Common Faults and Solutions of Commercial Dehumidifiers

In this article, you can learn about several common faults of dehumidifiers. Based on different fault manifestations, methods for troubleshooting and resolving faults will be introduced. At the same time, the troubleshooting ideas of our technical engineers are also shared.

 

Preair is a professional dehumidifier manufacturer. The vast majority of machines we produce are of high quality and affordable. Machine products can't maintain a 100% fault free rate in both theory and reality, especially considering external factors such as rough handling, bumpy transportation, and improper use. It is common for commercial dehumidifiers to encounter problems. If users encounter problems, they can preliminarily determine the damaged part of the dehumidifier based on the following aspects, then communicate with the manufacturer promptly, and jointly solve the problem.

 

Fault 1: The dehumidifier stops quickly after starting up and takes a long time to restart, resulting in poor dehumidification effect.

Check for faults:

(1) The measured wind speed at the air outlet is lower than the normal value.

(2) Using a multimeter to measure the resistance values between the various leads of the fan motor, it was found to be much lower than the normal value.

Repair method:

Based on the detection results, it is determined that the fault is caused by a short circuit between the turns of the fan motor winding coil, resulting in a decrease in fan speed and air volume. Replace the fan motor with a new one and troubleshoot the issue.

Cause analysis:

The compressor of the LGR dehumidifier is a rotary compressor with poor heat resistance. The speed of the fan motor decreases, resulting in a decrease in the air flow through the condenser and an increase in the discharge pressure of the compressor. This leads to overheating protection (shutdown) of the compressor. The compressor needs to be cooled for a long time before it can return to normal temperature, so it needs to be cooled for a long time before it can be restarted.

 

Fault 2: The dehumidifier is operating normally, with a relative humidity of 85% to 90% in the environment, but the dehumidifier has a small dehumidification capacity.

Check for faults:

Open the air inlet plate of the dehumidifier and let it run. Check the evaporator and find that only a few U-shaped tubes have condensed water, while the surfaces of the other U-shaped tubes are dry. Further inspection revealed oil stains on a pipeline interface. Diagnosed as a leak.

Repair method:

Release the refrigerant, weld the leaking interface, vacuum again, inject refrigerant, and troubleshoot.

 

Fault 3: After using the dehumidifier for more than a year, it was repaired once and tested normally. After being stopped for a period of time, it was found that both the compressor and fan were normal, but the dehumidification effect was poor. In an environment with a relative humidity of 83% and a temperature of 12 ℃, there was very little water condensation.

Check for faults:

(1) The surface of the air filter and evaporator condenser is very clean.

(2) There are no leaking oil stains on the surface of the pipeline.

(3) Frost appeared near the evaporator on the capillary tube, and soon the machine stopped. After some time, the frost melted and the compressor resumed operation.

(4) Wrap a hot towel around the interface between the capillary tube and the evaporator to ensure normal dehumidification. Diagnosed as ice blockage in the refrigeration system.

Repair method:

It belongs to an ice blockage fault. Clean all the refrigerants with high water content in the system, and blow the system clean by injecting nitrogen gas at a pressure of 0.3MPa. Then use a vacuum pump to evacuate for about 20 minutes, and add the required amount of refrigerant to the original machine. Run the refrigeration for 30 minutes, then stop and evacuate for 30 minutes or longer. After checking the vacuum degree to ensure it meets the requirements, fill the accurate amount of refrigerant, start the machine, and troubleshoot.

Cause analysis:

During the maintenance of the machine, water vapor may enter the system, or refrigerant with a high water content may be filled. Elemental water forms needle-shaped ice crystals at the interface between the capillary tube and the evaporator due to refrigerant throttling and cooling. When the temperature drops below 0 ℃, the ice crystals accumulate and slowly block the capillary tube, preventing the refrigerant from flowing and dehumidification. The compressor stops due to protection. Heating the capillary tube with air causes ice crystals to melt, and the compressor can resume operation. However, this repeated process results in poor dehumidification performance.

 

Fault 4: After repairing the dehumidifier and turning it on, it was found that the noise increased and the dehumidification effect was poor.

Check for faults:

(1) Check that there are no abnormalities in the structure of the dehumidifier and that it is placed smoothly.

(2) Check that the noise mainly comes from the compressor.

(3) The evaporator has no abnormal appearance and no frosting

(4) There is a lot of frost on the return pipe, indicating that the refrigerant charge is too high.

Repair method:

After draining some refrigerant appropriately, restart the dehumidifier and restore normal operation.

Cause analysis:

The dehumidifier was not filled with refrigerant according to the standard requirements, resulting in excessive filling and causing liquid hammer, which increased the noise of the compressor. The liquid droplets in the return air continued to evaporate in the return air pipe, causing frost on the surface of the return air pipe.

 

Fault 5: Frost formation on the surface of the low-pressure pipe of the dehumidifier, resulting in decreased dehumidification effect.

Check for faults:

(1) Frost formation was found on the rear section of the capillary tube, and oil stains were found at the interface with the low-pressure pipe. The fault was determined to be leakage.

(2) The front section of the capillary tube began to frost, and no oil stains were found in the pipeline, indicating that the filter was clogged.

Repair method:

(1) Leak detection, welding repair, and then pressure leak detection, filling refrigerant.

(2) Replace the filter.

 

Fault 6: After two years of use, the dehumidifier was repaired due to dirt blockage and was unable to dehumidify. However, when it was used again, the compressor and fan operated normally but did not dehumidify.

Check for faults:

(1) The surface of the air filter and evaporator is very clean.

(2) The working current of the compressor is different from the previous fault. The working current was high during the previous fault, but it is very low this time. It is judged that there is a serious refrigerant leakage.

Repair method:

Identify the leak, repair it, and troubleshoot the issue.

Cause analysis:

A large amount of refrigerant leaks. The displacement of the compressor decreases, the load decreases, and the working current decreases.