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Personal: Residential

What is a Heat Pump and How Does it Work?

A heat pump is an electrical device that extracts heat from one place and transfers it to another. The heat pump is not a new technology; it has been used in Canada and around the world for decades. Refrigerators and air conditioners are types of heat pumps.

Figure 1: Basic Heat Pump Cycle

Figure 1: Basic Heat Pump Cycle

Heat pumps transfer heat by circulating a substance called a refrigerant through a cycle of alternating evaporation and condensation. A compressor pumps the refrigerant between two heat exchanger coils. In one coil, the refrigerant is evaporated at low pressure and absorbs heat from its surroundings. The refrigerant is then compressed en route to the other coil, where it condenses at high pressure. At this point, it releases the heat it absorbed earlier in the cycle.

The heat pump cycle is fully reversible, and heat pumps can provide year-round climate control for your home – heating in winter and cooling and dehumidifying in summer. Since the ground and air outside always contain some heat, a heat pump can supply heat to a house even on cold winter days. In fact, air at –18oC contains about 85 percent of the heat it contains at 21oC.

The air-source heat pump, which absorbs heat from the outdoor air in winter and dumps house heat into outdoor air in summer, is the most common type found in Canadian homes at this time. However, ground-source heat pumps (also called earth-energy systems), which draw heat from the ground or ground water, are becoming more widely used, particularly in Ontario and Atlantic Canada.

Energy Management in the Home

Heat pumps are very efficient heating and cooling systems. They can significantly reduce your energy costs. However, there is little point in investing in an efficient heating system if your home is losing heat through poorly insulated walls, ceilings, windows, and doors, and by air leakage through cracks and holes. It often makes good sense to reduce air leakage and upgrade thermal insulation levels before buying or upgrading your heating system.

Heat pumps supply heat to the house in winter and cool the house in the summer. However, they require electricity to operate. If you add a heat pump to your heating system or convert from another fuel to a heat pump, and your old system was not equipped with central air conditioning, you will find that your electricity bills will be higher than before.

Certification and Standards

The Canadian Standards Association (CSA) verifies all heat pumps for electrical safety. A performance standard specifies tests and test conditions at which heat pump heating and cooling capacities and efficiency are determined. The performance testing standard for air source heat pumps is CSA C273.3-M1991. There is also a CSA installation standard for add-on air-source heat pumps (CSA C273.5-1980).

CSA publishes standards to test the efficiency of ground-source heat pumps (CSA C13256) and to ensure that they are installed properly (C445-1992). Minimum efficiency standards are stipulated in both the air-source and ground-source performance standards, and these levels are currently regulated in Canada by the Energy Efficiency Act and Energy Efficiency Regulations.