Baxi 100 HE Condesing Boiler

[Jim Cooper]

Hi, can anyone advise, m y Baxi 100 HE boiler keeps going onto 'Overheat' on a regular basis. Just recently every hour. Any advice would be appreciated.
R
Jim🙁

 

[cwrplumbing]

Hi, can anyone advise, m y Baxi 100 HE boiler keeps going onto 'Overheat' on a regular basis. Just recently every hour. Any advice would be appreciated.
R
Jim🙁

Need more information How many times is the red led flashings ?

*flashing 5 times a second dry fire lockout
*flashing 1 times a second safety lockout
*flashing 4 times a second thermister open circuit
*led on all time ignition lockout

Engineer needed to check boiler imho lots of thing to check !!!

 

[Jim Cooper]

Thanks cwr,

I cannot tell you at present how many times it is flashing per second, as I turned down the thermostat to 20degC and it hs not happened since. It is doing what it should do at this setting, just kicking in & out as it reaches this temperature. Without saying the obvious, does this explain anything

R
Jim

 

[Jim Cooper]

Had to get corgi fitter in. Problem was, seals to combustion chamber disintergrated. CF fitted new seals. Boiler back to normal.

I was suprised😱 to see how Baxi had packaged the seals. They were crumpled into a plastic bag, leaving them bent in places. Wouldn' it be preferable if they were attached in a straight position, to a peice of card. As they have to straightened out to be placed on the combustion chamber cover.

Has anyone else experienced this?

R
Jim

 

[TheGasEngineer]

Overheating Baxi 100 HE condensing boiler.

First of all switch that boiler off. It's DANGEROUS!! read on...

I think I know the answer to this one. It’s a loose burner ceramic face but it only becomes loose when it gets hot. When it does become loose it lifts and lets tons of gas into the combustion chamber. The boiler overheats enough to melt and distort all the lower parts of heat exchanger aluminium and wreck the door seals - it cinders them. There is no chance to do a gas rate to detect all the extra gas going in. Then it overheats and shuts down usually via the fan stat. On stopping the ceramic then drops back into the metal burner base. When it’s cool enough to handle the ceramic it's held rigidly in place again, sitting there all innocently.

About a year ago I was called to a 100HE and the sump of the heat exchanger and 2 to 3 inches of the lower side walls had melted. It was a mess. I could not think how sufficient gas had entered the combustion chamber to get so hot. Of course the ceramic element was sitting there as it should and was (apparently) secure in the pressed steel base.

I think I discovered the cause of the overheating today in a 100HE that has kept me baffled for a week. The flow switch had failed and the lower manifold was leaking just to add to the confusion. When to door came off the seals had gone but not cindered. I fitted new ones and left it running. This time it seriously overheated and melted the sump base. I thought I had not put the seals on properly. I talked to Baxi technical but they hadn't a clue. With a new base, flow switch and manifold o-ring in place the boiler overheated again (**Screeem**) and I saw it get red hot inside and heard it roar. I didn't know what the roar was. There was damage but not too bad and so I ran it up again and watched very carefully. Initially the flame looked as it always had from cold - blue and fairly quiet (normal even). And then bit-by-bit it started to roar and the internals of the combustion chamber turned cherry red. Then in an instant as it was really overheating I happened to see the ceramic lift. I couldn’t believe it at first but then it stuck half out and when it cooled down there it was jammed solid but at an angle.

However… there is a possibility the gas valve has malfunctioned and admits too much gas, but I’m not sure that a zero governor valve can do that.
I will be back with the further results or if lucky with the definitive result.

 

[Toddyplumb]

Interesting that took one out last year , 3 years old , bottom of heat exchanger melted.

 

[TheGasEngineer]

Definitive result: A new burner fixed the problem. It was very noticeable that the ceramic of the new one was much lower than the old one ie glued securely. As soon as the old one began heating it would lift and let extra gas flow into the combustion chamber. In fact there was so much gas that the working pressure dropped to 14mbar where now it runs at 17.2mbar (the meter regulator was shot and will have been replaced by now so I expect to find 19mb+ on the next visit) which, incidentally, would create an even more dangerous conditions if the burner failed again...

What seems to happen is the glue begins to fail and little by little the ceramic lifts - maybe over several weeks. So the boiler starts to run hot and I guess this contributes to the failure of the manifold O-ring and maybe even the flow switch. If you think about it, if there is overheating, it must be excess gas. It can't be anything else. The problem is that once the boiler shuts down the ceramic drop back on its seat, this glue solidifies and amazingly looks to all intents and purposes like a perfectly serviceable component.

I find it shocking that Baxi haven't recognised this fault. From what I see there are multitudes of these boiler breaking down like this and they could be salvaged just by replacing the burner every three years. It just needs Baxi to admit it and put out a general warning. I think a warning is necessary because it's a fire-bomb waiting to happen.

I rang Baxi tech support and really pressed them about the excess heat and they didn't have a clue. There was not one suggestion or offer of help or any interest at all. I told him about the low working pressure and he said this would seriously affect the performance of the gas valve. Rubbish!! Actually this is where the zero governor is a pain - as soon as the flow restriction of the ceramic was lowered (when the ceramic lifted off its seat) the flow rate through the fan rose exponentially and the valve just increased the flow of gas to match resulting in an inferno in the combustion chamber. If that is not a design fault then I don't know what is...

So if you service the Baxi 100 HE range (or any boiler that uses that burner) I suggest it's replace every third service.

 

[Billy Bob Bob]

just been asked to service one,the first i have ever seen(105e/he)more popular passing it on to heat team dont want to know(and i will work on most things)what a heap but it comes in many guises 100he,barcelona,solohe and what ever they call the potterton version

 

[TheGasEngineer]

I find that if I can understand the failure mechanism then it's easier to keep them working. For instance...

Have you ever had trouble with a damp condensate trap forcing flame failure?

 

[Toddyplumb]

Yep had that one , now carry kitchen roll and a hair dryer . If condensate line is open to a wind it splashes up in the trap and operates the blockage sensor

 

[TheGasEngineer]

So your point is not to have wind when servicing a Baxi? LOL 🙂

Sorry, couldn't resist... but interesting point. So extending your point, it might happen that flame failure lockout occurs more at windy times, perhaps? Never thought of it before.

I've just written this. Hope it's of interest
http://www.ukplumbersforums.co.uk/c...he-condensate-trap-causing-flame-failure.html

 

[Toddyplumb]

Yep , we fitted a 105HE years ago , everything was fine until customer chopped the end off the condensate line (To plant a bush !!!!!!!!) You could see the trap bubbling as the wind blew up the pipe.
And yes its not good to have wind when servicing😉

Jim , regarding the seals I agree the packaging is rubbish , we carry them as spares on the van for the reason you found .