Air to water heat pump heat exchanger

I am seeking information regarding heat exchanger medium. I plan to install either an air to water or ground source heat pump of around 12KW in a domestic environment. My main problem is to find out if the heated/cooled water is directly used in the heat exchanger mounted in the roof or do I need to have a refrigerant based condenser/evaporator, and what would be the efficiency of both when compared. our climate ranges from 5c to 45c winter to summer.
Many thanks in anticipation, I'm a new Australian member of your terrific forum.

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Not quite sure on your description so I'll explain how the heat pump works :D

Air sourced

The heatpump is in contact with external air and the heat is transferred directly
into the refrigerant from the heat exchanger (called the evaporator), this heat
is then transferred through another heat exchanger (the condenser) to the water
system in your house. This water then travels through radiators and or the hot water
cylinder to heat the house and water, also underfloor heating loops as well.

Ground sourced

Have a loop of water passing through the ground collecting the heat, this is transfered
into the refrigerant (via the evap) and then the heat is passed through the other heat
exchanger (the Condenser) and this is the water loop same as the air sourced that
passes through radiators or underfloor heating.

Hope that helps a bit?

Rob

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As for efficiency air sourced are subject to fluctuations as ambient temps
change but ground sourced is fairly constant and stable because the temp
of the ground at 2 mtrs down is fairly stable.

So if comparing air to ground the air will fluctuate in temps during winter
and summer but the ground would be a bit more stable and constant.

Rob

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