Dehumidifier Fire Forensic Investigations Expert Article

In this article, electrical engineer, Ken Kutchek, P.E. discusses household dehumidifiers, with a focus on possible failure modes that can cause fire hazards. The experts at Robson Forensic have investigated many fire incidents involving dehumidifiers and other small appliances.

Investigating Fires Caused by Dehumidifiers

In recent years there have been a significant number of home fires caused by portable household dehumidifiers. One of the most common failures in these appliances is overheating. The overheating can be caused by product defect, improper use, or poor maintenance.

Most modern appliances are manufactured to be small and compact with plastic housings, unlike the metal cabinets of the past. Investigating the cause of a fire includes determining the first fuel ignited. For a dehumidifier it includes determining whether the plastic housing, which is located in close proximity to heat generating internal components, was the fuel.

This article explains how dehumidifiers work, how the internal components most frequently fail, and also provides details on recent recalls.

Dehumidifier Introduction

Dehumidifiers are a common household appliance used to improve indoor air quality by removing excess moisture/humidity from the air. Excessive moisture can cause mold, mildew, musty odors, and condensation on windows. High humidity creates a favorable environment for bacteria, mites, viruses, fungi and other microorganisms to develop; which can contribute to a variety of maladies.

Dehumidifiers, like furnaces or refrigerators, are appliances that run as needed, unattended, 24/7. The dehumidifier functions in a simple, yet effective manner: A fan draws in moist room air through the intake grill; the air passes through a cold coil; the moisture in the air condenses on the cold coil; the cool dry air is passed through a hot coil and warmed back up; the warm dry air is released back into the room through the exit grill; the process repeats until the ambient humidity reaches the user set-point. A compressor is used to cool the cooling coil. The moisture that was in the air drips off the coil into a collection tank. Many systems require manually emptying the tank and others include a pump that empties the tank.

Dehumidifier Failures - Product Recalls

A significant number of dehumidifiers have been recalled in recent years for defects that can cause overheating and fire. Very often the problem can be traced back to a substandard part that overheats and ignites the plastic housing. Following is a summary of recent recalls.

Midea Recall - November 2016

Appliance manufacturer Midea recalled dehumidifiers because they can overheat, smoke and catch fire. The Midea dehumidifiers were manufactured in China and sold under numerous brand names, including popular brands: Danby, Frigidaire, GE, Honeywell, Kenmore, Keystone, Perfect Home, Professional Series, Sunbeam, Sylvania.

About 4.2 million units were sold in the US and Canada between Jan 2003 and Dec 2013. There have been 38 reports of smoke and fire and about $4.8 million in property damage has been reported thus far.

Gree Recall - September 2013

Appliance manufacturer Gree recalled dehumidifiers because they can overheat, smoke and catch fire. This recall was updated in October 2013 and expanded in January 2014. The Gree dehumidifiers were manufactured in China and sold under numerous brand names, including popular brands: Danby, DeLonghi, Fedders, Frigidaire, GE, Kenmore, Soleus Air.

About 2.5 million units were sold in the US and Canada between Jan 2003 and Dec 2013. There have been 471 reported incidents of overheating and 121 reported fires, and have caused approximately $4.5 million in property damages.

Midea Recall - November 2011

Appliance manufacturer Midea recalled dehumidifiers because the compressor can short circuit and overheat and catch fire. The Midea dehumidifiers were manufactured in China and sold under brand names: GE and Professional Series.

About 198,000 units were sold in the US and Canada between Feb 2007 and June 2009.

LG Recall - December 2009

Appliance manufacturer LG Electronics recalled dehumidifiers because an internal electrical connection can overheat and catch fire. The LG Electronics dehumidifiers were manufactured in Korea and sold under brand names: Goldstar, Comfort-Aire, GE, and Sears Kenmore.

About 98,000 units were sold in the US and Canada between Jan 2007 and June 2008.

Home Depot Recall - December 2009

Appliance importer Home Depot recalled Hampton Bay Dehumidifiers because an internal component can fail causing the dehumidifier to overheat and catch fire. The Hampton Bay Dehumidifiers were manufactured in China.

About 2,000 units were sold in the US and Canada between Nov 2000 and May 2007.

Whirlpool Recall - January 2002

Appliance manufacturer Whirlpool recalled dehumidifiers because an internal electrical connection can overheat and catch fire. The Whirlpool dehumidifiers were sold under brand names: Whirlpool, Kenmore and ComfortAire. About 1.4 million units were sold in the US and Canada between Feb 1997 and Dec 2001.

As the recalls show, dehumidifiers can cause fires. Also, dehumidifiers can be victims of attacking fires. Investigation of causes of fires requires examination of the evidence to see whether an appliance such as a dehumidifier should be ruled in or ruled out as a cause.

Dehumidifier Failures - Operation & Maintenance

A user should follow reasonable operating and maintenance instructions as provided by the manufacturer to ensure effective, reliable, and safe operation in order to prevent failures which can cause overheating and fire.

Dehumidifier Location

Most manufacturers recommend a minimum clearance of 8-12 inches around the dehumidifier. Airflow must not be restricted through the cabinet louvers on the front, back and sides. Restricted airflow can cause compressor or fan overheating.

Dehumidifiers must be operated in an enclosed area with the outside doors and windows closed. Little outside air should be allowed to enter the room. Running a dehumidifier in endless humid conditions can cause the unit to run non-stop and cause compressor overheating.

Room Temperature

Most dehumidifiers are designed to work at a room temperature of 65°F or above. Temperatures below 65°F can cause the coil to get too cold and freeze up. A frozen coil can cause compressor overheating. New “low temp” models are now available which allow operation down to 40°F.

