When you think about cooling a hot building, you probably don’t think of heat pumps. In fact, the words “air conditioner” are likely the first things that come to your head. As it turns out, a heat pump can both heat and cool, and in some applications, it’s preferred to separate heating and cooling systems. Simply put, a heat pump is a device that uses a small amount of energy to move heat from one location to another. Heat pumps are typically used to pull heat out of the air or ground to heat a home or office building, but they can be reversed to cool a building. In a way, if you know how an air conditioner works, then you already know a lot about how a heat pump works. This is because heat pumps and air conditioners operate in a very similar way. One of the biggest advantages of a heat pump over a standard heating ventilating and air conditioning (HVAC) unit is that there’s no need to install separate systems to heat and cool your home. Heat pumps also work extremely efficiently, because they simply transfer heat, rather than burn fuel to create it. This makes them a little more green than a oil or gas-burning furnace.
All heat pumps have an outdoor unit (called a condenser) and an indoor unit (an evaporator coil). A substance called a refrigerant carries the heat from one area to another. When compressed, it is a high temperature, high-pressure liquid. If it is allowed to expand, it turns into a low temperature, low pressure gas. The gas then absorbs heat. In the winter the normal heat pump system extracts heat from outdoor air and transfers it inside where it is circulated through your home’s ductwork by a fan. Even cold air contains a great deal of heat; the temperature at which air no longer carries any heat is well below -200 degrees Fahrenheit.
Even if you have an older home without ducts, there is still a solution! For homes without ducts, air-source heat pumps are also available in a ductless version called a mini-split heat pump.