The Impact of Blowing Agents on Residential Water Heater Performance

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The National Appliance Energy Conservation Act of 1987 (NAECA) requires the U.S. Department of Energy (DOE) to consider amendments to the energy conservation standards to increase energy efficiency in residential water heaters. A driving force affecting efficiency is the ozone-depletion regulation regarding blowing agents for insulation in all water heater fuel types. This paper presents results of cost and efficiency impacts of three potential blowing agents. Residential water heaters are typically insulated with polyurethane foam in the space between the tank and the jacket. Currently, water heater manufacturers use HCFC-141b, an ozone-depleting substance, as a blowing agent. After 2003, as a result of the Montreal Protocol (1993), manufacturers must use blowing agents that do not deplete the ozone layer. The analysis presented in this paper considers three replacement candidates, HFC-245fa, HFC-134a, and cyclopentane by comparing their efficiency and cost effectiveness when applied to water heater insulation. This analysis used computer simulation models and other analytical methods to investigate the efficiency improvements due to different design options, when alternative blowing agents are applied. The calculations were based on the DOE test procedure for residential water heaters. The analysis used average manufacturer, retailer, and installer costs to calculate the total consumer costs. Consumer operating expenses were calculated based on modeled energy consumption under test procedure conditions and U.S. average energy prices. With this information, a cost-efficiency relationship was developed to show the average manufacturer and consumer cost to achieve increased efficiency.

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