Forum considers better uses of hot water

BERKELEY, CALIF. — There are plenty of sexy water heating products out on the market and then there are the ones that really sell. Approximately 7.5 million tank type water heaters are sold in the U.S. every year, about half and half gas and electric. Fortunately, for consumers’ wallets and the country’s energy picture in general, the sexy stuff is slowly gaining ground.

Manufacturers, contractors, government officials, utilities and academics gathered here to talk about how to make the sexy stuff more attractive at the American Council for an Energy Efficient Economy’s 2011 Hot Water Forum.

From a small base, sales of tankless water heaters are growing 10% a year, said Mike Parker, vice president of marketing and strategic planning for A.O. Smith. Sales of high-efficiency Energy Star-rated residential storage water heaters are projected to hit a million units by 2013, up from about 800,000 this year.

Approximately 33,000 heat pump water heaters will be sold this year and, perhaps, 49,000-50,000 in 2012, which is faster than A.O. Smith had expected, Parker said. Approximately 130,000 square meters of solar collectors for swimming pool heating will be sold in 2012, totaling 34,000 residential installations in that year.

As sales of newer and different technologies increase, Energy Factor becomes even more useless than what Harvey Sachs, senior fellow in ACEEE’s Buildings Program, said it is today. The National Appliance Energy Conservation Act requires the use of EF as a measurement of water heater efficiency. EF can’t be used to compare commercial products, Sachs said. It can only be used to compare conventional tank-type units. It measures six equal draws at 135°F, a temperature heat pump water heaters can’t reach. Moreover, different regions have big differences in entering water temperature and different households have different needs.

All of these considerations are being looked at jointly by Air-Conditioning, Heating & Refrigeration Institute, the National Institute of Standards & Technology, and the Standard 118.2 Committee of the American Society of Heating, Refrigerating & Air-Conditioning Engineers.

The replacement for EF that might emerge could consider parameters such as steady state efficiency, standby losses and thermal decay, number of people in a household, and cold vs. moderate incoming water temperatures.

Hot water is important in terms of energy policy, said Gary Klein, managing partner of Affiliated International Management LLC, Sacramento, Calif., because it’s 50 times more energy intensive than cold water. Hot water usage is influenced by structural and behavioral factors, Klein noted, and while we can’t do a whole lot about people’s behavior, plumbing and heating practitioners can do a lot about the structural problems.

While the heat sources and the piping may differ, the overriding concept is to deliver hot water quickly, in two to three seconds, in the minimum quantity needed to do the job, and to minimize the amount of water wasted waiting for hot water to arrive and minimize the energy loss of unused hot water cooling in the pipes.

Given the energy ramifications of hot water use, the forum considered whether some applications need hot water or as much hot water as they have been given.

Andrew Flanagan, P.E., LEED AP, with Mazzetti Nash Lipsey Burch, said hospitals use about 504 gal./bed/day, according to a 2002 survey by the American Society of Healthcare Engineers. Hospitals’ main concerns are safety of patients and staff, cost of ownership, including operation and maintenance, and sustainability.

A great deal of DHW use is process, such as janitorial, sterilization or food prep. Patients and staff use hot water for hand washing, showers, emergency face-wash, and food and medicine prep.

Hospitals are required by code to have plenty of hot water, Flanagan explained, but a great deal of that capacity is not used. Hospitals don’t do laundry anymore; they send it out. Patients rarely shower. In today’s healthcare climate, if a patient is well enough to get up and shower, he’s sent home.

Hand washing is 28% of peak usage in a hospital but hot water isn’t necessary for sanitation. Washing hands for 20 seconds to remove fats and oils that are a food source for bacteria does the trick. With long pipe runs in many hospitals, the nursing staff is already washing its hands in cold or tepid water.

Because the ideal temperature for Legionella bacteria to flourish is 90°F-108°F, Flanagan questioned whether large central boilers or water heaters for DHW are really necessary. Incoming water could be heated to 65°F just with waste heat, then boosted to 75°F at the fixtures. In an emergency, a person can shower in 75°F water. Small tankless heaters in patient bathrooms could heat water for showers.

As a result, the hot water recirculation system could be replaced by single pipe distribution. Assuming 50°F incoming water temperatures and a load of 110-GPM heated to 120°F as typically seen with hospital central plants, a single pipe distribution system tempered by heat recovery and heated as needed with tankless units would cut a hospital’s DHW load by 57%, Flanagan said.

Eliminating hot water may not be an outlandish concept. Dave Kruse, president of L.J. Kruse Co., Berkeley, Calif., and a past president of the Mechanical Contractors Association of America, told CONTRACTOR that his firm had worked on a medical office building where the doctor had initially said that he didn’t want hot water. Plumbing codes that require hot water squelched that discussion.

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