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A Comprehensive Guide to Heat Pump Systems and How They Work

Author: The Engineering MindsetTime: 2024-01-26 21:15:03

Table of Contents

Introduction to Heat Pumps and How They Work

Heat pumps are an energy efficient way to provide heating and cooling for buildings. They can extract heat from outdoor air, ground sources, or water to provide heating. They can also dump unwanted heat from indoor air to provide cooling.

There are several types of heat pumps, including air-to-air, air-to-water, ground source, and water source heat pumps. They all work on the same basic refrigeration cycle principles.

Air-to-Air Heat Pumps

Air-to-air heat pumps are the most common type. They look similar to standard split air conditioners, with an outdoor unit and an indoor unit. They use a reversing valve to switch between heating and cooling modes. In heating mode, the refrigerant absorbs heat from outdoor air and releases it indoors through the heat exchanger. In cooling mode, the process is reversed - heat is absorbed from indoor air and dumped outdoors.

Air-to-Water Heat Pumps

Air-to-water heat pumps work like air-to-air heat pumps, but transfer heat to water instead of air. The refrigerant absorbs heat from outdoor air and transfers it through a heat exchanger to water stored in a tank. This hot water can then provide heating through radiators and taps throughout the building. Air-to-water heat pumps provide only heating, not cooling.

Ground Source Heat Pumps

Ground source heat pumps use pipes buried underground to extract heat from the ground. This heat is transferred to the refrigerant and used to heat air or water.

There are two types: horizontal ground source with pipes buried horizontally, and vertical ground source with pipes buried vertically in boreholes. Both work the same, just with different pipe configurations.

Horizontal Ground Source Heat Pumps

Horizontal ground source heat pumps have pipes buried in trenches 1-2 meters deep. The total length of trench required depends on the heating/cooling load.

Vertical Ground Source Heat Pumps

Vertical ground source heat pumps have pipes buried vertically in boreholes up to 200 meters deep. Fewer boreholes are needed compared to horizontal trenches.

Water Source Heat Pumps

Water source heat pumps extract heat from bodies of water. They are categorized as open loop or closed loop systems.

Open loop pumps draw water directly from a lake, river, or aquifer and return it. Closed loop recirculates an antifreeze solution through a loop of pipes in a pond or lake.

Open Loop Water Source Heat Pumps

In open loop systems, water is pumped directly from a body of water into the heat exchanger, where its heat is extracted. The water is then discharged back into the source.

Closed Loop Water Source Heat Pumps

Closed loop systems recirculate an antifreeze solution through a buried pipe loop. The solution absorbs heat from the water body and transfers it to the refrigerant.

Heat Pump Components and How They Work

The main components in a heat pump are the compressor, heat exchangers, expansion valves, and reversing valve (in heating/cooling models).

The compressor pressurizes the refrigerant vapor, the heat exchangers transfer heat between air/water and refrigerant, and the expansion valve lowers pressure and temperature before the refrigerant absorbs heat.


The compressor is the heart of the heat pump. It pressurizes the refrigerant vapor, raising its temperature so it can absorb heat.

Heat Exchangers

Heat exchangers transfer heat between the refrigerant and the air or water source. They have two separated coils - refrigerant flows through one and air/water through the other.

Conclusion and Summary of Heat Pump Systems

Heat pumps provide an energy efficient way to heat and cool buildings by transferring heat between indoor and outdoor air, the ground, or water sources. Several types exist, but all use the same refrigeration cycle principles.

Careful design, sizing, and equipment selection is needed to maximize efficiency and comfort. But when done right, heat pumps can greatly reduce energy use and emissions versus conventional HVAC systems.


Q: How do heat pumps work?
A: Heat pumps move thermal energy from one location to another using components like compressors, heat exchangers, and expansion valves in a refrigeration cycle.

Q: What are the main types of heat pumps?
A: The main types are air-to-air, air-to-water, ground source, and water source heat pumps.

Q: What is a ground source heat pump?
A: A ground source heat pump uses pipes buried underground to transfer heat between the ground and the heat pump refrigeration system.

Q: What is a water source heat pump?
A: A water source heat pump uses a body of water like a pond, lake, river or aquifer as the heat source and heat sink for the refrigeration system.

Q: How do heat pump reversing valves work?
A: Reversing valves switch the direction of refrigerant flow, allowing a heat pump to provide both heating and cooling.

Q: What components do heat pumps use?
A: Key components are compressors, heat exchangers, expansion valves, reversing valves, pumps, and fans.

Q: How efficient are heat pumps?
A: Heat pumps are very efficient at heating and cooling. They can provide 3-4 times more energy transfer than the electrical energy input.

Q: Can heat pumps work in cold climates?
A: Yes, heat pumps can operate efficiently even in very cold climates below freezing temperatures.

Q: Do heat pumps require maintenance?
A: Heat pumps require occasional maintenance like checking refrigerant charge, cleaning filters, and cleaning coils.

Q: Are heat pumps affordable to operate?
A: Heat pumps have very low operating costs compared to alternatives. Energy efficiency also makes them affordable.