Hot (and Cool) Heat Pumps
I have an electric furnace and I am thinking about installing a heat pump. Some friends with gas and oil heat also just installed heat pumps. What is new in heat pumps and which are the most efficient and comfortable?
—Ray W.
Heat pumps have had an unfairly bad reputation over the years. For reliability and comfort, new heat pumps are an excellent and efficient source of heating and cooling. The most efficient heat pumps can produce more than $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.
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.
The most efficient heat pumps use compressors, which produce two output levels. These heat pumps run at a low-output mode most 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 in the indoor air handler. When the heat pump is running at a low level, the variable-speed motor slows down. This reduces noise and eliminates the gust of cool air each time it starts. The slower blower speed also minimizes the common “chilly” feeling with a heat pump because the air coming out is warmer.
There are several two-level compressor technologies. The newest designs are two-stage scroll compressors. These have few moving parts and eliminate the need for pistons, valve, etc. 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.
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 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, can greatly improve dehumidification and comfort during the summer.
Ozone-friendly R410A refrigerant is being used in many compressors today. Although you can still purchase efficient models that use older R-22 freon, it would be wise to select an R410A model. Over the life of the unit, an R410A model should be less expensive to maintain.
Write for Utility Bills Update No. 842 for a buyer’s guide to heat pumps. Include $3.00, a business-size SASE, and Update number. Mail requests and questions to James Dulley, Kentucky Living, 6906 Royalgreen Drive, Cincinnati, OH 45244. Go to www.dulley.com to instantly download.
