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Tankless Water Heaters Can Provide Big Savings

September 26, 2012 - HVAC

Today's tip is to consider tankless water heaters for energy savings. Water-heating systems in institutional and commercial facilities typically consume more energy than any other system except HVAC. As a result, even small gains in efficiency can lead to large savings.

More manufacturers are offering a range of new tankless water heaters — also known as instantaneous or demand systems — that provide hot water only when necessary.

Tankless water heaters use highly efficient technology to transfer heat instantly to cold water as soon as demand occurs. When a building occupant turns on a hot water faucet, cold water enters the inlet of the tankless heater and flows through a copper coil, energizing the burner to provide temperature-controlled hot water.

Fueled by propane or natural gas, tankless water heaters offer operating costs that are 30 percent lower than natural gas storage-tank units and 40 percent less than electric storage-tank units. They also require less space, and stored water does not have to be reheated.

An electronic ignition lights the gas burner without a pilot light, so no gas is consumed when the system is dormant.

The typical capacity of a tankless water heater is 2-5 gallons per minute. For larger-capacity systems, a manifold arrangement links units. Condensing technology captures any exhaust gas heat and returns it to preheat incoming cold water, thereby increasing thermal efficiency to as high as 98 percent.

One new electric coilless, tankless heater comes with a rating of 2.5 gallons per minute at a 45-degree temperature rise or 1.7 gallons per minute at 65-degree temperature rise. Voltages for tankless water heaters range from 110 volts to 277 volts.

The necessary size of a unit depends on the user’s water flow and the required temperature rise. Typical utility water is 60 degrees, and the typical desired temperature for hot water is 100-120 degrees. In this case, the temperature rise required would be from 40 degrees to 60 degrees. If the water heater serves a kitchen sink with a water flow of 1.5 gallons per minute, then the heater's required capacity is a maximum of a 60-degree rise at 1.5 gallons per minute.


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