QUESTION: I have heard about an electric water heater that can help air-condition and dehumidify my house. What is it, and is it very energy efficient? Can I attach one to my present water heater tank?
ANSWER: You are referring to heat pump water heaters (HPWH) and they are very energy efficient. They are designed to draw heat from the surrounding room air and transfer it to your water heater tank. They can produce water at 140 degrees, hot enough for all household needs.
Some HPWHs can operate at a coefficient of performance (COP) above three. This means that you get three BTU of heat into your water for each one BTU's worth of electricity you pay for. Depending on your local utility rates, the operating cost for a HPWH can compare favorably with a gas water heater. You also get the bonus summer air-conditioning.
An HPWH works very much like a small window air conditioner. Instead of exhausting the heat outdoors, it is transferred through a heat exchanger to your hot water tank. This leaves the room air around the HPWH cool and dry. A low-voltage wire from the tank thermostat signals the HPWH to come on when more hot water is needed.
There are two types of HPWHs, integral and add-on. The integral type has the heat pump mounted on top of the tank. The add-on type is designed to be used with your existing water heater tank. Both types offer a hot-water production rate higher than most standard electric water heaters.
The small add-on HPWH (less than two feet wide and high) offers the advantage of being located remotely from your water heater. Therefore, you can locate it in a room or area that you want to cool and dehumidify. This can be a family room or a musty basement, for example.
In the winter, when you don't want to cool your living space, you can locate the HPWH near a furnace, wood-burning stove or in a utility room. There it draws its heat from excess waste heat around these heat generating appliances. A lot of heat is generated when washing and drying clothes.
If your building codes allow and you are familiar with tools, you can easily install an add-on HPWH yourself. Some of the do-it-yourself installation kits include a special coaxial water fitting.
You just remove the drain valve from the bottom of your water-heater tank and screw in the coaxial fitting. This carries cold incoming water to the HPWH. Hot water from the HPWH follows back into the tank through the same fitting. Since the hot water is less dense and the fitting is specially designed, the hot water naturally flows to the top of the tank.
You can write to me for Utility Bills Update No. 106, listing the manufacturers of add-on and integral HPWH's, hot-water output specifications, and a work sheet to determine the pay-back of installing a HPWH. Please include $1 and a self-addressed stamped business-size envelope. Send your requests to James Dulley, c/o Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.
Foam Insulation Best for Windows
Q: I am having new replacement thermal windows installed in my house. The contractor said he would put insulation in the gap around the window. What is the best type of insulation to use?
A: Expanding foam insulation from a can is the best type of insulation. It not only insulates, but it also seals out all air leakage. Stuffing fiberglass insulation in the gap helps, but air still leaks through.
Make sure the contractor is familiar with foam insulation so he doesn't overfill the gap. It can expand too much and bow the window frame.
Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.