HOW A DRYER WORKS
An electric or gas dryer is one of the simplest appliances in your home. It consists of little more than a motor to spin the drum, a heater element to supply the heat for drying, and a timer to control the length of time of operation. The simplest units have a timer that signals both the motor and the heating element when to start and when to stop. Many dryers also have a cool down cycle, during which the motor keeps going but the heating element is shut off. This allows the clothes to cool and fluff. In a dryer, hot air absorbs moisture, is vented away, and new air is drawn in, heated and gets vented away in its turn. Most often a small fan is used to force air movement. This fan is generally doing two jobs at once. A part of it pulls in new air and pushes it through the ducting across the heating element and into the drum. Another part of it pulls air out of the drum, across the lint filter, and out through the exhaust duct. As the clothes tumble in the drum, more surface area is exposed to the warmed and moving air.
The tumbling action is further increased by blades inside the drum. A motor is attached to the drum, usually through some form of pulley and belt system. (The same motor is usually used to drive the blower fan for air circulation.) The amount of heat and length of drying time is often determined by a timer mechanism. If the dryer has a cool down period, the timer will have two sets of contacts in it one for the motor and one for the heating element. If both go on and off together, a single set of contacts is used. More sophisticated units actually measure the wetness of the clothes in the drum, usually via contacts inside the drum. Since water conducts electricity, as the clothes touch the contacts a low current pulse keeps the dryer operating. The drier the clothes become, the less current they conduct; when dry, they do not conduct at all, and the dryer can shift into the cool down cycle. All dryers have a thermostat somewhere in the circuit.
In many cases, if the dryer doesn't doing the job properly there is a reason for the failure. Perhaps the lint trap isn't being cleaned often enough. Or the high-limit thermostat might not be working and is allowing the element to overheat on a regular basis. Many people clean out the lint trap religiously but forget that the exhaust duct itself can become filled with lint. (Take a look outside where the vent comes out. After a relatively short time you'll find a layer of lint.) On a regular basis (every six months or so) clean out the exhaust duct. This will not only let the dryer operate more efficiently, it can also increase the life of the unit, and will even serve well in protecting your home from a fire hazard.
The electric dryer requires a 240-volt outlet and always must have its own circuit.
A dryer should be stored only in the upright position. When moving them, even a short distance, keep them as upright as possible, and with as little jostling as possible.
All of the above tips are for informational purposes only. For your safety, we strongly encourage any gas or electric dryers repairs to be performed only by a certified technician.