On 22/10/2019 01:48, Rod Speed wrote:

Argh, so I really need to find data for the heating and the cooling
cycle.

Probably in the UK the heating cycle figures are more important as its
more likely to be fitted for winter heating rather than the few weeks
during the summer where you may benifit from AC to cool the air.

Try searching for Coefficient of Performance (COP) for heat pumps and
you may get some clues why different figures may be quoted and/or why
some of the claims made for the use of heat pumps in the rest of the
world may not directly apply to the UK. This doesn't stop companies in
the UK from making some of these rest of world claims.

Consider the average monthly temperatures in the UK and you may find
some of the higher quoted figures can never be achieved in our climate -
or possibly not achievable without a more specialised design which may
not have a payback period in a domestic environment. I do appreciate
that for some people saving the planet rather that saving on energy
bills is more important and cost is not a factor.

COP rises with a higher input temperature
COP falls with a higher differential temperature (higher output temperature)

In the UK the (air) source heat pump becomes less efficient as the
temperature falls during the winter AND if you attempt to have a higher
output temperature to run an existing "conventional" radiator system or
hot water the efficiency also falls. Hence why lower temperature under
floor heating and/or much larger radiators are recommended. In this real
world scenario you may be looking at (SEER/Heating) figures of 2 to 5
rather than the top line 14 minimum for the USA.

Even sites promoting heat pumps suggest that insulating the house is an
important part for the installation.





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