grant vortex combi 36 overheating

[boilerweary]

I have spent significant money on replacing a number of parts on my boiler. first was a complete new control panel then came the pressure vessel. the boiler has been working very well for a while but has suddenly started to overheat which shuts down the hot water and UFH. i have checked the pressure but this is fine. If i reset the boiler it then works fine again for another couple of days and then overheats again.

any suggestions as to what the problem could be would be most welcome

 

[oilhead]

Is the overheat occurring during heating use or hot water use? I service a combi 25 where the heating is all on underfloor with only a towel rail radiator, and when the mixing valve on the UFH goes into divert, there is too little pipework to disperse the residual heat; thus overheat. I de-rated the boiler to its lowest level and this cured it.
Turn the thermostat down as far as it will go and see if it makes any difference.

 

[boilerweary]

Many thanks. I'll give it a whirl. Your solution echoes what others have said. Will give it a couple of days and report back