Automatic clothes dryers consist of a motor driven revolving basket, an electric heating element or gas flame, thermostats, and a timer. Some models also have a selector switch. Air, heated by the electric element or gas flame, feeds through the tumbling clothes by a fan. The drive motor drives the fan. The temperature of the heated air, entering and leaving the basket, is controlled by thermostats, which maintain a balance between the air velocity, air volume, and air temperature. The temperature of the exhaust air is a measure of the dryness of the clothes.

After starting the dryer, the temperature inside the basket will rise rapidly. When the temperature reaches approximately 130F, the evaporation of the moisture in the load will absorb the heat as rapidly as the heater generates the heat. The temperature will not rise appreciably above 130F until the load is nearly dry.

When the load is nearly dry, there will not be enough moisture in the clothes to absorb the heat, and the basket and clothing temperatures will rise. This heat rise will continue until the discharge air reaches approximately 160F. At this point, a thermostat disconnects the heater circuit. The dryer basket will continue to revolve in the overrun period, and cool, fresh air will enter the basket to cool the clothes for handling. The overrun time may last from three to 10 min by either the timer or an overrun thermostat, which will stop the dryer.

Modern dryers of today, Maytag, Kenmore, GE, Whirlpool, Frigidaire, have a moisture sensor which relays moisture conditions inside the dryer to a control board which controls the cycle time and cool-down modes. The moisture sensor consists of two conductive metallic wires located inside the dryer and mounted to the plastic lint filter housing. One wire has a very low-current AC voltage applied to it and the other one is grounded. When moisture is present, a conduction path exists intermittently between the two wires. When the clothes are dry, there is no conduction path. When the dryer is in the automatic dry cycle, the control board will then advance to the cool-down mode.

Many appliance repair service calls are due to failure of the dryer moisture sensor. Since this sensor is what detects the moisture inside the drum, if there is no moisture, the control board or timer “thinks” the clothes are dry when the aren’t. The most common problem I find is a “film” of waxy dryer sheet material that has accumulated on the sensors. Many times, it is coated with detergent residue. You can remove this by rubbing the sensor bars with a clean Scotchbrite abrasive pad. These Scotchbrite abrasive pads are available at most department and grocery stores. I carry these in my service truck and make it a routine to clean these on every repair call.

Rich is the owner of Western Appliance Repair located in Boise Idaho. westernappliancerepairboise.com

Rich is the owner of Western Appliance Repair located in Boise Idaho. http://www.westernappliancerepairboise.com

Author Bio: Rich is the owner of Western Appliance Repair located in Boise Idaho. westernappliancerepairboise.com

Category: Home Management
Keywords: appliance, dryer, operation