Common Faults and Solutions of Air Source Heat Pumps

In recent years, with the strong promotion of clean energy reform by the government and equipment manufacturers, air source heat pumps have achieved significant development in both the northern and southern markets as well as import and export markets. Even in the overall sluggish real estate market, they have maintained steady and optimistic growth, with their market share continuously expanding and their application population becoming increasingly widespread.

However, as a complex system, air source heat pumps can easily cause users and maintenance personnel to feel frustrated and unsure of how to solve any malfunctions that may occur during their application. Therefore, this article has summarized and organized the four common faults and solutions of air source heat pumps, hoping to bring some help to everyone.

High voltage alarm

The common causes of high pressure alarms in air source heat pumps are generally water system problems or electrical control system problems——

01 Waterway system

High pressure alarms caused by water system failures are usually divided into two situations: one is when the main engine works normally for a few minutes or a period of time before the high pressure alarm appears, and the high pressure gauge is higher than 3Mpa, which is not related to water temperature and is mostly caused by blocked or disconnected circulating water circuits. The judgment method and solution measures are:

① Check if there is any blockage caused by the waterway valve not being opened. If so, simply open it;

② Check if the high temperature cannot dissipate due to the low water level in the water tank. If so, add water to the water tank;

③ Check if the "Y" filter is blocked by impurities, and if so, replace or clean the filter;

④ Check if there is air blockage in the circulation pump, and if so, exhaust the circulation pump;

⑤ Check whether there is freezing inside the heat exchanger (when the weather is cold). If there is, perform de icing treatment or replace frozen parts, and do a good job of anti freezing in the later stage.

Another type of water system malfunction is the occasional occurrence of a high-pressure fault alarm, where the low water temperature operates normally, but the heat dissipation becomes poor when the water temperature increases and the pressure increases (>3Mpa), resulting in an alarm. The common reasons and solutions are:

① Insufficient water pump flow, replace with a suitable water pump;

② The heat exchanger is clogged due to scaling, and can be cleaned with a specialized descaling agent;

③ The circulation pipeline is too long and has too many bends. It can be designed and constructed according to the standard: the distance between the main engine and the water tank should not exceed 3 meters, preferably kept within 1.5 meters. The shorter the circulation pipeline, the better. The number of bends in the circulation pipeline should not exceed 6, preferably kept at 3-4, and it is best to use a 45 degree bend.

02 Electrical Control System

The high-voltage fault caused by the electronic control system is manifested as a high-pressure alarm immediately appearing as soon as the main engine is powered on (the water pump, fan, and compressor have not yet started); Or the pressure gauge value is normal but there is an irregular high pressure alarm. The former is generally caused by damage to the water temperature probe, defrosting probe, high-voltage switch, or motherboard, while the latter is mainly caused by damage to the high-voltage control chip of the motherboard. The judgment method and solution measures are:

① If there is a significant difference between the displayed water temperature and the actual water temperature, the water temperature sensor needs to be replaced;

② If the displayed water temperature is consistent with the actual water temperature, the high-voltage switch terminal can be short circuited. If there is no more alarm after short circuiting, it is a problem with the high-voltage switch, which can be replaced;

③ If the high voltage switch terminal still alarms after short circuiting, replace the motherboard or chip.

Low voltage alarm

There are two main situations when an air source heat pump generates a low pressure alarm:——

01 Low voltage display is normal

When the unit is working, the low pressure display is normal (above 0.1Mpa), but a low pressure alarm occurs. The causes of this malfunction can be divided into:

① Low voltage switch or motherboard fault, the inspection method is: short circuit the low voltage switch, then turn on the machine for testing, if the fault still shows, it is that the motherboard is broken and needs to be replaced; Troubleshooting indicates that the low-voltage switch is faulty and needs to be replaced;

② The evaporator is clogged or frosted, causing poor ventilation and low pressure alarm. In this case, the evaporator can be cleaned or defrosted;

③ The external fan is not running. If the ventilation is poor, remove any obstacles; If the fan is damaged, replace it promptly.

