Yet another boiler thread!

[52classic]

Help needed please... Saulier Combi about 5 years old...
Trips out. i.e. the red light comes on and it needs to be reset.

Plenty of pressure in CH system. Good hot water delivery but after 20-30 mins running it 'trips out.' Just resetting the button gives it another 20-30 mins. Just the sort of fault that would have said "thermocouple" on a conventional but this one has me stumped.

So.. Do we have a plumber/heating engineer in the house?

[dealmaker]

Any rads switched off or thermostatic rad valves turned down (especially at etxremity of loop?) - this sometimes trips ours - water wants to circulate and if the pump is having to try too hard it sometimes fires the trip.

[52classic]

No. All clear. Went 'round bleeding everything earlier today. Found the bleed screw behind the pump was weeping slightly but otherwise no problems.

Problem is unpredictable, sometimes it will sustain the overnight 'off' period then strike up OK in the morning, other times it will just trip off without warning.