Water Heating: It's a Gas

Sometimes, energy savings alone can dictate the replacement of an older, inefficient building component. That has been the experience at Prince Haven, a 50-unit residential complex for the elderly located near Plymouth, N.H.

Built in the late 1970s, each of the 10 buildings on the property received a supply of domestic hot water from its own commercial water heater. Until recently, these units were 50-gallon electric models—the building's original equipment. Installing electric-powered water heaters made sense 20 years ago because of the low electrical rates in New England. But times, and energy rates, have changed.

The property managers decided to replace all 10 units with new, 80-gallon liquid-propane gas units. Even though the goal was lower energy costs, this new installation actually increased heater tank-storage capacity by 60 percent. It was calculated that the community could increase the supply of hot water, while still providing an economical heater that would consume less energy.

Because the previous heaters were electric, no chimneys were available to vent the byproducts of the new heaters' gas-combustion process. Some type of direct-vent water heater was in order.

The issue was resolved as the particular heaters installed featured a power direct-vent design that draws fresh makeup air directly from the outside, while moving combustion gases to the exterior. Movement of the intake air and exhaust gases through the dual-pipe system is powered by an integrated blower.

The units, which burn up to 20,000 gallons of propane annually, are expected to provide a major reduction in fuel costs, generating sufficient enough savings to pay for themselves within two years.