Don't ignore the obvious cryptic - there's a lot going on in a modern combi - and they way they interact isn't always obvious. I had one that would now and again stop producing hot tap water - turned out the bearing on flue fan was a bit rough - now and again it would slow down, the pressure difference across the fan would drop which tripped the pressure switch and the PCB shut down the burner. Didn't seem to happen in heating mode - possibly it wasn't running quite as hot then or wasn't producing quite the same volume of exhaust gasses.
Don't ignore the obvious cryptic - there's a lot going on in a modern combi - and they way they interact isn't always obvious. I had one that would now and again stop producing hot tap water - turned out the bearing on flue fan was a bit rough - now and again it would slow down, the pressure difference across the fan would drop which tripped the pressure switch and the PCB shut down the burner. Didn't seem to happen in heating mode - possibly it wasn't running quite as hot then or wasn't producing quite the same volume of exhaust gasses.