Humidistat Setting

The humidistat on the dehumidifier sets the desired humidity level in the air. Setting it too low can cause the unit to run non-stop, potentially overheating the compressor.

Cleaning the Air Intake and Exhaust Grilles

Dehumidifier air intake and exhaust grilles must be periodically cleaned with a vacuum cleaner to ensure proper airflow through the cabinet. Undue stress on the fan can cause it to overheat and fail. Restricted airflow can also cause compressor overheating.

Filter Replacement

Air intake filters must be replaced as needed to ensure proper airflow through the cabinet. Undue stress on the fan can cause it to overheat and fail. Restricted airflow can also cause compressor overheating.

Cleaning the Coils

The dehumidifier condenser (reheat) coil must be periodically cleaned with a vacuum cleaner. Over time the air can cause a thick buildup of dust and dirt on the coils. Undue stress on the fan can cause it to overheat and fail. Restricted airflow can also cause compressor overheating.

The dehumidifier evaporator (cooling) coil must be periodically cleaned with a vacuum cleaner. Over time the air can cause a thick buildup of dust and dirt on the coils. This buildup may cause water to freeze on the coils. A frozen coil can cause compressor overheating.

Dehumidifier Components & Common Failure Modes

Fan

The fan pulls room air into dehumidifier and pushes dry air out into room

Compressor

The motor driven device which compresses and expands a refrigerant gas like freon to cool the dehumidifier’s cooling coil. A compressor serves as the heart of the system. Although heat is a normal consequence of compression, a system that gets too hot will overheat. Overheating is one of the most common causes of compressor failure. Excessive overheating is controlled and prevented by a compressor thermal protector.

Compressor Thermal Protector

The compressor thermal protector is one of the most important safety devices on a dehumidifier. The thermal protector protects the compressor from overheating or overcurrent conditions by sensing a rise in temperature. The thermal protector will open and stop the compressor before it reaches dangerously high temperatures and possibly catch on fire. The contacts of the thermal protector need to make good contact to prevent overheating of the contacts. Failure of the compressor thermal protector can allow dangerously high temperatures and fire.

Compressor Relay and Capacitor

The compressor relay and capacitor controls the starting and running of the compressor motor; it switches from start to run windings after the compressor motor has reached the running speed. The compressor relay and capacitor is typically mounted on the side of the compressor. Failure of the compressor capacitor can cause short cycling and compressor overheating.

Evaporator (cooling coil)

The evaporator pulls moisture from the air using condensation. The moisture extracted from the air drips into the collection tank. The cooling coil must be kept clean of dust, lint, dirt and kept free of ice to ensure proper operation and prevent compressor overheating.

Condenser (reheat coil)

The condenser removes heat generated by the cooling process. The reheat coil must be kept clean of dust, lint, dirt to ensure proper operation and to prevent compressor overheating.

Control Board

Newer dehumidifier models use an electronic control board to control the dehumidifier process. It receives inputs from humidity sensor, temperature sensor, humidity set-point, water level switch, defrost sensor, ON/OFF switch, and then controls the compressor and fan.

Humidistat / Humidity Sensor

Some older dehumidifiers have a traditional style manual humidistat, which allows you to control your desired level of humidity. A typical household humidistat includes a set-point dial, a moisture sensing element and an electric relay. The relay turns the dehumidifier on or off based on the measured humidity level and the humidity set-point.

Most electronic control dehumidifiers will have a humidity sensor which is wired to the control board. The control board receives the humidity set-point from the user input display. The control board controls the relay to turn the dehumidifier on or off based on the measured humidity level and the humidity set-point. If the sensor or relay is defective it may not correctly measure the humidity and/or may not turn the dehumidifier on or off when required.

Defrost Control

Ice accumulation on the dehumidifier cooling coil can reduce the unit’s operating efficiency and can cause compressor overheating and compressor failure. Some dehumidifier models are equipped with automatic defrost control. When ice builds up on the cooling coil, a sensor detects the formation of ice and stops the compressor. The fan continues to run so that air from the room can assist in the thawing process. Once the coil is defrosted, the system returns to normal mode again.

Tank Full Switch / Bucket Level Switch

The water collection tank has a switch to monitor the tank level. The water level switch prevents the tank from overflowing. When the tank fills and the switch is tripped, the compressor and fan are turned off until the bucket is emptied. An indicator lamp should illuminate to notify the user.

Summary

Dehumidifiers are a convenient and cost effective means of improving home indoor air quality by removing moisture from the air. However, improper use, poor maintenance, manufacturing defects, and/or design defects can cause failure and overheating/fire. In recent years, dehumidifiers have been plagued by numerous recalls due to defects and failures which have become increasingly apparent in our own forensic investigations.

Electrical Engineering Forensic Investigations

The electrical engineers at Robson Forensic are Licensed Professional Engineers with extensive hands-on experience in the design, operation, manufacture, installation and maintenance of appliances and other electrical systems and equipment. They routinely investigate incidents related to fires of electrical origin and electrical shock injuries.

If you have a case or claim involving an appliance fire or another issue for our electrical engineers, please submit an inquiry through our website so we can put you in touch with the expert who is best qualified to assist.

Featured Expert

Kenneth J. Kutchek, P.E., C.F.E.I., C.M.S.E.

Electrical Engineer & Industrial Controls Expert

Ken is an electrical engineering expert with more than 30 years of hands-on experience in industrial controls, automation, machinery, equipment, industrial safety and machine safeguarding. He applies… read more.