On Thu, 01 Mar 2007 14:29:59 -0800, kevinbecken wrote:

I have a Myson boiler. The water boils, the overflow pipe make a noise
like thunder as hot water overflows into the header tank in the loft
with a tremendous gush. The overflow pipe is very hot to touch, and
the water in the header tank is hot and steaming. Is this a boiler
thermostat problem? The boiler does this after a couple of hours of
being on for HW and CH and is up to temperature. When I turn the
temperature control on the boiler front panel down to off, it stops.
The pump is working. What's the likely cause, and is it a DIY job to
fix it?
Thanks
Kevin

Is this a boiler with a dial thermostat or simply a high/low switch?
Either way the thermostat in the boiler has gone.
This model clearly doesn't have any sort of over-heat stat.


--
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