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

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.  A high temp commercial dishwasher uses an internal heater to heat water to 180 degrees Fahrenheit in order to kill any germs and effectively remove grease from dishes.  A low temp commercial dishwasher relys 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.

For more on commercial dishwashers, check out these links:

• Why you should use a water filtration system
• How to make your dishwasher energy efficient