I've installed a low mass direct vent oil burning boiler (140Kbtu) by LAARS a year ago and twice this year it sooted up so much that it choked itself to the point of burning terribly rich. (thick black smoke out the flue) I'm wondering if it could be my oil, I never had this issue until the last delivery. (This is my second season with this boiler...) I also wonder if using too small of a nozzle can cause this. I'm currently using a .65gph nozzle due to my heating load being relatively small. (Only half of my house is currently on the boiler, I wanted to prevent short cycling the burner.) I opened the fire box and totally cleaned everything from the opening of the flue, clear through all of the internal baffles in the boiler to the intake air line. It was incredibly clogged with soot. Now about a month later, it appears to be in the beginning stages of sooting up again. This morning the boiler locked out, but restarted with ease... but I noticed the black smoke out of the flue again.
Why not check with a LAARS dealer? I would think they could give you some ideas why you're having this reocurring problem.
maybe ur venting needs cleaning or bad fuel oil
Needs jet setting up at correct pressure for the type of fuel that you ars using, sorry no short cuts on this one.
I'm not a boiler expert but it seems to me that you are burning too rich all the time. Isn't soot a product of incomplete combustion? Like you said fuel could be the cause. I remember when I was much younger and traveled across the country I was forced to adjust the carburetor and timing on my car as fuel qualities varied. What would happen if you increased the available air for combustion or maybe even went to an even smaller nozzle? Like I said, I'm not a pro in this area, just trying to do what you are doing, applying common sense. Good luck, It seems to me the soot could even cause safety problems. I hope you get an expert on here that gives a perfect answer and damn quickly.
You really should have a boiler technician come in and do, at minimum, a combustion test. This test will tell you how to set the boiler for proper and efficient combustion. This setting is done with both the flue adjustment, incoming combustion air adjustment, and proper burner nozzle size. You have to have the proper test equipment and know how to read the analysis. Make sure when you call a technician, he explains exactly what he is going to do during the service call. If he isn't testing, call another. This will get your burner operating at optimum efficiency. Good luck!
