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brianc1

hey lads,

have noticed a couple of riello 40s that i have serviced and set up with fga starting to produce some black smoke after a few weeks. they are both old and when i went back and inreased the air intake a little bit they worked fine. im presuming the burners are just on their last legs and parts are starting to wear. any other suggestions?
 
Could be wrong oil pressure or air settings incorrect, or failing oil pump, or blocked up flue.
 
oil pressure and air was correct and had tweaked it with a flue gas analyzer. anyway if they were wrong i would be getting incomplete combustion and therefore black smoke straight away as opposed to a few months later. im not sure if a blocked would create black smoke????? or just cause lockout. co2 usually around 12%. i set them up keeping the co below 80ppm and excess air around 25% and usually the cos is around 12% then automatically.
 
Maybe set too fine. Use an ordinary smoke pump first, & set air setting. Set smoke number to zero on smoke scale. Don't listen to anyone saying the smoke number is ok if higher than zero for that burner. The co2 should be 10.5% or more on Riello 40 but don't expect it to be above 11% always. If boiler has a low level flue or a short standard flue, then keep the air setting a tad higher, as you risk boiler going sooty later. You could always have had nozzle problems, & as has been said, check ventilation.
 
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think its the same ventilation thats been there for years and anyway when i went back and opened shed it was still puffing out black smoke until i adjusted it. plenty of air getting into shed through eves. it may be pump pressure regulator failure so more oil is being burnt than i had set it for. not sure the mechanical workings of the pressure regulator in an oil pump. anyone know?
 
thanks best. to be honest i got a smoke pump the same time as my analyzer but never use it. i find that once i keep the co below 80 and have 25% excess air to allow for inconsistencies with oil the smoke number would be as low as possible. i adjut air until co stars to rise then tweak it back a bit so its always a good as i can get it. and as i said the co2 nearly always works out around 12%.nozzle is new and identical to what i took out. why would boiler risk getting sooty later because of a short/low level flue? tanx
 
bod,, its not due yet but anyway that wouldnt explain why it was burning cleanly and then after a few months starting burning black. im still thinking pump failure. it's either air intake decreased or oil flow increased(simulating lack of air).
 
is your fga due for calibration ? just a thought maybe ?
Sounds likely. I would have it compared with another analyser. Riello 40s even when worn don't give much bother. Their oil pumps when old, tend to only work at 7 bar, which is ok. I would guess faulty nozzles, as common enough, or air setting not enough which can take a month or two for boiler to get worse.
 
thanks again best. cant see though how if you set the air up with a flue gas analyzer(even if its faulty) how it would burn cleanly and only get worse after a month or two. one of these boilers was actually done in january and only went black few weeks ago and i have done lots of other boilers since january with fga and had no prob with them. the two burners in question were made in 1991 so im thinking its the burners and not he analyzer.....
 
thanks best. to be honest i got a smoke pump the same time as my analyzer but never use it.
I would def recommend you use a smoke pump solely, at first to set up burner. Obviously after you check pump pressure. Get the smoke spot from slightly coloured & then fine tune to white. Perhaps a tad more air, then use your analyser. Probably find readings good. I wouldn't set co2 above 11 % on a Riello 40 running with 0.5 - 0.6 nozzles.
 
best, why not above 11%? high co2 is a sign of good combustion. for me to adjust settings down to reduce co2 i would be increasing co? and reducing efficiency?. what am i missing??????
 
Obviously you want co2 as high as possible, but lower output burners often have less co2. Be careful with them, especially the older burners for some reason, like the Riello 40. Settings for them years ago, on local manufacturers spec, was 10.5 co2 for small boiler. That is correct, & although it can be a bit better, you will find sometimes smoke number above 0 a little. That is why I say go by smoke gun. Often better not to set too fine, & you will still have good readings. Use old spec of boilers, if you can get them, for settings, but you can only do your best & you want the boiler to be fairly clean running & not so close to running sooty.
 
just wondering best, would u always use smoke pump even when your fga is working correctly????? to me thats like pumping a wheel up with a hand pump then checking it with a compressor... do you not fully trust the fga?? i would presume because of the technology involved the fga is more accurate and if it wasnt why bother buying an analyzer in the first place? maybe its an age thing as i started with an fga
 
Think oftec book said that maximum theoretical co2 is 15% for oil burning fully, but not achievable as boiler would soot up.
 
never read that to be honest best, done a servicing course and as far as i remember the higher the co2 the lower the co so what makes it soot up??? not questioning your knowledge, just trying to increase mine :)
 
