Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Combustion air question, and soot

jdb Member Posts: 22
I'm probably in the category of newbie/homeowner, so take it a little easy on me. I was wondering about the combustion air requirements for my oil burner. So I will list things I can think of: 1) Added a new vinyl window in attic, which probably makes the attic tighter. 2) Weatherstripped the basement door, which is near the oil boiler, so was wondering if I should make it less airtight. 3) There is an electric dryer near the oil burner, which is vented with solid galvanized pipe, with a nylon mesh bag (used to strain latex paint) over the end of a 2-foot section--pointing away from the oil burner, but it is INSIDE the basement, not vented to the outside. 4) There is soot on the floor to the rear of the oil boiler, just a light dusting before, but heavier since the oil burner has been serviced. Also, the dryer was not there the previous heating season, but not sure it has anything to do with the combustion air or the soot. My daughter, who lives there, said the service man was vacuuming "forever". My guess was that the soot was seeping out of the galvanized stove pipe before the chimney. She is away for a couple weeks at the moment. So I was wondering if I made the house too tight. It is an old brick house. Also, would like it be soot-free, as it was for many years. Did the service man do something wrong or incomplete? He installed  a new transformer on the oil burner. Do we need to ask him to come back? I do have a drain on the floor, that probably vents out the roof; it's cast iron, and part of the waste disposal system of the house. The washer sets on it, which I think is ok, it's not blocked off, I would think.

My basic question(s) is that (1) I want it to be safe, as far as CO, and (2) would like to not have it sooting on the floor. My original thought was that it seems to be burning a lot of oil for such a mild winter here in the Lehigh Valley, PA. But in the end, I'd rather be safe, primarily, and clean, secondarily. The basement is about 40'L by 9'W by about 7'H.

So I need to ask you to read this carefully; I just want to be sure everything is safe. It started sooting last heating season; it is doing it more now, apparently. And the things I've read about sooting aren't exactly good. But my primary thought was that I may have made the house too tight, but most people would laugh about that, it being an old brick house with solid brick walls. I could just loosen the weatherstrip around the basement door frame to let more air in, but it wasn't tight last heating season when the sooting started. 

Edit: The boiler is a cast iron converted coal boiler, so the serviceman was vacuuming the combustion chamber, and the stovepipe, I would think.


  • Steamhead
    Steamhead Member Posts: 14,850
    A modern oil burner should not create soot

    if it does, there's something wrong.

    The way to determine if the boiler room lacks air is by performing a "worst-case depressurization test". The short description of this test is that you turn on all the exhaust fans in the house, all the combustion equipment that vents outside of the house (which they all should, even a gas kitchen stove in some jurisdictions) and see if the atmospheric pressure in the boiler room drops, using special test equipment. Also, one would check that the chimney is not down-drafting. Obviously you need someone with the right equipment and know-how for this.

    But I suspect the burner is just badly tuned, especially since there was a lot of vacuuming needed at the last servicing. This is more likely if the oil supplier worked on it- since they're selling the oil, they have no incentive to make the unit run efficiently. We all have our horror stories about this.

    What make and model of boiler or furnace does your daughter have? What burner is on it? Where in LV is she located?
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,318
    C'mon Steamhead....

    "This is more likely if the oil supplier worked on it- since they're selling the oil, they have no incentive to make the unit run efficiently.'  That's quite an indictment to people who sell heating oil/own a heating oil me.

    I rather you say the burner wasn't tuned right, or wasnt firing right...original posted stated it needed a new ignition transformer..then make a blanket statement like that.  You much more experienced and smarter then that.  You may have had that experience, but sheesh.

    Let me ask you this.  Suppose I tune all my customer's burners to fire a little less efficiently.  Do you honestly think the little bit of money I would make on oil would compensate for the extra time it would take to clean these heaters, and the service calls they generate, especially contract customers, to justify your statement?

    My feeling is, get the tech back out.  Show him your concerns.  Let him perform a complete combustion analysis of your heating system, including smoke, CO2, efficiency, excess air, draft, and CO--both ambient CO and whats in the stack-and have him show you the results.  He should let you watch.

    You could have a just a small combination of things 'not just right' contributing to your problems.  Also, the burner couldve been tuned in the summer, and not enough allowance made.

