Dishwashers and Warewashers

The unit that best suits an operation depends on the kitchen, the restaurant’s volume and the items it will wash.


Purchasing and Maintaining Warewashers

Although warewashing tends to get overlooked because it does not generate revenue, the dishwashing area typically features some of the most expensive equipment in any foodservice operation. The type of unit that best suits an operation depends on the kitchen, the restaurant’s volume and the type of ware being washed.

warewashers tablewareHigh-temp door machines have a higher chamber height and can wash anything up to 27 inches tall. Lower-volume restaurants tend to choose single-door machines, which have a 19-inch opening, rather than the taller version.

Door-type machines have many wash cycles for various cleaning needs. The normal cycle can handle glassware, like beer mugs and pitchers, along with plates and utensils. Pots, pans and heavily soiled items benefit from the extra-heavy cycle, which lasts about five minutes versus one minute for regular washing and sanitizing.

Larger operations can consider conveyor machines, available in 44- and 66-inch sizes. Higher-volume restaurants that require increased throughput should consider these units.

Glass washers are small undercounter machines between 36 and 38 inches tall. Rotary-type machines wash and sanitize glassware in about 15 seconds, while other types have 90-second cycles. In the past, the only glass washers available were low-temp machines. Because these only heat water between 120 degrees F and 140 degrees F, these units require chemical sanitizing.

Operators prefer this type of warewasher in specific applications. For example, unlike high-temp units, low-temp glass washers do not release steam into the bar area when the door is opened after washing. The downside, though, is the smell of chlorine and possibility sanitizing chemicals that will impact the taste of beverages. Newer ventless glass washers have systems that evacuate the steam out of the unit at the end of the cycle, eliminating hot and potentially damaging clouds of steam.

Becoming more popular in the last eight years or so, ventless warewashers eliminate the need for hoods or exhaust fans as they do not emit steam that needs capturing. With these units, a fan draws steam out of the chamber at the end of the rinse cycle, pulling it into the warewasher’s heat exchanger. When staff open the door after the rinse cycle, no steam escapes. By pulling out the steam, the warewasher can utilize this to heat incoming wash water. This increases energy and saves money on electricity typically used for heating the water from 110 degrees F to 180 degrees F for washing.

Operators should check local codes and requirements before committing to a ventless warewasher.

Commercial dishwashers that have earned the Energy Star designation are said to be on average 40% more energy efficient and 40% more water efficient than standard models. The designation applies to high-temp (hot water sanitizing), low-temp (chemical sanitizing) and dual sanitizing machines. This includes undercounter, single tank, door type, single tank, conveyor, multiple tank, conveyor, and flight-type machines. Glass washing machines as well as pot, pan and utensil machines are also eligible.

Features that conserve energy and water incorporate advanced controls and diagnostics, improved nozzles and specific rinse arm designs.

Purchasing Considerations

Which unit an operation should use varies by application. Undercounter machines remain a popular option in bars, kiosks and low-volume operations. These units are built around one or two dish racks and clean in 45 seconds to 2 minutes.

Door-style machines come in single- and dual-rack models and remain a popular choice among small- and medium-size restaurants or smaller schools. Similar in style to undercounter warewashers, door-style machines are taller and connect to dish tables. Capacities for door-style units range between 21 and 60 racks per hour.

Rack or circular conveyor units remain popular for full-service restaurants and higher-volume applications, such as universities and healthcare foodservice operators. These continuous motion machines feature an average production rate between 100 and 300 racks an hour.

Flight type or rackless warewashers are best suited for large cafeterias, banquet halls and catering operations as they can wash more than 21,000 dishes per hour with belt speeds as high as 14 feet per minute.

Speciality units such as pot, pan and utensil machines offer between a 6- to 60-pan capacity.

With booster heaters and water use, warewashers can consume a lot of energy and other resources. Today’s models often are more energy- and water-efficient than previous generations, typically using less than a gallon of water per rack for each wash cycle.

Larger pans that need accommodating are best served by a taller unit, and bigger operations may require a conveyor machine. These pull racks through the wash tank and a rinse area, and then out, as opposed to dishes staying in the zones and washing and rinsing happening in same place. This speeds up and even triples the dishwashing volume. Instead of 1 rack per minute or 60 racks per hour, conveyor machines can handle 180 to more than 200 racks per minute.

Operators should also consider water softness or hardness, which contributes to lime and scale buildup. This can result in the need for more detergent during the wash cycle.

Since different wares have distinct washing requirements, operators must determine what they intend to wash in order to specify the correct unit. Operators also should consider the warewasher’s design and what items need cleaning. This will help determine if racks or tables are appropriate.

Verify capacity or throughput. Compare the ratio of usable cubic inches of wash area to the unit’s overall footprint. Tank sizes are measured in 6-inch increments.

Assess throughput speed. This will determine how fast the system can wash the items required. The bigger the warewasher and the faster it runs, the more efficient it will be.

Consider the costs associated with the many consumables that relate to warewashing, such as detergent, rinsing agents and other chemicals.

Also consider energy consumption and water usage. Energy Star-rated warewashers may save money over time.

Examine the location of the wash jet to get a better picture of the wash action consistency.

If an operator plans to wash a variety of items in the unit, look at the model’s flexibility. When the ability to wash varied loads that are intermixed becomes important, consider a system that offers random loading capabilities.

Ergonomics represents another factor when specifying warewashers. Consider how employees will load and unload the unit.

Take into account the space constraints for this equipment, keeping in mind that it may be best to purchase a unit that is larger for increased efficiency, flexibility, capacity at peak periods and future expansion of the operation.

Care and Maintenance

Manufacturers recommend cleaning dishmachines after every shift since flushing the water removes accumulated soil from the machine, which in turn improves washing performance and reduces detergent usage. This practice also preserves the longevity, sanitation and cleanliness of the machine.

Some machine features can also help keep the wash water clean, including multi-stage tank filtration systems, active filters or systems that divert water between tanks to reduce soiling. In addition, scrap screens or filters should be washed and cleaned regularly.

Regularly drain and clean flight and rack machines as well as continuous pot and pan washing systems.

Depending on usage and water quality, clean wash and rinse arms weekly or as necessary.

Keep pumps and fans properly lubricated.

When to Replace a Warewasher

Tank leaks may signify that the welds are giving out. Also, problems can be caused by water leaking from the boosters. In either case, the warewasher may need to be retired.

If the warewasher’s controls are not operating properly or pump pressure is lost, consider replacing the unit.

The results of the unit are a key indicator that the warewasher is not operating at 100%. If items are not being cleaned and sanitized properly, this may be an indicator that wash and/or rinse arms are wearing out.


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