C.H hot water Kettles if room stat over 15c. I have turned down boiler temp.dial from high to low but this still happens even if domestic hot water is on or off. When I turn the boiler temp. dial there is no clicking sound as you would expect when the thermostat clicks on or off. The pump has been replaced.
Could the boiler theremostat be faulty? Thanks

Ivan C., November 2008

Sounds like the thermocouple (the cigarette-shaped bit) has gone in the thermostat control (part number 800849 for your model) which is labelled 9 in diagram 11.1 in the online manual at

http://www.glow-wormorders.co.uk/manuals/pdf/Boilers/Ultimate40FF.pdf

This will render the thermostat dial inoperative, and allow the water to boil.

Mark, November 2008

prob dirty system water or scaled heat exchanger

matt, November 2008