    Let him address the combustion air issues.  Then if your still not satisfied, you could try another company.
  • jdb
    jdb Member Posts: 22

    Below is a post I made in '08, which should spell out what needs to be known. Tim McElwain said this particular boiler cannot be fired at less than 100,000 btu (per hour?) So I was wondering if the nozzle being at one gallon per hour is too much. Is that 140,000 btu's? Did a calc, and came up with 0.72 gph, which would be 100,000 btu, based on 1 gallon being 140,000 btu. On another note, the boiler was last serviced in 2003, so the soot accumulation could have been over a 7-8 yr. period.

    Also, the house was vacant for almost 3 yrs. (2008-2011), and the thermostat was set at 50 degrees during that time.

     So, below is the post:


    Replacement or other options


    @ April 13, 2008

    8:23 PM in Oil to Gas boiler


     I need some help. I

    asked on the Wall about changing out my old cast iron coal conversion boiler to

    a new gas boiler, but I did not get much of a response. I notice you're pretty

    detailed, so I'll try to be detailed as well. Weil-McLain originally a coal

    boiler, size 5-W-19, Series-D. I need to know the size of this boiler in BTUs,

    or would like to. Converted to oil in????????? We've lived here since 1984, and

    everything is still the same, no circulator, gravity hot water system, with radiators.

    The oil gun is a Beckett Models "A", "AF", may be suffixed

    MP, 1192 Series burners, 0.4-3.0 gph. A date of 1968 is on it, which is either

    the year of manufacture, or the year the model first came out. The nozzle is

    rated for 1.0 gph, which computes to 140,000 BTUs/hr. Our house is all brick

    masonry, except a small 40 sq. ft. addition to the back, which is framed but

    not insulated, 2 stories plus attic, no insulation anywhere. Total living space

    with rads is about 700 sq. ft. The attic is additional and is not heated, but

    it stays in the low 50 degrees most of the time, a result of heat loss through

    the ceiling, and up through the attic door. It has been converted to living

    space, so that heat loss is ok. Problem is, we use 600-650 gallons of heating

    oil every year, regardless of any attempts to use supplemental space heating or

    any other measures. However, I've been reading up on tightening the envelope,

    etc., so have been working on that. I've concluded that the culprit must be the

    boiler, and its inefficient gravity system. I've tried to do the heat loss

    calcs and EDR, the heat loss seems to be consistent at about 58K BTUs/hr. Allentown,

    PA, which has a design day of either 6 or 9 degrees Fahrenheit, depending on

    the source, is my location. We rarely have single digits, and the heat loss

    calc was done with a 10-degree design day. EDR X 170 gives 41,310 BTUs/hr. The

    problem is, the burner nozzle is rated for 1.0 gph, which is 140,000 BTUs/hr.

    Not knowing the efficiency of the boiler, BTUs may be hard to determine.

    Knowing the size of the boiler would help, if that info is available. Burner

    efficiency was listed as 79% in 2003. We don't get it tuned every year, it's

    never made a difference. 650 gals./yr., 600 with a mild winter. I asked on the

    Wall about swapping out the old boiler with a new gas boiler, and keeping the

    inch-and-a-half steel pipes. But I got 1 response, and not a direct one. We may

    move in the forseeable future, and want to keep the change as non-invasive and

    cost-effective as possible. With oil at $3.669, a comparable amount of ng is

    $2.114, approximately. My other alternative was derating the nozzle, insulating

    the pipes, installing a vent damper or barometric flue damper. Supposedly the

    last item would cost only about $100. I could go for a new flame retention

    burner or gas burner, but if I go that far, I might benefit more from a

    replacement boiler. Also, a new burner might not work for various reasons (age

    of boiler being the most obvious. It could be 75 years old, according to a page

    I found online with this exact boiler.) My original question had to do with

    choosing a gas boiler that would involve the least amount of retrofitting. An

    opinion on derating, insulating (the pipes, that is), dampers, the envelope,

    etc. would also be appreciated. I have aluminum replacement sashes with storms,

    and just installed door sweeps on the door bottoms. The heat loss calc was done

    with the free version from, and was pretty thorough, I think. I'm

    thinking, with 41,000 BTUs of radiation, and 58K heat loss, why do I need a 1.0

    gph nozzle? Also, the boiler itself and steel vent/flue pipe leading to the

    chimney seem pretty leaky. If I were staying here forever, a replacement boiler

    would be a no-brainer, and a Biasi with dual-fuel possibilities would be an

    option. I apologize for the length of this. Any insight you would be willing to

    offer would be appreciated very much. I guess I just need an objective

    viewpoint after focusing on this for so long.

