10 Symptoms And Causes of Abnormal Frosting in Air Source Heat Pumps

Frosting and defrosting of air source heat pumps were originally normal phenomena. All units have automatic frost function to ensure normal heating and hot water for users. The current mainstream defrosting method does not require stopping the compressor or switching the four-way valve during the entire defrosting process. The indoor unit does not blow cold air and has little impact on the temperature inside the room. It has good comfort and users can rest assured!

However, there are also some cases that result in abnormal frosting of the air to water heat pump , which is the main reason for the failure of the heat pump operation. The abnormal frosting and freezing of the unit are only superficial symptoms of the unit's "malfunction". The frosting symptoms are different, the pathology is different, the cause is different, and the shape and form of frosting are different.

Frosting Symptom 1: Bottom Frozen

Reason: The water flow in the water accumulation tray is not smooth, and icing spreads to the evaporator

Solution: Deicing, cleaning dirt, and ensuring smooth water outlet.

Frosting Symptom 2: Local freezing of the evaporator

Reason: There is no frost at the defrosting sensor, and the defrosting point is incorrect

Solution: Manually force defrosting and move the defrosting sensor to the freezing/frosting area

Frosting Symptom 3: The evaporator is full of frost/ice and does not defrost

Reason 1: Malfunction of defrosting sensor and ambient temperature sensor

Solution: Manual forced defrosting, resistance drift, replacement of sensors

Reason 2: Lack of fluorine or system blockage

Solution 2: Add fluorine according to the standard and remove blockage after welding.

Reason 3: Defrosting and four way directional valve not reversing; The bypass defrosting system solenoid valve does not operate

Solution 3: Check if the valve components are powered on; Check whether the valve components operate normally

Frosting symptom 4: Unclean and incomplete defrosting

Reason 1: The temperature setting of the defrosting coil is too low, causing the defrosting to exit before it has completely melted.

Solution 1: Adjust the defrosting parameters, increase the exit defrosting temperature, and observe if it can completely defrost.

Reason 2: The placement of the defrosting coil probe is not appropriate, and it is not placed in the most severely frosted area.

Solution 2: Adjust the position of the defrosting probe and place it in the most severe frosting area.

Frosting Symptom 5: Short term frequent frosting

Reason 1: The finned heat exchanger is dirty, blocked, or obstructed by foreign objects.

Solution 1: Clean the heat exchanger or remove foreign objects.

Reason 2: The fan motor is damaged or the fan air volume configuration is too small

Solution 2: Repair and replace the motor or replace the fan with a larger air volume.

Reason 3: The refrigerant filling amount is too small.

Solution 3: Add refrigerant to the appropriate pressure.

Reason 4: The opening of the throttle expansion valve is too small.

Solution 4: Increase the opening of the expansion valve.

Reason 5: The area configuration of the finned heat exchanger is too small.

Solution 5: Require the manufacturer to replace the finned heat exchanger and increase the area.

Frosting Symptom 6: Frosting is very severe, with all fins covered in thick frost layers

Reason 1: The temperature setting of the defrosting coil is too low, or the defrosting time interval is set too long, resulting in the inability to enter the defrosting action in a timely manner.

Solution 1: Adjust the defrosting parameters, increase the temperature when entering the defrosting process, shorten the interval time, and observe if the defrosting action can be entered in a timely manner.

Reason 2: The placement of the defrosting coil probe is not appropriate, and it is not placed in the most severely frosted area.

Solution 2: Adjust the position of the defrosting probe and place it in the most severe frosting area.

Symptom 7 of frost formation: uneven frost formation, locally thick frost formation, and locally non frost formation

Reason 1: Uneven distribution of refrigerant, with high flow in some pipelines and low flow in others.

Solution 1: Require the manufacturer to adjust the structure of the refrigerant distributor to match the flow rate with the evaporation capacity.

Reason 2: The structural design is unreasonable, such as the high height of the upper and lower parts of the finned heat exchanger, resulting in a significant difference in the upstream and downstream wind speeds.

Solution 2: Require the manufacturer not to set the height of the heat exchanger too high or increase the fan air volume.

Frosting Symptom 8: Low pressure protection during defrosting process

Reason 1: The low-pressure detection during the defrosting process was not delayed or the delay time was too short.

Solution 1: Low voltage protection during the defrosting process requires delayed processing or extended delay time.

Reason 2: The throttle expansion valve is blocked or the opening is too small when reversing.

Solution 2: Replace the expansion valve or increase the opening of the expansion valve.

Frosting Symptom 9: High pressure protection during defrosting process

Reason: The temperature setting of the defrosting coil is too high, resulting in the high pressure protection still not being defrosted.

Solution: Adjust the defrosting parameters, lower the exit defrosting temperature, and observe if it can completely defrost.

Frosting Symptom 10: The fins do not frost and there is also a defrosting action

Reason: The temperature (or temperature difference) of the defrosting coil is set too high, resulting in misoperation.

Solution: Adjust the defrosting parameters, increase the temperature (or temperature difference) when entering the defrosting process, and observe the appropriate degree of frost formation on the fins before defrosting.

If you have any air heat pump problem, you can contact us, we can give you professional support as we are a long term experience heat pump manufacturer.