Just read up on how a dishwasher works. It was acting up yesterday, so I had to figure it out. I bet many haven’t even thought about the working algorithm. Well, hot water under pressure is poured onto the dishes, with the dirty water going into the sewage system. It seems straightforward, but there are many nuances.
First, water fills the inside, after which, if there’s a water heater (see below), it turns on. Hot water begins spraying through either rotating or stationary spray arms. Moreover, if they are rotating, there are no motors — they spin by the force of the water jets. The water drains down and flows into a container, from where it again travels up the spray arms to the dishes. So, the first point – the water is heated not somewhere inside but right in the dishwasher’s tub. Well okay, that was obvious. Moving on.
Then there’s a difference — in the USA, dishwashers are meant to be connected only to hot water, whereas in many parts of the world, cold water suffices, and the dishwasher heats the water itself. The latter category has a heat exchanger built into one of the walls. While the water heats up and sprays from the spray arms, new water is poured into the heat exchanger. Next, the temperature of the new batch of water gradually increases – while the ambient temperature in the chamber gradually decreases. The washing cycle ends when these temperatures align. Hence, the second discovery — the condition for stopping the dishwashing is dynamic, not just based on a timer.
This approach, incidentally, prevents thermal shock to the dishes when switching from dirty to clean water. Clean water in the next cycle comes from the heat exchanger, already warmed to the temperature of the draining dirty water. And ultimately, there are no sharp temperature shifts within the chamber.
This concerns many European dishwashers, where cold water enters and is heated. In my dishwasher, like most in the USA, connecting to cold water is technically possible, but highly unrecommended – it would significantly reduce the quality of the process. Thus, there’s no heat exchanger, and no thermal shock occurs because the water is already hot at the inlet.
It’s funny that Europe does a lot because of the Kyoto Protocol, which the USA did not support. For example, both water and air in my home are heated by gas. Thus, the dishwasher emits CO2 🙂 The second reason is that heating 10 liters of water with 110 volts is simply slow, and connecting the dishwasher to a separate outlet, like for a washing machine and dryer, is overkill.
Next – how drying works. After rinsing, cold water is poured into the heat exchanger. From the existing heat, it gradually warms up – meanwhile, all the moisture in the chamber will condensate on the side wall, on the heat exchanger. Naturally occurring air circulation in a closed space will cause it to move near the cold wall – where water will settle. As I understand, a heating element is also turned on to accelerate the process.
There’s a separate compartment for rinse aid. This agent reduces the surface tension of water, making it easier to evaporate, not gathering in droplets, thus leaving no streaks on dry dishes from the dishwasher with rinse aid.
The amount of resources consumed depends directly on the amount and dirtiness of the dishes: the more and dirtier they are, the longer the process will take and the more water will be needed. But how does the dishwasher know how much and how dirty the dishes are? This is also interesting.
Let’s start with the volume of dishes. The dishwasher knows how much water it has poured in, and how much has drained out. The difference — is what remains on the dishes. Essentially, this delta is proportional to the surface area of the dishes. Changes are detected by special sensors – if there’s a significant lack of water, more is drawn from the water supply.
How does the machine determine that the dishes are clean? By the water returning to the container: if it contains a lot of impurities and coloring agents, special optical sensors – turbidity sensors – detect this. Thus, the process continues until the required level of cleanliness in the water returning from the dishes is achieved.
The turbidity sensor consists of two main elements. On a board, shaped like the letter U, a LED and a phototransistor are placed opposite each other. The board is housed in a clear plastic case. After the main washing cycle and the first rinsing stage, the LED emits an infrared beam towards the phototransistor. The light must travel through the water to reach it. If the water is clean enough, i.e., contains only a small amount of detergent residues and food particles, the light reaches the phototransistor, which then sends a signal to the control module. The module adjusts the program trajectory, canceling an additional rinsing stage.
Additionally, many dishwashers (not mine) have a built-in water softener – a cation exchange resin. One part is filled with levatit resin granules. This substance softens the water. The dishwasher receives decalcified water. But levatit has the property of depletion. Ordinary salt regenerates the levatit. There’s a special container in the machine for the salt. Sodium ions from the salt solution replace the calcium and magnesium ions, restoring the ion-exchange properties of the resin and preparing it for a new water softening cycle. This regenerative quality is why dishwasher salt is called regenerating salt.
Then another interesting note, there are two compartments in the door for detergent – Pre-wash and wash. So, capsules only fit in the wash. This means that for the first 15 minutes, the dishwasher operates without any agent at all, just on water, if capsules are used. However, if you use powder, that first cycle will be much more effective. In other words, capsules – not so great. I should try buying powder.
I was very pleased with GE because inside the machine there’s a brochure with a plumbing scheme and details important for maintenance by a technician. How to enter service mode, how to run auto-tests, etc., electrical wiring. None of this is in the user manual. And on the website, you can download CAD files and order individual components. Absolutely fantastic!
Hi, I'm Rauf Aliev. 