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Greg McGuire covers the foodservice industry for The Back Burner and also works for Tundra Specialties, a restaurant supplies, equipment, and parts company in Boulder, CO.

Commercial Dishwashers: High Temp vs. Low Temp & How To Size A New Unit

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By Greg McGuire

February 3, 2010

Are you a high temp person or a low temp person? It seems like most restaurants have either one type of commercial dishwasher or the other, and the owner/manager is a big believer in one or the other, with very little crossover between the two. No matter which side you come down on, there are some clear advantages to high temp dishwashers, and even if you’ve sworn that low temp is the way to go, some hard truths about low temp dishwashers may very well change your mind.

First things first: what are high temp and low temp?
These two terms refer to the sanitation cycle of the dishwasher. High temp commercial dishwashers use an internal heater to heat water to 180 degrees Fahrenheit in order to kill any germs and effectively remove grease from dishes. Low temp commercial dishwashers rely on a chemical bath to sanitize dishes.

Here’s a quick rundown of the benefits and drawbacks of each:

High temperature dishwashers:

* Use heat to sanitize dishes and glassware
* Must achieve 180 degrees Fahrenheit to meet NSF regulations
* Use slightly more energy than a low temp dishwasher
* Do not require the regular purchase of chemicals
* Do not damage flatware and plastics
* Dishes flash dry at the end of the wash cycle, reducing food safety risks
* High temp dishwashers usually wash dishes faster

Low temperature dishwashers:

* Use a chemical bath to sanitize dishes and glassware
* Are not as effective at removing grease
* Are slightly more energy efficient than high temp models, however, they use more water and deposit chemicals into drainage systems
* Can damage flatware and plastics
* Require you to purchase chemicals on a monthly basis

Those in the low temp camp argue that the cost of chemicals for a low temp dishwasher is much less than the increased energy savings versus a high temp unit. The initial purchase cost is usually less as well.

While this may be true, the main factor to consider when you are trying to decide between a low or high temp dishwasher is the damage to flatware, plastics, and dinnerware that might occur with a low temp model because of the sanitation chemicals used.

How To Size A Commercial Dishwasher

Buying the right sized dishwasher is critical to your kitchen or bar’s ability to keep up with demand. Most dishwasher manufacturers list the number of racks per hour a particular model can process.

In general, racks can hold 18 dishes or 36 glasses.

Calculate how many dishes you generate per hour and then weigh that number against the number of racks the dishwasher you’re looking at can handle.

When calculating how many racks you need to wash per hour, consider the following factors:

* About 35 racks of dishes are produced for every 100 meals served
* Your dish machine should be able to easily handle peak demand volume like Valentine’s Day dinner rush
* Dish machines have a 5 – 10 year lifespan, so add 10% – 20% capacity for future growth

Also don’t forget to account for dishes created in the kitchen. In general, most restaurants need a door type dishwasher to accommodate pots and pans and other things that need washing in the kitchen. Door type dishwashers can typically handle 100-150 racks per hour, making them perfect for the dinner rush in most small and medium sized establishments.

Make sure you take future growth into account! A dishwasher should have about a 10 year life, and in that time your business should be growing. If you purchase some extra capacity at the beginning, you’ll save yourself some time later on.

Greg McGuire manages The Back Burner blog for eTundra.com, a restaurant supplies, equipment, and equipment parts website dedicated to the food service industry.

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Posted by Jeffrey Schmidt on 3/11/10 at 9:10 AM EST

Interesting article. There are a few points that I believe need clarification however. Both high and low temp machines require chemicals to be used. If the machine is being leased from a company that supplies chemicals, there will be requirements to purchase chemicals from them. If the chlorine sanitizer is set properly on a low temp machine there will not be any damage to the plastic or stainless ware. Presoaking anything in bleach will cause damage to the finish.
Dish racks will hold an average of 4 place settings, as a national average. This does not take into account pots & pans, or high end place settings with multiple pieces of silverware.
Regarding life span, low temp machines will have a life span of about ten years. High temp machines should last about twenty years with proper service.
When sizing a machine, it should be done by the number of seats in a facility, the size of the dish area, and and how often the facility is at peak capacity. Thirty years ago when utilities were cheap it was common to over size. Now proper sizing is very important. Door machines will accomodate usually one large pot, kettle or sheet tray at a time. Conveyor machines will process these on a continual basis.
Single rack low temp machines will typically wash 37 racks per hour, using an average of 1 to 2 gallons of water per rack., depending on the manufacturer. Single rack high temp machines will process 60 to 72 racks per hour, using .85 to 2 gallons of water per rack, depending on manafacturer. Conveyor machines will wash up to 244 racks per hour, using as little as .49 gallons of water per rack. Obviously the less water used, the lower the chemical costs, the water and sewer bills, and the utilities to heat the water.
A good chemical rep can help you size your operation.
Posted by Mark Horban on 6/13/12 at 1:59 AM EST

The 180 degrees is acually incorrect. NSF/ANSI 3 states that a 160f will be maintained at the dish level. 180F is at the final rinse manifold which cools to 160F by the time it leaves the nozzles and gets to the dishes. 160F at dish level is what you should be concerned with.

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