How do Heat Pumps Work?

Heat pumps are a type of heating and cooling technology that has been used in Canada for decades. They extract heat from a low-temperature source and deliver it to a high-temperature place. This type of technology is used in everything from refrigerators to air conditioners. An air-source heat pump could be a good option for heating and cooling your home efficiently, especially if you live in a moderate climate. Here’s how a standard air-source heat pump works.


Components of a Heat Pump

A typical heat pump system consists of two main components: an outdoor unit, which looks a lot like the outdoor unit of a central air conditioning system, and an indoor unit. Each contains several subparts:

Outdoor Unit
The outdoor unit contains a coil and a fan. The coil operates as a condenser or an evaporator, depending on which mode the heat pump is operating in. The fan blows outside air over the coil to facilitate the heat exchange.

Indoor Unit
The indoor unit, commonly referred to as the air handler unit, is like the outdoor unit in that it contains a coil and a fan. The coil operates as a condenser or an evaporator, depending on which mode the heat pump is operating in. The fan moves air across the coil and through the ducts in the home.

Refrigerant is the substance that absorbs and rejects heat as it circulates through the heat pump system.

The compressor pressurizes the refrigerant and moves it through the heat pump system.

Reversing Valve
The reversing valve reverses the flow of the refrigerant, allowing the heat pump system to switch between heating and cooling.

Expansion Valve
The expansion valve acts as a metering device, regulating the flow and temperature of the refrigerant as it passes through the heat pump system.


How an Air-Source Heat Pump Works

A common misconception about heat pumps is that they create heat. This is not the case. Rather, they redistribute heat from the air (or ground in the case of a ground-source heat pump) and use the refrigerant circulating between the indoor and outdoor units to transfer heat.

When an air-source heat pump is in cooling mode, it absorbs heat inside the home and releases it outdoors. When a heat pump is in heating mode, it absorbs heat from outside and releases it indoors. Here is how it works:

  1. Liquid refrigerant is pumped through the expansion valve in the indoor coil, which acts as the evaporator. Air from inside the house is blown across the coils, where the refrigerant absorbs heat energy. The cool air is then blown through the ductwork in the home.

  2. The gaseous refrigerant then passes through the compressor, which pressurizes the gas and causes it to heat up. The pressurized refrigerant then moves through the heat pump system to the coil in the outdoor unit.

  3. A fan in the outdoor unit moves outside air across the coils, which serve as condenser coils in cooling mode. Since the outside air is cooler than the gas refrigerant, heat is transferred from the refrigerant to the outside air. The refrigerant condenses back to a liquid as it cools and is pumped through the system to the expansion valve in the indoor unit.

  4. The expansion valve reduces the pressure of the liquid refrigerant, which significantly cools it. It is then ready to be pumped back to the evaporator coil in the indoor unit and restart the cycle.

These steps describe how a heat pump works when operating in cool mode, and you may see that it is fairly similar to a central air conditioning unit. However, unlike central air conditioning, a heat pump can operate in heating mode. When doing so, it works in the same way, except that the flow of refrigerant is reversed using the reversing valve. Then the heating source becomes the outside air (even when the external temperature is very low), the outside coil functions as an evaporator, and the indoor coil functions as a condenser. However, the physics are the same and result in warm air being released in the home.

A heat pump is an efficient system that can both heat and cool your home by absorbing heat from one area and releasing it in another. The experts at Napoleon can help you evaluate your requirements for heating and cooling and recommend the best heat pump system for your home.