I Page 20 RAIN April 1981 damaged by freezing temperatures. Unless you live in a very mild climate, the obvious solution is to put the heat pump inside your house. The problem with this approach is that the heat that goes into your hot water is being taken from someplace else. A standard size heat pump water heater can drop the temperature in a heated 12' x 10' x 8' room by about 10°F (6°C). If you live in an area with a cooling load, that may be an advantage part of the year. In most areas, it is a definite drawback. Incredibly, at least one major manufacturer is recommending inIn real life, however, solar systems have not always done as well as they are supposed to. stallation in a heated space, claiming that the heat pump will utilize only " waste heat" from people, lights, and appliances. Needless to say, there are many cheaper and easier ways to utilize that " waste heat" than putting what amounts to a large air conditioner in your house in the dead of winter. From an energy standpoint, the whole concept is slightly warped. With the exception of the Pacific Northwest, most electrical utilities get their power from thermal plants that are a little over 30% efficient. In such a situation. a heat pump water heater operating at a COP (see box) of about 2 (which is the standard average COP being thrown around these days) has a total end use efficiency of around 60% . But if the heat source is an oil, gas, or wood furnace operating at an efficiency of 75%, the total system efficiency is about the same as that of a regular resistance water heater. Any dollar savings are strictly a result of the fact that gas and oil are cheaper fuels than electricity in most parts of the country. A similar situation exists in homes that use electric space heating. Although this is less of a problem where utility grids are based on renewable energy sources, such as hydro, the total end use efficiency is still conside.rably less than it should be to make heat pump water heaters cost-effective options. What that means is that heat pump water heaters are best installed in a ventilated, unheated, insulated area, such as a crawl space or unheated basement. Their efficiency is less than ideal under these conditions, but utility tests have i ndicated that an annual average COP of two can still be expected in mild climates. Since that space cannot be allowed to freeze, it appears that heat pump water heaters will find their fi rst effective applications in the Southern Tier and states along the Pacific Rim. One manufacturer is in the process of developing a design that is suitable for colder cfunates as well . If successful, heat pump water heate.rs could become a practical alternative nationally, although the cold weather designs can be ACCESS: HEAT PUMP WATER HEATERS Energy Utilization Systems 365 Plum Industrial Court Pittsburgh, PA 15239 EUS has been heavily involved in the development of the current generation of heat pump water heaters. Their heat pump is unique, consisting of an integral water tank with the condenser heat exchanger sitting directly inside the tank. Other manufarnlfers pump water from the tank to a separate unit. The EUS design has the advantage of being slightly simpler and more efficient, since no pump is required. It is also harder to service, and is only suitable for new, permanent installations. Whether or notthe EUS approach is a sound one remains to be seen. One point of debate among heat pump wate.r heater manufacturers is whether the heated water should be returned at the top or the bottom of the tank. A tank that is heated from the bottom will have more uniform temperatures, which means that more hot water is available at any given time. It also means that recovery time is much slower once the hot water has been used up. A resistance backup may be required under these circumstances. A top-heated tank has a faster recovery, but will tend to stratify. If the tank is undersized, there may not be enough hot water available during peak usage (this can be a problem with s'ome one-tank solar systems as well). EUS and Oregon heat pumps heat the water from the bottom. The other units heat it from the top. The one you choose should reflect your hot water consumption habits. EUS is marketed unde.r the lTade..oame " Temcor. " E-Tech 3570 American Drive Atlanta, GA 30341 E-Tech was another early pioneer in the field, and most other manufacturers have modeled their units after the E-Tech design. E-Tech tends to be at the low end of the price range for heat pump water heaters, and their units proved to be slightly more reliable than the EUS units during initial utility test programs. Real life test results from other heat pump manufacturers are not yet available, and it may be a while before we know how they all compart E-Tech originally recommended using flexible plastic hose to hook up the unit to the tank. This proved to be a disaster, and E-Tech now recommends (as all manufacturers should) that the unit be hard plumbed to the tank. E-Tech is marketed under the name "Efficiency II." Fedders Woodbridge Ave. Edison, NJ 08817 Fedders is out to become the Chevrolet of the heat pump water heater world, and has launched an aggressive sales campaign to match. Their unit is relatively expensive, and their instructions include a number of fascinating suggestions, such as disconnecting your auxiliary water heater and putting the heat pump unit in your kitchen. We'll see how It wor.ks out. Fedders is marketed under the Pedders, AtrTemp, and Climatrol brand names. Oregon' 5 emphasis is on quality. The company is small, and each unit is hand assembled, with a lor of attention to detail . Oregon is currently the only manufacturer with plans to market different designs to meet the needs of. different climatic regions. They also offer the only heat pump water heater with freeze protection, although it won't work if there is a power failu re . The quality is reflected in the price, and Oregon water heaters are by far the most expensive around. They are likely to remain indige nous to the Northwest for quite some rime, but plan to eventually expand to a national ma rket. Northrup, Inc. 302 Nichols Dr. Hutchins, TX 75141 Northrup recommends an inside installation, with the suggestion that the cold air be ven teQto the outside during the heating season. They fail to point out that the air that is being dumped outside has to be replaced somehow, and that the effect is to increase infiltration into the house from the cold outside air. While there may be a slight gain in comfort, there is no gain in efficiency. As of this writing, the Northrup unit is not yet on the market. alt.hough it should be available soon. Oregon Water Heating Heat Pump 8190 SW Nimbus Ave. Progress, OR 97223
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