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What is a heat pump?

What is a heat pump?

A heat pump is a two-component appliance that transfers heat energy from one place to another. A popular example of the device is found in refrigerators, where cooling and evaporation of the liquid are used to regulate the temperature of the storage compartment.
Nowadays, heat pump technology is used to extract potential energy from the ground or air outside and feed it directly into your house, which can be compressed and transferred through a series of coils. It sounds like magic, right? The science behind this technology is relatively simple.

Although the pumps use a relatively small amount of electricity to run, they are considered highly efficient in heating a home. They are also very clean because they extract energy from the environment rather than burning fossil fuels. They perform best in a moderate climate and have proved efficient in providing heat even during winter when the temperature falls at or below 0 degrees Fahrenheit.

Types of Heat Pumps

There are various heat pumps whose working mechanisms depend on the type of medium where they extract their energy.

Air Source Heat Pumps

If you live in a settled or moderate climate, an air source heat pump is best. It can provide the necessary heating in homes and offices, especially during the winter. The pump is normally fitted on the building wall to draw in air from outside and transfer it by compression to the conductive copper tubing coils indoors.

When warm air is needed, the liquid refrigerant extracts heat energy from the air and evaporates. The vapor is then passed to the inside coil that converts the vapor back to liquid to produce the required heat that can be fed to the household heating system.

Ground Source Heat Pumps

The outside air is the most readily available source of heat energy for the heat pumps, but not the only valuable source. Solar energy or underground water can heat the heat pipes laid into the earth to run the heat pumps. This type of heat pump, commonly known as a geothermal heat pump, has higher efficiency than other pumps because the temperatures in the ground are much more constant.

Hybrid Heat Pumps

A hybrid array is a heat pump that works alongside another source like a gas boiler to produce a very constant source of heat at a higher efficiency level. Another configuration of this type of pump mixes the air and ground source pumps. This configuration operates at full efficiency throughout the year. If the air outside is too cold, the hybrid pump draws heat from the ground and vice versa.

Vital Components of a Typical Air Source Heat Pump System

There are two major components of the air source heat pump, each of which has other important subcomponents:

Outdoor Unit

This component contains a fan and a coil. The coil plays two roles, creating the heating or cooling mode depending on the user’s preference and the prevailing temperature. The fan rotates relatively faster to blow air over the coil to facilitate heat regulation.

Indoor Unit

The indoor unit has an internal fan and a coil. The coil heats or cools the air, while the fan forces air from the external coils across the internal coils.


This component works like the air conditioner or refrigerator. The only difference is that the refrigerant can work in reverse, hence being referred to as a reverse refrigerator. It carries and controls the heat of the air in the heat pump system.


This component compresses the refrigerant at extremely high pressure and pushes it throughout the system.


The condenser generates the heating effects in the house. When the refrigerant reaches the condenser at very high pressure and temperature, it makes the condenser coil very hot, producing the heating required in the room.

Expansion and Reversing Valves

These two valves regulate the movement of hot and pressurized refrigerant in the system to allow the switch between cooling and heating effects.

How Does the Heat Pump Work?

The operating principle utilized by the heat pumps is that hot and pressurized air or heat energy naturally tends to move to regions of low temperature and pressure.

The Heating Cycle

Step 1

The low temperature and pressure refrigerant liquid in the outdoor unit absorbs heat from the outdoor air and vaporizes (forms a very hot gas). The compressor then compresses the gas at high pressure, increasing the temperature further.

Step 2

Hot and highly pressurized refrigerant is channeled to the indoor unit through the refrigerant lines (pump lines that pass through the wall of the building to connect the indoor and outdoor units).

Step 3

As the hot and high-pressure refrigerant circulates through the cooler indoor coils, the hot vapor cools and condenses back to a liquid state. This condensation (an endothermic change) heats the air in the indoor coil up, providing enough heat that facilitates heating effects. The air blower blows this heated air into the entire room.

Step 4

The refrigerant has completed its work at this stage and is forced through the expansion valve (pressure reducing part), where it regains its low temperature and pressure liquid state. It is channeled through the refrigerant lines back to the outdoor coil, and the cycle continues.

The Cooling Cycle

Heat pumps have a cooling-to-heating thermostat that makes reversal possible.

Step 1

Switching the thermostat to cooling mode activates the reversing valve and concurrently changes the movement direction of the refrigerant, aided by the compressor.

Step 2

The indoor coil absorbs heat from the in-house environment, which turns the refrigerant liquid into a gaseous state. The gas is channeled through the refrigerant lines to the outdoor unit.

Step 3

The outdoor coils (now assuming the role of condensation coils) cool the hot refrigerant and expel the hot air. The compressor squeezes the refrigerant back to a low temperature and pressure liquid state, which marks the end or the beginning of the new cooling cycle.


Heat pumps are efficient and versatile heating and cooling systems. They have crucial outdoor and indoor components such as expansion and reversing valves that control the movement of the refrigerant to cool or heat a home. Do the processes still sound magic to you? Hope not. Their functionality is based on scientific principles coupled with technological advancement.

At King, Heating, Cooling & Plumbing, a certified local HVAC carrier, we have a team of highly trained and experienced professionals with profound skills to evaluate and recommend the best heating and cooling requirements and heat pump systems. Contact us today to enjoy our best professional services.