The Components Of A Heat Pump And How These Systems Work

If you’re considering upgrading your current heating and cooling system, you may have heard about heat pumps and be curious to learn more. These systems have been getting more popular over the last 15 years, and they’re about to become even more commonplace.

The technology behind them just keeps getting better. And, you can find plenty of rebate opportunities, from federal incentives down to manufacturer offers, to make them even more affordable.


Here, you’ll find a comprehensive guide to everything you need to know about heat pumps. I’ll cover the basics of what a heat pump is, how it functions, and its various components.

Then, we’ll dig into the different types of heat pumps and how to optimize their performance.

This guide is the result of over a decade of research and experience in the HVAC industry. I’ve been product manager at Peirce Phelps, specializing in high-efficiency equipment and cutting-edge heating and cooling innovations, for nearly 15 years.

I also work closely with HVAC contractors throughout Pennsylvania, New Jersey, Maryland, and Delaware. We keep each other up-to-date about new developments, what’s happening in the field in real-time, and what consumers need to know.

If you’re interested in learning more or exploring your options, you can get a free consultation with a certified local HVAC contractor in any of the aforementioned states. Use the dealer locator button to find an installer in your area.


What is a Heat Pump?

A heat pump is an energy-efficient heating and cooling system that transfers heat from one place to another, rather than generating heat itself. It can extract heat from the air, ground, or water, and move it indoors or outdoors, depending on the season and desired temperature.

Heat pumps can be used for both heating and air conditioning, making them a versatile option for homeowners.

Different types of heat pumps available

There are three main types of heat pumps available: air-source, ground-source (geothermal), and water-source. Air-source models are by far the most common for homes in the mid-Atlantic region. So, I’ll focus mostly on those in this article and touch briefly on the others.


Air-source heat pumps work by extracting heat from the outside air and transferring it indoors. These heat pumps are typically less expensive to install than other types, and work with existing ductwork or in other configurations.

Their efficiency can decrease in very cold temperatures, but stronger models can work even in subzero temperatures.

Ground-Source (Geothermal)

Ground-source, or geothermal, heat pumps work by extracting heat from the ground and transferring it indoors. They are highly efficient and can be used in a wide range of climates, and last up to 50 years.

But, they’re much more expensive to install than air-source heat pumps, and they require large amount of space for installation. So, they’re not really suitable for residential use.


Water-source heat pumps extract heat from a nearby water source, such as a lake or river, and transfer it indoors. They are highly efficient and can be used in most climates, but require a large amount of space and a body of water. They’re usually used in industrial or large commercial settings.

Ductless Mini Split

Ductless mini-split heat pumps are a type of air-source heat pump that do not require ductwork. Instead, they use an indoor air handler unit that is mounted on the ceiling or wall. The indoor and outdoor components are connected by refrigerant lines (I’ll explain more about those later).

Ductless mini-split heat pumps are more expensive than ducted systems. But, they are much more efficient, come in a variety of sizes and capacities, and customizable when it comes to installation.

Heat Pump Components

There are two main components of a heat pump: The outdoor unit and an indoor unit, that work together to transfer heat, or thermal energy. It can switch between heating and cooling by reversing the flow of heat exchange from moving in or out of the house.

Outdoor Unit

The outdoor unit of a heat pump is responsible for transferring heat from the outside air, ground, or water to the indoor unit. It consists of several key components.


The refrigerant, or coolant, is the substance that carries heat between the indoor and outdoor units. It absorbs heat, moves it between the units, and releases it at the condenser coil.


The compressor is the heart of the outdoor unit. It compresses the refrigerant gas and pumps it through the system.


The outdoor unit has two coils: the evaporator coil and the condenser coil. The evaporator coil absorbs heat from the outdoor air, ground, or water and converts the refrigerant from a liquid to a gas. The condenser coil releases the heat absorbed by the evaporator coil to the indoor air.


The outdoor unit has one or two motorized fans that draw outdoor air over the evaporator coil and condenser coil. The fans help to transfer heat and improve the efficiency of the heat pump.

Expansion Valve

This component regulated the flow of the refrigerant as it travels through the system. More or less pressure affects the temperature of the coolant.

Reversing Valve

The reversing valve reverses the heat transfer process to switch from heating or cooling. The system heats a house by moving warmth into the it and cools the space by moving the thermal energy out of it.

