On Sun, 17 Sep 2006 15:36:25 +0000, ARWadsworth wrote:


"Ed Sirett" wrote in message
news
On Fri, 15 Sep 2006 18:03:47 +0000, visionset wrote:


New Vaillant combi.
Any cold mains tap or valve is closed boiler seems to sense increase in
pressure and turns itself on. I imagine without investigating further
that it is heating the small hot water store as it does do intermittently
anyway. This happens every time so it isn't coincidence.
Any ideas?

In addition to AG's reply which I believe to be correct. You can switch
your boiler from intermittently heating the HW by turning the HW knob
fully anticlock and then back to where it was. This will save gas but
the HW will take longer to come through hot.


My parents WB combi (there is no HW storage in this one AFAIK but I would
have to check) also fires up when certain cold taps are used. This is only
caused when the outside tap or utility room cold taps are used and these are
the only taps between the combi and the main stop tap. No other taps cause
this "problem"

Is there any chance that these taps are causing a pressure drop that makes
the combi think HW has been called for?

I still think you need some sort of dead leg (or maybe very poorly clipped
pipework) after the boiler on the HW pipes to get this effect.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards