Heating on but thermostat off?

[duffy78]

My question is as per the topic.

Woke up this morning feeling a bit hotter than usual, fnar fnar.

felt the radiator and the central heating was blasting, went down stairs to check the stat and it was down at 10oC as usual. turned it up to check it was working and got the familiar 'click' as it got to about 26oC. clicked it back off and went to check the boiler.

it was on as expected, so knocked it off via the timer.

any ideas why this should have happened? its a fairly new stat and timer that i had fitted not long ago.

not a combi boiler system

 

[twgas]

usually a motorised valve problem, ie not shutting off completely after a demand due to dirt in system.