After the show is over—after the food has been prepped, cooked, plated and served, after the dishes have been whisked away—the foodservice production line ends in the dishroom. In a medium-sized operation, the centerpiece of this room will probably be a rack-conveyor warewasher.

It’s a pricey yet unglamorous piece of equipment, typically operated by the least-skilled and lowest-paid employees. Yet the optimal functioning of the warewasher and dishroom is essential to the success of the entire operation. And because the water and energy consumption of conveyor dishmachines has plummeted as technology has advanced in the past few years, it may be time for you to consider replacing your workhorse of the dishroom.

Who uses a conveyor warewasher? Rack-conveyor warewashers are the medium-duty choice for larger full-service restaurants and medium-size noncommercial operations such as schools, universities, corporate dining and smaller hospitals. (More modest foodservice operations use door-type machines; the biggest employ flight-type warewashers—large continuous-motion conveyors that don’t use racks.) A 200-seat restaurant will typically use a rack-conveyor warewasher, but the amount of dishware per diner and the rate of throughput needed are more important than the number of seats.

Why are today’s rack-conveyor dishmachines better than those of a few years ago? The water consumption of a rack-conveyor warewasher is on a downward trajectory; today’s equipment uses far less water than similar machines did a decade ago.

This is true even though many published water-usage rates don’t reflect actual water consumption, says David Zabrowski, G.M. of the Food Service Technology Center, San Ramon, Calif., which recently conducted a study of rack-conveyor dishmachines in cooperation with California water districts. Stated usage rates often don’t take into account factors such as prewash, wash and rinse tank top-offs that deal with water loss during operation, Zabrowski explains. So a machine rated at 100 gal./hr. of water may actually use 300 gal./hr. or more. However, the difference between stated water usage rates and actual usage rates is even greater with older dishmachines. He says, “We’re seeing legacy machines using as much as 1,100-1,200 gal./hr. So there’s a massive business case for adopting these new machines.”

Since heating water uses significant energy, lower water consumption means lower energy usage. (Most conveyor dishmachines are powered by electricity, but gas and even steam alternatives are available.) Energy Star’s rating of the more efficient rack-conveyor dishmachines reflects lower energy consumption. The Environmental Protection Agency says operators can save $16,000 over the life of a conveyor dishmachine by choosing an Energy Star-rated model rather than a non-Energy Star-rated alternative. (Energy Star is a constantly moving target, since it recognizes the most efficient appliances in each category at a given time.

The EPA last updated its Energy Star criteria for rack-conveyors in early 2013 and is expected to release new numbers for the category as soon as late ’16.)

What newer technologies reduce energy and water consumption further? One development is heat recovery systems, which capture waste-heat from the hot water and vapor from the running machine and channel it to preheat cold water entering the dishmachine. Using pre-warmed water, the booster heater does not need to work as hard to get water to 180°F for the rinse operation. That means that hot-water fi ll for the dishmachine’s tanks may only be needed at the start of operation and for tank top-offs. Once the machine gets going and generates heat, it can get by with a cold-water supply.

Heat-recovery rack-conveyor warewashers may also be ventless, collecting water vapor that would normally escape the machine. The effect is to further reduce the machine’s energy and water consumption, eliminate the need for an expensive hood and venting system, and keep the dishroom cooler and dryer. Manufacturers consider the advent of ventless conveyor dishmachines a game-changer, saving operators thousands in installation costs and hundreds of dollars annually after that. Look for more of these machines to be rolled out in the coming year.

I’m sold! I’m buying a new rack-conveyor dishmachine. What size do I need? To determine the racks-per-hour throughput you need, figure your peak number of patrons per hour over each meal period, multiply by the typical number of pieces per diner (such as dinner plate, salad bowl, water glass, wine glass, etc.; count five silverware utensils as one piece) and divide by 20 (the typical number of pieces that will fi t in a rack). Typically, a fine-dining restaurant that uses many small plates per diner will place greater demands on the conveyor dishmachine than a lower-price-point restaurant with the same seating capacity.

The physical size of the machine is another important consideration. The smallest conveyor dishmachines are 44 in. long. That may be the only size that can fit into a cramped dishroom. However, Zabrowski cautions that 44-in. rack-conveyors are less effi cient than larger machines, since mingling of the overspray between the wash and rinse cycles (despite the curtain between the sections) means that these conveyors use more water and energy to wash the same number of dishes.

The theoretical maximum throughput of a rack-conveyor dishmachine may not be realistic given the human and logistical limitations of your dishroom. A single operator might be able to process 75 racks/hr.; if you want to purchase a machine capable of washing 150 racks/hr., you may need to add another employee (as well as larger pre-wash and post-wash tables).

How many sections/tanks/cycles do I need in my conveyor, and why? A 44-in. conveyor dishmachine will almost always be a single-water-tank machine, although one manufacturer offers a 44-in. model with a small rinse tank. But generally speaking, a larger conveyor machine with a higher racks-per-hour throughput also has more sections and tanks, increasing the total time that dishes are exposed to water—boosting the machine’s cleaning power.

