What is a Heat Pump | How Does it Work?

There are several ways to go about heating and cooling your home. Many residential houses use a gas furnace for the cold months and may or may not have a central air conditioning system for the warm months. A heat pump gives you the best of both worlds. It works very similarly to a central air conditioner but can also provide warm air to the home. A heat pump is powered by electricity and uses a refrigerant system to provide heating and cooling throughout the year.

Homeowners in moderate climates throughout the US can rely on a heat pump as an energy-efficient way to heat their homes. Let’s learn more about how a central heat pump works.

Components of a Heat Pump

An air-source heat pump consists of two major components, an indoor unit and an outdoor unit, each with various 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 programmed. 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 operates. The fan moves air across the coil and through the ducts in the home.

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

Compressor:
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 heat pump operates by redistributing heat from the air (or ground in the case of a ground-source heat pump) and using 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 the heat pump system works when it is operating in cooling mode:

The liquid refrigerant is pumped through the expansion valve in the indoor coil, which acts as the evaporator. Air drawn 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.
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.
A fan in the outdoor unit moves outside air across the coils, serving 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.
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.

The cycle is the same in heating mode, except the refrigerant flow is reversed using the reversing valve. Then the heating source becomes the outside air (even when the air temperature is very low), the outdoor coil functions as an evaporator, and the indoor coil functions as a condenser. As a result, warm air is released throughout your home.

Difference Between an Air-Source and Ground-Source Heat Pump

Air-source heat pumps are the most common pump for residential heating and transfer heat between indoor and outdoor air. They cost less upfront than ground-source heat pumps and do not require as extensive installation.

Ground-source or geothermal heat pumps transfer heat between indoor air and the ground outside. They are more expensive to purchase and install because they require ground loops to be installed on your property. However, because the ground tends to have a more consistent temperature, they are more efficient than air-source heat pumps and have a lower operating cost.

Unlike a gas furnace, a heat pump does not burn fossil fuels and is a cost-effective way to heat and cool your home. A Napoleon expert can help evaluate your heating and cooling requirements and recommend a heat pump that will work for your needs.

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