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Wet spots on smoke test

Advancedplumbing
Advancedplumbing Member Posts: 16
edited January 2019 in Oil Heating
I just replaced a burner on an old Utica SF 3100W. I replaced a riello which had an oil like on the piston that opened the air shutter as well as a cracked housing where the primary attached.

I installed a Beckett AFG. I followed the specs from the Beckett guide. 3-5/8 air tube, F3 Head. Specs called for a 1.00 80B nozzle I believe. This is a 100KBTU boiler but it is old and the customer couldn't afford to replace so I replaced the burner. When I fired it up I got smoke pouring out everywhere. No matter what I did with the air, I got smoke and it sounded rough. The old riello that was in there had a .65 80 W so I tried that. Now I'm running the Beckett at 100psi and I'm not sure what the riello was set at. Anyway, the smoke was a little better but still sounded rough. During the smoke test I was getting wet spots on the paper. Thought it might be un burnt oil but it was clear. My combustion analysis wasn't good either. I could barely get 10% CO2 even with air turned down all the way. O2 was around 8%.

I'm thinking I want to try an "A" type nozzle. The burner chamber in this boiler is very small. Sorry the only pic I have is of the boiler itself. Any thoughts on what is causing the wet spots? I've tried several different nozzles and got the same result. I currently have a .60 80W in there and the burner at least sounds better but I get wet spots about every third smoke test. I've gone through a stack of test paper on this.

As you can see from the photo, I did vac the heat exchanger which is clear.


Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    The F3 head is too large for a .65 nozzle. I would go with a smaller head and a .50 nozzle that's a small boiler and put the oil pressure back to 140 or whatever Beckett recommends. Then run the test again. What is your stack temp?? What's your breech and overfire draft??

    I would check with Beckett and see what nozzle they recommend as far as angle and spray pattern. I wouldn't fire that thing over.75 or .8 with the right oil pressure
  • Advancedplumbing
    Advancedplumbing Member Posts: 16
    OK. Thanks. So Maybe a .50 nozzle with an F0 head? Beckett recommends a 1.00 nozzle with an F3 Head at 100 psi. I don't know why
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    From Utica's site .85 80B @140 psi Beckett AFG will give you 1.00 gph if you want to fire it that hard. Me I usually go 1 size down with the nozzle. lower stack temp and stays cleaner. the F3 head is .75 to 1.25 so I would change the head if you go lower . Usually run better at the higher end of the head. Is the chamber/target wall ok??
  • Advancedplumbing
    Advancedplumbing Member Posts: 16
    I will try that. Yes the chamber looked ok. I was very careful to check it thoroughly when I had the burner off. The section that is against the burner, not the target wall, is a little rough though. I'll try a .75 80B running at 140 and see what happens. The Beckett F0 head only goes up to .75 so if I run a .75 at 140 I shouldn't use that correct?
  • Advancedplumbing
    Advancedplumbing Member Posts: 16
    Also, I put on a 3-5/8 air tube. Does that really matter? I don't see what the difference is as long as it mounts to the boiler and is recessed properly from the inside wall.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    Tube length doesn't matter. Yes try the .7580B @140 should give you about .9 gph and see what you get with the f3 head. Did you check the Beckett Z dimension? nozzle to end of head
  • Steamhead
    Steamhead Member Posts: 16,830
    In addition to the above- the static disc on the drawer assembly should be 2-3/4" diameter rather than 3-3/8".

    I have an OEM Spec Guide from a few years ago that specs a 1.00x80S nozzle at 100 PSI with the AFG on this boiler. The S was probably for a Steinen solid-cone nozzle, which AFAIK is pretty similar to a Delavan B. However, if the Z dimension is correct and the flame still strikes the rear target wall with the 80B, try an 80W (semi-solid) or A (hollow) Delavan nozzle. The flame must not hit any part of the firebox.

    I also suggest running with a 140-PSI pressure and dropping the nozzle size to compensate. A 0.75 nozzle at 140 PSI will give about a 0.90 GPH firing rate. The higher pressure gives a finer oil spray which burns cleaner. The F3 is still the proper head for this rate.

    Let us know how you make out.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Advancedplumbing
    Advancedplumbing Member Posts: 16
    Thanks guys. I will update you later. I did set the Z dimension properly. Used the Beckett electrode gauge.
  • HVACNUT
    HVACNUT Member Posts: 5,829
    edited January 2019
    In addition to the above, if you cant get the CO2 high enough and O2 low enough, you can install the AFG low fire baffle.
    The SFII in the 3 section indeed has a very short chamber so like @Steamhead said, you might have to experiment with nozzles so theres no flame impingement.
    The WM 66/68 series was similar with a short chamber.
    In those situations when an 80°B @140 psi is spec'd, I'll use a downfired 70°A and 9 times out of 10 I can dial in DOBA.
  • Advancedplumbing
    Advancedplumbing Member Posts: 16
    I went back today and tried a few new nozzles. I tried .75 80 B and .75 80 A. Set pump pressure to 140. I was still getting issues with oil on smoke paper and sometimes soot no matter what I did with the air. I ended up getting it to run ok by putting a .65 80W nozzle in at 140 psi. The O2 was high and the CO was low around 9.5% but at least it was burning clean and I felt it was safe. So frustrating.

    I set the Z dimension by using the Beckett electrode gauge. It fits right in the end cone and contacts the face of the nozzle. It is a perfect 1-1/8". Is this the right way to set it?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    Yes, I usually use a hacksaw blade and a rular.

    Just wondering if the flame is impinging on something?? I guess if the chamber/target wall are ok and the boiler is clean that's the best you can do. Maybe give it a quick look in a month or so if you can
  • Advancedplumbing
    Advancedplumbing Member Posts: 16
    The target wall looked fine. I couldn't see any impingement when I looked at the flame through the inspection hole. But, then again, I couldn't really get a great look at it. I really want to put a new boiler in. Thanks for your help. I appreciate it.
  • Airgood
    Airgood Member Posts: 1
    @Advancedplumbing Hello. Were you able to fix the wet smoke test issue? Just yesterday I was doing smoke test and also having every third test wet.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,828
    edited December 2022
    Condensation of flue gas. When I had that problem, I would dry out the sample tube with a pipe cleaner. (the kind you get at a tobacco store for cleaning smoking pipes). Then I would make sure that every time I took a smoke test, the sample tube was pitched up from the sample hole all the way to the smoke paper. This way the condensation does not run down the tube and make the paper wet.

    If the paper is wet, then the condensation may have washed some of the residual soot from previous tests, inside the tube, on to the sample paper. So a wet test is not accurate.

    I also found this thread about smoke testing. https://forum.heatinghelp.com/discussion/comment/1624417#Comment_1624417
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics

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