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Low Draft? .02 draft at breach

Jud_AleyJud_Aley Member Posts: 13
I have a 65 year old Sears & Roebuck Oil fired Hot Water boiler. Model # 204 419. I ran the boiler for 10 minutes and then checked the draft at the breach with Bacharach Mzf draft gauge and the best I can get is .02.

From everything I have read .02 is low, shouldn't the draft be .04 to .06. ?

Just had the chimney cleaned, it is unlined brick. I cleaned out the smoke pipe myself after my oil company did a marginal job of brushing out the heat exchanger. The oil company did not want to open the fire box, said it was too old. When the boiler had cooled off I stuck a vacuum in the fire box and got some soot and debris but most of it seems baked on and rock hard.

It has a brand new Fields Controls draft damper, but the damper is located in a bull head tee, which the Fields Controls does not recommend for oil fired burners, could this be why I am getting such a low draft reading?

Thanks - Jud


  • Jud_AleyJud_Aley Member Posts: 13
    Here is a photo of the Bull head Tee

  • HVACNUTHVACNUT Member Posts: 3,412
    The bull of the tee is exactly where the draft regulator should be on an oil fired appliance.

    The chimney should be 3 ft. higher than any peak or obstruction within 10 ft.

    65 year old Sears boiler huh?
    Maybe it's time to think about upgrading. Buderus specs -.02 breach.
  • STEVEusaPASTEVEusaPA Member Posts: 4,203
    I assume your draft readings are negative numbers.
    Unlined brick is not code, it should have a liner.

    You should be able to practically climb in there and clean the heat exchanger, but you may want to pull the burner and clean the combustion chamber too. Just make sure you have a new burner flange gasket available, and DON'T break any bolts.

    The first question is, were the numbers always like this or is this new?
    Did anyone stick a mirror in the chimney base and look to see daylight (a nice square showing no blockages)? Could be a bird/squirrel/nest, etc lodged in there.
    What was the breech draft, close to the boiler?
    Is the boiler under-fired?
    Was everything taken apart put back correctly and all sealed up with gaskets, rope, etc.?

    Yeah the tee is wrong. I would put an elbow there, then the Tee with the damper in the correct position.

    Usually on those old units, if clean, the draft and breech are almost the same, and the stack temp is so hot, the damper will need to be almost always run wide open to get the over fire draft down to -.02.
    What were the rest of the combustion numbers, including smoke?
    I'd also have a personal CO monitor running (and/or use my analyzer) to see if any products of combustion are spilling into the room.
    Also I would've checked/cleaned the burner blower wheel (almost always not done) to make sure it's creating maximum static pressure.

    That's a very old, inefficient boiler, I'm sure you know a modern, properly sized/properly installed, efficient boiler would be a good investment-better efficiency, easy to maintain (get parts) & save you money over the long haul.

    One last thing, are you sure your draft gauge is working correctly?
  • GilmorrieGilmorrie Member Posts: 117
    That Field draft controller should have an eccentric weight on the door - it can be adjusted to increase or decrease the draft.
  • STEVEusaPASTEVEusaPA Member Posts: 4,203
    edited October 2018
    HVACNUT said:

    The bull of the tee is exactly where the draft regulator should be on an oil fired appliance.

    You better look's wrong. If you open that regulator you can look right at the chimney base.

  • HVACNUTHVACNUT Member Posts: 3,412
    > @STEVEusaPA said:
    > The bull of the tee is exactly where the draft regulator should be on an oil fired appliance.
    > You better look's wrong. If you open that regulator you can look right at the chimney base.

    Sorry, the pic didn't come through at first. The OP said the bull, so I thought the regulator was in the bull.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,089
    Not supposed to use a tee with a draft regulator. I would clean the boiler, chimney and smoke pipe and fire it up. Tune it with a combustion analyzer. The draft may be low because the chimney is cold. Check the draft when the chimney is warm.

    With an old chimney with no tile liner you should really consider a chimney liner
  • GilmorrieGilmorrie Member Posts: 117
    Agree with Ed. Consider installing a corrugated metal liner. But first, adjust the Field draft regulator.
  • captaincocaptainco Member Posts: 451
    The barometric is slightly open which is going to lower the draft below it. If your chimney got wet it will not draft better until it dries out. Measure the draft above the barometric to see what the total draft in the flue is. Draft does tend to be lower in milder weather but their should always be at least -.03" draft in the flue minimum.
  • GBartGBart Member Posts: 753
    edited October 2018
    oye vey
  • Jud_AleyJud_Aley Member Posts: 13
    edited January 2019
    So here is an update.
    The flue is lined, I went up on the roof and looked down in, its red clay tile. The guy who cleaned the chimney told me there was no liner…..he wanted to sell me a SS liner.
    The oil company tech cleaned the heat exchanger, but I’m not sure how good a job he did, I’ll do it again when the weather is warm, and I can shut the unit down for half a day. I bought the wire brushes and vacuum hose for this job
    I’ll clean the combustion chamber this summer and maybe put a Lynn Quickie in it….maybe not
    The boiler was downsized from a 1.25 to a 1.00 and now it is at .85 gph
    Three different oil company techs over the last year would not check the efficiency, they all said the boiler would be below 50% so why bother. I called the oil company and told them I wanted it done and please send someone specifically for that purpose since it is listed in their annual tune up and that is what I paid for it.
    This guy was the best tech so far, he cleaned the blower wheel and the flame retention head.
    The burner is a Carlin CRD 101, but it has a Beckett the blower motor & burner control and a Webster pump.

