Heat pump
What it is
Frost forms on the outdoor coil during heat pump operation.
Ducted air source heat pumps use your home's existing ductwork to deliver heating and cooling.
Residential and light commercial air conditioning and heat pump systems | 700 | January 1, 2025
Its parts
- Thermostat
- If you have a heat pump, you may require a special programmable thermostat to maximize your energy savings year-round.
- Compressor
- Yes, you can continue to repair your existing refrigeration, air conditioning, and heat pump system. This includes replacing a major component like a condensing unit or compressor.
- Transitioning to a new refrigerant requires the redesign of heat pump and air-conditioning systems. New systems incorporate compressors and other components designed for use with specific refrigerants.
- Many types of air conditioning systems are called split systems because they are made up of an outdoor unit, which contains the condenser and compressor, and an indoor unit, which is often connected to a furnace or heat pump.
- Reversing valve
- During the defrost cycle, the reversing valve switches the heat pump from heating mode to cooling mode temporarily.
- Defrost cycle
- Both heat pumps use a reverse cycle strategy to defrost the outdoor coil.
- Under certain operating conditions, the heat pump must enter a defrost cycle to melt ice accumulated on the outdoor heat exchanger.
- Expansion valve
- If overfeeding of the expansion valve causes intermittent flooding of liquid into the suction line, the compressor may be damaged.
- Liquid refrigerant enters the expansion valve, is reduced in pressure and temperature at the valve port, and enters the evaporator at point A as a mixture of saturated liquid and vapor.
- Auxiliary heat
- In the case of typical electric resistance auxiliary heat, the heat pump can continue to contribute simultaneous to the auxiliary heat.
- Even in relatively warm climates, heat pumps have traditionally been installed with a backup heat source (auxiliary heat), usually an electric resistance element (Figure 2).
- Air handler
- upflow air handler for a traditional heat pump has an electric resistance auxiliary heating element located at the top of the unit (circled in red).
Related pages
- Glossary: Heat pump
Its entry, and the guide's pages that use it.
- Heat pumps
How a heat pump heats and cools, and how it copes with Chicago cold
Sources
- U.S. Department of Energy. Quantifying and Reducing Defrost Energy Use.
- ENERGY STAR. Clean Heating and Cooling.
- U.S. EPA. Restrictions on the Use of Certain HFCs under Subsection (i) of the AIM Act.
- U.S. EPA. Guide to Energy-efficient Heating and Cooling.
- U.S. EPA. EPA Frequent Questions on the Phasedown of Hydrofluorocarbons.
- U.S. EPA. Purchasing and Repairing Home Air-Conditioners or Heat Pumps.
- U.S. Department of Energy. Energy Saver 101: Home Cooling.
- U.S. Department of Energy. Decarbonizing Building Thermal Systems: A How-to Guide for Heat Pump Systems and Beyond.
- U.S. Department of Energy. Laboratory Test Report for Fujitsu 12RLS and Mitsubishi FE12NA Mini-Split Heat Pumps.
- ASHRAE. ASHRAE Handbook—Refrigerant Control Devices.
- U.S. Department of Energy. Cold Climate Heat Pump Sizing and Selection.