"mike.james" wrote in message
...

"IMM" wrote in message
...


6%?? look at http://www.sedbuk.com More like 12% according to sedbuk.
If
the system is engineered to take advantage of a condensing boiler, then
more
like 25%.


Now this brings me back to my original point.
What does "engineered to take advantage" mean - lower return temperatures?

Yes. Larger rads.

Hence my "silly" idea of putting the pool's heat exchanger in the return
flow.

Your idea will only work when heating is on, as the heat exchanger is on the
return pipe, which is "silly".

As Andy and myself have highlighted, a boiler should work "inside" a
flow/return temp difference. Outside this for sustained periods can cause
big problems. When control is on the boiler you are fooling it and it may
not react the way you expect, or want.

Look at a swimming pool. What is the ideal temp? 23C? Most of the time the
return temp from the pool will be between 15-22C, cold enough for excellent
efficiencies in a condensing boiler. Assuming the pool is indoors. If
outdoors then the return temps may be very much lower. The boiler will be
operating all night to raise it a degree or two. Most swimming pool have
the pool heated all day and the temp setback at night. It is knowing when
time the night setback has to return to normal day temp, as it will take
hours to raise the temp.

I would go for basic condensing boilers, and have stand-alone control for
the pool heater, DHW and CH. This is a commercial setup, so control it as
such. The likes of the ICOS and Keston Celsius are for domestic properties.

B&Q have for sale the Ravenheat CSI for £400. This is basic. Two of these
will do with separate stand alone controls.

On the pool heat exchanger have a blending valve set to the minimum the
boiler heat exchanger can have. Say 80C flow and the boiler heat exchanger
temp diff is 20C, then set the return to 60C. There is a danger with a pool
of having a very large temp diff, so the blending valve puts the heat
exchanger into the correct temp diff range. You could have the blending
valve set to 40C and the boiler flow temp to 60C.



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