How do Dishwashers Work?

When you open the dishwasher, you will normally see some standing water in the bottom of it. This water helps to keep the seals from drying out. When you first start your machine, it will drain this water first, and then refill it with fresh water.

After you load your dishwasher, you set the controls to the settings you need for the dishes you want to wash. The selector switch lets you choose the length of the wash cycle, the water temperature, and the drying temperature. You’ll probably want to check your owner’s manual to determine the settings you need to use.

Once it is loaded and you have the settings where you want them, you want to make sure that the door is latched and locked properly. This will engage the door switch and keep the water from leaking out. If the door switch is not engaged, the dishwasher will not operate.

Turn on the dishwasher with the start switch. At the bottom of the dishwasher, behind a panel, is a water-inlet valve that controls the flow of water into the dishwasher. When the timer gets to the right spot, it sends power to the valve which causes it to open and let water into the dishwasher sump. Just above the floor, on the inside, is a small plastic cylinder that floats up as water fills the dishwasher. When the water reaches the proper height, the float switch tells the valve to close. Some models of dishwashers may also have a heating element in the sump. During these cycles, most dishwashers will pause as they wait for the water to reach the desired temperature. Sometimes, the water entering the dishwasher is too cool, and the heating element can take up to a half an hour to heat the water to the correct temperature. The heating element in the bottom of the dishwasher cabinet will heat the water to about 140-150 degrees Fahrenheit if it’s not already hot enough.

When the timer calls for it, a bi-metal switch or a wax motor actuates the detergent cup, releasing the detergent into the wash water. The timer switch is usually mechanical, and is motor driven with cams to open and close switches. Some models may use an electronic control circuit board to accomplish the same thing. The timer tells the dishwasher what to do next by sending the instructions and power to the dishwasher’s parts at the right time.

Many dishwashers employ a two-way motor. When the motor turns one way, it pumps the water-soap mix through the sprayer arms which spin around from the water pressure similar to a water sprinkler and sprays the dishes. The water goes back into the sump where the larger food particles are filtered out. The water is pumped back up to be sprayed again, and this process is repeated until the cycle is ended. When the motor turns the other way, it pumps the water out through the drain. If the motor in your dishwasher only turns in one direction, then an actuator or solenoid unit moves a valve to divert the water to the spray arms or to the drain, whichever is needed at the time.

Some dishwashers, especially newer ones, make use of a soil sensor to determine how clear the water is during rinse and wash cycles. This can save you electricity and water, as well as give you cleaner dishes. The wash water then gets drained and clean water is sprayed over the dishes to rinse them. If your dishwasher is able to use rinse aids, now is the time that your controls would release the rinse aid into the rinse water. The rinse water is then drained, and then the heating element heats the air inside the dishwasher to help dry the dishes. Some dishwashers have a fan to help in this drying process.

Most dishwashers have a thermostat that monitors the wash and rinse water temperature, as well as the drying temperature. Thermostats help to protect the dishwasher, dishes, and you or your children by controlling the heating element that heats the water or the air in the dishwasher. The thermostat will turn off the heating element when it has reached the pre-set temperature.


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