Single-tank rack-conveyors may offer a pre-wash before the main wash chamber, useful in knocking the last food soil off dishes before the main wash. Some machines also have a post-wash rinse zone, known as “dual-rinse,” with its own auxiliary tank to remove the soap before the final sanitization step, rather than making a single rinse serve both purposes.

Additionally, some rack-conveyors have a built-in blower dryer, reducing the space, labor and time needed for drying and returning dishes to service more quickly. Blowers are very helpful for drying plastics, including melamine and domes and trays in hospitals, for example.

What’s the difference between high-temp models and low-temp models? Essentially, low-temperature dishmachines wash and also rinse at 120°F-140°F and require chlorine sanitizers at the end of the wash cycle; high-temp models include a booster-heated rinse at 180°F, high enough to sanitize dishware without chemicals.

One advantage of low-temp models is the ability to get by without a booster heater, reducing the machine’s power demands. Disadvantages of low-temp models include the ongoing cost of sanitizing chemicals and the chance that the chemicals could damage some of your dishware.

Dishes in a high-temp unit may dry faster, but the conveyor also will require installation of a condensate hood in the dishroom (unless the unit is a new ventless model). And 180°F water is not supposed to go down the drain into the sewer system, since it could damage pipes and could flush too much grease into the sewer rather than the grease trap. Not all municipalities enforce this, but manufacturers can add an optional tempering mechanism so that the superheated water is mixed with cold water before it goes down the drain; in multi-tank machines, the sanitizing water is mixed with the cooler water from the other tank before going down the drain, or recycled back to the pre-rinse.

Side-drive vs. center-drive mechanisms—why does it matter? Center-drive machines are cheaper. But most manufacturers say side-drive mechanisms, without a central pull bar running through the machine, make the racks easier to remove, the scrap tray easier to access and the dishmachine easier to clean. (However, one manufacturer is developing a continuous-motion rack-conveyor warewasher with a center drive—a new idea for this size and type of dishmachine, on which a start-and-stop mechanism has been standard.)

What do I look for in the spray arms? Most important in spray arms is their shape and mode of action; each manufacturer can explain how its design reaches all parts of the wares going through the racks. Other key factors to consider are durability (stainless rather than plastic); the spray holes themselves (inward-punched holes can more easily get clogged with debris); and ease of removal, cleaning and correct reinstallation.

Tell me about labor-saving features. Dishroom employees don’t get a lot of training, the pace is exacting and turnover is high, so manufacturers are making every effort to make rack-conveyors easier to operate and maintain. Insu-lated and properly ventilated machines keep the dishroom cooler, dryer and safer. Food-debris trap screens are larger, fewer and easier to remove and reinstall than they once were. Large cabinet-style doors give machine operators full access to the inner chamber. A “conveyor dwell” feature allows the operator to stop the machine so that racks filled with heavily soiled items get more soak time (reducing the need to manually scrub these items).

Increasingly, manufacturers are color-coding warewashers: anything the employee has to operate, move, remove, clean and/or periodically replace is colored blue. Sometimes, icons on the exterior will help explain what needs to be done. Digital-display error messages are in plain text or icons, not codes that someone has to look up in a manual. A deliming notification is another option; deliming is done only when needed, saving on chemicals and down time. Self-cleaning cycles are another labor-saving feature; they don’t remove the requirement for manual wash-down and detailed cleaning, but they can help to reduce soil buildup in the machine.

In addition to features that help dishroom employees, advanced diagnostics help service technicians know what to do before making the service call and what parts and tools to bring with them.

What do I need to know about setting up the dishroom? Consider work flow. To get the optimal throughput for a specific size of conveyor warewasher and number of dishroom employees, it’s important to set up the room with an adequately sized soiled dish table and scrapping trough for pre-scrapping, and a large-enough clean dish table at the other end.

Some operators struggle with a clearly inadequate dishroom. In these cases, manufacturers can offer suggestions for better flow logistics. For tight spots, some suppliers even offer corner feeder tables that allow staff to load the dishmachine from a 90° angle.

Top Dishroom Mistakes

  1. Not pre-scrapping adequately. The scrap trap is not meant to be a garbage disposal. Grit, beans, bits of egg and similar items can clog the trap, compromise the quality of the wash and make the dishmachine break down faster. (However, a dishmachine with a power pre-wash section will be able to handle heavier dirt than one without.)
  2. Laying trays or sheet pans flat for washing. Manufacturers bemoan the problem of flat trays blocking the action of spray arms and deflecting water. There are peg racks made to stand trays and sheet pans upright. Operations that do a lot of baking can order an extra-tall rack-conveyor model to better accommodate these items.
  3. Using the wrong type of rack. Peg racks allow operators to prop up items like plates, bowls and saucers; a standard 20 in. x 20 in. rack holds 16 dinner plates or 24, 6-in. saucers or bowls. Glassware racks come in many types; they typically hold 25 tall glasses, 36 juice glasses or 16 coffee cups. Combination racks include baskets for silverware.
  4. Running partially filled racks through the dishmachine. Running only full racks can save hundreds of dollars annually.
  5. Not changing water or not dumping the scrap tray often enough. Taking 15 minutes of down time to drain and refill the water in the machine—at least once a day, or once every meal period or even every two hours, depending on the volume of the operation—can make for more efficient warewashing. Dump and clean the scrap tray at the same time, and hose the machine down with a spray nozzle.
  6. Not checking the float valve. If the center float valve gets stuck in “open” mode, the machine will try to constantly replenish the tank.
  7. Not changing curtains regularly. Worn curtains between wash and rinse sections can mean water overspray and reduced efficiency.
  8. Not asking your chemical supplier to make sure the dispenser is working properly. It should be checked once a month.
  9. Not checking the numbers for proper operation. Water temperature and rinse pressure should be within the manufacturer’s guidelines for that machine.
  10. Not turning off the dishmachine at night. Heaters can waste energy heating unneeded water.