02 Low voltage display abnormality

When the low pressure of the unit is below 0.1Mpa during operation and a low pressure alarm occurs, it is caused by insufficient or no refrigerant. In this situation, it is necessary to identify the leakage point, repair the leakage point, re evacuate and inject the rated capacity refrigerant according to the nameplate of the unit.

Evaporator frosting

Generally speaking, in environments with low temperature and high humidity, frosting and defrosting of air source heat pumps are normal phenomena. However, if the evaporator cannot defrost normally or even freezes after frosting, it is considered a fault and can be divided into various situations——

① Bottom frosting: The water flow in the water tray is not smooth. Use hot water to rinse the frosty area and remove any blockages.

② Localized frosting: The defrosting sensor (probe) is not in the appropriate position, adjust it to the position with the most severe frosting.

③ Uniform frosting: Place the defrosting probe in the frost and let it stand for three minutes. If the temperature displays above 5 ℃, it indicates that the defrosting probe is damaged and needs to be replaced; If there is no suction sound or refrigerant flow sound after opening the four-way valve, it indicates that the four-way valve is damaged and needs to be replaced. If there is suction sound but no refrigerant flow sound, it indicates that the four-way valve body is stuck. You can try knocking out foreign objects or replace it directly.

④ Incomplete defrosting: The defrosting end temperature is set too low or the defrosting duration is set too short. Adjust it accordingly.

⑤ Short term frequent frosting: If the finned heat exchanger is dirty or clogged with foreign objects, cleaning is sufficient; If the fan motor is damaged or the air volume configuration is too small, repair or replacement is sufficient; If there is a shortage or leakage of refrigerant, it is necessary to replenish refrigerant or check the leakage point and repair it; If the opening of the throttle expansion valve is too small (low pressure protection may occur during defrosting), increase it; If the area configuration of the finned heat exchanger is too small, it can be replaced with a large-area finned heat exchanger.

Exhaust temperature too high

To identify the root cause of high exhaust temperature in air source heat pumps, the following troubleshooting steps can be followed——

① Check the water temperature

First, measure whether the actual water temperature is consistent with the water temperature displayed on the water temperature probe. If the actual water temperature is significantly higher, it indicates that the water temperature probe is broken or not properly placed and needs to be replaced or adjusted; Check again if the set temperature is higher than the upper limit temperature of 60 ℃. If so, simply lower the water temperature.

② Check if the return air temperature is normal

To prevent refrigerant reflux, the superheat of the return air should generally be controlled at 20 ℃. If the insulation of the return air pipeline is not good, the superheat will exceed 20 ℃, and for every 11 ℃ increase in return air temperature, the exhaust temperature will increase by 1-1.3 ℃.

③ Check if there is a low suction temperature

Firstly, turn off the power and restart the fan to see if it is working properly. When the fan does not work in winter, it can cause the suction temperature to be too low, the compression ratio to increase, the compressor to operate at overload, and the exhaust temperature to rise sharply. In this case, repair or replace the fan; Then check if the evaporator is frozen or dirty, as poor ventilation can also cause the suction temperature to be too low and the exhaust temperature to rise. In this case, clean the evaporator.

④ Check refrigerant and condensation pressure issues

Excessive power of the air source heat pump compressor may also be caused by refrigerant leakage leading to a decrease in refrigerant volume, or high condensation pressure, improper selection of refrigerant, etc. The manifestation of refrigerant leakage is that the temperature rises very slowly during operation, which can be solved by adding refrigerant to fill the leak; As for the situation of high condensation pressure, it is relatively complex. After ruling out the problems of insufficient power of the condenser itself and blockage of the condensation pipeline, it may also be due to air entering the condenser, which should be promptly vented.

⑤ Other issues

Other issues such as a faulty expansion valve causing a decrease in opening, low evaporation temperature, or even damage to compressor bearings leading to excessive internal friction can also result in high exhaust temperature of the compressor. Corresponding components should be repaired in a timely manner.