Indoor Unit

The indoor unit of a heat pump is responsible for transferring the heat collected from the outdoor unit to the indoor air. It consists of several key components:

Air Handler

The air handler is the indoor unit’s component that moves the conditioned air throughout the home. It contains a motorized fan that circulates the indoor air over the indoor coil.

Air Filter

The air filter traps dust, dirt, and other particles, keeping the indoor air clean and healthy. IT works just like the filter in a traditional furnace and central air system.

Thermostat and Control Systems

The thermostat allows homeowners to set the desired temperature. It provides feedback to the heat pump system to maintain that temperature.

Parts of a Heat Pump In A Mini Split

A mini split uses an air-source heat pump, but the setup is a little different than with ducted heat pump systems.

Heat Pump

With a mini split, the heat pump is the outdoor unit. It houses the compressor and coils. . It absorbs heat from the air outside and transfers it to the indoor unit. In the summer, it removes the heat from the house.

Air Handlers

The air handlers are the indoor units that distribute conditioned air throughout the room. They consist of an evaporator coil, a motorized fan, and a filter that removes dust and other particles from the air. They also control the humidity levels in the summer.

These are usually mounted on the wall and are in every room you want to treat. The refrigerant runs between these units and the heat pump.

Mini split systems are ductless, which makes installation easier and more flexible, as air handlers can be installed in different zones of the home without ductwork.

How A Heat Pump Works

The heat pump cycle transfers heat energy from one place to another. In cooling mode, it removes heat from the indoor air and transfers it to the outdoor air. In heating mode, it extracts heat from the outdoor air and moves it inside to warm up the indoor air.

To do this, the system relied on physics.

Heat Transfer

Heat transfer is the process of moving heat from one place to another. A heat pump uses a refrigerant to transfer heat energy. When the refrigerant absorbs thermal energy from a heat source, it changes from a low-pressure liquid to a high-pressure gas. Then it releases the heat when it changes back to a low-pressure liquid.

Refrigeration Cycle

The mechanical-compression cycle refrigeration system is the process by which a heat pump removes heat from one place and releases it in another.

The refrigerant moves in a closed loop between the indoor and outdoor units. It continually undergoes pressure and temperature changes to move heat from one place to another.

Cooling Mode

In cooling mode, the heat pump removes heat from the indoor air and transfers it to the outdoor air. Similar to how a central air conditioner works, it does this by circulating refrigerant through the indoor and outdoor coils. As the refrigerant absorbs heat from the indoor air, it changes from a low-pressure gas to a high-pressure gas.

Then, as it releases the heat to the outdoor air, it changes back to a low-pressure liquid.

Heating Mode

In heating mode, the heat pump extracts heat from the outdoor air and moves it inside to warm up the indoor air. Even when the temperature is below freezing, there is still enough heat energy in the outdoor air to extract and transfer indoors.

Defrost Mode

In subfreezing temperatures, ice can form on the outdoor unit’s coils, reducing the heat pump’s efficiency. To remove the ice, the heat pump goes into defrost mode. During this process, it reverses the refrigeration cycle to heat up the outdoor coil and melt the ice.

Tips For Optimizing Your Heat Pump’s Performance

If you invest in a heat pump system, you’ll want to keep it in great shape. That way, you’ll get excellent comfort with lower energy bills. These systems can last 20 years or more. Here are three easy ways to optimize your heat pump’s performance:

Professional Maintenance

You should call for two heat pump or mini split tune-ups every year. That’s when a professional HVAC technician checks your heat pump’s refrigerant levels, cleans indoor and outdoor parts, and lubricates the motorized fan to ensure everything works correctly.

The recommendations are one in spring to prepare for summer and another in the fall to prepare for winter.

Annual Deep Cleaning

Dirt, debris, dust, and moisture naturally build up in the air handlers. Over time, they can affect the performance. Mold can also start growing in the dark, damp, warm inside of the components. Fortunately, an annual deep cleaning prevents this from happening.

General Upkeep

You can also take a few regular steps to keep your heat pump working great. These include changing the air filter regularly, keeping the outdoor unit clear of debris and vegetation, and ensuring that the thermostat is set to the appropriate temperature.

You can also keep humidity levels in check by using a dehumidifier or adjusting the fan speed on the indoor unit.

If you still have questions, you can learn more is with a free, no-obligation consultation with one of our certified HVAC contractors. Use the dealer locator to find a heat pump installer with great reputation in Cherry Hill, PA or anywhere in New Jersey, Delaware, Maryland, or Pennsylvania.