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Heat pumps are an energy-efficient alternative to traditional heating and cooling systems. This in-depth guide will provide you with everything you need to know about heat pump technology, types, components, operations, and more.
A heat pump is a system that transfers heat energy from a source of heat to a destination called a heat sink. Heat pumps move thermal energy in the opposite direction of spontaneous heat transfer, by absorbing heat from a cold space and releasing it to a warmer one. A heat pump uses a small amount of external power to accomplish the work of transferring energy from the heat source to the heat sink.
In heating mode, a heat pump absorbs heat from the cold outdoor air and pumps it into a warm indoor space. In cooling mode, the indoor space is cooled as a heat pump absorbs heat from the indoor air and discharges it outdoors. Heat pumps can provide year-round climate control with greater efficiency than furnaces and air conditioners.
While heat pumps and air conditioners are similar systems, a key difference is that air conditioners only provide cooling, while heat pumps can provide both heating and cooling.
Air conditioners use the refrigeration cycle to remove heat from the indoor space. They discharge the absorbed heat outdoors, leaving the indoor air cooler. However, an air conditioner requires supplemental heat from a furnace or heating system in winter.
Heat pumps are able to reverse the refrigeration cycle to provide heating or cooling as needed. The same heat pump system can extract heat from outdoor air in winter and act as an air conditioner by rejecting heat outdoors in summer.
There are several benefits that make heat pumps an attractive home heating and cooling solution:
There are two main types of heat pumps used in homes: air-source heat pumps and ground-source (geothermal) heat pumps.
An air-source heat pump transfers heat between the inside of a building and the outside air. It works like a reversible air conditioner, with an indoor unit mounted on a wall or ceiling and an outdoor unit.
During winter, an air-source heat pump takes heat from the outdoor air and pumps it indoors. The refrigeration system allows heat transfer to take place even when the outdoor air is colder than the temperature inside the home.
In summer, the system reverses to cool indoor air by transferring heat from inside to outside. Air-source heat pumps work best in milder climates but can also provide effective heating at sub-zero temperatures with a backup heating system.
Air-source heat pump system with indoor and outdoor units
Ground-source, or geothermal, heat pumps tap into the stored solar energy in the ground to provide heating, cooling, and hot water. These systems transfer heat between a building and the ground instead of outdoor air.
Pipes buried in the shallow ground or submerged in an underground pond absorb heat from the soil/water. The heat pump compressor then raises the temperature of the heat absorbed by the refrigerant as it passes through the system.
In summer, the process reverses as heat is extracted from the indoor space and transferred to the ground through the buried pipes. While geothermal systems have higher installation costs, they can provide greater efficiency than air-source heat pumps.
Geothermal heat pumps use buried pipe loops to exchange heat with the ground
Heat pumps operate on a refrigeration cycle that allows them to absorb heat at one place and release it another. Here is an overview of the basic heat pump operation:
A reversing valve switches the direction of refrigerant flow between heating and cooling modes. This allows the indoor and outdoor heat exchangers to alternate roles as evaporators or condensers when their function needs to reverse for heating or cooling.
While heat pumps, furnaces, and air conditioners all control indoor comfort, they differ in how they generate and distribute heated or cooled air:
Important factors in choosing an appropriate heat pump system include:
Heat pumps are well suited for heating and cooling needs in mild to moderate climates. Colder regions may require a dual-fuel system with supplemental heating.
While heat pumps work optimally in temperatures above freezing, advances in cold climate heat pump technology allow them to operate efficiently in sub-zero weather.
Rather than choosing either a furnace or heat pump, dual-fuel systems integrate the two technologies for maximum comfort and efficiency:
Complete heat pump systems are comprised of an outdoor unit, indoor air handling unit, distribution network, controls, and a supplemental heat source.
This exterior component has:
The indoor components include:
Refrigerant fluid transports heat between the indoor and outdoor heat exchangers. Insulated refrigerant lines connect the external condenser/evaporator unit with the indoor evaporator/condenser coil.
A reversing valve alternates the direction of refrigerant flow between heating and cooling modes.
Smart thermostats like the Ecobee SmartThermostat monitor indoor and outdoor temperatures, stage multiple heat pumps, and switch between heating and cooling modes. Zoning systems allow different temperatures in different rooms.
Dual-fuel heat pumps combine a heat pump with a propane or natural gas furnace. Electric resistance heat modules provide backup heat for cold climates.
Heat pumps operate in reverse cycles for heating and cooling:
The heating mode process essentially runs in reverse:
Given the complexity of heat pump systems, installation is best performed by qualified HVAC technicians like those at Simply Smart Home. Our heat pump expertise includes:
By understanding how these high-efficiency heating and cooling systems operate, you can make an informed heat pump purchase and installation decision. Contact the experts at Simply Smart Home to determine if a new heat pump is the right choice for your home comfort and energy savings.
Aman is an experienced home improvement writer with a passion for energy efficiency and smart home technologies. He is dedicated to helping homeowners adopt sustainable practices that enhance their daily lives while reducing their environmental impact.