What Is a Heat Pump and How Does It Work?

Air source heat pumps are part of a heating and cooling system installed outside your home. Just like an air conditioner, it can cool your home, but it can also provide heat, a three-function heat pump provides hot water in addition to floor heating and cooling, and the recycling principle, hot water is almost free.

 

During the cooler months, the heat pump draws heat from the cold outside air and transfers it indoors, while during the warmer months it draws heat from the indoor air to cool your home. They are powered by electricity and use refrigerant to transfer heat, providing year-round comfort. Because they handle both cooling and heating, homeowners may not need to install a separate system to heat their home. In cooler climates, hotplates can be added to indoor fan coils for extra functionality. Heat pumps do not burn fossil fuels like furnaces and are therefore more environmentally friendly.

 

How does a heat pump cool and heat?

Heat pumps do not generate heat. They redistribute heat from the air or ground and transfer it using refrigerant circulating between the indoor fan coil (air handler) unit and the outdoor compressor.

 

In cooling mode, the heat pump absorbs heat in your home and releases it outside. In heating mode, the heat pump absorbs heat from the ground or outside air (even cold air) and releases it indoors.

 

What types of heat pumps are there?

The two most common types of heat pumps are air source and ground source. Air source heat pumps transfer heat between indoor air and outdoor air and are more popular for residential heating and cooling.

 

A ground source heat pump, sometimes called a geothermal heat pump, transfers heat between the air in your home and the ground outside. These are more expensive to install due to consistent ground temperatures throughout the year, but are generally more efficient and less expensive to operate.

 

Where do heat pumps work best?

Heat pumps are more common in milder climates, where temperatures typically don't drop below freezing. In cooler regions, they can also be combined with furnaces for energy-efficient heating on all but the coldest days. When the outside temperature drops too low for the heat pump to operate effectively, the system turns to the furnace to generate heat. Such a system is often referred to as a dual fuel system - it is very energy efficient and cost effective.

 

What are the components of a heat pump system?

A typical air source heat pump system consists of two main components, an outdoor unit (which looks like the outdoor unit of a split air conditioning system) and an indoor air handling unit. Both indoor and outdoor units contain various important subcomponents.

 

1. Outdoor unit

The outdoor unit contains coils and fans. The coil operates as a condenser (in cooling mode) or as an evaporator (in heating mode). A fan blows outside air over the coils to facilitate heat exchange.

 

2. Indoor unit

Like the outdoor unit, the indoor unit, commonly referred to as the air handler, also contains coils and fans. The coil acts as an evaporator (in cooling mode) or a condenser (in heating mode). The fan is responsible for moving air through the coils and the ducts in the home.

 

3. Refrigerant

The refrigerant is the substance that absorbs and releases heat as it circulates throughout the heat pump system.

 

4. Compressor

The compressor pressurizes the refrigerant and moves it throughout the system.

 

5. Diverter valve

Part of a heat pump system that reverses the flow of refrigerant, allowing the system to run in the opposite direction and switch between heating and cooling.

 

6. Expansion valve

The expansion valve acts as a metering device, regulating the flow of refrigerant as it passes through the system, thereby reducing the pressure and temperature of the refrigerant.