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Appliance Science: Dishwashers

dishwasher-1We tend to take things in our home for granted, casually accepting the miracles of chemistry, physics and biology that our appliances involve. Take your dishwasher, for instance: a device which cleans all manner of foods from a huge pile of dishes, quickly and efficiently. When you actually stop and think about it, the amount of work this involves is impressive, and the physics of this process are more complex than you might first think.

So how does a dishwasher use the power of water to wash dishes? Let’s take a look at the physics of water and how dishwashers use these forces to scrub your dishes.

Although the specifics differ, all dishwashers have the same fundamental design: a sink at the bottom that fills with water, a pump that moves this water and spray arms, sprayers and other devices that squirt this water onto the dishes.

When you look inside any dishwasher, one of the most obvious things you’ll see is a wash or spray arm, a rotating bar that sprays water onto the dishes, helping to dislodge the food. The dishwasher pumps water through this, but there is no motor to rotate the arm. Instead, the dishwasher uses the pressure of the water to spin it around.

The water jets on the spray arm are angled, so the water sprays out at an angle, usually about 45 degrees off the vertical. The force of this water pushes the arm, and it rotates. This shows the third of Newton’s laws of motion. As the man himself said in Latin in his 1687 bestseller, “Actioni contrariam semper et aequalem esse reactionem.” To translate: “For every action there is an equal and opposite reaction.”

So, as the water sprays out of the spray arm, it pushes the spray arm back again, sending it spinning. It’s the same principle that rockets use: hot gas gets pushed out of the bottom, forcing the rocket up, up and away.

To save water, all dishwashers recycle water. After it has been sprayed over the dishes, it collects in the sink at the bottom of the dishwasher, where it is then pumped it back up to wash the dishes again. A filter catches most of the large waste, but the smaller waste particles remain suspended in the water. So, how does the dishwasher know when the dishes are clean?

Older dishwashers ran for a set amount of time, depending on the program you chose. You would set them to a shorter wash for lightly soiled dishes and longer for pots and pans. Most modern dishwashers have an automatic mode, where they can tell when the dishes are clean, thanks to a device called a turbidity sensor.

This neat device allows the dishwasher to see how clean the water is by measuring how much grunge is in the water as it is pumped out of the sink: if the water is dirty, grunge is still washing off the dishes. If the water is clean, all the dirt has been washed off the dishes, and the wash is done. It works by shining a light (usually an infrared, or IR, light) through the water onto a sensor that measures how much light reaches it. As the water passes through, the grunge dissolved in the water and larger particles reflect it away. So, if the water is clean, most of the light passes through. If the water is dirty, less light passes through and is detected by the sensor.

Call Absolute Appliance Repair NOW if you have any problems with your dishwasher!
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(415) 388-0690 Marin County
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DISHWASHERS NEWS

When you buy a dishwasher these days, it’s not just about clean dishes, sparkling glasses and avoiding the dreaded dishpan hands. Many people want a quiet, sleek-looking appliance that conserves energy at a decent price.
The Winning Models from  http://www.goodhousekeeping.com
ASKO (model D3530): Best Overall. The top performer of all the dishwashers tested, this model is very stylish, with stainless steel interior and hidden controls. The inside lights up, for easy loading and it also features fold-down tines (the prongs that stick up) and cup shelves. This model used less water than the other dishwashers tested, with only 11 gallons for normal and heavy duty cycles combined
KitchenAid, model KUDS01FLBL: The best thing about this model is that it’s easy to load. A removable and height-adjustable upper rack helps you fit big platter and pots, making it easy to load. A large flatware basket caddy provides space for long cooking utensils and a mesh sack can be filled with smaller items, such as measuring spoons or small lids.
Miele, model G892SC: This dishwasher works great for pots and pans. This stainless-steel dishwasher excels at scrubbing hard to clean casseroles and sauce pans. Glasses with milk crust came out virtually spotless. It also features a height-adjustable upper rack that makes way for big platters and pots.
Kenmore Elite, model 16482: This dishwasher seems to have baskets for everything, including knives, spatulas and serving spoons. Sensors detect the load’s size and soil level and then adjust water volume and temperature. Other special features include sanitizing rinse, delayed start and a child lock.
Frigidaire, model PLDB998CC: Great performer at great price. Out-cleaned many models that were more expensive. Can wash just upper or lower rack to save time and water if you have less than a full load. The water hits both top and bottom but more of it hits the top or the bottom, whichever you request. Other features include delayed start, high-temperature sanitizing rinse and child lock.

