Problems with dehumidifiers

Updated February 21, 2017

To efficiently remove excess humidity from enclosed spaces, dehumidifiers must be properly adjusted and regularly maintained. Common problems include full collection tanks, icing of coils and excessive noise. Constant running without collecting water might mean the refrigerant has leaked out of the system. A machine that won't start might have an improperly adjusted tank, a poor connection to the power outlet or problems in the control system.


Dehumidifiers work much like air conditioners. The compressed refrigerant passes through the hot coil first, then condenses in the cold coil. The cold condenser plates draw moisture out of the air and move the water to a holding tank, usually at the bottom of the unit. Room air is drawn over the cold coil first and then the airflow passes over the hot coil. The air blown back into the room is dry.


The heart of a dehumidifier is a piston compressor. Though well-designed compressors are fairly quiet, they cause a lot of vibration. Loose mountings anywhere in the unit can cause noise. Panels in the cabinet that are not securely joined can rattle against each other at high volume. You sometimes can easily tighten loose mountings, but cabinet problems are touchier. Making sure the cabinet sits with all four feet firmly on the floor can help.


Maximum settings will make the dehumidifier run constantly, stopping only when the holding tank is full. Lowering the settings will reduce humidity in the room's air without overuse of the dehumidifier. You will not have to do maintenance chores, such as cleaning the grill, coils and filter or emptying the holding tank, as often if the dehumidifier is correctly set.

Holding Tank

Unless a dehumidifier is equipped with an outlet and hooked to a drainage hose and drain, the holding tank gradually fills with water and the weight presses a switch, turning off the machine. You must remove the tank and empty it. Take care to replace the reservoir correctly, or the machine will not start again. You also must regularly clean the tank to prevent mould and mildew from growing inside.


Unless otherwise noted by the manufacturer, a dehumidifier is designed to work at temperatures above 18.3 degrees Celsius. Below that, the temperature of the condenser coil could drop below freezing, causing ice to collect on it. Most machines will automatically turn off until the ice melts, but for efficient operation the surrounding air temperature should be at least 18.3 degrees C.

Small Spaces

In small enclosures where powered dehumidifiers are not practical, chemical dehumidifiers could be the solution. These small, alternative units use chemicals to draw moisture out of the air. Small enough to fit in closets, RV's and boats, chemical dehumidifiers require no power source and are completely silent.

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About the Author

James Young began writing in 1969 as a military journalist combat correspondent in Vietnam. Young's articles have been published in "Tai Chi Magazine," "Seattle Post-Intelligencer," Sonar 4 ezine, "Stars & Stripes" and "Fine Woodworking." He has worked as a foundryman, woodturner, electronics technician, herb farmer and woodcarver. Young graduated from North Seattle Community College with an associate degree in applied science and electronic technology.