What Causes Failure of a Dehumidifier That Will Not Condense Water?

Dehumidifiers work in much the same way as air conditioners: by cooling air flowing across a heat-exchange system. A fan draws humid room air across the cold side of the system, and the moisture condenses on the cold metal. As the air blows over the hot side, the waste heat returns to the room air. Apparent failures can be caused by several types of safety shut-offs that prevent the dehumidifier from starting in unsafe situations.

How Dehumidifiers Work

A dehumidifier uses a sealed network of coils to circulate a liquid that boils at room temperature. A compressor forces the coolant into the evaporator coil where the change to vapor cools the metal coil. On the condenser coil side, the vapor condenses on the inside of the tubing and heats the metal. Liquid coolant then flows back to the compressor to renew the cycle. A fan blows air over both coils, but the cold evaporator coil collects the water that drips into the dehumidifier's holding tank. When the appliance runs, both the compressor and fan should work constantly.

Start-Up Problems

Adjustable humidity sensors allow the selection of a desired humidity level. When the room humidity matches the setting, the sensor turns the appliance off. Faulty sensors won't allow start-up. A new unit that shipped on its side might not work properly because liquid coolant pooled in the wrong part of the heat exchanger. Place the new unit upright and let it sit for an hour before turning it on, Frigidaire advises. Also, check the bucket, which must sit flat in its holder to activate the dehumidifier. Other possible problems include power surges that trip the unit's circuit breaker or blown fuses.

Operating Problems

Dehumidifiers don't work in temperatures near freezing or in extremely hot weather. The operating temperature range falls between 41 degrees Fahrenheit and 89.6 degrees Fahrenheit, according to the home appliance corporation De'Longhi. At the coldest operating temperature, the evaporator coil can ice up instead of dripping water into the bucket. At the high end of the range, the condenser coil can't shed waste heat, and cooling stops. Dehumidifiers automatically stop when the humidity falls to the preselected level and can't reduce humidity below 30 percent. If the humidity in the room falls below 30 percent, the dehumidifier won't condense water.


To protect the coils from insulating dust, a dehumidifier draws air through a filter hidden within the cabinet. A blocked air filter prevents air from reaching the cold evaporator coil. Cleaning the air filter regularly keeps the appliance working properly. Dehumidifiers can include safety switches that turn the machine off if tipped or if important fittings disconnect. Dehumidifiers without drain systems work only until the bucket fills. The weight of the full bucket turns the appliance off, so empty the bucket as needed to keep the dehumidifier working. Consult the owner's manual for guidance on other special safety features.

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