Installing a heat pump
can cut bills in half

Q: Dear Jim: I have an electric furnace and I am thinking about installing a heat pump. What is new in heat pumps and which are most efficient and comfortable! - Ray W.

A: Dear Ray: Heat pumps have unfairly gotten a bad reputation over the years. From both reliability and comfort standpoints, new heat pumps are an excellent and efficient source of heating and cooling. Installing one can cut your utility bills by more than half as compared to your electric resistance furnace. The most efficient heat pumps can produce $3 of heat for each $1 on your utility bills.

With gas, propane and oil prices increasing, installing a heat pump with a furnace may make good economic sense. During mild fall and spring weather, a heat pump can heat your home less expensively than a gas, propane or oil furnace. When the outdoor temperature drops, making the heat pump less efficient, the system automatically switches to the furnace.

A heat pump works as a central air conditioner when cooling. The cooled refrigerant flows through the coils in the air handler (blower) inside your house. This absorbs heat from the house air and pumps it to the outdoor unit. There, the very hot refrigerant gives off heat to the hot summer air.

When in the heating mode, the heat pump works to warm the house by switching the reverse valve. This draws heat out of the cool outdoor air, which, along with the compressor energy, heats the refrigerant. The hot refrigerant flows into the coils in your blower and heats your house air. As the weather gets colder, it is more difficult for the heat pump to draw heat from the outdoor air, so the backup electric resistance, propane or oil furnace must come on to keep the house warm.

There are many new heat pump models and options to select from depending on your needs and your budget. The most efficient heat pumps are also the ones that provide the best heating comfort and indoor air quality. Since a heat pump is used year-round for conditioning the air, you will get the same benefits during the summer in the cooling mode as well.

18 | Illinois Country Living | www.icl.coop

The most efficient heat pumps use compressors, which produce two output levels of heating and cooling. These heat pumps run at a low-output mode the majority of the time. Running a heat pump at the efficient low-heat output is an advantage because it runs for a longer time period each cycle. By running longer, it keeps the room temperatures more constant and improves the indoor air quality. This is a plus for allergy sufferers.

Most two-level heat pumps use a variable-speed blower motor in the indoor air handler. When the heat pump is running at low level, the variable-speed motor slows down. This reduces the noise level and eliminates the gust of cool air each time it starts. The slower blower speed minimizes the common "chilly" feeling with a heat pump because the air coming out is warmer.

There are several two-level compressor technologies used. The newest designs are two-stage scroll compressors. These have few moving parts and eliminate the need for pistons, valves, etc. used in standard compressors. They operate quietly and reliably. At the low-level, they produce about 65 percent of the high-level heat output.

Other two-level compressors use conventional piston designs which at low-level provide about 50 percent of the maximum output. In some two-cylinder designs, only one piston works when the compressor rotates in one direction, but both pistons work when it rotates in the opposite direction. Another design uses two smaller compressors and either one or both run.

For homeowners on a budget or if the ultimate comfort is not a top priority, installing a single-output-level heat pump with a scroll compressor is a good choice. This is the type of heat pump I use in my own all-electric home. Even though it is not necessary, consider installing a variable-speed blower motor with this type of heat pump. It uses less electricity and, with the proper thermostat, it can greatly improve dehumidification and comfort during the summer.

Write for (instantly download - www.dulley.com) Update Bulletin No. 842 - buyer's guide of the 20 most efficient, comfortable heat pumps listing output levels, efficiency, compressor, refrigerant, size, blower speeds, and a savings/payback chart. Please include $3 and a business-size SASE. James Dulley, Illinois Country Living, 6906 Royalgreen Dr., Cincinnati, OH 45244.

James Dulley is a mechanical engineer who writes on a wide variety of energy and utility topics. His column appears in a large number of daily newspapers.

19 | January 2004 | www.aiec.coop