Anyone who has ever opened up a dishwasher mid-cycle or taken dishes out immediately after the cycle ends can attest to the fact that dishwashers get hot. It takes hot water to clean the caked on food that routinely covers dishes, but how does the dishwasher heating element work?
How Does a Dishwasher Work?
While dishwashers can seem exceptionally complex given all that they do in a short period, the mechanisms of a dishwasher are fairly simple and straightforward. Dishwashers are essentially automatons that run with only a few functions: filling, heating, spraying and draining.
The control mechanism is the overarching entity in charge of the dishwasher's functions. It generally sits behind the control panel in the dishwasher's door. These are usually run with a timer. A clock helps to pinpoint the time for the mechanisms to change over, and aside from the connection to the water heater and the pump that brings water in and drains it out, that is essentially the limit of the dishwasher's mechanical sophistication.
The Dishwasher Cycle
A lot is going on every time you run your dishwasher, but mechanically speaking, the dishwasher is only carrying out a few operations. However, these are important operations, and the order in which they are performed is critical. Not only does a dishwasher have to know exactly when to add soap, when to rinse and when to cool down, but they also have to do everything in between. Yes, a human user needs to be able to add the detergent, stack the dishes and turn the machine on, but after that, the machine pretty much takes it from there.
While it may seem like dishwashers fill with water because they are airtight, the fact is that they don't fill with water. Instead, jets shooting hot water turn on at a specific period in the washing cycle, and add the detergent that you provide before turning on the machine. That's what creates the hot suds that get your dishes clean.
All dishwashers have what is essentially a small computer running the program. From the time that you press Start on the dishwasher, the dishwasher knows that it has to add water into the cycle, then heat that water up, push the water through the contained jets to reach the dishes, add dishwashing detergent and eventually drain the dirty water. Then, the dishwasher has to flush the dishes with hot water again to rinse them, and then gradually drain that water and end the cycle.
How Dishwashers Heat Up Water
Before its entry into the dishwasher, it's the responsibility of the water heater in your home or office to heat the water. The small basin at the base of the dishwasher heats the already-hot water to 140 F, or thereabouts. From there, the water is pushed up into jets that spray the water out with heavy pressure. The water is what sprays onto the dishes, with the bonus that the jets often rotate like a sprinkler.
Once the heated water has filtered into the dishwasher, there is an additional heating element shaped like a tube that helps to bring the water up to a higher temperature. This is done for several reasons. Dishwashers heat water up to around 140 F, which is the temperature that needs to be achieved to kill most bacteria. When water first enters the dishwasher it is about 20 degrees cooler than is necessary for proper sanitization.
There is a mechanism within the overruling system in the dishwasher that prevents the temperature from ever getting too hot, and prevents the dishwasher from overflowing with water. Once the cleaning cycles have finished, the dishwasher drains the hot water, keeping the door locked to avoid any spilling. At this point, the pump within the dishwasher that brought the water in slowly helps it to drain out.
Dishwasher Heating Element Functions
Aside from sanitizing dishes and increasing the temperature enough to get heavy dirt and bacteria off of utensils and detailed cookware, the heating element performs other functions. Many dishwashers have different styles and settings. A Bosch dishwasher condensation drying style makes the process of washing your dishes much more energy efficient because it doesn't require a heating element.
Bosch Dishwashers 101 explains that at the end of a Bosch dishwashing cycle, a condensation method rather than a heating element is utilized to dry dishes. This is done by creating condensation within the dishwasher. A stainless steel tub at the bottom of the dishwasher cools more rapidly than the dishes do at the end of the washing cycle.
Once the washing cycle has finished and the dishes have begun to cool down, the basin at the bottom of the dishwasher will have already cooled down significantly. When the hot air comes into contact with the cooler stainless steel tub, the heat and moisture will begin to turn into small droplets of water, all of which will trickle down to the bottom of the tub, leaving your dishes dry. The case is the same for the Bosch dishwasher extra dry setting.
Scraping Plates Before Dishwasher Use
Adding plates covered with food to your dishwasher is not recommended. While modern dishwashers are more powerful than the dishwashers of the past, there is still a significant amount of energy expended to ensure that all the debris in the dishwasher is washed away without clogging the pipes or the pump.
Leftover food like cake, mashed potatoes, meat and other edibles can at best cause a mess in the internal dishwasher chamber, and at worst clog up the dishwasher, making it unable to be filled or drained. While it can feel like it defeats the purpose of having a dishwasher, cleaning the majority of food off of your plates and cutlery before placing them in the dishwasher means that you're much less likely to clog your dishwasher or impede its ability to clean.
Why Dishwashers Have Different Cycles
Dishwashers have different cycles largely to account for the fact that certain load sizes are smaller than others and that certain materials or types of dishware need different treatment than others. The goal of every single dishwasher cycle is to make the cleaning process as hassle-free and as sanitary as possible. Certain cycles are also dedicated to certain types of cookware.
By heating the hot water inside of the basin, a dishwasher can make the most of a "pots and pans cycle," while some cycles that focus attention on utensils will use less water than if they had a full load to clean and will concentrate more on the utensil area both in terms of temperature and intensity of water.
While water is the most important part of the cleaning process, detergent also plays a critical role in optimizing the dishwasher's functions and getting dishes as clean as possible. All the elements in a dishwasher work together, including additions like a drying fluid. Drying fluid helps to break up the bonds in water molecules so that they slip off of the surface of your dishware.
Ashley Friedman is a freelance writer with experience working in the home, design and interiors space.