Common Air-cooled Heat Pump Units Problems and How To Solve Them

Air-cooled heat pump units are energy-saving and convenient, and are widely used in commercial, industrial and residential scenarios, mainly for heating, cooling and hot water supply. Long-term operation, by the installation, environment, maintenance and other factors are prone to failure, resulting in decreased efficiency, increased energy consumption, serious damage to the equipment, downtime.

This paper combines hands-on maintenance experience, for the unit common faults, dismantling the causes, investigation and solution methods, to provide a floor guide to help maintenance personnel to quickly solve the problem, the user to master the basic ideas of judgment, to achieve low-cost maintenance, to protect the stability of the unit, to extend the life of the equipment.

Phase Sequence, Phase Failure and Phase Reversal Protection Failure

Phase sequence, phase failure and phase reversal protection are the most easily triggered safety protection mechanisms in the power supply system of air-cooled heat pump units, which directly affects the normal startup and stable operation of the units, and the failures are mostly triggered by the wrong wiring of power supply or voltage abnormality.

Step-by-step troubleshooting and solution:

• No need to replace the parts, only need to access the unit’s power supply adjacent to the two inlet lines to the right, adjust the completion of the restart of the unit, you can lift the protection.
• Check one by one the stability of the accessed power supply and the tightness of the connecting wires; replace the loose or broken connecting wires; ensure that the power supply is normal and the wiring is reliable, so as to avoid damage to the unit’s components due to phase loss.

Maintenance tips: reverse-phase protection is the most common type of this type of failure, most of the cases do not need complex testing, prioritize checking the order of power supply wiring, which can greatly enhance the efficiency of the investigation.

Air Switch Tripping Fault

Air switch tripping is an important feedback of the unit’s circuit safety protection, mainly divided into two scenarios of “unable to close the gate” and “occasional tripping”, the cause of the fault is closely related to the circuit short circuit, wiring, and environmental humidity.

Step-by-step investigation and solution:

• For the case of the air switch can not be closed, first replace the new air switch and check whether the wiring is loose, if the replacement is still unable to close the door, you need to further test whether the compressor is grounded, whether the motherboard is short-circuited, diagnosed after the replacement of the damaged compressor or motherboard;
• For occasional tripping, focus on checking the air terminal, tighten the loose wiring, if the air is located in a humid environment, the need to relocate to a dry, ventilated location, to avoid moisture triggered false protection.

Water Flow Protection Failure

Water flow protection failure is the most common type of failure in the installation and daily operation of air-cooled heat pump unit project, excluding the installation of non-standard factors, the core causes are mainly divided into two categories: poor circulation of the water system, the water flow switch itself is damaged, the vast majority of failures stem from the water system problems.

Step-by-step investigation and solution:

investigation priority treatment of water system problems, the first step to check and clean up the pipeline filter, remove impurities within the filter, scale, to avoid clogging resulting in poor water flow;

second step to check whether the pipeline valve is completely open, circulating pumps are running normally, if the valve is not open in time to open, if the circulating pump is damaged, then repair or replacement;

If the above investigation are not a problem, it can be judged as the water flow switch Failure, this time the water flow switch can be shorted to start the unit, if the unit can start normally, you can confirm that the water flow switch is damaged, replace the new water flow switch can be restored to normal.

Maintenance tip: When investigating the water flow protection failure, no need to prioritize the replacement of the water flow switch, you should first focus on cleaning up the water circuit, checking the valves and circulating pumps, which can effectively reduce the cost of maintenance and enhance the efficiency of the investigation.

High-pressure Protection Fault

High-pressure protection fault is mainly related to the water circuit system abnormality, when the unit is running, the system high-pressure pressure exceeds the safety threshold, the control board will trigger high-pressure protection, to avoid the compressor and other core components due to high-pressure damage, need to be assisted in the troubleshooting through the pressure gauge.

Step-by-step investigation and solution:

If the system high pressure is too high, you need to check the above water circuit faults one by one, clean the blocked valves, filters and scaled heat exchangers, replenish the missing water in the water system, exhaust the air in the system, adjust the flow rate of the circulating pump and the water temperature setting, and make sure that the water circuit system circulates normally;

If the system high pressure is normal, check the wiring of the high pressure pressure switch first, and re-plug the wiring to ensure that the contact is reliable, and then shut down the machine with a multimeter to make sure that the pressure is not too high.

