Vokera Excell 80sp pilot goes out with any demand

[symills]

Hi could someone help Vokera excell 80sp. Pilot lights and is stable. As soon as there is a demand fan picks up to speed fan pressure differential switch clicks pilot goes out?? Take vacum hoses off pressure switch pilot stays on so the fan is not blowing pilot light but as soon as contact made inside pressure switch no pilot no main burner? Have asked other more experienced lads and all scratching heads and i am getting fed up cos know i must have missed something. Dont want to blame a PCB until I can prove it. An ex gas board guy said it cant be electrical? but its the switch tripping it all out. Please help

[Puddle]

Well I will take it main burner not lighting at all
So first check gas supply to boiler/gas valve/gas valve filter and isolation valve not nearly closed as what happens is you have enough gas going through gas valve to keep pilot alight but when main gas valve opened for main burner small amount of gas going to gas valve is diverted away from pilot to main burner and pilot goes out
Or
This boiler has problems with its gas valve push in spindle sticking so you light pilot and it stays alight when you release knob but metal arm inside plastic knob has stayed in the same position as if you were still holding it in,thus valve not open correctly,you turn power to solinoid and movement can be enough to close pilot as it should of done when you release plastic knob,remove plastic cover and light pushing metal arm in and pull out so you now correct,if problem greese arm or better replace gas valve

or.......

[symills]

Thanks. I did think that I already changed gas valve to see but still same problem so put old one back on. Checked pressure switch good resistance but tried new one still no good. Had 21mbar at appliance too..?

[Puddle]

Thanks. I did think that I already changed gas valve to see but still same problem so put old one back on. Checked pressure switch good resistance but tried new one still no good. Had 21mbar at appliance too..?

Yes but what is working pressure also when power to valve do you get a burner pressure before valve closes due to pilot going out,unscrew solinoid screw,effectively turning off gas to burner when valve opened,does pilot go out then
Also could be the pilot to small or pilot spreader blocked and flame facing burner not operating so presure from burner when lighting,pulls flame away from jet and puts out,the pilot spreader on this boiler has a pointed shield towards burner to direct pilot flame maybe burnt away so although looks like flame at front of assembaly,would not be spreading forward enough,also check main burner clean/clear direcly infront of pilot

or.....

[gas man]

not familer with this boiler is it a combi?

[Puddle]

not familer with this boiler is it a combi?

Yes its a combi,were a good boiler but getting on now,put quite a few in during the mid/ late ninties
Towards the end of the manufacture they changed outer casing suppliers and the pilot viewing slit in casing was in the wrong place,about 4" to high,fitted a few like that,volkera said they would change but never did,but the boiler was good

[gas man]

i have had similar problems to this on early ferrolis,partly blocked low water presure switch or a cooked high limit stat can cause rouge tear your hair out type faults on them what is curious is the pilot light stays on had this once with a ferroli the stat had lost its heat sink compound strange i know but i cured it

[symills]

Yes but what is working pressure also when power to valve do you get a burner pressure before valve closes due to pilot going out,unscrew solinoid screw,effectively turning off gas to burner when valve opened,does pilot go out then
Also could be the pilot to small or pilot spreader blocked and flame facing burner not operating so presure from burner when lighting,pulls flame away from jet and puts out,the pilot spreader on this boiler has a pointed shield towards burner to direct pilot flame maybe burnt away so although looks like flame at front of assembaly,would not be spreading forward enough,also check main burner clean/clear direcly infront of pilot

or.....

Sorry working pressure at appliance was 21mbar at tp1 couldnt get a pressure at all at tp2 for burner pressure.Pilot looked like spreading well and stable.Had earlier observed what looked like burner lighting but flickered away to nothing over burner.? Referance the pointed shield even tried undoing pilot assembly to get closer to burner to see if that was a problem pilot too far away but didnt work. Appreciate you trying to help puddle as customers not being to good think I havent a clue not doing my confidence much good as have always really done installs but i really want to get good at this fault finding and repairs..

[gas man]

strange how your getting nothing at tp2 is the valve adjustable?

[Puddle]

Well think points towards gas supply badly restricted as mentioned in first post

[gas man]

think i would agree