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Checking Proper Draft

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Servicewiz_3
Servicewiz_3 Member Posts: 72
in Oil Heating

I would like to know , how that proper draft would be checked on an oil fired boiler.

This boiler does have a barometric damper.

I also would like to know , if there is any difference in checking the draft on an oil

fired furnace. Thanks in advance , for any help provided!!!!

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,765

    Most boiler and furnaces should have a -.02 draft reading over the fire. There is usually a 5/16" hole in or around the burner observation port.

    You need to run the boiler long enough to heat the flue (10-15 min) in the summer should be good enough. Then check the draft

    Adjust the barometric damper as needed (open it for less draft, close it fore more draft.

    Should do a combustion test as well.

  • HVACNUT
    HVACNUT Member Posts: 7,595
    Screenshot_20260810_210401_Samsung Browser.jpg
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 12,620

    I would check the draft over the fire on this furnace at the screw that is filling the test port where the yellow arrow is pointing. That is why the manufacturer put that hole there. You can then measure the draft at the breech using the same hole you make for the combustion analyzer.

    I like the last section of the first elbow coming off the exhaust opening of the furnace. That location should have the least amount of leakage air entering the flue connector, while also avoiding radiant heat from the heat exchanger that could cause a false stack-temperature reading.

    image.png

    When looking at a boiler, you look for the small port near the flame-sight opening for checking over-fire draft (yellow arrows), and then check the draft again at the flue connector.

    Screenshot 2026-08-10 at 11.59.41 PM.png

    In my opinion, both boilers and furnaces have the same basic features and requirements when testing and adjusting draft over the fire. You just need to read the equipment instructions for the manufacturer's recommended settings. Some boilers and furnaces operate properly with a slight positive pressure over the fire, but most of the appliances you will work with will require a negative draft over the fire.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • HVACNUT
    HVACNUT Member Posts: 7,595
    https://forum.heatinghelp.com/discussion/comment/1901772#Comment_1901772

    Is that an AI pic? It has a Wayne manufactured QB-180 burner designed for Weil McLain boilers in a Buderus that I've never seen.

  • Robert O'Brien
    Robert O'Brien Member Posts: 3,598
    Chapter-6.pdf

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