Baxi 100 HE overheats and melts heat exchanger - an explanation

[buckley plumb]

as this post states only noticed the burner panel lifting on full hw max gas rate as stated by thread starter one to watch for - this customer was lucky from what the thread says the heat ex could melt .

 

[TheGasEngineer]

These are brilliant photos. Thanks to Buckley Plumb. I wish we could find more examples and then I would be willing to go back to my MP. In fact I may just do that anyway. I know there are other boilers out there that are much worse. This is not too different from the one I encountered in 2010 which finally made me think about what was happening. I mean, would you look at that burner and think there was anything wrong with it? Probably not. Clearly a really hot flame has come from, presumably, the burner. But then there is the dilemma of how could that happen? Once it is explained that the glue of the ceramic gives way and allows the ceramic to lift and create a big gap around its edge, then the downwards flame becomes a realistic proposition.

The Sherlock Holmes - type mystery is then put in place by the ceramic settling back into the burner base making it look perfectly OK. And once it has cooled the ceramic will be secure and not give any clues that it is faulty. The one I saw in 2008 had a totally melted heat exchanger but the burner looked just the same as above. I didn't take a photo ... aarrrgggh!

I actually think this boiler would work perfectly well if this fault did not exist. Ok, the trap would be a pain; but there would be none of the lock-out or overheating issues. I have replaced burners on a couple of these and they are running fine. I have a note when the third anniversary is due, and the customers are happy to pay for new burners as I have recommended.

Actually I think BPs customer was lucky because this boiler could easily kill. It could start a fire as easily as can be. There may already have been incidents. A full-blown fire would destroy the boiler though and effectively destroy the evidence that shows how the fire started. Baxi are fully aware of this issue now because I have told them. They know however that any fire would destroy the evidence that would otherwise condemn the boiler. The only way we can make the authorities take notice is to find more pictures and installers who would be willing to tell their story.

 

[Dotty]

Right, now we've non verified gsr's joining in on this. I've been uneasy about where this thread was and letting it ride but enough's enough.

Moving to the private forum.

 

[arran197]

There's a few of these on my patch, I've changed 3 burners so far I think. I'm just waiting for the next one to go.

 

[SafeGasInstall]

I have re system boiler at the new house , boiler does not responded to thermostat knob and only cuts out on the high limit ..... thermistor reads 2.6 k ohms
high limit stats are on 0.5 ohms .... Burner pressure is 18.5 mbar
any one experienced this ?

 

[arran197]

I have re system boiler at the new house , boiler does not responded to thermostat knob and only cuts out on the high limit ..... thermistor reads 2.6 k ohms
high limit stats are on 0.5 ohms .... Burner pressure is 18.5 mbar
any one experienced this ?

Have you checked the inner door seals? The red seal crumbles away and the fan limit stat trips, throwing the over heat light. The boiler might not actually be getting that hot for the control knob to work.

 

[buckley plumb]

Have you checked the inner door seals? The red seal crumbles away and the fan limit stat trips, throwing the over heat light. The boiler might not actually be getting that hot for the control knob to work.

in worse case the burner can lift causing melt down

 

[SafeGasInstall]

I have cheked all burner seals and they are good . CO is 15ppm and ratio 0,0002
the problem I had was exp vessel lost pressure and I pumped it up and had a air lock in hex ..... All running smooth now