Page 144 - WaterSense at Work

4-50
October 2012
4.10
Commercial Dishwashers
Equation 4-22. Water Use of Commercial Dishwasher (gallons per year)
=Water Use per Rack x RacksWashed per Day x Days of Facility
Operation
Where:
••
Water Use per Rack (gallons per rack)
••
Racks Washed per Day (racks per day)
••
Days of Facility Operation (days per year)
Water Use After Replacement
To estimate the water use after replacing an existing commercial dishwasher with an
ENERGY STAR qualified commercial dishwasher, use Equation 4-22, substituting the
water use per rack washed of the new machine. ENERGY STAR specifies maximum
water consumption rates per rack for undercounter, stationary single-tank door-,
single-tank conveyor-, and multiple-tank conveyor-type machines.
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Water Savings
To calculate water savings that can be achieved from replacing an existing commer-
cial dishwasher, identify the following and use Equation 4-23:
••
Current water use as calculated using Equation 4-22.
••
Water use after retrofit as calculated using Equation 4-22.
Equation 4-23. Water Savings From Dishwasher Replacement (gallons per year)
= Current Water Use of Dishwasher –Water Use of Dishwasher After
Replacement
Where:
••
Current Water Use of Dishwasher (gallons per year)
••
Water Use of Dishwasher After Replacement (gallons per year)
Payback
To calculate the simple payback from the water use associated with replacing an
existing commercial dishwasher, consider the equipment and installation cost of the
ENERGY STAR qualified commercial dishwasher, the water savings as calculated in
Equation 4-23, and the facility-specific cost of water and wastewater.
ENERGY STAR qualified commercial dishwashers also use less energy due to lower
idle energy rates and a reduction in the use of hot water. This energy savings will
further reduce the payback period and increase replacement cost-effectiveness.
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EPA and DOE’s ENERGY STAR. Commercial Dishwashers Key Product Criteria,
op. cit.