Today I’m going to be looking at how does a dishwasher work now I’ve been around dishwashers most of my life but I never quite fully understood exactly how they worked and they’re a very interesting machine and certainly a very widespread machine that many people in North America And worldwide Have and use almost every day just a little history on the dishwasher.
I was actually quite surprised to find out that the dishwasher is older than I originally thought for many years.
I was under the impression that the dishwasher was an invention that came along in the 1950s but it actually came out long before then and to give you a little history of the dishwasher.
It was actually invented by Josephine Cochrane who was From Shelbyville Illinois and she actually invented the dishwasher in 1887 believe it or not so long before the 1950s and Josephine’s early dishwashers were very very primitive they did not run on electricity.
They were completely operated by hand and completely mechanical so certainly, a very sort of primitive device compared to the ones we have
While dishwashers can differ from model to model they all operate on similar principles
In this article, we’ll show you how does a dishwasher work and we will address the five basic stages of dishwasher operation as well as potential problems you may encounter.
How does a dishwasher work step-by-step
In most cases, the filling cycle actually begins with draining the water from the appliance although some of this water is retained in the sump housing to prevent the seals from drying out in cracking when the dishwasher is not in use.
Most dishwashers have a timed fill cycle that will allow no more than two gallons of water to enter during operation.
The homes water supply line connects to the water inlet valve on the dishwasher,
When you select a wash cycle the control sends 120 volts of alternating current to the inlet valve solenoid opening the valve and allowing the proper amount of water into the tub.
Depending on the model the voltage sent by the control will keep the valve open for Between 90 and 120 seconds if the control fails and doesn’t shut off the voltage to the valve afloat will actuate a switch that shuts off the water.
keep in mind that the purpose of the float is to prevent overfilling the float itself does not monitor or control the amount of water entering the tub.
Having the proper amount of water is vital to the performance of the dishwasher if the tub is underfilled the dishware will not clean properly.
Commonly under Filling is caused by a restricted water inlet valve, to help determine this:
1. Poor one to two quarts of water into the bottom of the tub.
2. Run the dishwasher.
If the wash performance improves the valve is probably restricted and should be replaced.
Note: trying to clean out an old valve is not recommended due to the risk of part failure after repair.
Once the proper amount of water enters the tub the washing stage begins.
Three factors that affect the wash cycle are:
- Water circulation
- Water temperature
The control sends voltage to a circulation motor the motor drives a pump that uses an impeller to force the water up through the wash arms the arms are driven by the water jetting out of the holes.
If the arms are not rotating or you experience pour wash performance the cause could be a worn or damaged impeller.
As the food debris is Cleaned from the dish where it collects in the sump which filters and retains the larger particles this filter prevents the food particles from being circulated through the wash arms.
Over time some particles may still reach the wash arms clog the holes and reduce wash performance so you may need to clean out the holes periodically
Also, be aware that it’s normal for the arms to feel a little loose when not in operation.
As the water circulates through the arms a Wax motor or solenoid causes the dispenser to open releasing detergent that mixes with the water.
Since dishwasher detergent does not create suds like other detergents or soaps you should only use detergent designated for dishwasher use.
You should also be aware that too much detergent may result in pitting or etching on glassware so follow the manufacturer’s recommendations.
Depending on the setting the dishwasher may use a heating element during the Wash cycle the control will send voltage to the element periodically to maintain a water temperature between 120 to 160 degrees Fahrenheit.
If a problem develops a high limit thermostat will switch off the voltage to prevent damage to the dishwasher.
If you suspect the heating element is not working you can test the element for continuity to determine if a continuous electrical path is present.
At the completion of each wash cycle, the dishwasher will drain the dirty water from the tub.
The control sends voltage to a drain pump that uses an impeller to force water through the drain hose to dispose of the drainpipe.
To ensure proper draining and prevent the water from flowing back into the tub you must make sure the drain hose has a loop that goes above the drain.
If the water does not drain first check the drain hose for any obstructions.
If the hose is clear the drain pump may be defective and require replacement.
The dishwasher will go through several rinse cycles which are similar to the wash cycles and may also use the heating element.
The final rinse cycle introduces rinse aid from the dispenser instead of detergent.
Rinse aid helps to dry the dishware and prevent streaking caused by hard water the harder the water the more rinse aid will be required.
You should consult the owner’s manual to determine the optimum rinse aid setting for your use.
