Other Kinds of Heat Pumps

If your home doesn't have air ducts to distribute heat, you could use a special kind of heat pump called a mini-split heat pump. A mini-split heat pump connects an outdoor air-source unit to multiple indoor units that in turn connect to water heat or space heaters. Ductless mini-split systems are useful for retrofitting a home with a heat pump system, as their locations outside and inside the home are flexible, and installation only requires a three-inch (7.6 cm) conduit to come through the wall. The indoor air handlers for a mini-split system may be installed in the wall, ceiling, or on the floor, and are relatively small.

Another special type of air-source heat pump is a reverse cycle chiller (RCC). Instead of heating and cooling air, this kind of heat pump heats and cools water. In an RCC system, the heat pump connects to an insulated water tank that it heats or cools. Then a fan and coil system pumps heated or cooled air away from the tank and through the ductwork to one or more heating zones. An RCC system can also pump hot water through a radiant floor heating system. In a typical air-source heat pump, a backup burner has to supply temporary heat when the system switches into reverse to defrost the coils. This backup burner prevents the system from blowing cold air through the registers while the coils defrost. The clever thing about an RCC system is that it uses the hot water from the tank to defrost the coils, so no backup burner is needed, and the system never blows cold air when it shouldn't.

A new type of heat pump showing promise for extreme climates is the Cold Climate heat pump, which operates efficiently at extremely low temperatures -- even below 0 degrees Fahrenheit (-18 degrees Celsius). The Cold Climate heat pump detects the minimum amount of energy needed to provide the desired level of heating or cooling and adjusts its output up or down, so it never wastes energy.

The All Climate heat pump is another new kind of pump, which can operate in temperatures as cold as -30 degrees Fahrenheit (-34 degrees Celsius) and can increase efficiency by up to 60 percent over a standard heat pump [source: EERE]. The All Climate heat pump is designed primarily for heating and won't work efficiently in climates where the heat pump would be in cooling mode most of the time.

Even special heat pumps have limitations. Read on to learn about the pros and cons of heat pumps, and what you need to know before buying one.