Boosting The Rinse Factor
Need new booster heaters? Comparison shop and consult lifecycle costing guides to spec the right one for your operations.
By Jan Sellers Ashton
Warewashers do a complex job. They physically move dishware, measure soap and maybe other chemicals, and precisely measure and spray water. They sport a lot of moving parts and electronic gizmos.
And yet regardless of whether you're talking about low-temp (chemical) or high-temp sanitizing, all the warewasher's work is for naught if the temperature of the water isn't right. And that's where the warewasher's partner in grime, the unsung-hero booster heater, comes into play. It's the booster that gets the water up to temp and keeps it where it's needed.
It's a tough job, requiring a lot of energy to go from idle to heating water to high temperatures and doing it quickly for rapid turnaround. In a busy facility the process might be repeated dozens of times a day. In most operations, the building's water heater takes incoming water up to, say, 110°F or 120°F, which isn't enough for sanitizing anything. From there the water goes to the booster, where, in high-temp applications, the water is boosted to a lofty 180°F. At that temperature, not only are sanitation requirements met, but the extra heat also serves as a safety margin while speeding evaporative drying.
The Big Picture
Like everything else, booster heaters have advanced in recent years. Today, electronic temperature controls with digital display and front access for service are the norm, as are electronic leak detection controls. And the business end of the booster heater, the heat exchanger, is vastly more efficient than in days of yore. Exchangers are now very good at transferring heat quickly and efficiently from electric elements or gas burners into the water.
Sizing runs a pretty broad spectrum, with most units possessing 6- to 16-gal. tank capacities. For smaller needs, in-sink boosters and mini units are also available for use in bar, compartment and pot sinks.
Tanks, Or Maybe No Tanks
Stainless steel is the material of choice for strength and corrosion resistance, with fiberglass or polyurethane foam insulation. And the insulation is important. These units spend several hours a day consuming energy in a "ready-to-use" mode. The insulation reduces standby or idle-energy heat loss, and thus reduces energy consumption while maintaining the needed water
Under the stainless skin and the insulation, most units have water tanks in one of a few different styles, with manufacturers handling the challenges of water pressure, heat spikes, sediment and so on in a variety of ways. One supplier lines its tanks with a material best-likened to cement in its imperviousness to water damage; another says no lining is necessary for its heavy-duty stainless tanks. Want water-softening systems in your booster to reduce scaling? They're out there. Some booster heaters on the market feature low-water cutoff, which shuts off power to heating elements and prevents burnout; power is automatically reset when water levels return to normal.
Inside the tank is the metal-sheathed heat exchanger, which transfers the heat from the electric elements or the gas flame to the water. The exchanger can be in one of several materials; one manufacturer goes with copper for its superior conductivity.
And then there are tankless booster heaters. Newer to the market, these gas-fired units take in water from the dishroom's primary source and boost its temperature through copper tubing in the heat exchanger as it flows to the rinse cycle. Without a pump or tank, makers say pump burnout and standby heat loss are not issues.
Note To Self: Install It Close
Regardless of the size or style you choose, make this item number one on your list: Locate the booster as close as possible to the dish machine, or whatever else you might be boosting, because the farther the water has to travel to its point of use, the more heat loss and inefficiency you're looking at. Most booster makers recommend 5' or less. Too close can create other issues, however, and at least one maker recommends a shock absorber between the booster and dish machine to reduce the pounding effects of "water hammer."
Some words on specifying: Booster makers provide guidelines for specifying the correct booster for a warewasher, based on manufacturer model and usage. Among usage criteria: peak volume, total daily volume, inlet water temperature and required rinse temp. All of these determine booster volume and necessary recovery rate, which in turn tell you how much or how little energy you'll need.
Most models are rated based on their ability to deliver a 40°F or 70°F rise from the incoming water source. For example, a 6kW model can deliver 60 gph of 180°F rinse water when boosting water temperatures by 40°F from the primary source; if the temperature must surge 70°F, the same booster can deliver 34 gph.
And remember to look at lifecycle cost, rather than first cost. Run some numbers at the lifecycle calculators maintained at www.nafem.org or www.fishnick.com.