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Why is a Commercial Dishwasher Not Drying Properly?

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A dishwasher is one of the most essential appliances in any restaurant or commercial kitchen. Most technicians get calls about a unit not drying dishes and other wares correctly. Not sure what's causing the issue? Don't worry. This guide will help service techs identify potential issues so they can fix it quickly.

What is a Commercial Dishwasher? 

Dishwashers are mainly used to wash dishes, cutlery, glasses and other wares. Generally, commercial dishwashers are used in restaurants, hotels, schools and other commerical kitchens where a large number of items need to be washed quickly. 

High-temp commercial dishwashers wash dishes with hot water (150-160 degrees Fahrenheit) and then rinse out at a 180° Fahrenheit temperature. However, the temperature varies by company and model. 

Low-temp commercial dishwashers usually have washing and rinsing temperatures of 120° Fahrenheit and 140° Fahrenheit, respectively. 

5 Major Reasons Dishwasher Stops Drying

The dishwasher might malfunction for a variety of reasons. The following are four probable causes:

Heating Element

One of the most common issues a commercial dishwasher encounters when it does not dry dishes properly is a fault in the heating element. So, the first step is to inspect the dishwasher's heating element. 

Testing of the Heating Element

  • Step 1. To test the heating element, you must turn off the dishwasher and remove the heating element by detaching wires connected to the terminals on the heating element. 
  • Step 2. Use a multimeter to test continuity. Connect both probes to both terminals of the heating element. If the multimeter shows readings (you can check readings on the dishwasher's user manual), then the heating element is not defective. If the continuity test doesn't yield any readings, it needs to be replaced. 

Note: Before running continuity tests, set the multimer to the lowest resistance range. 

Vent Assembly

Many dishwashers use a vent assembly with a motorized door to let out hot steamy air generated during the rinse cycle. If the vent fails to open all the way, the moisture can remain on the dishes. Check the vent assembly to see if it is blocked or a problem with the motor. If the vent is blocked, then you should open it. In the case of the damaged vent, you must replace it. 

Vent Fan Motor

Most commercial dishwashers use a vent fan motor to blow the heated air out of the vent as soon as the rinse cycle is finished. If the fan blades are damaged or the motor itself is defective, the dishes cannot be appropriately dried. Like the heating element, you can continuously test the vent fan motor using a multimeter. If it shows no readings, you'll need to replace it.  

Note: Before running continuity tests, set the multimer to the lowest resistance range. 

Thermostat

Dishwashers come up with high-limit thermostats, which act as safety switches to save them from overheating. If a thermostat malfunctioned, it would turn off the dishwasher and stop the drying process. In this case, test the thermostat. 

Testing of the Thermostat

  • Step 1. The first step is to turn off the dishwasher by unplugging it. 
  • Step 2. Take out the thermostat, which is usually on the bottom of the dishwasher. 
  • Step 3. Conduct a continuity test on the thermostat by connecting probes of a multimer with the thermostat terminals. 
  • Step 4. At room temperature, if the multimeter shows the readings, the thermostat is not faulty. 
  • Step 5. Now, take the thermostat closer to the heater/lamp and see if the thermometer reads 0 reading. Otherwise, the thermostat must be replaced. 

Note: Before running continuity tests, set the multimer to the lowest resistance range. 

Rinse Aid Dispenser

Another major issue that may cause a dishwasher to stop drying is a defective rinse aid dispenser. If a rinse aid dispenser is not present in a dishwasher and is faulty, dishes won't properly get rid of moisture.

Unplug the dishwasher and take off the cap from the inside of the dishwasher door. Check for the existence or absence of a rinse aid dispenser. If the dispenser is not present, you should introduce it into the dishwasher. In the case of a damaged dispenser, you must replace it to ensure the proper functioning of the dishwasher.