Couldnt get the CO down

[Bunker]

Had an old Danesmoor 20/25 the other day, had to change the pump. I set the pp to 110 as per MI and stuck a .65 80 EH in - or whatever it usefully said on the label). I set the CO2 to 11.2 easily, got the Xair ok (33.9) but the CO just wouldnt get below 90. I wasnt that fussed but it bothered me. I ran it for a good 20 mins.
From memory this usually happens if the flame is licking the back or sides but without a window - how do you know?

 

[jensda]

with a co2 of 11.2 id be expecting the excess air to be nearer 37/38 % but I understand exactly where your coming from you would like to know the reason for the high co

 

[keltoyboy]

possibly a slight weep at the nozzle seat..... try a wrap of ptfe on the nozzle and see if that helps....

 

[Best]

I use a smoke pump first. Some old burners won't go up to high CO2 unless smoke number is too high.