combi not switching off even tho return water is up to temp

[theboykidney]

HI,
When my combi boiler is on timer and is heating the house, it doesnt switch off when the return water is hot, it just stays on until the timer switches it off.
Are there are tests, checks I can do to further diagnose the problem, or is this common and theres and easy solution?
cheers,
tbk.

 

[dcawkwell]

If you have no wall thermostat to tell the boiler the house has reached temperature the boiler will continue to maintain the water in the central heating pipes at the set temperature. That is it's function.
Modern combi boilers can modulate their burners down to maybe 5 kw.
So if the heat loss in the radiators exceeds this the burner of the combi will continue to fire all the time as it works most efficiently in this mode.