Luftkällan

Luftkällan is a Swedish term that literally means “the air source.” In the context of heating and cooling, it refers to a class of heat pumps that use outdoor air as the source of heat. There are two common configurations: luft-luftvärmepump (air-to-air) that heats indoor air directly, and luft-vattenvärmepump (air-to-water) that heats water for radiators or underfloor heating and can supply domestic hot water.

How it works: The outdoor unit draws in outside air, and a refrigerant absorbs heat from it. The refrigerant is then compressed to a higher temperature and transfers heat to the indoor air or to a water circuit. In cold weather, efficiency declines and many systems use a defrost cycle to remove ice from the outdoor coil. The resulting heat is distributed through the building, either as warm air or via the heated water circuit.

Efficiency and performance: The heating efficiency is described by the coefficient of performance (COP), which varies with outdoor temperature, humidity, and system design. Modern luftkällor often achieve COPs in the range of approximately 2–4 during typical winter conditions, with seasonal performance (SCOP) reflecting changes over the heating season. Some installations include auxiliary or backup heating for very cold spells or high-load periods.

Applications and considerations: Luftkällan systems are widely used in residential and small commercial buildings due to relatively lower installation costs and the absence of ground work. They are well suited for moderate climates, but performance drops at very low outdoor temperatures. Proper sizing, ventilation, noise considerations, and integration with other heating sources are important for optimal operation.

Regulation and standards: Installation and operation are governed by energy labeling, building regulations, and refrigerant safety rules. In Sweden and the EU, regulations increasingly emphasize energy efficiency and low global warming potential refrigerants.