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  • Writer's pictureAbu Hurara

Air-to-water heat pump

Updated: Nov 29, 2021


Air-to-water heat pumps or air heat pumps embody the most modern technologies, the most promising for use and development now and in the future. An inexhaustible source of heat for them is unlimited air space, they are safe for the environment and do not emit harmful substances into the atmosphere. There are different types of heat pumps, but we will now focus on air-to-water installations.

Working principle of air source heat pump

The source of low-grade heat for them is the ambient air. Using 1 kW of electricity from the network to drive the drive, the air heat pump "produces" up to 5 kW of thermal energy to heat the house and heat water.

The operation of an air heat pump is based on the process of accumulation of low-potential heat of the air during evaporation, circulating in a closed refrigerant circuit, and the subsequent transfer of heat to the heating system during condensation of the refrigerant.

Outside air is directed by a fan to the heat exchanger of the heat pump evaporator. The heat exchanger contains liquid refrigerant, the temperature of which is always lower than the outside air. When low-grade heat from the outside air enters, the refrigerant boils and goes into a state of heated steam.

After that, the gaseous refrigerant enters the compressor, where it is strongly compressed. When compressed, the pressure of the refrigerant, and therefore the temperature of the medium, increases even more. The mechanical energy of the compressor is converted into heat energy.

The refrigerant, in a highly heated and compressed state, enters the condenser heat exchanger, where it cools and gives off heat to the heating system. In this case, the refrigerant condenses and passes into a mixture of liquid and vapor.

For even more cooling, the liquid refrigerant mixture is passed through the expansion valve, after which the pressure drops to its original value and the liquid refrigerant enters the evaporator again. The cycle repeats itself.

Composition of the heat pump unit kit

The air heat pump equipment set consists of:

  • An external monoblack or two units (internal and external - split system),

  • A hot water tank or a boiler with a built-in heating element (when working in tandem with an additional electric heater - in bivalent mode),

  • Heat distribution systems (underfloor heating, fan coil units, convectors or radiators),

  • Control automation (sensors, control thermostats, controllers).


Due to the availability of the heat source - outdoor air, the use of water furnace air heat pumps is very diverse. They are installed:

For heating systems of private houses, mansions, apartment buildings, office buildings or institutions;

For heating water in swimming pools;

For heating greenhouses and farms;

For heating industrial buildings;

For the installation of heating systems in new buildings;

To improve or replace gas and other boilers in houses already built for a long time.

Advantages of air-to-water heat pumps

The most cost-effective type of heat pump - with minimal investment and low operating costs.

Versatile functionality for the best comfort: work for heating, heating and air conditioning, for heating water.

  • There are high and medium temperature models for working with radiators, convectors, underfloor heating and fan coil units (for air conditioning).

  • High energy efficiency of the air heat pump, high energy conversion coefficient: COP - up to 5.0.

  • Energy efficiency class is very high: A +++.

  • A wide range of models, the possibility of installation in a cascade.

  • Powered by a single-phase or three-phase network.

  • Possible work in stand-alone mode or in combination with a boiler.

  • Weather-dependent control, programmable operating modes, control via the Internet.

  • Control of several heating circuits, regulation of the temperature of heating water for domestic needs, efficient heating of water for the pool.

  • Possibility to control additional heat sources: boiler, electric heater or solar collectors.

  • Easy installation and simple maintenance.

  • Maximum cost savings when registering a tariff for electric heating.

Article on the topic: “Ground Source Heat Pump? "

Features of the use of air heat pumps

Taking into account the decrease in the heat output of the air heat pump at very low air temperatures, starting from a certain temperature (-7 ... - 11 ° C), it is recommended to connect an additional heater (boiler, electric heater, etc.). This removes the peak load from the heat pump, and the maximum design capacity, and therefore the cost of the entire system, is significantly reduced. This dual mode heat pump operation with support from an additional heater is considered the most cost-effective and provides the fastest return on investment.

Installation of air source heat pumps does not require special permits or expensive earthworks, no drilling space or a large area for a heat collector. The outdoor unit can be removed at some distance from the house, mounted on a wall or on a walkway near the house. The indoor unit, usually mounted, has a compact size.

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