"IMM" wrote in message
...

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

Yes. Larger rads.

Can't fit larger rads hence my "silly" idea.

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".

No that isn't the reason its silly.
Its easy to arrange for the exchanger to be connected to the flow when the
house heating is off (really off as in summer).

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.

Why do you think my arrangement would put the boiler outside its temp
difference.
If you read the previous post you'd see that it brings it into its desired
delta T.

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.

Currently the pool gets 6 hours of heating in winter and the house 12 hours
plus.
I can't see there is a problem in extending the pool to 12 hours - or as
long as it
takes using a thermo controller.
At this point you seem to be telling me that it might work.

My main point is that in this situation there is a huge heat sink that could
be used to cool the return flow and hence increase efficiency - its a fairly
unique situation.

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.


I need to think about this one.
mikej