# Air to Air Heat pumps



## colm5 (30 Apr 2011)

Hi folks,

Was wondering if anyone has any experience with air source heat pumps providing space heating in the home through hot air circulation such as in the links below.

Was thinking about this as an alternative for a conventional wet system which needs replacement in an old dwelling and would welcome any experiences from people using these and how effective they are, plus are they effective in old buildings etc..

Rather than a conventional wet system, just one of these pumps on each floor and a combi boiler for hot water, and so eliminating the cost of the plumbing system replacement plus radiators. Additionally, these should operate cheaper than a gas system per kW ouput.

http://heatpumps.scanhome.ie/
http://www.worcester-bosch.co.uk/homeowner/products/air-source-heat-pumps/air-to-air-heat-pump

Thanks 
Colm..


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## DenisP (2 May 2011)

If you have natural gas available you won't beat it as a fuel choice. The only benefit to be gained from a heat pump is at night time when you can avail of cheaper night rate electricity. Using heat pumps during the day will not stack up on a KWhr cost vs natural gas. 
With day time electricity approx 17c kwhr and a heat pump with a COP of 3 you are looking at 17/3c Kwhr. You will never get the heat up to pack back for itself if you intend to use it during the day. A wet system has the advantage of using the thermal mass in the floor as a heat store. How air systems can't do this.


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## Trilogy 1982 (3 May 2011)

I would have serious doubts about air to air heat pumps in a domestic situation. Air to water, fair enough but the example in the first link seems to depend on you leaving doors open throughout your house to leave the heat circulate (which I doubt it will properly)

Add to that the cost of €2900 each. Thats €5,800 for 13.2 kW of heat. Add another €1500 for you combi. Thats €7,300 for a system that relies on you leaving doors open to heat you house. Also 13.2kW is not a lot to heat an old house with (obviously depending on its size)

To get the system to work some way effectively you will probably need to duct the air around the house, so thats another cost.

In addition, as the link says these systems are used in many Scandanavian homes. Scandanavian homes are built to an extremely high standard when it comes to insulation and air tightness and would have little in common with an old building in Ireland in these areas.  

This system will pressurise your house and old buildings leak air, therefore the heat will be forced out at a greater rate with a conventional wet system.

One final point that is worth bearing in mind is that the COP quoted is likely based on a certain set of "ideal" temperature conditions and may not reflect the seasonal COP of the unit.

I'm not out to rubbish air to air heat pumps but like any technology they are suited to some applications more than others and I dont think yours is one of them.


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