June 2006
SPECIAL REPORT:
Undercounter Warewashers Take the Test
By Brian Ward

Turn on the tube, read a newspaper or just stare at your utility bills. Energy and water costs are up and rising. How much? A lot of places that paid 7 or 8 cents a kilowatt hour five years ago now pay 10 or 11. Natural gas that used to cost 60 cents a therm in 2001, is widely over a dollar now. In California? More like 13 to 15 cents a kWh and north of $1.25 a therm.

All of which has caused a lot of activity. The Environmental Protection Agency’s Energy Star programs now extend to foodservice reach-ins, fryers, hot holding cabinets and steamers. The California Energy Commission is setting requirements for more categories of equipment every year. ASTM Int’l. currently has standardized test methods on the books for more than 30 categories of foodservice equipment.

Utilities are now such a big deal for operators, in fact, that the National Restaurant Association’s annual survey of concerns now puts energy at the top of the list. When has that ever happened before? Never.

With all this in the background, we figured it was a good time to take a hard look at warewashers. As a category, they’re huge users of utilities, gulping water and the energy to heat it in vast quantities, not to mention the load they create for direct ventilation and HVAC systems. We wondered how warewasher makers were responding to the new cost pressures

So we went where we always go for such projects, Pacific Gas & Electric’s Food Service Technology Center in San Ramon, Calif. We pitched Don Fisher, of Fisher-Nickel Inc., the consulting firm that operates the FSTC. Could the FSTC team help us set up a group bench test? For that matter, could the FSTC invent such a test, considering no standardized warewasher test for utility efficiency yet existed? Never one to pass up an interesting experiment, Fisher took about two seconds to say yes. Todd Bell would run the program, assisted by Dave Zabrowski.

Undercounters would be the category, we all agreed. Several new, more efficient models were hitting the market, and besides, undercounters were much easier to ship to the lab than, say, 44” conveyors. In the end, four manufacturers jumped on the opportunity to get third-party data in a new kind of test.

Starting Where NSF Leaves Off

NSF Int’l. had already tested the units to certify they delivered the proper amount of energy to the rinse water and the dish for a proper 180°F sterilizing rinse, so the FSTC didn’t need to reinvent that wheel. And unlike most ASTM test methods born at the FSTC, this one wouldn’t measure throughput, again because NSF has its own such measurements.

The focus here, instead, would be on a kind of typical usage, and the costs involved with gas, electricity and water consumption. Determining exactly what to measure, and how, was an exhausting process. Scores of details had to be considered and second- and triple-guessed.

Without wearing you out with the minutiae, the test would delve into preheat time, preheat energy, idle energy rate, wash energy rate, wash cycle time and water consumption in gallons per rack and total. The gas heat for the building’s central water supply, which delivered 140°F water, would be included. With some estimates of typical usage in the field, annualized costs could be projected.

The test method itself began with providing 140°F supply water from the building’s gas heater, which produced said water at a rate of about 142 gals./therm. Then came preheating each warewasher and “running one empty rack through the factory-set wash cycle to stabilize the wash compartment temperature,” project engineer Todd Bell said. “After the empty rack was removed and the water tank heating elements had cycled off, the first rack of plates was loaded.”

Racks were 20” x 20” peg types, each loaded with 10 clean plates, 9” glazed ceramics weighing 1.3 lbs. each, give or take less than an ounce. Each rack was run through the full wash cycle, with four minutes between each rack for typical loading, unloading usage. In all, 10 racks would be washed in each set. After the last rack was removed, and the wash tank heating elements cycled off, indicating the thermostat’s set temp was restored, time, energy and water consumption were measured. For each washer tested, the process was repeated three times to assure reliable data. In addition, idle-test data were collected over three-hour idle periods.

A 40% Spread

And the results? All four undercounters handily outperformed comparable units from just a few years ago. The bar chart in this story clearly shows the overall cost data. Model A costs about 10% less in water and energy than its nearest competitor. And Model D brings up the rear, fully 41% more expensive than the pack-leading Model A and nearly 27% more costly than the third-place finisher.

But as always, digging a little deeper reveals more interesting bits—more interesting in the sense that there’s much to be learned about how different designs have different strengths and weaknesses.

Water Matters

At the risk of saying what seems obvious, water consumption is a critical design focus. Yes, it matters because water and sewer charges are shooting upward like so many Roman candles. In fact, a look at the chart will show you how water costs in this test compared to the gas costs for preheating the incoming water—the water costs are more than 60% as high as the gas bills.

But the more important reason water consumption matters is that it drives the gas and electrical usage. More water per rack means more gas for preheating and more electricity for pumping and in-tank heating. The particulars vary depending on local utility rates, of course, but the correlations are important everywhere.

Tank Heat Costs Money

What’s glaringly apparent in this test is that tank heat is mucho expensive, and you want to pay attention when you’re specifying warewashers. In the test scenario, electrical costs consistently account for more than twice as much as gas plus water combined. That means electrical runs 65% to 70% of the total utility bill for these diminutive units. In some parts of the country, like in the Southeast, for example, where electricity is relatively cheap, the ratios will be different. But even there, the juice will run as much or slightly more than gas and water combined.

Accordingly, it appears the engineers at three of the four manufacturers have done their level best to optimize electrical efficiency. Model C manages to heat 3.67 gals. per kWh, while Model B’s close at 3.22. Then the overall champ comes in third at 2.88 gals. per kWh. All in all, a fairly competitive spread.

But the big surprise—make that disappointment—in this test was Model D’s electrical usage. Put plainly, it wasn’t in the same league. How could the water-sippingest washer in the bunch use so much electricity? Testers suspect a reservoir that was larger and shallower than the others’. That meant it had more surface area for its volume, more surface for heat loss. That, combined with smaller heaters, led to a cycle time that was virtually endless. If the engineers take a second look at that part of the design, they should be in good shape. The water and gas data are already class winners.

Annual Projections—Your Mileage May Vary

After the data were collected, the team had to decide how to turn the whole works into annual consumption rates. Out in the field, hours of operation range all over the board, so it’s hard to pinpoint a profile.

For projection purposes, the FSTC decided to assume a longish day, 18 hours, knowing full well that many operators would adjust that assumption but needing some standardized starting point. These undercounters typically are used in not-so-high volume applications, so the group settled on 75 racks per day (roughly four per hour) as a round guesstimate for test purposes.

And idle time? Most undercounters are left on in between runs, some only sporadically and some all day long. This projection would assume the units are turned on and left on. The whole works would then be multiplied by 360 workdays in a year.

All of which means your mileage may vary, but at least you can see the component data and adjust your own assumptions. In this test format, for example, a lot of idle time is involved, which is why Model D’s high idle rate is such a killer. Idling at 1.2 kW, it’s sucking more than 2.5 times as much energy as the closest competitor’s 0.44 kW rate.

Conversely, if your washer doesn’t spend all day idling, water-per-rack is the big priority, in which case Model D moves to the top slot by a clear margin.

Eventually, Bell says, the FSTC will probably put some kind of warewasher calculator up at www.fishnick.com to go with the ones already there for fryers, ovens and steamers, so you can plug in your own variables and make your own calculations. But for now, you can do it the old-fashioned way—with a hand-held calculator and a pencil.

And remember—utility costs will only go up.