Electric Clothes Dryer
© 2006-2009, Dr. Ray Franco, PhD., PE r.a.franco@ieee.org
Statistical Data
The U.S. Consumer Product Safety Commission (CPSC) estimates that in 1998, clothes dryers were associated with 15,600 fires, which resulted in 20 deaths and 370 injuries. Fires can occur when lint builds up in the dryer or in the exhaust duct. Lint can block the flow of air, cause excessive heat build-up, and result in a fire in some dryers. CPSC Document # 5022
According to data gathered between 1999 and 2002 by the National Fire Protection Association (NFPA), 4% of all reported structural fires involved a clothes dryer [1].
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[1] NFPA: U.S. Home Product Report, Appliances & Equipment, November 2005.
Lint Build Up - My Dryer
On January 3, 2009, my wife said, "the dryer is turning, but it will not heat". Upon investigating, I found the thermal cutoff, which is a non-resettable part, had activated. I knew that there had to be a reason that it activated. The culvert was PCV pipe going to the outside vent. It was packed with tint. It had only been 17 years since I cleaned it. After cleaning the outside vent pipe. I told my wife, I had to order a part. She said, "she needed her clothes dry". I bypassed (jumpered around) the thermal cutoff, and I told her to be very carefully, and not to leave the house with the dryer on. She thought I was a genius; the truth is I was stupid for bypassing the manufacturer's safety device. Furthermore, I know now that when the thermal fuse melts, the contacts on the high limit thermostat are usually welded together! I have seen more than one fire occur because someone bypassed the thermal fuse, and they never got around to replacing it. On some dryers, you have to take the drum out to get to it. Who wants to disassemble and reassemble a dryer - twice.
For Maximum Resolution, Click on the Body of the Picture.
My Kenmore Washer & Dryer Purchased in 1992.
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Lint Build Up - It happens in the Best of Homes.
An Electrical Schematic was on the Inside of the Bottom Cover.
My Dryer with Bottom Cover Removed.
My Dryer with Lint Shoot Removed.
My Dryer's Lint Shoot was Full.
Lint removed from My Dyer's Lint Shoot.
Both the Thermal Cutoff (non-resettable) and the High Limit Thermostat are located on the Dryer Heater Box.
Both have to be replaced. If the Thermal Cutoff activated, then the High Limit Thermostat Failed.
You can not purchase just the Thermal Cutoff - the High Limit Thermostat comes with the Thermal Cutoff.
When I tested my High Limit Thermostat (250°F), it didn't open at 400°F.
Both the Operational Thermostat and the Thermal Fuse are located on the Return Air. These contacts are always energized!
Lint Build Up & Bypassed Thermal Cutoff (F09-021)
In December 2008, lint build up and a bypassed thermal cutoff causes a dryer fire. Clothes and wood paneling in the laundry room caught fire. The operational thermostat for the Maytag dryer was located near the bottom of the dryer on the exhaust vent. With lint clogging the exhaust, there was no air circulation, and hence, no hot air for the operational thermostat to monitor. The only thing regulating the temperature was the high limit thermostat at the heater box. The high limit thermostat is an overload device; it is not designed for thousands of operations. Eventually, the contacts on the high limit thermostat became welded together. The only other safety device was the thermal cutoff. Apparently, this was not the first time this dryer had been clogged with lint. In fact, the thermal cutoff had previously activated. The get the dryer to work, they bypassed (jumpered around) the thermal cutoff. Because they failed to replay the thermal cutoff, a fire occurred. You can not blame fires like this on the manufacturer
For Maximum Resolution, Click on the Body of the Picture.
Top, Front & Side of Maytag Dryer.
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Back of Dryer - Heat Patterns on Heater Box Vent Holes.
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Excessive Lint in the Lint Filter.
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Excessive Lint in the Flexible Vent Duct.
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No Damage to Wire Insulation in the Control Section of the Dryer.
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Excessive Heat at Heater Coils & Damaged High Limit Thermostat.
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High Limit Thermostat Contacts Welded Together.
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Heat Pattern inside the Drum due to Overheating of the Heater Coil.
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Heat Patterns on the Heater Box.
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Missing Thermal Cutoff & Taped Wires.
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Bypassed (Jumpered) Thermal Cutoff.
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Parts of the Thermal Cutoff were found at the Bottom of the Dryer.
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Heater Coil Resistance - 11.7 ohms.
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The Operational Thermostat was located near the Exhaust Fan.
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Operational Thermostat opens at 146°F and closes at 122°F (146-24).
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Bottom of Dryer with Drum Removed.
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Drum Motor - 115 Volts, 5.5 Amps, 1/3 HP, Thermal Protected.
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Electrical Schematic Found in Control Panel of Dryer.
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Electrical Diagram Found in Control Panel of Dryer.
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Kenmore/Whirlpool Dryer Fire
The Kenmore/Whirlpool depicted below was purchased at a garage sale. Five of the wires in the bottom on the dryer were spliced. The female spade connectors were not properly crimped to the wires. This resulted in a loose connection, which caused resistive heating. After four years of use, the connection failed and ignited lint in the dryer.
For Maximum Resolution, Click on the Body of the Picture.
Very Localized Dryer Fire (F06-009).
The Fire is on the Opposite Side of the Heater Box (F06-009).
Wires Spliced with Wirenuts and Butt Splices (F06-009).
A Screwdriver and a Socket Were Found in the Lint Chute (F06-009).
Electrically Severed Wire with Copper Beads on Both Ends (F06-009).
Dryer Thermostats (F06-009).
Dryer Heater Coils (F06-009).
Burnt Lint on Heater Coils (F06-009).
Dryer Motor (F06-009).
Dryer Motor Tag - 1/3 HP; 1645 RPM's; 115 Volts; 5.6 Amps;
Thermally Protected 40° C (F06-009).
Dryer Motor Winding Resistance (F06-009).
Back of Dryer Control Panel (F06-009).
Maytag / Amana Dryer: Model #: NDE2330AYW Manufactured in June 2004.
This Amana dryer was being used when a fire was discovered in the carport. The Laundry room is adjacent to the carport. The electric service entrance, meterbase, and two electrical distribution panels were in the carport. The cause of this fire is believed to be a recalled cruise control deactivation switch on a Ford Expedition. Since the dryer in use at the time of the fire and the cable that powered it passed through the attic of the carport, it was necessary to ascertain that the dryer did not overload the circuit.
For Maximum Resolution, Click on the Body of the Picture.
Amana Washer & Dryer (F06-013).
Back of 2004 Amana Dryer (F06-013).
2004 Amana Dryer Drum (F06-013).
Back of Amana Dryer Control Panel (F06-013).
Amana Dryer Exhaust/Lint Chute (F06-013).
Amana Dryer Thermostat Locations (F06-013).
Amana Dryer Cycling Thermostats (F06-013).
Amana Dryer Heater Box (F06-013).
Amana Dryer Heater Resistance (F06-013).
Amana Dryer Heating Element.
Amana Dryer with Drum Removed (F06-013).
Amana Dryer Motor (F06-013).
Amana Dryer Motor Winding Resistance (F06-013).
Amana Dryer Electrical Schematic (F06-013).
