On Wed, 1 Oct 2003 13:53:50 +0100, "Christian McArdle"
wrote:

I wonder whether otherwise you could alter the behaviour of the boiler
by arranging a zone valve and bypass in effect across the flow and
return of the CH circuits - i.e. to open when any of the CH zone
valves open.

Not quite sure I get you. Do you mean mix some flow water into the return so
fooling the boiler to modulate down?

Exactly. If you think about it in terms of an electrical circuit,
it becomes clear.


To be honest, I'm surprised boiler manufacturers don't have facilities to
control the flow temperature programmatically. It seems a common
requirement, particularly for underfloor heating and now that condensing
technology promotes lower radiator temperatures (but still requires nice hot
water in the cylinder).


I know. It would make sense, wouldn't it.

At this point, heat banks are not that common, but the idea of being
able to transfer maximum energy into even a conventional cylinder via
coil so that the boiler is off line with respect to the CH for the
minimum time is pretty obvious and a common scenario.

The CH might have a max allowed temp. of 82 degrees if you are
replacing an old boiler and not the radiators - it will still modulate
down when the weather is warm enough not to need full output (and this
is virtually all the time); 70 degrees if you increased radiator
capacity so that there is enough heat output even when it's very cold
and as you say UFH with max temperature of 50 degrees.
Since there are cases where at least two of these might be in use plus
DHW, controllers should really be more flexible. After all, with a
decent controller, essentially firmware based, there is zero
incremental cost to do this.

I suspect that the reason it isn't widely done is because the average
installer is conservative anyway and often does not make three digits
regarding IQ.




Christian.


..andy

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