oil boiler flue gas analysis

[brianc1]

hello all, if you cant get the excess air below 75percent without the co going very high, during servicing an oil burner. does it need a new burner or is there anything else you can do

 

[SimonJohns]

Sounds like you have got a nozzle problem

 

[brianc1]

put in a brand new nozzle just before analysis. can the nozzle spray pattern have an outcome on the co/co2 emissions? if i change the nozzle pattern is it possible that the oil/air will mix better and i will get better combustion, therefore less co2 and excess air?

 

[dontknowitall]

I put a brand new nozzle in a while back and had similar results - then broke my fga. I thought, "Brand new, can't be the nozzle" - but it was.

The distance the electrodes are from the nozzle can have a bearing as can the distance of the blast tube from the front of the nozzle. Also not putting the fga in the testing hole far enough can give false readings.

 

[kimbo]

What boiler what settings etc. De rating it might get it back.

 

[Best]

Need to know what burner? Some of the older ( but not necessarily very old) burners have a high smoke number when set as best as you can. If it is a modern burner you shouldn't have trouble. Nozzles can be faulty, even if you are careful not to damage them. Smoke pump, used right should have boiler properly set with new burners normally.

 

[Best]

put in a brand new nozzle just before analysis. can the nozzle spray pattern have an outcome on the co/co2 emissions? if i change the nozzle pattern is it possible that the oil/air will mix better and i will get better combustion, therefore less co2 and excess air?

If you get better combustion, you will, as you say, get less excess air but the co2 will get higher - as it should do. Surely that is the advantage of modern burners & what service engineers should be aiming for, :- high as possible co2 with less excess air & obviously smoke number more or less zero. Co2 is the indication of how well the oil is being burned. The very old burners needed excess air so didn't burn the oil as well as newer burners.

 

[brianc1]

thanks all, will post more info on burner later. in a hurry now. best , it was actually co i meant to type not co2....

 

[brianc1]

hi again. it was an 1991 bentone burner, not sure of the model. the boiler was an old dual fuel thing. you were saying BEST that the older burners needed excess air, i done a servicing course about 5 years ago and the lecturer said you should always set up the burner with about 25% excess air to allow for cold weather, impurities in the oil or bad quality oil etc. what do you think of that?

 

[WHPES]

On some of the older burners, the nozzle holder can get worn with taking them in and out and can leak oil around the sides. Check for evidence of this and if there is, put it in with PTFE round it and try again.

A new burner is a bit extreme to try and solve a problem.

Check the distances between the nozzle, blast tube, electrodes etc are correct for the burner.

Oil pump could be on its way out

Check for air getting drawn into the fuel

 

[Best]

hi again. it was an 1991 bentone burner, not sure of the model. the boiler was an old dual fuel thing. you were saying BEST that the older burners needed excess air, i done a servicing course about 5 years ago and the lecturer said you should always set up the burner with about 25% excess air to allow for cold weather, impurities in the oil or bad quality oil etc. what do you think of that?

When I said older burners, I meant generally the burners from way back in time, that had slow motor speeds and " dead" looking hairy flame. They often relied on excess air. This meant they didn't have high levels of co2. The chimneys/ flues tended not to be" wet", like new flues are, partly due to excess air & often boilers were not made as efficient as now, so high flue temp. Nowadays the reduced excess air is not diluting the gases as much & added to that the burners & boilers, even on standard eff. are more eff. Not sure what lecturer meant by cold weather, as boilers with too much air are more likely to fail on cold starts in very cold days.