 

Dishwasher Problem?

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DIAGNOSING DISHWASHER PROBLEMS

Unlike some of your other household appliances, your dishwasher will give your specific symptoms to indicate what’s wrong with it. By diagnosing the problems with your dishwasher, you can save money by cutting down on repair times. You may even be able to take care of the simpler problems yourself. Read the tips listed below and learn about how you can diagnose dishwasher problems yourself .

A leaking dishwasher can indicate several problems.

  • Overloading By putting too many dishes in each load, you may cause the machine to leak. Try fitting in less dishes and see if the leak persists.
  • Faulty Door Seal Check the plastic seal around the door of your dishwasher. If there are cracks or holes, it may cause the machine to leak. Replacing the seal is an easy and cheap problem to fix.
  • Excessive Detergent Check your detergent tray. If there’s a soap residue left over, you’re putting in too much soap per load and causing your machine to leak.
  • Faulty pipe connections Check the pipes in the back of your machine. By tightening any loose pipes, you may be able to stop your dishwasher’s leaking.

If your dishes are coming out of the dishwasher dry and still dirty, it means that your dishwasher isn’t filling with soap and water. This can be caused by one of the following:

  • The hot water valve isn’t open. Check under your sink to see if the hot water value is fully open. If it’s not, opening the valve will allow your dishwasher to fill with water.
  • The inlet valve is clogged. If the valve is plugged with debris and residue, cleaning it will repair the machine and enable the dishwasher to fill.

A little water in the bottom of your dishwasher is normal. But if you think there is an excessive amount of water, you may have a problem with your drain hose. Refer to your machine’s manual to find your dishwasher’s drain hose. Check that the drain hose has no holes, isn’t damaged in any way and is free of debris or soap residue.

Call Absolute Appliance Repair NOW if you have any problems with your dishwasher!

Phone lines

(415) 831-1259 San Francisco
(415) 388-0690 Marin County
(650) 525-0512 South SF / Daly City / Pacifica

 

 

 

 

Tips for your dishwasher performance

Here are a few tips that helped us with our dishwasher’s efficiency

  • Use a granular dishwasher soap instead of gel
  • Clean sprayer arms with picture hanging wire and a white vinegar bath
  • Remove grit and reside from fine and coarse filters
  • Check underneath the coarse filter for grime
  • Eliminate hard water scale buildup with Lemi Shine

Call Absolute Appliance Repair NOW if you have any problems with your dishwasher!

Phone lines

(415) 831-1259 San Francisco
(415) 388-0690 Marin County
(650) 525-0512 South SF / Daly City / Pacifica

 

DISHWASHER WATER-SAVING TIPS

Most of the energy used by a dishwasher is for water heating.

  • Check the manual that came with your dishwasher for the manufacturer’s recommendations on water temperature; many have internal heating elements that allow you to set the water heater in your home to a lower temperature (120° F).
  • Scrape, don’t rinse, off large food pieces and bones. Soaking or pre-washing is generally only recommended in cases of burned- or dried-on food.
  • Be sure your dishwasher is full (not overloaded) when you run it.
  • Avoid using the “rinse hold” on your machine for just a few soiled dishes. It uses 3-7 gallons of hot water each use.
  • Let your dishes air dry; if you don’t have an automatic air-dry switch, turn off the control knob after the final rinse and prop the door open slightly so the dishes will dry faster.

