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Puff of Smoke from top of Boiler

ACG Member Posts: 8
I have a weil mclain SGO 3 oil boiler. My flue pipe is connected in the rear of the boiler. Every so often, perhaps once a week or once every 2 weeks, the boiler will be running through a cycle or trying to, and then the damper will flap a few times and then grey to black smoke will puff out of the top of the boiler, causing the collector hood and flue cap to pop up slightly. The smoke is not continuous, just a single puff, enough to stink up the basement but not enough to set off a fire alarm or carbon monoxide detector.

Any idea what may cause this?  


  • Damon
    Damon Member Posts: 32
    Call a pro NOW!

    Looks like this has been going on for a way to long. I'm not a pro but could be a number of things like a puffback, clogged HX or clogged flue. Doesn't really matter since you are calling a pro now...right?
  • billtwocase
    billtwocase Member Posts: 2,385

    as to why smoke would be coming from the top of the boiler. The optional rear or top flue is a great option on these. If it is rear flue, then the flue collector on top should be capped off with the supplied cover tightened. After the unit is fully serviced, and any ignition issues resolved, have the cover checked, The top is access to the flue passage ways.
  • icesailor
    icesailor Member Posts: 7,265
    Puffing Gaskets:

    Good point Bill2,

    I always replace the OEM gaskets on the flue collector after the first time I clean them because the gaskets don't hold you. They get hard and usually half stick to the boiler and flue collector. I use some Lynn rope which I glue to the top of the boiler with High Temp RTV and then slather the bottom of the flue collector with Never-Seize. So it comes off the next time. I clean a lot of WGO's. I've never had a problem with them once I do this fix.

    You need to be very careful when putting them back. Put Never-Seize on all the bolts for ease of removal.

    I cleaned a V-3 yesterday that was full of Kibble and Bits from being a cold start and 3" of K&B's piled up in the chamber. No Never Seize on the collector. Not good.

    And it was cleaned by "someone else" since the install when the house was built before 2001. And serviced 11/09.

    No one will ever convince me that a cold start boiler filled with Kibbles and Bits is more efficient than a warm start that has run for 2+ years and has only a brown ash/dust.
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