Put simply, a heat pump is a mechanical device that moves heat from one space to another. As such a heat pump can be used to heat a building and it can also be used to cool a building.
Historically heat pumps were not practical for regions that had severe winters as they didn’t work efficiently in anything but moderately cool temperatures, but in recent years technological developments have changed that and today’s heat pumps can be used in areas where the outside temperature is well below freezing. In other words they are a great idea for our region.
What do they do?
A heat pump doesn’t burn fuel to create heat, it transfers heat that already exists. Here’s how it works. A fan sucks air into the outside unit. The air passes over a coil filled with a gas transfer fluid – typically Freon R410A, which boils at -44°F.
The Freon boils and vaporizes inside the coil (think water boiling in a pot on the stove top turning into steam) and, as it does so, it absorbs heat from the outside air – even if that outside air is cold! – but the gas is still relatively cold.
Next the Freon gas is passed through a compressor. Freon gas is highly compressible and the more it is compressed, the hotter it becomes (think of the water boiling in a pressure cooker rather than an open pot). This hot, high-pressured gas is then passed from the compressor to an inside coil where the refrigerant gas re-condenses and releases its heat to the indoor air via the ductwork.
The now-liquid refrigerant returns to the outside coil to begin the cycle all over again.
The beauty of the system is that the transference of heat takes relatively little energy, no fossil fuel is burned in the process, and the entire unit can be reversed so that your winter heat pump becomes your summer air conditioner.