Compared to a standard or high-efficiency clothes washer, a clothes dryer is a very simple appliance. Every dryer , from the most simple to the most expensive, uses a combination of heat, air, and motion to dry clothes by removing moisture. Every clothes dryer uses heat to speed the drying of clothes.
The heating element can be fueled by electricity, natural gas, or propane gas. In dryers powered solely by electricity, the heating coils are similar to those used in ovens or hot water heaters. An electric current is sent through the coil, which is designed to create resistance. The resistance builds up electrons and creates energy or heat.
The metal coils become very hot from the electron buildup. The heat is transferred to the surrounding air and forced throughout the dryer by a blower or fan. Natural gas or propane gas dryers depend upon a pilot light, which ignites the gas, creating heat. Gas dryers use metal plates designed to transfer the created heat into the air. Again a blower moves the heated air throughout the dryer to the wet laundry.
While gas is used to create heat, all gas dryers also require electricity to power other components of the dryer. All dryers use thermostats and thermal fuses to regulate the temperature within the dryer. These parts are key to the safe operation of the appliance, preventing overheating, which can lead to fires. When one of the fail-safe components fails, it is important to look for the root cause of the problem.
A blown fuse means the dryer is overheating. A good cleaning to get rid of lint may be all that is needed to prevent a problem down the road. Air circulation is essential to efficient clothes drying. Think about how much more quickly clothes dry on a clothesline when there is a breeze.
Here is a view of the back of the cycle switch. Attached to the back is a little motor. The picture below shows the motor unscrewed from the switch. The tiny gear on the motor turns very slowly; and it engages a bigger gear inside the switch that makes the switch turn even slower.
The motor turns the gear on the dial , which is connected to a set of four cams stacked on top of each other. Each of the cams engages one of the four contacts in the switch. Each of the four contacts has a bend in it, and each bend is located at a different height inside the box.
Starting with the bottom left contact , the heights increase in a counterclockwise manner; the bottom left contact is the lowest, the top left contact is the highest. A different cam engages each of these contacts. In the pictures below, you can see the four cam layers; each of these layers corresponds in height to one of the contacts. The cycle switch determines how long the elements stay on. In conjunction with the heat setting buttons , it also controls which heating elements are on at a given time.
If none of the heating elements are on, only cool air blows through the clothes; if one is on, the air is warm; and if both are on, the air is hot. If you press any of the top four buttons, they stay depressed. If you then press a different button, the first one pops up, and the new button stays pressed in. A really neat set of plates that work like the tumblers in a lock make this feature possible, and also control which heating elements are engaged.
Inside the switch are a set of four contacts. Depending on which button is pressed in, the plates open or close various combinations of the contacts. The following set of pictures illustrates how pressing the buttons causes the plates to line up in different ways, raising or lowering the bars that make the contacts. The dryer also has a couple of safety features that help to prevent overheating. There are two temperature shut-off switches. When these switches reach certain preset temperatures, they break contact, which shuts the dryer off.
The first switch is located near the lint screen. The picture above shows the front of the dryer , with the front panel partially removed. The first temperature sensor is on the right. And to the left, you can see a set of six holes in the outer edge of the tumbler. These holes are only there to blow hot air on the sensor every time they go by.
If the temperature in the tumbler gets too hot, this sensor cuts the power, shutting the dryer off. But what happens if the belt breaks and the holes don't happen to be in front of the temperature sensor? Or if the fan gets clogged and no air is coming out of the tumbler?
This is where the second temperature switch comes in. The second sensor is located close to the heating elements. If airflow is shut off for any reason, the air near this sensor will quickly heat up to the temperature that triggers this sensor, and the sensor will shut off power. The timer control either regulates the length of time the dryer runs or it works in conjunction with a moisture sensor that measures the water vapor in the drum to determine when the clothes have dried.
The temperature selector controls the maximum temperature inside the drum with the aid of thermostats. The heat turns on and off as needed to maintain the temperature. When the timed cycle ends, or the moisture sensor determines the clothes are dry, the drying cycle ends and typically a buzzer sounds to signal that the cycle has ended. Some dryers have a wrinkle prevention feature that will tumble the dryer every few minutes to prevent wrinkles from setting in. Gallery Reviews Search. How a Gas Dryer Works T he dryer works by tumbling the clothing and blowing air through the drum.
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