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Can you power vent boiler up chimney?

Weezbo Member Posts: 6,232
Yes. Buh Why?

there are so much better boilers on the market these days... and construction practices have along with the price of fuel, basically eliminated over sizing of heating plants in your home.


  • Mike Kehoe_5
    Mike Kehoe_5 Member Posts: 3
    Power venting nat gas steam boiler up chimney?

    Hi, I need to have a new nat gas steam boiler installed. My chimney is very old and unlined. My chimney contractor has informed me that he cannot fit a liner large enough to meet the requirements of the new boiler. So, my plumbing/boiler pro says we will have to power vent the boiler. Can the boiler be power vented up the chimney, through a liner that is smaller than would be required for normal venting? The reason I ask is that I would prefer not to have the vent pipe out the side of my house, right outside my living room window. Thanks!
  • John Mills_5
    John Mills_5 Member Posts: 935
    Which boiler?

    Many can be chimney vented through an appropriately sized metal liner but might be wise to post which boiler you are considering so someone familiar with it can say for sure.
  • Mike Kehoe_5
    Mike Kehoe_5 Member Posts: 3

    Thanks for your reply. The literature is at home, so I can't say for sure what model at the moment It is one of the larger Weil McClain (we calculated the sq. footage of steam needed to be 503, if my memory is correct)
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Might be an EG-55

    521 square feet EDR rating with a 7-inch flue. Your chimney won't accept a 7-inch liner?

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • bruce_21
    bruce_21 Member Posts: 236

    If the chimney is high enough you can sometimes use a smaller liner than the breeching (pipe from boiler to chimney). You have to do some research in the code book which has many different charts and tables giving the permitted relations between Btuh input, diameter, breeching length, and overall height. I got a 5 section Weil McLain into a six inch liner six years ago. The chimney top was about 40 feet above where the breeching entered it. It has been firing fine all this time.
  • You can't

    reduce the size of any flue. If the breech is 6" then that is the minumum size you can use no matter how high the chimney.

    Also there are not many power vented steam boilers around. The last one I knew about was the Burnham Independence.
  • tim smith
    tim smith Member Posts: 2,397
    Yes on the smaller liner w/ power venter

    If you find who the Exhausto rep is in your area, they can run the sizing criteria in the software program and size one up. They have chimney top exhausters that are very quiet and High quality. Cast aluminum blade and housing. Pretty nice! I myself am not a big fan of power venting but some times you do what you gotta do.... Tim
    Ps, there is also Fields and Tjernlund who can do same but not quite as high quality but then again not as much money.
  • Keep in mind that

    liners have 20% less capacity than a comparable Type B vent so this must be considered. It has been my experience with power venters into chimney liners that condensation issues arise about 75% of the time. There are a lot of things that manufacturers are telling you that it is okay to do but they must work is the bottom line.

    The use of PVC and CPVC should be stopped as a venting material is just one example. It usually takes someone getting hurt or killed before everyone wakes up and pays attention.
  • tim smith
    tim smith Member Posts: 2,397
    Re: liner for chimney

    I would be more inclined to use AL294C ridgid stainless as the liner product w/ clean out tee at bottom, will last a loooong time and handle any condensation problems. Tim
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    Induced draft will work versus power venting

    Based on induced draft venting charts you can vent into a 5" standard chimney, maybe a 6" liner up to 279,000 btus with just an inducer instead of power venting. Induced draft doesn't pressurize the flue and still works off of negative chimney pressure.

    There are some tricks and special set-up for this installation. It is always mandatory to have 2 or 3 minutes of post-purge to prevent condensation in the flue liner. In reality some modification will be necessary on the boiler to insure it will vent properly along with some additional safeties.

    It will take a contractor really familiar with this type of venting to install it and set it up properly. If so it will not be a problem.
  • tim smith
    tim smith Member Posts: 2,397
    Weezbo, I agree but maybe it is just not in the cards at

    this time???? Tim
This discussion has been closed.