Baxi Combi 105e Flame Failure Problem

[quietman]

Baxi Combi 105e fitted in my home, 6yrs old, me - time served plumber but out of the trade for 20yrs although I have kept my hand in.


Brief history -
31/05/11 Fault - flame failure, Cause - contaminated gas valve filter reduced min pressure setting, Remedy - adjust min pressure to compensate. See thread (http://www.ukplumbersforums.co.uk/central-heating-forum/21591-baxi-105e-flame-failure-problem.html)


06/12/11 - Fault - flame failure, Cause - unsure as min pressure seemed ok, Remedy - fiddled with min pressure adjuster and convinced myself that I freed a sticking component in the gas valve.


This weekend, heating tried to come on timed (wife had heating on Friday night, can you,believe it!) but went into flame failure. Decided it was time to change gas valve (bought one last year in case). Went to commission gas valve and experienced -:


Ch and dhw calling for heat, max pressure on u gauge correct, removed modulator wire to set min pressure, boiler shuts down, flame failure.


Ch and dhw calling for heat, boiler lights and runs correctly, dhw tap shut off (no flow) causes boiler to shut down, flame failure.


Ch on, no dhw flow, boiler lights, flame reaches flame sensor then boiler shuts down, approx 6 secs, flame failure.


Dhw only calling for heat, boiler lights with no problem, adjusting dhw flow and boiler appears to modulate flame accordingly, remove modulator wire and boiler shuts down, flame failure.


Current situation, no ch available, dhw working fine although unsure of min pressure setting.
Starting to think PCB might be the problem but would really appreciate any help in further fault finding before shelling out.


ps. Min gas pressure adjustment nut, which direction increases gas pressure?


Thanks for your help.

 

[Poxi]

If its not staying alight with one of the black leads pulled off, Then the min gas must be out espically as the gas valve has been changed (these are not preset, Have to be done when fitted). Small nut goes clockwise to increase min BP Set to roughly 2mbar

 

[quietman]

Poxi, thanks for the reply. I thought that the min pressure might be too low, thats why I asked about the adjustment direction. Whether that might have anything to do with the heating failing to stay on is another question. I really appreciate you taking the time to reply! Thanks.

 

[Poxi]

Poxi, thanks for the reply. I thought that the min pressure might be too low, thats why I asked about the adjustment direction. Whether that might have anything to do with the heating failing to stay on is another question. I really appreciate you taking the time to reply! Thanks.

Yes it would, The heating starts on low flame

 

[quietman]

Got something on tomorrow, fishing Wednesday, then I'll get right on it. Thanks again for the help.

 

[Poxi]

Got something on tomorrow, fishing Wednesday, then I'll get right on it. Thanks again for the help.

Tight lines, Carping or Match fishing ??

 

[quietman]

I like mine with teeth, Pike and Perch, saying that anything that cares to come along!!

 

[quietman]

Crap fishing so time to sort the boiler out. All seems ok now but the fact that when you turn one adjustment nut the other turns as well doe'snt make things any easier. Fingers crossed thats the end of that, watch this space.