Worcester 350 Combi CH problem

[Mike Doyle]

I have a Worcester 350 combi-boiler with a repeatable problem that the service guy can't seem to fix! After about 2-3hrs of being on, the central heating cycle of the boiler stops and the pipes go cool. The pump still pumps the water round, but it's not firing up to heat it. Have replaced the temperature sensor and a variety of other things.

I found I could temporarily resolve it: power the boiler off and on, or press the reset-buttons (day and min) on the front panel to reset the clock to 12:00am (if it got scrambled this is what it says to do). This pretty much always works. For another 2 hours.

What do I need to replace to fix this?

Mike

[Ed Sirett]

In the face of things it sounds as if the clock/programmer unit is giving trouble. Given that the only thing you do is to reset the clock and the HW works fine (implied in your post) then replacing the clock should work.

It might also be possible to by pass the clock and use some sort of external programmable thermostat.