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Combustion Analysis Results

JeffBrown Member Posts: 67
Sorry for double posting but I put this in the wrong place initially.

Hi, I have a 2009 Weil-McLain SGO-3 oil steam boiler that has been converted to gas using a Carlin EZ-Gas gun

Burner is firing around 105k BTU vs the rated input of the boiler which is 114k

Combustion analysis indicates CO2 @ 9.5%, 300deg stack temp, 84.5% efficiency.  Air band is set a bit under 20%.  over fire draft=.02, breech draft=.03

Stack seems low, or not?  I know the efficiency is calculated, how accurate are they?  84.5% is higher than what the boiler is rated for using an oil gun.

I have complained in the past about a loud low pitched rumble from this setup and the adjustment of the airband to its current location has made an appreciable difference in this sound.

I had a tech out because of the rumble noise but also because I had a stainless flue liner installed several months ago and I wanted to have the combustion and draft checked/adjusted



  • earl burnermann
    earl burnermann Member Posts: 126

    Have posted your oil burner question in the gas forum.
    If the women don't find you handsome, they should at least find you handy!
  • JeffBrown
    JeffBrown Member Posts: 67
    not so fast...

    you will note that it is an oil BOILER but a natural gas GUN

    I'm sure we can argue all day about where it should be, I think it's more of a question about the gas gun setup than about the oil boiler
  • BobC
    BobC Member Posts: 5,232
    I notice the rumble as well

    In my Smith G8-3 steam boiler with the EZ Gas.

    Because the EZ-Gas was firing at 110,000 BTU (283+ sq ft of steam) and I only have about 200 sq ft I changed the orifice from7/32 down to 3/16 and the boiler is now firing at about 77,,000 BTU. The rumble is still there but is not as loud as it was initially.

    I suspect it might be related tothe height of the chimney but I'm not sure. I think this rumble exists in many installations of the EZ-Gas and I don't know of any way to fix it

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • JeffBrown
    JeffBrown Member Posts: 67
    Bob, I tried something you suggested

    I opened up the airband setting and this did eliminate a lot of the rumble but I think, like you, this introduced way too much excess air.

    The service tech set the air band to slightly lower than 20% and this has also helped but not as much as when I set it to like 30%

    Anyway, the rumble is now acceptable...I'm thinking of adding some sound proofing to the basement ceiling

    The remain question I have is whether a 300deg stack temp is a big deal.  Too low and you may create condensation.  Tech didn't say but I have to assume that is net temp.  The slip I got indicated co2 9.5% and stack temp but didn't list any other parameters other than two draft readings which are within range
  • BobC
    BobC Member Posts: 5,232
    No signs of condensation.

    My co2 was almost 10% and my o2 3%,, the stack was 310; I've seen no signs of flue condensation so far. My chimney runs up the middle of the house.

    As i understand it my burner / boiler combo can go down to about 65,000 BTU without a problem, yours may be different.

    As i said the noise is much reduced and if t bothers me I turn the stereo p a bit more.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    combustion readings

    Your flue temperature is too low. It should be close to 400 degrees.  I did not see any CO readings. 

    Putting less fuel into equipment doesn't take advantage of all the surface of the heat exchanger.  It takes temperature difference to get heat transfer.  Your steam temperature is around 215 degrees and the flue temperature is 300 degrees. Not much transfer is going to occur in the top of the boiler.

    O2 below 3% are unusual on residential equipment without making CO.  If opening up the air shutter quiets the boiler down then maybe opening the shutter and giving more fuel will bring everything closer in line,

    Actual boiler efficiency is not 84%.  With it being underfire it is most likely is the 60% range.   Maximun efficiency without condensing would be around 73%.

    Analyzer calculations for efficiency are rarely representative of actual efficiency.
  • JeffBrown
    JeffBrown Member Posts: 67
    Any Experts in the Boston area available to help in person?

    I have had ZERO luck finding someone in my area to help me get this thing setup correctly.  Let me clarify, someone who actually knows what they are doing!

    I am in Medford, MA which is about 10 minutes north of Boston right on I-93

    [email protected]
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