When shopping for a new dishwasher, look for the ENERGY STAR label to find one that uses less water and energy than required by federal standards. They are required to use 4.25 gallons of water per cycle or less — older dishwashers purchased before 1994 use more than 10 gallons of water per cycle.

HOW TO REPAIR A DISHWASHER

The control panels on the latest dishwashers can look intimidating. They’re loaded with so many dials, push buttons, and other features that the machine looks too complex to repair. This is actually not the case. With the exception of the control panel, dishwashers haven’t changed much in basic design over the last two decades. You can repair most dishwasher malfunctions yourself, and we’ll discuss tips for do-it-yourself service and maintenance in this article.

Dishwasher parts can be replaced as a unit, which is often easier and less expensive than having a professional service person make repairs. If you aren’t sure a part is still usable, remove it from the dishwasher and take it to a professional for testing. You can then decide whether to buy a new part or have the old one repaired on the basis of the repair estimate.

­Dishwashers usually run on 115-volt or 120-volt power. The water they use comes directly from the water heater, and wastewater is drained into the sink’s drainpipe. The dishwasher is not connected to the cold-water supply. For best dishwashing results, set the temperature control of the water heater to no less than 140 degrees Farenheit. Water cooler than this usually doesn’t get the dishes clean, unless your dishwasher is a newer model that preheats incoming water. The water shutoff for the dishwasher is typically located below the adjoining sink.

Caution: Because the dishwasher is connected to both the plumbing system and the electrical system, you must consider both systems when working on this appliance. Before doing any work on the dishwasher, make sure the unit is unplugged or the power to the unit is turned off, and remove the fuse or trip the circuit breaker that controls the circuit at the main entrance panel or at a separate panel. Shut off the water supply to the dishwasher at the shutoff in the basement or crawl space under the kitchen.

Call Absolute Appliance Repair NOW if you have any problems with your dishwasher!

Phone lines

(415) 831-1259 San Francisco
(415) 388-0690 Marin County
(650) 525-0512 South SF / Daly City / Pacifica

 

 

DON’T PUT GRANNY’S GLASSWARE IN THE DISHWASHER

Most dishwashers have a gentle cycle but if you treasure your grandmother’s china or crystal, it’s best to clean them the old-fashioned way, by hand. Our experts offer this advice.

When hand washing your fine china and porcelain, line the sink with an old towel to prevent chipping and use a mild dish detergent. Here are some other items that can be damaged or ruined if put in the dishwasher.

Wood. Wooden cutting board, salad bowls and spoons may swell and warp or crack.
Kitchen knives. Putting table knives in the dishwasher is fine but avoid washing your fine cutlery in the machine as the knives may become dull.
Gold. Gold-plated dishes or dishes or flatware with gold trim can become discolored or the trim may even wash away.
Crystal. Fine crystal is sensitive to heat and may crack. The detergent may also etch the glasses, causing them to lose their brilliance.
China. Expensive china, especially pieces with a pattern, may become worn with repeated washings.
Metal. Keep anything made of pewter, brass or bronze out of the dishwasher as it will tarnish.

 

THE BEST DISHWASHERS OF 2012

Dishwashers are available at a huge range of prices and sizes, but which are the best of 2012? This particular appliance is a significant investment, and you want to make sure your dollars are well spent. Luckily, consumer reviews and professional analyses are available to point you in the right direction. Here are the best dishwashers of 2012.

Size Comes First 

Typically, a kitchen dishwasher will fit a 24-inch space under the kitchen counter and has a hot water pipe, drain, and electrical wiring to hook up. While this is the most common, this is not the only size out there. There are designer drawer dishwashers that are typically more expensive, but they are also sleek, compact, and allow for separate washing cycles. The drawback is that consumers have found this individual style does not clean as effectively as the larger group wash. There are compact and even portable dishwashers as well, starting at $400 for those who have smaller living spaces. But when most people purchase a dishwasher, they are selecting the standard built-in model.

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