If the system high pressure is normal, first check the wiring of the high pressure switch, re-plug the wiring plug to ensure that the contact is reliable, and then stop the machine with a multimeter to detect whether the pressure switch is on or not, if it is not on, then it means that the pressure switch is damaged, and replace with a new one.

Low water outlet temperature

The low water outlet temperature fault will directly affect the heating and hot water supply effect of the unit. The cause of the fault is mainly related to the temperature detection parts and water system, and the problem should be investigated by comparing the actual temperature with the displayed temperature.

Step by step investigation and solution:

Compare the display temperature and the actual water temperature, if the deviation is large, directly replace the water temperature probe;

If the two are the same, you need to check the accuracy of the water tank temperature sensor, clean up the pipeline filter, to ensure that the water circulation is smooth, and at the same time, check whether the pipeline valve is completely open, whether the circulating pump is functioning properly, to ensure that the circulating pump flow rate in line with the requirements of the unit, to avoid the insufficient flow of water to avoid low temperature of the water. Low water temperature due to insufficient water flow.

Water Pump Does not Start

Water pump as the core component of water system circulation, its non-starting will directly lead to interruption of water circulation, which in turn triggers a series of chain failures such as water flow protection, and the core causes are mainly divided into three categories: water pump card shaft, no output signal from the motherboard, and burnt out water pump relay.

Step by step investigation and solution:

1. Check the status of the water pump, touch the water pump is hot, use a screwdriver to rotate the fan blade, if the fan blade rotation difficulties or can not be rotated, indicating that the water pump stuck shaft, need to disassemble the maintenance or direct replacement of the water pump;
2. If the pump is not abnormal, use a multimeter to measure the voltage of the pump load port, if there is no voltage output, indicating that the motherboard has no output signal, replace the motherboard can be;
3. If there is a voltage output but the pump still does not start, use a multimeter to measure the pump relay normally open port, if the measured resistance value is infinite, indicating that the relay burned, replace the new relay can be restored to normal.

Water Level Switch Failure

Water level switch failure mainly affects the water level regulation and control function of the water system of the unit, resulting in the unit can not be normal water replenishment, drainage, and then affect the stability of unit operation. The cause of the failure is relatively simple, mainly related to abnormal wiring or damage to accessories.

Step-by-step investigation and solution:

1. When checking the priority of checking the wiring: the first step to check the wiring order of the high and low water levels, if there is a problem of reversal, adjust the corrections in a timely manner.
2. The second step is to check the wiring terminals of the low water level device, tighten the loose parts to ensure that the wiring contact is reliable to avoid abnormal signal transmission.
3. If there is no abnormality in the wiring, start the unit for testing; if the water level control is still abnormal, it can be determined that the main board failure, replacement of the motherboard can rule out the problem.

Water Outlet Overheating Protection

Water outlet overheating protection is a common manifestation of abnormal temperature control of the unit, the core cause of which is related to the installation and status of the temperature sensor, and in some cases it involves the motherboard failure.

Temperature sensor placement is not correct, can not accurately detect the water temperature; sensor and blind pipe wall contact is not close, the detection signal distortion; sensor wire broken, the signal can not be transmitted; temperature sensor resistance drift, abnormal detection data.

Step-by-step troubleshooting and solution:

1. Check the temperature setting of the unit to confirm whether the set temperature is reasonable, and then check the installation position of the temperature probe, adjust the probe position to ensure that the probe is in close contact with the blind pipe wall;
2. Compare the water temperature value displayed on the control panel with the actual water temperature, if the deviation between the two is large, indicating that the temperature probe is damaged, directly replace the probe;
3. If there is no problem with the above troubleshooting, and the unit still triggers overheating protection, it is necessary to check the main board, check whether there is a fault on the main board, and replace the main board if necessary.

Exhaust Temperature Overheat Protection

Exhaust temperature overheat protection is mainly used to protect the core component of the unit, the compressor, when the exhaust temperature exceeds the safety threshold (usually 120 ℃), the unit will automatically trigger the protection mechanism to prevent the compressor from burning due to high temperature. The cause of this fault is more complex, mainly involving temperature sensors, refrigerant systems and core components of the unit and other dimensions.

