Baxi 100/2 HE PLUS - Overheat Lockout problem

[mustard]

My Baxi 100/2 HE PLUS - is 4 1/2 years old, it replaced a 4 year old Baxi Barcelona condensing boiler which was so unreliable that Baxi agreed to provide a new unit at a special very low cost.

Now this 100/2HE has started locking out on overheat i.e. the red light flashes. When I press reset it will work well for perhaps several days, then lockout again!
Following Baxi's Fault Finding proceedure I have just replaced the flow pipe black stat & thermistor, also the combustion chamber seal, it has locked out once since then and is now leaking condensate water when cool. What next! I am a competant Engineer & am satisfied I am working safely. Advise appreciated please.

 

[Agile]

First you need to spell the word competent like this!

If you were fully competent to work on boilers then you would not need to ask questions here. I dont see why you would want to replace thermistors. What resistance did they measure?

Unless you are gas qualified then I cannot recognise you are competent to work on gas. We only give advice on gas matters to qualified people who can be authorised to access the special part of this forum.

This may be the model which has had issues with the ignition lead.

Tony

 

[powell30]

If it's locking out on overheat tony i doubt it is an ignition problem

OP. Your issue is heat exchanger related. Unfortunately it will require an RGI to fix for you

 

[Agile]

Sorry, I did not mean to infer that his fault was associated with any ignition issue.

Changing the combustion seal is beyond what a non gas person should have done and all the implications are that a gas registered person will be required to diagnose the fault ( apart from checking that the seal is safely fitted ).

Tony

 

[mustard]

Agile, powell30, thanks for your comments & spelling lesson -it was a typo really!
Of course I also totally agree most of this work must be carried out by a RGI, -certainly where the majority of clients are concerned. (I received training in the past & have also watched the Homeserve & other Engineers work on my boiler so many times that I could do most of the work with my eyes closed!!) Replacing the combustion door gasket is hardly rocket science Agile!
Getting back to Baxi 100/2HE boilers, my original posting was intended to tease out known faults & repairs because I experienced similar breakdowns with the earlier Barcelona model. It appears to be a weak point which Baxi have not designed out yet.
It is mighty irritating to have to keep looking out for the red lockout light or noticing that the house is getting cold -again! The reliability of many condensing & combi boilers is appalling in the UK, or are they made with built in faults to keep the trade busy? -OMG should I say that!

 

[Agile]

I would suggest that the owners are more to blame for not having the boilers properly fitted and then never getting them serviced.

 

[whigwood]

My Solo HE 50 did this for three months and had virtually every electronic component renewed, plus a chamber door seal, plus a new pump, plus a system flush. Some expense!

In fact there was a hairline crack across the right front corner of the burner plate, causing extra flame on that side - which is the side where the thermostat is. This flame wasn't visible through the inspection window since it was well off to the side. When the fragment eventually blew off completely, the ignition sequence became quite spectacular because of gas in large quantity coming through the new hole.

The plate is now reversed and the broken piece is wedged inplace by bending the retaining lip. A new plate is awaited. Lockout has stopped!

 

[Agile]

My Solo HE 50 did this for three months and had virtually every electronic component renewed, plus a chamber door seal, plus a new pump, plus a system flush. Some expense!

All of that is as a consequence of inadequately trained/experienced people who were unable to properly identify the real fault.

The OP made a comment that "changing the combustion seal is hardly rocket science".

I would totally disagree with that statement. The 1986 Challenger shuttle launch exploded and killed everyone on board just because the combustion seals on the booster rockets failed !

Changing combustion seals in NOT a DIY job because after it has been done the boiler needs to be checked with a flue gas analyser. At £500+ thats an instrument few DIYers are likely to have.

Tony Glazier

 

[45yearsagasman]

It was the Challenger Tony. All on board Apollo 13 returned safely.

 

[Agile]

I was correcting it as you were typing that.

The Apollo 13 mission is memorable because it nearly ended in disaster when the oxygen tank exploded.

Cleverly the crew transferred to the landing module with its own oxygen supply for the rest of the flight and I think used their spacewalk suits for the re-entry.

Regardless, the boiler combustion seals perform exactly the same function as those rocket seals! As we saw both can fail !

Tony

 

[whigwood]

@agile
I didn't mean to imply that I did any of that work myself. Don't know what the RGI would say in response to your comment though, especially as at least some of the wasted work was done at Baxi's recommendation!

 

[mustard]

This particular unit has been serviced by a RGI Pro, overheat lock out still occurs very very occasionally, I have now turned the boiler thermostat down to about 11 o'clock (from 12 o'clock) -since when it has not failed, I now think it may have been simply running too hot, -what do you guys think?
Regarding the combustion seal, to compare this with the space shuttle seal is doing NASA a disservice, there is no technical comparison, except they are seals! I am quite capable of removing the old one & applying a new one with out gaps!