Hot water tank boiling and bubbling

[traceylattimore]

I've got an old-ish floor standing Potterton boiler, and whenever I set the hot water to come on (gas), about 20 mins later the hot water tank in the loft will bubble and rattle like mad. I've seen it happen and it looks like boiling water is coming out of the pipe in the loft. It's really scary, but a local plumber couldn't find a problem, though I suspect it would be due to a thermostat.

Any ideas? I will call out another engineer, but would like to understand what may be causing this first.

Incidentally, we are now only using the immersion system to heat the hot water, but even though it is set to 60 degrees, the water is scolding when it comes out. But surely this is a separate system and thermostat?

Any help appreciated - thanks!

Tracey

 

[Agile]

I think you need a competent plumber! How could he come and say there is nothing wrong?

A better one can reset your immersion heater temperature.

Tony

 

[namsag]

Two completely separate faults but both thermostat related .

Boiler stat has gone and is out of calibration and needs replaced .

Immersion stat may need turning down (turn power off) then remove top of you will see a little dial with an arrow this should be around 55/60 if its higher turn it down if its already at that then new stat is req which is usually a 5 minute job it just pulls out after disconnecting the wires