No. Analysers are great, & you can get print outs etc. A smoke pump is a dead cert way of testing the " smoke " from the gases. To be totally honest, after you set the oil pressure on most burners with fixed nose cone set up, how many would you do anything more with, other than set the air intake? Most burners are spot on after smoke pump is used properly, & analyser will prove it. Smoke pump can often be used just 2 or 3 times at most when you are used to certain burners probable air setting, so can be very quick.
 
never read that to be honest best, done a servicing course and as far as i remember the higher the co2 the lower the co so what makes it soot up??? not questioning your knowledge, just trying to increase mine :)
I am always trying to learn bits myself! I think it's like this :- an oil burner burning the oil as best as possible creates soot - sadly too much, so it's a compromise between less efficiency but cleaner burning & more eff but impossible sooting ( which even a small amount reduces eff anyhow ). If you put the air setting far to high, you often have a spotless boiler but the fumes was half burnt oil.( co2 very low).
 
when you say half burnt oil do you mean soot. as soot is created by incomplete combustion can you get soot with too much air as well as too little. (cant remember as its a long time since i was at one with too much air)
 
Yes too much air can cause soot and too little can cause soot. If you check the Riello handbook there is a graph that shows you outside temperature is just as important,A boiler can be set up spot on in winter and if it is tuned right on the borderline , in the summer it can go sooty. I agre with best a smoke pump is definetly one of the most important items to have. If you did a servicing course they should have told you to use the smoke pump first otherwise if you put your fga into a sooty boiler your filter will get blocked and then you will get all the wrong readings. The smoke pump doent lie and it can be used even if your fga packs up.
Take a look at the danfoss website there is a small manual that answers all the questions you may want to ask about the behaviour of boilers and combustion. If I can find the link I will post it.
Riello 40,s are very reliable and normally dont soot up without a valid reason. You dont say what boiler it is on.
 
What I meant by half burnt oil is that when the burners have too much air, they are often spotless inside, & will run for years, but some of the oil is not fully used & is wasted into the flue gases. If you breathe any of these gases, they are nasty. Yes, to your point about, can too much air cause soot? - in extreme cases it can produce tar/ soot. Can make the boiler shell coated like bitumen paint. I saw a boiler in this state after service twit had put 2 wks prior, a 0.5 nozzle instead of a 1.0 one!
 
kimbo, which riello handbook is it? have you a link? when you say borderline do you mean borderline not enough air or borderline too much air???
 
Booklet supplied with Riello burners gives outside air - co2 graph. Think that is what Kimbo means. You can look it up by just :- " oil burner combustion adjustment - Riello burners ". Note how the co2 has to be reduced as air temp reduces. Fairly sure by " borderline" Kimbo meant, the burner air intake set too finely, ( slightly too little air) & therefore boiler at risk of sooting if slight variations occur, like outside air temp, or higher nozzle output due to wear, or even fluff or cat/dog hairs gathering slightly over air intake on some! Oil burners are too crude for to set extremely finely, tempting as it can be.
 
thanks best. thats why i usually set them up with 25% excess air as i was tought on course. do riello expect people to get their burner settings adjusted as the seasons change
 
Guess all you can realistically do, is set to slightly lower co2 readings for the colder air temperatures & that will mean the co2 will be actually higher on warmer days. Good to hear you are so keen to do it right.
 
good advice best. i just dont like doing things for the sake of doing it, i like to understand why im doing it.:)
 
Kimbo, thanks, that book would be great for anyone working with oil pumps. It should be part of oftec books, rather than the irrelevant rubbish.
 
Hi have you noticed whether the blades on the fan and/or diffuser are totally clean. Have found in the past that these often gather a coat of sticky grunge, and even a fairly light coating of crap can have a disproportionate effect on air delivery. Such crap obviously takes a period of time to accumulate. While not familiar with the particular burner, I see it has the facility to be fitted with an automatic air damper. Do yours have this - and if so is it opening fully each time?
On a different tack - is there a filter built in to the back of the nozzle. These (as I'm sure you know) can clog slowly, reducing the effective throughput of oil. Less throughput = less velocity of fuel, and reduced atomisation - bigger droplets and impaired combustion
 
possibly a stupid thing to say but you changed the nozzle for one the same as was in the burner ! was the nozzle in the burner the correct one for this boiler/burner ?
 
thanks kimbo,darkhorse. mjph, the burner worked fine before with an identical nozzle and for months with new nozzle so doubt its the nozzle
 
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