As I have learned over the years I have been publishing Green Lodging News, the kitchen can be a hub for inefficiency. Leaky freezers, fans that don’t stop running, and wasted food are just a few examples. Of course the kitchen is also a place with plenty of potential for significant water waste. Where there is a faucet, there is waste just waiting to happen. This past week I posted an article about a study that was conducted by Pacific Gas and Electric Company Food Service Technology Center (FSTC). The study, entitled “Conveyor Dishwasher Performance Field Evaluation Report,” documents the energy and water savings and economic benefits of replacing an old inefficient dishwasher with a new efficient or best-in-class dishwasher. The study also highlights how dishwashers become less efficient over time and how many dishwashers (at any age) fail to operate to their design specifications. When was the last time you had your dish machines checked to see if they are operating as they should?
For the study, the folks at FSTC included performance data from 18 dishwashers. One of the testing sites was the Claremont Hotel, Club and Spa in Berkeley, Calif.
The normalized results from 18 sites showed roughly a 70 percent reduction in water and 55 percent reduction in energy use by replacing old conveyor dishwashers with new high-efficiency models. Specifically, the water use of the average conventional rack conveyor, at 691 gallons per hour of rinse operation, was reduced by 65 percent when replaced by an average high-efficiency unit, using 261 gallons per hour. Similarly, the energy use was reduced by roughly 55 percent. The water savings from flight conveyor dishwashers was even greater—representing a reduction of 75 percent. Water use of the average conventional rack conveyor, at 1,115 gallons per hour of rinse operation, was reduced to 267 gallons for the average high-efficiency unit. Similarly, the energy consumption was reduced by 55 percent. Impressive savings!
Less Water Equals Greater Savings
Old inefficient conveyor dishwashers were replaced with Energy Star qualified high-efficiency models at four sites. The average cost savings per site based on average California utility rates was approximately $22,000 per year. In each case, the cost savings were driven by the substantial reduction in water use.
For my article, I spoke with Amin Delagah, Research Engineer IV, Fisher-Nickel, Inc. (operator of FSTC). He told me, “Older machines do not have good diagnostics. A lot of these machines can become really inefficient. Malfunctions don’t get caught.”
On an average day, the flight conveyor at the Claremont Hotel, Club and Spa used 6,018 gallons of water. Tanks fills, for the most part, were not close to the manufacturer’s specifications. Daily water waste over the period ranged from zero to 4,916 gallons per day. The dishwasher averaged 4.9 tank fill and dump operations per day with an average fill of 477 gallons which is 3.5 times more than equipment specifications. Rinse water use was 8.6 gpm which is 50 percent over the manufacturer’s specifications at 5.6 gpm. There were other problems with the machine as well.
Studies of the dish washing machines at the Claremont Hotel, Club and Spa and the other sites demonstrated that model specifications, according to FSTC, “were a crude way to estimate real world water use.”
Don’t Go By Printed Specifications
The research showed that old conveyor dishwashers consume two to three times more water than was predicted based on the rated rinse flow and tank volume specifications. High-efficiency conveyor dishwashers used 70 percent to 85 percent more than the rated specifications.
In its research, FSTC found that facility operators oftentimes will perceive that the operating time of their machine is higher than it actually is, leading to the oversizing of new machines—again, more waste.
“A lot of these facilities don’t need the machines they are using,” Delagah says.
Inefficiencies found during FSTC research also emphasize the need for proper machine maintenance in order to eliminate water and energy waste. The study also found that oftentimes machines are not used properly. Placing back of house wares in machines not meant for them can lead to additional water waste.
The Importance of Submetering
Delagah says that to better document actual water and energy consumption, you should really be submetering your dish machines. “Technically, it is not very difficult to submeter,” he says. “It allows the facility to keep up to speed on the operation of the machine by identifying maintenance issues and when staff training is appropriate to get back to the benchmark operating parameters documented when the machine was commissioned.”
Alternatively, FSTC encourages the purchase of smart dishwashers that minimize water and energy use while having integrated water and energy meters and logging and communications hardware.
Be sure to read the FSTC study for additional suggestions on how to better monitor and operate rack and conveyor dishwashers. Also be sure to watch for an article here soon on the latest smart machines available from suppliers of rack and conveyor dishwashers.
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