Boiler Thermostat

[JohnE]

I moved into a house a few months ago which has a very old gas boiler (probably 25 years old) which heats the central heating and hot water. There is a control on the boiler, number from 1 to 6 (we have this on 2)which I think just controls the temperature of the hot water (the radiators do not have thermostats) so the radiators are either on or off.

Last week the hot water and the radiators suddenly became extremely hot. So now, from having radiators and water which was just what I would call hot, they are now very hot, almost scalding. There is a new hot water tank in the airing cupboard (this has a thermostat). There is a lot of pipework in this airing cupboard with a blue thing which I assume is some sort of pump (by now you will have gathered I know nothing about plumbing). This pump is now also scalding hot.

Would I be correct in assuming that the thermostat on th boiler has stuck open?

 

[jackthom]

If the boiler is anything like the 20 year old Myson unit I just got rid of, this control will also have an OFF position at full anti-clockwise.
With the boiler running hot I would check it does actually switch OFF at this position. It should of course switch before that point when hot and if it's working you should hear a click as the microswitch operates part way up the scale.
If not, I suppose the probe at the end of the narrow copper tube may have been pulled out of the hole in the boiler.

A new boiler sounds like the best solution.

 

[kevplumb]

A new boiler sounds like the best solution.