How a Dryer Works
First off, there are many different types of dryers: top loading, front loading, gas dryers, electric dryers, stand alone dryers, stackable units, and many others. Although there are many different types, the basic principles of how a dryer works are very similar. Each dryer contains a tumbler (the round holding chamber where the clothes go), a heater, a lint trap, and an exhaust vent.
For this description, we'll start from the top, just like you're doing a load of laundry.
First, you open the door and place your wet clothes into the tumbler. After you shut the door, you adjust the heat settings. Most dryers have three settings—low, medium, and high heat. Next, you set the timer. It's usually a dial-type timer with various settings. You can set the timer for a specific length of time, like 20 or 80 minutes, or you can let the dryer decide when it's time to turn off. Newer dryers have cycle settings like "optimum dry," "less dry," "fluff," and various others. Some have controls for cotton clothes or permanent press, or other options. Also included is a notification switch, that when set on "loud," sounds a buzzer to let you know the dryer's done. After all the settings are set, you press the "start" button.
The motor begins to turn and the belt rotates the tumbler. At the same time, air is drawn into the dryer. Also at the same time, the heating coil flares to life (or the pilot light ignites the heater in a gas dryer) and warms the incoming air. The tumbling clothes heat up and the water within them turns to steam. The exhaust carries the steam out of the dryer, usually through a duct that sends it outside.
Sounds simple enough, right? But how does the dryer know not to get too hot, and how does the timer actually work?
When you open the control panel on the dryer—which is not recommended unless you know what you're doing, by the way—there will be wires going this way and that. The cycle controller is usually square and has a round device attached to the top of it. The round device is actually a small motor. The motor has a small gear on it that connects to a larger one with a dial inside the cycle controller. As the gear on the motor turns, it turns the dial very slowly. The dial usually has a set of four cams attached to it. As the dial turns, the cams engage certain contacts within the cycle controller. The contacts determine everything that happens, from the length of the drying cycle to whether or not the air gets heated.
To ensure your clothes don't go up in flames, dryers have temperature sensors installed in them. They are little silver discs, about the size of a quarter, and there are usually two of them. In most dryers, one is located near the heating coil and the other is in the front section of the dryer. They also have a set of contacts within them, so that when the temperature gets too hot, the contacts separate and the dryer automatically turns off.
If you take the top and front of the dryer off (again, not recommended), you will see the exposed tumbler. A belt goes around the tumbler and winds around a pulley that's connected to a motor. There are rubber wheels underneath that sit in a groove in the tumbler to ensure an even and smooth rotation. Depending on the dryer you have, the motor may control the exhaust fan as well.
One of the most important factors in how a dryer works is air flow. The dryer has to bring in air to heat in order for everything to work. Most dryers have a hole or ventilation duct located on the front of the machine. It's not visible with the cover on. Air is sucked in through that hole and is forced past the heating element. The heated air flows into the tumbler to heat the clothes. The steam is then sucked out of the dryer through the lint trap and out of the building. The lint trap is usually located right below the door of the dryer. For your dryer to work as efficiently as possible, make sure to clean the lint trap after every load. A fan is used to both bring the air in and send it out. It is located between the lint trap and the ductwork leading outside.
For all intents and purposes, the dryer is a very simple machine. It is designed so well that the only thing that really changes over the years is the look of them. But just because they're designed well doesn't mean you'll never have a problem with them. If you are currently having a problem with your dryer, check out our easy repair guide before calling in an appliance repairman. The problem may be an easy one to fix, and you could save yourself a bundle.