Firebird c20 sooting problem

[Gazzt]

Anyone had issues with firebird condensing boilers sooting. They are a pain to clean, and they dont run well at 11.5 C02 you have to leave them around 11.0 C02. Has anyone got advice on this.
In my opinion the design is all wrong.

 

[WHPES]

Yes, on one of the two I look after I have played around with the pump pressures and air settings to find the optimum efficiency. On the other one, which is the same boiler, it seems to perform fine at 11.5. I don't like them much myself.

 

[Best]

Would it also depend on the flue length and terminal location?
Reason why I am asking that is the more resistance, negative pressure that a condensing oil boiler has, the more excess air needed and so the CO2 would need lower.
I dislike Firebirds and never will install them.
On Grant Vortex I can get 12% running well, but just reluctant to leave them that fine set.

 

[SimonG]

Like the firebird.