mode:
• The compressor draws in low-temperature, low-pressure liquid refrigerant and compresses it into high-temperature, high-pressure gas.
• The high-temperature, high-pressure refrigerant enters the condenser (which acts as a radiator at this time), and exchanges heat with the outdoor air introduced by the fan through the fins, releasing heat into the air and cooling itself into a high-pressure liquid.
• After being depressurized by the throttling device, the liquid refrigerant enters the evaporator (which acts as a heat absorber at this time). During this process, it absorbs heat from the indoor return water (or directly from the indoor air) and evaporates into a low-temperature, low-pressure gaseous refrigerant.

• The evaporated refrigerant is drawn back into the compressor to begin the next cycle.

2. Heating mode:
• The four-way reversing valve activates, changing the direction of refrigerant flow so that the evaporator becomes the heat-absorbing end (absorbing heat from the outdoor air), while the condenser becomes the heat-releasing end (releasing heat to the indoor water supply system).
• The rest of the process is similar to the refrigeration mode, except that the direction of heat transfer is reversed: the refrigerant absorbs heat from the outdoor air and evaporates in the evaporator, and then is compressed into a high-temperature and high-pressure gas by the compressor; in the condenser, the refrigerant transfers heat to the circulating water, condenses itself into a liquid, and then returns to the evaporator to continue absorbing heat after being depressurized by the throttling device.

Common faults and troubleshooting methods:

1. Poor cooling performance:
• Possible causes: insufficient or leaking refrigerant, dirty condenser or evaporator, clogged air filter, severe scaling or dust accumulation in the heat exchanger, fan malfunction, control system malfunction, etc.

• Troubleshooting methods: Check the refrigerant charge level and replenish or repair leaks if necessary; regularly clean the condenser and evaporator, and replace or clean the air filter; descale or clean the heat exchanger; check the fan motor and its drive circuit, and repair or replace faulty parts; verify the control system parameters or repair controller malfunctions.

2. Decreased heating performance:
• Possible causes: inaccurate refrigerant charge, malfunction of the four-way reversing valve, failure of the defrosting system, low ambient temperature leading to reduced unit efficiency, and severe frost buildup on the heat exchanger.
• Troubleshooting methods: Recharge or adjust the refrigerant to the specified level; check and repair or replace the four-way reversing valve; check the defrost sensor and control system to ensure that the defrost function is normal; in extreme low temperature conditions, auxiliary electric heating or other heat sources may be required; defrost regularly or optimize the defrost strategy.
3. Compressor malfunction:
• Possible causes: overload, power supply problems, poor lubrication, internal mechanical wear, high temperature caused by prolonged operation, etc.

• Troubleshooting methods: Check the power supply and voltage stability to ensure they meet the compressor specifications; regularly replace or replenish the lubricating oil to maintain good lubrication; replace damaged compressor parts or the entire unit as needed based on fault indications or professional diagnosis; set operating parameters appropriately to avoid prolonged full-load operation.

4. Control system malfunction:
• Possible causes: sensor failure, control circuit board damage, software error, communication failure, etc.

• Troubleshooting methods: Check the accuracy of data from each sensor and replace any faulty sensors; inspect and repair or replace any faulty control circuit boards; update the control system software to the latest version and fix any known software issues; ensure that communication lines are properly connected and verify the compatibility of communication protocols.

5. Water pump malfunction or water flow problem:
• Possible causes: pump motor damage, impeller blockage, water system valve malfunction, pipe blockage or leakage, etc.

• Troubleshooting methods: Inspect the water pump motor and bearings, and repair or replace damaged parts; clean debris from the impeller to ensure smooth water flow; inspect valves and repair or replace faulty valves; check water system pipes and repair leaks or remove blockages.

System maintenance and upkeep points

Regular preventative maintenance is crucial for ensuring the long-term, efficient, and stable operation of air-cooled heat pumps. The following maintenance procedures are recommended:

• Daily/Weekly Inspections :

• Observe the unit for any abnormal noises or vibrations during operation.

• Check the controller panel and record whether the operating parameters (pressure, temperature, current, etc.) are within the normal range.

• Check the air-side heat exchanger (fins) for obvious debris or blockage.

• Monthly maintenance :

• Clean or replace the indoor return air filter (if applicable).

• Check if the fan blades are dusty and if the rotation is smooth.

• Check refrigerant lines, water lines, and valves for oil stains (which may indicate a leak) or abnormal condensation.

• Quarterly/Annual Maintenance (Recommended to be performed by professionals) :

• Cleaning the heat exchanger : Use a special cleaning agent and a high-pressure water gun (pressure must be controlled to prevent the fins from collapsing) to thoroughly clean the outdoor finned heat exchanger, removing dust, catkins, etc., to ensure ventilation and heat exchange efficiency.

• Inspect the electrical system : tighten all power terminals, check the condition of contactor and relay contacts, and measure the insulation resistance of the motor.

• Check the refrigeration system : Measure the high and low pressure operating pressures, and add refrigerant if necessary (the leak must be located and repaired before adding refrigerant). Check the compressor lubricating oil level and color.

• Check the water system : Clean the water-side heat exchanger (plate or shell and tube type), check the water pump operation status, clean the water filter, check the system water quality, and add corrosion and scale inhibitors if necessary.

• Calibration system : Verify the accuracy of temperature and pressure sensors. Check and test the operation of key valves such as the four-way directional valve and electronic expansion valve to ensure they function correctly and reliably. Conduct a comprehensive test of the automatic defrosting function in heating mode.