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Air to Water Heating Systems

These units utilize the heat in the outside air and can operate in temperatures below –10°C. Their efficiency is much lower than that of the Water to water as more power is consumed moving the air and raising the temperature through a greater temperature difference. Also a factor which is not considered in the efficiency calculation is the energy required for defrost. In Ireland we have a damp, humid climate. Therefore the air contains alot of moisture giving rise to alot of ice forming on the evaporator. Unbelieveably, this is not a problem in much colder countries where the air temperature is sub-zero as no moisture is contained in the air. Even though their ambient temperature is lower their heat pumps often operate more efficiently.

Another aspect is that as the ambient temperature falls so too does the performance of the unit. Therefore when you most need heat the unit produces less. For this reason the industry considers this type of heating as by-valent (requires back-up/assist). Many units incorporate immersions as this back-up, this in return reduces efficiency from 350% to 100%.
Air to water units are rated to operate at 2°C and 35°C at this temperature an efficiency of up to 350% can be expected. The benefit is that no earth works or well boring is required for the Air to water units, resulting in reduced capital expenditure. An Air to water heat pump can be used for central heating, domestic hot water or a combination of both.

We recommend using a small air to water heat pump to suppy domestic hot water outside the winter months and using a water to water or other ground coupled heat pump for winter time heating.

The use of an electric immersion can be avoided completely with energy savings of up to 75% when an air to water heat pump is utilized.


Enviritech Engineering Ltd,
Unit 6, Enterprise & Research Centre, Institute of Technology Carlow, Kilkenny Road, Carlow, Ireland.
Tel: +353 (0)59 91 76261 | Fax: +353(0)59 91 76377 | Email:
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