Summer months in the food preparation area at Hospital Food Services (HFS) of Ottawa, Ontario, Canada, once resembled a steam bath more than a work area. With ovens still warm from baking, relative humidity (rh) levels typically surpassed 90% during daily washdowns.

HFS provides 16,000 lbs of finished food product daily for 140 local hospitals within the province of Ontario from its 48,000-sq-ft food processing plant. In its quest to improve employee comfort levels and reduce maintenance costs associated with high humidity, HFS enlisted the help of Ottawa-based consulting engineering firm, Clemann, Large, & Patterson (CLP), mechanical contractor, Carmichael Engineering Ltd., and indoor air quality manufacturer, Dectron Internationale (Roswell, GA).

An easy solution would have been the installation of a simple commercial dehumidifier. However, George Matrahazy, a CLP senior mechanical design associate, specified an hvac system that not only dehumidifies to the necessary 50% rh and air conditions to temperature setpoints of 70°F to 76°, but can also heat up to 280 gal of hot water/hr (200 gal/hr in dehumidification mode) at no extra cost from a unique energy-recovery process.

"It reclaims all of the heat from the compressor, all the heat from cooling, and all of the heat from dehumidification, to provide free heat for a lot of hot water - a good approach and clients always like it when a mechanical engineer can save them money," said Matrahazy.

Total Energy Recovery

Packaged into one rooftop unit that was custom-manufactured by the ThermoPlus Air division of Dectron Internationale, the WaterWise AC® is the first product in the hvac industry to provide air conditioning dehumidification and free hot water heating as a result of total energy recovery from the refrigeration cycle.

"I'd like to see manufacturers innovate more products like this that take the heat generated by the refrigeration process and reclaim it economically for other uses," said Matrahazy, who was first approached with the WaterWise AC idea by manufacturer's representative, Chris Harrison, Longhill Energy Products (Ottawa).

"Besides the intended benefits of reduced humidity and free hot water, I also like the fact that there's less mist, which makes the area much easier to clean and maintain," said Christien Rochon, HFS's maintenance manager. "Although we've never had mold or mildew problems, the possibility of them occurring now are remote, too."

The combination of air conditioning with free hot water presents marketing opportunities to contractors with clients that experience high humidity levels and consume large amounts of domestic hot water such as hotel laundries and restaurants, according to Chris Smith, sales, Carmichael Engineering Ltd.

For example, a WaterWise AC unit that delivers approximately 10 tons of cooling can also heat 2,500 or more gal of hot water/day. "You're reaching your goal of providing air conditioning or reducing humidity, but you're also reducing your client's operating costs by adding the free hot water factor," said Smith, who believes the WaterWise AC will give him a competitive bidding edge on suitable applications.

Controlling humidity was the top concern in HFS' 500-sq-ft wash-down area where Canada's very first Douglas walk-in pot cleaner pressure washes the day's cooking accessories. A Honeywell (Apple Valley, MN) humidistat activates the dehumidification function on the WaterWise AC.

Ductwork corrosion was a concern for Carmichael Engineering, which ran specially fabricated aluminum duct wrapped in 1-in.-thick insulation with aluminum vapor barriers to prevent premature condensation as the return air flows to the rooftop WaterWise AC. The supply air runs through conventional galvanized sheet metal ductwork.

The Savings Go On And On

Air conditioning is equally important in the improved employee comfort process because the WaterWise AC's 10-ton air conditioning capacity lowers heat levels caused by four large Europa baking ovens and several commercial stovetops.

But the added benefit of the whole process is the free hot water heating. Once the water is heated, it's collected into an 80-gal A.O. Smith, (Irving, TX), (TS-80) storage tank and eventually added to the building's domestic hot water piping loop.

The 20-year-old HFS has significantly improved employee comfort levels and also saves an estimated $7,000 annually by heating a significant amount of the thousands of gallons of domestic hot water it uses daily. The savings will pay for the premium on the equipment in less than 18 months. ES