    I just need to know what it would take to keep this going until we can sell the house. Was also wondering if I have tightened the house up too far. Is this even possible on an old brick house, built around 1900-1920? Boiler is probably the first and only one this house has had. 
  • chapchap70
    chapchap70 Member Posts: 139
    A few thoughts

    Eight years is too long of a time between servicings.  It makes sense that the man was down there vacuuming "forever". 

    A dryer close the the burner may cause sooting due to lint conditions.  If the lint is not vented out of the basement properly, the oil burner fan can suck it in decreasing the air into the burner. 

    A real quick way to see if the basement has severe combustion air issues is to open the basement door a crack.  If the door gets sucked shut when the burner comes on, the basement area is not providing enough air for combustion and the boiler could soot up quickly.  You would need to get more air there via louvers, etc.

    A new boiler would use around 40% less fuel.  Since you have a gravity setup with lots of water, the installer needs to take this into consideration with lower water content boiler.  It would need a bypass, primary secondary piping, or a combination of the two.  Fresh air can be piped directly from the outside to the new burner.
  • Paul48
    Paul48 Member Posts: 4,470
    75 years old

    This would be a 40 year temporary fix?
  • Steamhead
    Steamhead Member Posts: 14,850
    edited December 2011
    This is pretty typical

    of what we find around here. Firebox full of soot and sulfur, flue cleanout covers loose, and a nice clean oil company tag where all the alleged "techs" logged in after maybe wiping the burner off so it looks clean on the outside. If you want to know which oil company effectively convinced this customer to switch to gas, I'll send you a PM.

    So yeah, the oil companies are their own worst enemy. Trouble is, it makes everyone in the heating business look bad, and that's getting real old.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Steamhead
    Steamhead Member Posts: 14,850
    I remember that post now

    you have a round boiler, also known as a "pancake" or "snowman" type.

    The high fuel consumption is typical of these old round boilers. They were never great on coal, and one of my Dead Men's Books says they typically cannot achieve better than 40% efficiency on oil, because of the relatively small heat-transfer surface and unobstructed flue-gas travel. I've baffled these things when replacement was out of the question, but even with a good baffle job you're lucky to get the stack temp down below 600° F or so. Replacement is the only sure cure for these things.

    The soot is another issue. The Beckett burner you have is designed so that when installed, tuned and maintained properly, it will run for an entire season without making smoke or soot- unless something goes wrong like a plugged nozzle or filter etc. It doesn't take a rocket scientist to set up a burner properly.

    This is a hot-water system rather than steam, right?
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • icesailor
    icesailor Member Posts: 7,265
    Kibbles & Bits in the chamber:


    I see this stuff all the time. Especially in the boilers that are about to go gas. The "cleaners" just take the top off and brush the K&B's all down where it falls between the chamber or "rug, or into the chamber. That one is almost as bad as the worst one I have ever seen, the soot was being made from the bottom of the flame, hitting the K&B's in the chamber.

    You know, it takes a lot of time to pull the burner so you can suck that crud out. With the newer boilers with the swing out doors, there is no excuse for not cleaning the chambers out. I have an account that has three W-McL WGO-7's that run on reset. No way to control the low temperature. So they condense a good part of the year. Every summer, I clean them. Top to bottom. I pull between 30# and 35# of K&B's out of the three of them. It takes time. A soot saw and a piece of threaded rod. And there's NO soot in these boilers. 

    I've seen boilers leak from the sections being pushed apart from the crud falling between the sections. An oil company that is so cheap that they don't make their techs clean a boiler properly, doesn't want to be in the oil business. Once all their customers have switched to gas, there's nothing left.

    Then, there's the guy around when asked when he was going to combustion test the new oil boiler install he did, commented, "Ive been doing this for over 35 years. I've been looking at flames for over 35 years. I don't need no stinkin' gadget to tell me what I already know. I know a good flame when I see one and I know how to make it."

    Nuff Said. 
  • SWEI
    SWEI Member Posts: 7,356
    dryer venting

    I assume since this an oil boiler that you have an electric dryer?  You might want to try a water-filled lint trap.  Ace Hardware has them, probably a few other places as well.  If you keep them clean and wet, they catch far more lint than a mesh filter will. 
This discussion has been closed.