Following the rinse cycles will be a final drain cycle as we mentioned earlier some water will remain in the tub to preserve the seals and prevent cracking.
Once the dishware has been washed and rinsed and the water has been drained from the unit the drying process will begin.
Two things are required to dry the dishware efficiently:
Some models will use a heating element to heat the air inside the tub other Models will rely on the heat generated by the final rinse cycle.
The hot moist air will either exit through a permanent vent or through a vent in the door which is open by a wax motor or solenoid.
Without proper venting, the moisture or water vapor would condense back into the liquid and collect on the dishware.
How does auto mode work on a dishwasher?
It works much like an automatic clothes washer only smaller.
There is no agitator the cups, dishes, and flatware just sit there and get sprayed with warm water, then soap and hot water a lot by a wand-type arm with jets drilled into it.
As the electronic timer moves to rinse the soap and other additives stop being included in the cycle and pure warm water rinse is sprayed onto all that is inside along with a spray of Jet dry that makes the water wetter(wetting agent).
After the rinse cycle is done a heater comes on to dry the dishes and flatware. At the end of cycles, the dirty water is pumped out down into your sink drain. When it’s done some washers beep to let you know.
There are many other cycles that can be included for different types of loads that need to be washed as well. Some have a presoak as well.
How does a dishwasher air gap work?
I think this question refers to the way that dishwashers drain into the nearby main sink drain.
The drain hose comes out of the bottom of the dishwasher and has a high loop, then empties (typically) into a connection on the sink drain pipe above the sink trap, or into a fitting on the side of the garbage disposal.
The air gap refers to air in the drain hose loop at the high point.
The purpose of this loop is to prevent the sink from draining into the bottom of the dishwasher.
The purpose of the air is to prevent siphoning of water from the sink drain into the bottom of the dishwasher.
How does a dishwasher flood switch work?
Most dishwashers contain a small float connected to a switch that will cut power to the fill solenoid in the event of a timer failure that left the fill valve on.
In later years the same switch would start the drain cycle immediately if an overfill condition was detected. I’ve seen where a float switch was gummed up with dry food and detergent and failed to move when the fill valve stayed on.
Needless to say, it was a big mess. The float should be lifted up and down once in a while to ensure it moves freely.
How does a dishwasher flood switch work?
The term “float Valve” implies a float connected to a valve such that when the water reaches a certain height it will directly shut off the water supply. A float valve is used in toilet cistern/tanks etc.
I have been involved in appliance service and design since 1964 and I have never seen a float valve per se incorporated in a dishwasher or for that matter even in a washing machine.
It is possible that one or more brands of models of dishwashers had a true float valve but it would have been very, very old.
Due to water level/turbulence in the wash chamber and the fact that a considerable quantity of water in a dishwasher is in suspension, I would wonder how practical this might be if it existed – I guess it could be made to work.
Many years ago some machines had a float that actuated a switch when the required level was achieved – this switch then opened the supply circuit to the inlet solenoid and in many cases actuated the timer motor circuit to commence the wash cycle time.
I have seen float actuators both within the wash chamber and even in a Bendix (once a very popular brand) washing machine whereby an external tube in common with the wash tank incorporated afloat within the tube and rose with the water level thus tilting a mercury-filled tube having electrodes. This machine was probably from the 1950s or earlier.
Most machines utilize a diaphragm switch control – wherein a drum-type skin is stretched across the top of a shallow ‘cup’.
The bottom of the cup is connected to an air tube leading to a low point in the wash chamber. As the water level rises the air pressure increases in the tube and thus the cup of the control – this pressure distends the diaphragm which actuates a switch incorporated with the control.
Another old system incorporated a diaphragm switch control directly in the base of the wash chamber.
(Many washing machines utilizing this system had adjustable water levels or multi-level controls, some even had a plurality of diaphragm switches.)
Some dishwashers used a timed fill and this might be problematic due to varying water pressure.
Another water level control system incorporates a current sensor on the wash pump motor circuit – the pump commenced upon the start of the fill.
when the correct quantity of water was being pumped the motor current rises and via the main control the water inlet solenoid valve closed. Other systems have been devised.
Some machines include a ‘safety’ float switch in the base of the machine so that in the case of an overfill or leak onto the base, the machine may cease filling, stop entirely or even pump out any water within the machine.
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Knowing how does a dishwasher work will help you to know your dishwasher and will help how to use your dishwasher and start it properly as we mentioned the dishwasher work through five steps filling, washing, draining, rinsing, drying.