ENERGY STAR REPORT
Warewashers Welcome The íStar
By Mike Sherer
An obvious energy target, one using a lot of fuel and losing a lot of it in the form of heat gain, warewashers had to be addressed sooner or later. In October 2007, just in time for the North American Association of Food Equipment Manufacturersí NAFEM Show in Atlanta that year, Energy Star finalized its specs for commercial warewashers.
The fourth equipment category to get the nod from Energy Star, warewashers was another category that was tough to wrestle with due to its wide variety of types. The warewasher standard covers four types of dish machinesundercounter; stationary, single-tank, door-type; single-tank conveyor; and multiple-tank conveyor.
Start With Standard 3
Warewasher ratings and performance start with NSF/ANSI 3, or NSF 3 for short, the standard required by most local health codes. Standard 3 sets the parameters for wash- and rinse-water temperatures, chemical-sanitizer concentration and so forth. Energy Star simply sets the bar for how efficiently warewashers meet those NSF standards.
Standard 3 says proper sanitation requires dishes to be exposed to enough hot water in the final rinse to deliver at least 3,600 "heat-unit equivalents" to the surfaces of the dishes, which means raising their temperature to 165°F for 10 seconds. In essence, the temperature of your sanitizing rinse water should be at least 180°F when it leaves the manifold to accomplish that.
Since most facility water heaters raise the temperature of incoming water to about 140°F or less, dishwashers usually need a booster heater to raise final rinse temps to 180°F. Booster heaters often are separate from the warewasher, and for that reason, Energy Star doesnít really address them. Instead, Energy Star is only concerned with the onboard heater that raises wash-water temps up to about 160°F in high-temp machines.
Hence the challenges in creating the standard began. The Environmental Protection Agency also wanted to take into account both energy use and water use in determining a level of efficiency that would set the bar high enough.
Measuring WaterTo Measure Energy
Energy Star performance standards are based on two criteria: a machineís rate of energy use when idle and its water consumption in gallons per rack. The latter measure also indirectly gets at overall energy efficiency, since most of the energy used by the machine when itís in use is to heat water (which it also does when idle), with the remainder used to pump that water through spray arms that clean your dishes.
Energy Star also had to take into account the fact that there are both high-temp and low-temp machines on the market, i.e., those that use a hot-water sanitizing rinse and those that use a chemical sanitizer. So they developed two sets of criteria to account for that difference. And machines designed to be interchangeable in the field from high temp to low temp (and vice versa) have to meet efficiency standards for both types to qualify.
As with most Energy Star equipment categories, standards had to wait until test methods were developed to accurately measure energy usage and efficiency. The team at Pacific Gas & Electric Co.ís Food Service Technology Center in San Ramon, Calif., answered the call, developing test methods for single- and multiple-rack conveyor machines. Once those standards, F1696 and F1920, were approved as standard test methods by ASTM Intíl., manufacturers and Energy Star were able to compare apples to apples.
The resulting requirements to qualify as Energy Star are listed in the table.
Saving Big Money
Energy Star estimates that each qualified commercial dishwasher can save businesses about 90 MBtus in energy over "average" warewashers, or an average of $850/year on energy bills. In addition, businesses can expect to save more than $200/year and 52,000 gals./year of water due to more efficient designs that lower water consumption.
Like other Energy Star qualified equipment, warewashers that have earned the Energy Star label are usually in the top 25% in terms of efficiency. And in this category, that means use of both energy and water.
Visit www.energystar.gov/index.cfm?c=comm_dishwashers.pr_comm_dishwashers for a list of qualified models.