mike.james wrote:
Thanks for all the comments - as always the subject of condensing
boilers seems to stir a reply :-)

I appreciate the "condensing boiler is always more efficient"
argument but my friend is running a small hotel and been quoted
(rough figures)
£800 for a conventional boiler to do the job and £1600 for a
condensing boiler. So if the efficiency advantage isn't fairly large
the payback time is
going to be long. It seems that there really is a choice to be made
here.
I have the same problem justifying a condensing boiler. Conventional combis
are cheap and easy to fit.
The best case difference in efficiency afaik is no more than 6%.
This would save me perhaps £25 a year. So as far as I'm concerned the
condenser is not viable esp as I don't intend to stay in this house forever
and I don't think having a condenser vs. normal combi would help to sell the
house at all..

As to my "silly" idea of putting their pool heat exchanger in the
return loop
I'm still not sure how silly it really is.

If you were to do this it would be equivalent to putting radiators in series
which is just not done.