Step-by-step investigation and solution:

If the exhaust temperature is normal, first check the wiring of the exhaust temperature sensor to ensure reliable contact, and then use a multimeter to detect the sensor status, and replace the sensor if it is damaged, and if the sensor is not abnormal, then check the circuit board, and replace it if necessary;

If the exhaust temperature is too high, first check whether the unit’s high and low pressures are normal, and then check whether the expansion valve is clogged or not, whether the refrigerant piping is open or not, and then replace the missing refrigerant, and then check the four-way valve and the compressor if there are any problems with the four-way valve and the compressor.

Check whether the four-way valve and compressor have the problem of stringing gas, one by one after eliminating the faults, the exhaust temperature can be returned to normal, and the protection mechanism is lifted.

Temperature Sensor Failure

Temperature sensor is the core component of the unit temperature detection, distributed in the water, exhaust, environment and other locations, the sensor failure will lead to abnormal temperature detection, and then trigger all kinds of temperature protection faults, fault judgment can be assisted by resistance detection.

Step-by-step investigation and solution:

The first step to check the sensor and the motherboard wiring connector, tighten the loose wiring, check whether the motherboard failure;

The second step to use a multimeter to detect the sensor’s resistance value, compared to the corresponding temperature under the standard resistance value, if the resistance value is abnormal, indicating that the sensor is damaged, replace the sensor with a new one;

If the resistance value is normal, re-plugging the wiring, the unit is still faulty, it can be judged as a failure of the motherboard, replace the motherboard can be. Replace the main board.

Low-pressure Protection

Low-pressure protection fault is a common fault in the refrigerant system of air-cooled heat pump unit, the core of which is closely related to whether the refrigerant quantity is sufficient and whether the heat exchange effect is good, and it is necessary to combine with the pressure detection during the troubleshooting, and prioritize the troubleshooting for the lack of fluorine, fluorine leakage, which is the most common cause of the problem.

Step by step investigation and solution:

• The first step is to measure the low-pressure pressure with a pressure gauge under the state of shutdown, if the low-pressure pressure is lower than 0.5MPa, focus on checking whether there is leakage or blockage in the fluorine circuit, find the leakage point and make up for the leakage, replenish the refrigerant to the standard amount, and unblock the blocked fluorine circuit;
• If the low-pressure pressure is higher than 0.5MPa, focus on checking the low-pressure protection switch and expansion valve, use a multimeter to check whether the low-pressure pressure switch is on, if not, replace the switch, check whether the expansion valve is clogged, and clean or replace it if necessary;
• At the same time, if the unit fins frost serious, clean up the fins frost, check whether the fan is running normally, clean the evaporator for a long time without maintenance, to ensure that the heat transfer effect is normal.

Control Panel Display Failure

No display on the control panel display means that the control terminal of the unit can not work normally, and it is impossible to operate the unit and check the operating parameters. The causes of the failure are mainly related to the power supply, fuse, motherboard or display itself, and the troubleshooting needs to be carried out step by step from the simple to the complex.

Step by step investigation and solution:

• The first step is to check the power supply of the unit, confirm that the power supply is stable and the wiring is not loose, and ensure normal power supply to the control terminal of the unit.
• The second step is to check the fuse of the equipment, if it is found that the fuse is blown, replace it with a new suitable fuse in time to restore the power supply circuit of the control terminal.
• If there is no abnormality in the power supply and fuse, and the display still does not show up after starting the unit, it is necessary to test the main board and display one by one, and replace the damaged parts to restore the normal display function of the unit.

Host Failure

The host does not run is the most intuitive failure of the air-cooled heat pump unit, which will directly lead to the inability of the unit to play the core functions of heating, cooling, etc. The causes of the failure are more diverse. The causes of the failure are more diverse, mainly involving parameter settings, power supply and core component conditions, etc., and priority should be given to verifying the basic parameter settings and power supply of the unit when troubleshooting.

