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347 Member Posts: 136
edited May 2016 in Gas Heating
Hello All,
I know I'm missing something here, having a brain lock
Customer called with a spill switch that was tripped, they reset and I went out to take a look.
140,000 btu boiler and 40,000 btu water heater. 6" wye with a 4" connected for the water heater, boiler was installed about six years ago, I was told their was a new liner installed.
Put my draft gauge in the 6" boiler flue will making steam and had very little draft(just passed the 0 line). Boiler shuts off and damper closes and the draft gauge goes up to 2.5" wc.
My question is why would it rise after the damper shut and not during it running?


  • Jamie Hall
    Jamie Hall Member Posts: 21,506
    To which I might add that it wouldn't take that much of an obstruction to kill the draught while the boiler is running, but still allow the chimney to pull well when it was off.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • GreenGene
    GreenGene Member Posts: 290
    New liner I assume in chimney, did they put a cap on it to keep out nests? Could be squirrel, racoon, bird, you never know.

    I had a boiler go down once because baby racoons died in the top of it blocking the passages, then I looked in the chimney and saw the nest and quickly slammed the pipe back on until I was sure mom was gone.
  • GreenGene
    GreenGene Member Posts: 290
    "boiler was installed about six years ago", was that the last time the bottom T was cleaned out?
  • ChrisJ
    ChrisJ Member Posts: 14,925
    Hopefully it's rare, but there's a chance it could be like mine was.

    They stuffed a 6" liner down a chimney that only had a 4xsomething opening and it ended up in 3 different pieces because of an offset in the chimney. So the chimney looked lined, but there were at least two gaps in the liner.

    Basically, the liner made the chimney completely unsafe. Far worse than it would've ever been if it was left alone and I'm not saying that was safe either.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Firecontrol933
    Firecontrol933 Member Posts: 73
    Did you check for sufficient combustion air? Door to outside open and then check again?
  • 347
    347 Member Posts: 136
    Thanks for the replies.
    Hatt, I hear what your saying about the straw, just don't know why more resistance when the damper is open, boiler has a built-in draft hood off the back and all is clear.

    Jamie, found no oddveous blockage.

    Green, chimney has a cap, I did not take the flue apart to check for blockage at the tee.

    Chris, I may have a chimney guy come in to take a look down and see what's going on.

    Fire, the room is open. Bye the letter of the code their is not enough air (nobodies basement ever has enough). I thought of that and opened two windows in the boiler room and nothing changed.

    I don't understand this happening after 5 years that's what's puzzling me. Nothing was done to the house to change anything with the flue.

  • 347
    347 Member Posts: 136
    I will look into the possibility of a blocked flue or over sized one.
  • Jack
    Jack Member Posts: 1,046
    How tall is the chimney? How long is the vent connector and how many 90's, wyes, etc. How much rise off of the boiler before the first fitting. You can disconnect the vent connector and with a good flashlight and inspection mirror get a good idea of what is in there. Having worked for 5 yrs and now showing problems? Blockage or perhaps the vent damper is not opening all the way. One of the most effective ways to improve operation of a natural draft system is to insulate the vent connector. B-vent for you. The Wye for the water heater should be at or as close as possible to the vertical flue.
  • 347
    347 Member Posts: 136
    I'd like to add a picture of the smoke pipe, just cant figure out how to do it.
    chimney is about 25' tall. 1 6" 90 going into the wye, about 18" of rise. 4" has 1 90 and run of about 2' with basically not rise.