Rack-Conveyor Warewasher Gallery:

CHAMPION VENT-LESS RACK CONVEYORThe Vent-Less Rack Conveyor dishmachine incorporates a variable-speed fan and heat pump to capture 100% of the operating exhaust heat and vapor, converting it into useable energy to heat the wash and rinse water. This energy exchange saves up to 10kW over traditional rack-conveyor dishmachines. The Vent-Less Rack Conveyor emits less than 70°F cool air with very low humidity back into the dishroom. It washes 208 racks/hr., consuming .53 gal./rack.

CMA’s EST conveyor dishmachines come equipped with electrical mechanical parts—no digital boards or microprocessors—making them inexpensive to maintain. Choose a high-temp model with a built-in E-Temp booster heater, or a low-temp model for chemical sanitizing. Built with stainless for durability, the machines sport soil-purging systems with external scrap accumulators to get dishes clean the first time. These Energy Star-rated models wash 243 racks/hr. with a water consumption of .46 gal./rack.

With a capacity of up to 200 racks/hr., this 44-in. machine provides up to a 50% reduction in utility costs by reducing water and energy use with 1-pass, low-water warewashing. This model consumes .57 gal./rack of water. The Apex also automates common procedures such as end-of-day cleaning, deliming and the wash-tank change process to help make operations run more efficiently.

The CL44eR Advansys is the latest Energy Star-rated rack-conveyor warewasher from Hobart. Washing 202 racks/hr., the CL44eR features Energy Recovery and Opti-Rinse technology that, combined, can save operators more than $11,000 annually. Features include an auto-timer to save energy; tanks designed to retain water temperature and reduce energy consumption; a cascading water system to save water, energy and detergent; and self-aligning wash manifolds with anti-clogging nozzles.

This rack-conveyor dishmachine comes with an optional Ventless Reclamation System, saving up to $7,500 annually in energy costs by using environmentally friendly refrigerants to eliminate the condensate and a water heat exchanger to recapture and reuse wasted heat to heat the wash tank. With no hood requirements, this model saves hood hardware and installation costs. It’s energy efficient, using .63 gal./rack (final rinse consumption) and has a capacity of 233 racks/hr. The patented CrossFire Wash System uses high-pressure nozzles that target spray from the top, bottom and side.

The Energy Star-rated RackStar 44 conveyor dishmachine from Jackson provides superior performance while keeping water consumption at .35 gal./rack to clean 223 racks/hr. Its dual-rinse feature incorporates 2 Rainbow Rinse arms—Econo Rinse for normal operations, Turbo Rinse for heavier-soiled loads. Other features include digital LED controls, dual pawl bar system, self-cleaning wash arms, hinged doors, adjustable vent cowl collars and optional onboard booster heater.

The MEIKO M-iQ rack-conveyor dishmachine series offers high-temp sanitization with a standard built-in booster heater and multi-tank design. Standard features include heat recovery, blower dryer, active water filtration in each tank and a 3-speed conveyor. MEIKO’s unique air management improves heat retention and increases cleaning ability and efficiency. The color-coded components simplify training and cleaning. Capacity ranges 209-298 racks/hr. and water consumption .15-.21 gal./rack (both depend on model).

This Energy Star-rated, high-temp rack-conveyor dishmachine cleans as many as 219 racks/hr. using .59 gal./rack; it measures 44 in. long. Standard features include a vent fan interlock connection, built-in diagnostics, Energy Sentinel (for low water usage), anti-jam conveyor and extended vent cowls. Convert the machine’s direction of operation in the field; the model sports single-point water and electrical connections. Table limit switch connection, 2-hp wash pump and convenient, top-mounted controls come standard; a booster heater comes optional.

This Energy Star-rated rack-conveyor dishmachine uses a 30-in. scrapper section (doing the work of a manual pre-rinse), recirculating heated wash and rinse tanks followed by a fresh-water rinse—all within a 94-in. footprint. The unit processes 270 racks/hr., using .49 gal./rack. The rack-activated final rinse provides additional water savings. Access the machine’s interior for cleaning and maintenance using 2 large cabinet-style inspection doors. Opt for the corner loading conveyor for corner installations.




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