Ferrolli sigma 40-60 trips fga.

[Gary80gas]

Im stuggling to get a ferolli sigma 40-60 within fga limits. It passed ok about 4 weeks ago but I revisited to fix a tripping fault but that is now ok, just a loose cable. However I retested and the co trips my analyser. If the fan runs well enough for the air pressure switch to get the burner to light, can it be said there is no problems with fan pressure or fan speed? The boilers burner pressure and the gas rate look ok. The flame picture looks good but as the casing is put back in place I can see the flames go soft yellow orange, starved of oxygen. The fan looks to be running at speed. Im going to pull the burner and fan assembly apart tomorrow, but dont want to change parts without very good reason . I dont want to cap off a second time. Although ive been installing and fixing simple faults for years Im working hard to learn more about fault finding and would appreciate very much any help or ideas.

 

[PhoenixServices]

Personally if a ferroli was tripping out and having high co, I would be ripping it off the wall.
Is the flue air intake clear? Recirculation of poc?

 

[ShaunCorbs]

air intake/flue blocked ?

 

[bewsh]

I think these suffer with the flue seals failing.

 

[lame plumber]

some ferrollis have flue restrictors, which if removed, cure the problem

 

[Billy Bob Bob]

cant you do a flue integrity test on this? check the 02 side see if co is mixing

 

[ambrosia]

within fga limits

which limits do you mean the gas reg ones or the manufactures ones?

the gas reg ones are very lenient, any boiler which comes close has serious problems and if you can see the flame picture going orange thats a dangerous boiler and in my opinion should not be left working

 

[Gary80gas]

Update-I took entire fan/flue assembly to pieces and replaced flue seals venturi/apc connections all had perished. Problem solved. Thanks all.