Baxi 105e Combi CH fault (only when boiler is cold!)

[Damoegan]

Hi Guys

I've got a very strange problem with a baxi 105e and need a little advice please.

The problem is that when the boilers is stone cold (first thing on a morning or after work on a evening) and the CH timing trys to fire up it gets a 'flame failure' fault on it..

Now, if I reset the boiler, turn on the hot tap, the boiler will fire up fine and I get hot water. If while the hot water is running I turn the CH on it will stay on! And when there is some heat in the system the CH will work from the timer just fine, until the morning or evening...

When the failure occurs (cold boiler) everything seams to work in the correct sequence, pilot rails light but go straight out!

I've replaced the CH temp sensor and DHW diaphragm in the diverter valve, still the same. I've prove out the microswitches & cleaned the combustion chamber..

Now if I go through the fault finding sequence off the Bxi pdf it points to the gas valve and/or PCB. I've sort of rueled out the gas valve as it works just fine on DHW so surely it only leaves the PCB?

Thanks in advance
Damien

 

[Agile]

We dont encourage or advise that DIYers do any gas work and that includes opening the combustion chamber.

The obvious advice is to call a competent gas registered engineer!

Crezer does not seem to know the forum rules!

Tony

 

[Damoegan]

I'm a fully qualified engineer (electrical and mechanical) and all gas, water and power were isolated while opening the combustion chamber...

I will not be changing any gas parts myself, I'm just trying to get a handle on what the problem could be.

Thanks

 

[Agile]

Regardless of what other work you may be qualified to do you obviously have not received training or accreditation in gas work. Otherwise you would have know that you should not have opened the combustion area.

Thats irrelevant anyway as the forum rules prohibit giving gas advice to ANYONE even if they are gas qualified for the obvious reason that anyone can read it.

If you are a well qualified C Eng then you are going to have a proper job at a good salary and be well able to afford to engage a qualified person.

Tony