    Here is what I see on the print out
    401.2 F Stack Temp
    13.1% Oxygen
    -0.072 Breach draft
    77.2 Efficiency Gross
    155.3 Excess air
    5.88 % CO2
    I bought a 3 year old Weill-McLain Ultra Oil for $ and it is sitting in the basement, but if my 60 year old Sears boiler is really running at 77% efficiency and the best I can get out of a new boiler is 87% and the oil company tells me its about $ to swap it out I’m not sure I’m in a hurry to do it…. Or should I be?

  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,089
    It's time for something new. Sinking any money in the old one is money down the drain. Your Co2 is low indicating a bad burner or air leakage into the boiler or a technician that knows nothing. A smoke test would help point to one of those things

    If it's running ok wait till spring to change it.

    You know what? The most important thing you need is a competent installer. Probably not the cheapest one.

    We cannot discuss prices here
    Erin Holohan Haskell
  • Jud_AleyJud_Aley Member Posts: 13
    My plan is to change it in the spring. I have no doubt it leaks air, there is a hinged inspection door with no gaskets or rope.
    What would be a good Co2 reading?
  • STEVEusaPASTEVEusaPA Member Posts: 4,203
    Don't worry about a good CO2 reading, you're not going to get it.
    That 77% is the burner efficiency. System efficiency and transferring heat into the home as opposed to up the chimney is probably in the 50% range at best.
    In your situation the only way to determine the proper nozzle firing rate and angle is to do a nozzle substitution test.

    Your breech draft is too high, don't know your overfire draft, or smoke.
    To me you appear to be way underfired if you need that much excess air.
    Plus like Ed mentioned, probably air leaks in a number of places.
    If you can swap out for what you mentioned (please remove price from you post), you should do it.
    But before you do it, a complete heat loss so you don't oversize the boiler.
    And you should line the chimney, unless you're going with a balanced flue design.
    DZoroErin Holohan Haskell
  • SlamDunkSlamDunk Member Posts: 832
    how much oil do you burn per month?
  • icy78icy78 Member Posts: 351
    I dont do oil but youre way underfired. Essentially you are diluting the flame with far too much excess air, resulting in a much cooler flame and sending much of your heat up the chimney. Change the nozzle back to the oem and go from there. (If you must keep it.)
  • Jud_AleyJud_Aley Member Posts: 13
    The smoke test was clean, virtually white.
    ? How do I remove the cost from my previous post?
    I ll check oil usage for the last year or two and get back here and post that
  • SlamDunkSlamDunk Member Posts: 832
    edited January 2019
    I inherited an old, oil fired octopus furnace that had 14ppm CO, 357% excess air, 51% efficiency gross, 16.7 Oxygen. we burnd 225 gallons in two weeks virtually soot free. Replaced with new 85% efficiency furnace, and we are burning 150 gallons every four weeks, with 65 deg round the clock . I was hoping for better but that isnt a bad reduction.

  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,089

    you said 225 gal/2 weeks with the old furnace and150gal/month with the new furnace.

    if that is correct you went from 450/month to 150/month

    that's a 67% reduction in fuel
  • SlamDunkSlamDunk Member Posts: 832
    edited January 2019
    yes. Turns out the house is not as insulated as we thought. we were aiming high.

    What blew my mind was the lack of soot in chimney base after that kind of consumption. Nothing was cleaned or tuned for at least five years. I thought the flue would be plugged with that kind of consumption. I removed a five gallon bucket worth of soot.

    What I wanted to get across to the OP was not to struggle with the
    cost of modernizing, pay back will be quick. His combustion numbers were bad and flue gasses clean-like mine. His consumption should be included in his consideration
  • Bob HarperBob Harper Member Posts: 843
    Chimneys must be lined-period. Since 1927 in the first codes. A chimney must be suitable for the class of service according to current codes-period. A tile lined flue has a 99.9% chance of not meeting that requirement. Aside from sizing they are typically code with a weak draft but worst of all, the mortar joints fail quickly. Revisit your 8th grade chemistry: acid + base = salt + water. The flue gas condensation converts your alkaline mortar into sand and salt so it fails and falls down. That's a main reason masonry chimneys require cleanouts- planned failure. You should get a properly sized listed stainless steel chimney liner. Refer to Field Controls for placement of the baro. damper but no, it should not be in a bullhead tee on oil. Also, you want the baro. at least 1.5 duct diameters from the appliance collar. Ignore those efficiency numbers--they're fiction. All you need are your stack temp, draft, O2 and CO to tune it.
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