"Andy Hall" wrote in message
...
On Mon, 20 Sep 2004 00:19:40 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Sun, 19 Sep 2004 23:50:08 +0100, "IMM" wrote:


"Tom" wrote in message
...

Thanks Andy, would you agree that the Alpha might induce condensing
conditions in my standard boiler, assuming that thermostats and TRV
are
susceptible to frequent adjustments in my household :-(

As long at the boiler is set to 80C this is highly unlikely when the
system
is warmed up.

You may require a minimum flow through the boiler. Then I would forget
the
Alpha a go for am open rad and room stat.


You can set the nominal power level on the Alpha above or below
nominal setting.

If all TRVs are close, no flow. It is best to get a flow switch rated at
the minum boiler flow. below this flow the boiler burner is cut out.
The
pump can still pump through the boiler.

http://www.crydom.co.uk/
http://www.axdistribution.com/FluidM...ow_switchs.htm

I see your point, but these are far from being precision devices.
For example, the Crydom ones have a 2:1 or 3:1 switch on/off flow
rate, and these are max and min figures.

One would have to put some valves around and in series with the
switch to tune it to the correct behaviour.

That is the cheap way. Precise flow switchs, even adjustable, are
available, but not cheap as they tend to be for commercial applications.

I suppose a more accurate flow sensor that measures the flow coupled
to some electronics sould be used, but this is going to cost a bit.

Even so, I agree that if the existing pump is OK, it makes more sense
to try that first and only switch to an Alpha if there is a problem
with noise in the radiators closed down case (i.e. reduce pump
setting), but that that is not enough wit everything open.


.andy

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.andy

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