Step-by-step investigation and solution:

• The first step is to verify the parameter settings of the unit, confirm that the core parameters such as temperature and operation mode are set reasonably, and if there are abnormalities, adjust them to the standard parameters in time;
• The second step is to check the power supply of the unit, confirming that the power supply is stable and normal, and that the terminals are fastened and secure, so as to prevent failures caused by abnormal power supply or loose wiring;
• The third step is to check the compressor contactor, troubleshoot and tighten the loose wiring; if the troubleshooting is not a problem and still does not run, the probability is that the compressor triggers overheating protection, turn off the unit to be cooled down and then restarted, and then to avoid prolonged operation of the compressor under high load.

Low Heating Capacity

Low heating capacity will affect the heating effect of the unit, especially in winter, the impact is significant, the cause of the failure is complex, involving the heat exchange system, refrigerant system, core components, insulation effect and other aspects, need to be comprehensive investigation.

Step by step investigation and solution:

1. Clean the air heat exchanger and pipe filters to remove dust and scale, and improve the efficiency of heat exchange and water flow;
2. Leak check the refrigerant system and replenish the refrigerant to the specified amount to ensure normal refrigerant circulation;
3. check the fan motor, repair or replace the faulty motor, clean the evaporator of accumulated frost, and restore normal heat exchange;
4. Check the pipeline insulation, if the insulation effect is poor, re-insulate the pipeline to reduce heat loss;
5. Check the refrigerant system, dredge the blocked parts; the sixth step to test the compressor, if there is a failure, timely repair or replacement, to ensure that the heating output is normal.

Unclean Defrosting

Unclean defrosting will lead to excessive accumulation of frost on the fins and coils of the unit, affecting the heat transfer efficiency, which in turn will lead to a decrease in the heating capacity and an increase in energy consumption, and the causes of the failure are mainly related to the probe, parameter settings, and refrigerant quantity.

Step-by-step troubleshooting and solution:

1. Check the coil probe, adjust its installation position to ensure that the probe can accurately detect the thickness of the frost layer, if there is damage to the probe, replace the new probe in time;
2. Recalibrate the defrosting parameters, set the defrosting time and frequency reasonably to ensure that the frost layer is cleared thoroughly to avoid residual frost affecting heat exchange;
3. Conduct a comprehensive leakage check on the refrigerant system of the unit, replenish the missing refrigerant in time to ensure sufficient defrosting power and eliminate the problem of incomplete defrosting caused by lack of fluorine.

Fan Failure

fan is an important part of the unit heat transfer, fan does not turn will lead to a sharp decline in heat transfer efficiency, and then trigger a series of faults such as high pressure, low pressure, temperature protection, the cause of the failure is mainly related to the fan motor, contactor, capacitor, control signals.

Step-by-step investigation and solution:

The first step to check the fan motor, if the motor is burned, repair or replace the motor;

The second step to check the contactor and fan capacitance, use a multimeter to detect the state, replace the damaged contactor or capacitance;

The third step to check the motherboard, measuring the motherboard whether there is a fan start signal output, if there is no output, it means that the motherboard is faulty, the replacement of the motherboard can be, to ensure that the motherboard can normally control the fan start.

Communication Failure

Communication failure will cause the control side of the unit and the executive side cannot communicate normally, which is manifested as invalid control panel operation, the unit cannot start normally, abnormal operation parameters, etc. The causes of the failure are mainly related to the communication line and control components.

Step-by-step investigation and solution:

1. Check the shielding line, confirm that the line is not disconnected, re-insert the two ends of the wiring to ensure reliable contact;
2. Check the material of the communication line, if it is not a copper core line, replace it with a copper core communication line to ensure stable signal transmission;
3. Check the control board, if the control board is damp, dry it and test it, if it still can not communicate properly, replace the control board; the fourth step by step test the control panel and circuit board, replace the faulty parts to ensure that the communication is normal.

Conclusion

air-cooled heat pump unit common faults are concentrated in the core of the power supply, water, temperature, refrigerant, core components of the five categories, most of which can be predicted and do not require complex maintenance, grasp the correct investigation ideas, combined with hands-on, prioritize the simple causes and then check the complex parts, can be quickly resolved.

Regular preventive maintenance is the key to reduce the failure, simple cleaning, inspection, calibration can avoid most of the failures, extend the life of the equipment, to ensure the stable operation of the unit. Complex faults such as compressor burnout and motherboard short circuit, it is recommended to contact a professional for maintenance to avoid secondary damage.