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Chimney liner?

davey73 Member Posts: 8
I currently have gravity steam with a oil fired Burnham boiler. I’m considering installing a gas fired boiler to replace my old oil fired boiler. The old one is leaking water. Do I need to add a chimney liner for the new gas fired boiler? 


    EBEBRATT-Ed Member Posts: 9,708
    Most likely you do need a liner. Weather you do or not depends on your location and other factors

    Colder climate usually requires one.

    Outside chimney usually requires one.

    Also depends on BTU input of boiler and size of the existing chimney flue.

    So there are a few factors involved.

    Need more information
  • Bob Harper
    Bob Harper Member Posts: 882
    All chimneys must be lined and must be suitable for the class of service. When you change fuels, NFPA 211 calls for a level II inspection, which will undoubtedly call for a liner sized to the new appliance. Note you'll need a stainless steel liner. Aluminum is approved for CAT I gas but only if that flue has not served oil or coal.
  • Tim McElwain
    Tim McElwain Member Posts: 4,477
    Bob Harper as always is correct!
  • captainco
    captainco Member Posts: 483
    "Bob is brilliant. Side note - No matter what a liner should always be stainless or it will rot out fairly quick.
  • Bob Harper
    Bob Harper Member Posts: 882
    LOL. Ok Tim and Jim--I owe you both a chicken dinner. Aluminum liners and B-vent were developed back when appliances were much lower efficiencies and have draft hoods. An 80% furnace will eat them up even if a draft hood equipped water heater is common vented adding a little dilution air. A side benefit is that ss conducts heat about 1/3rd as fast as aluminum. This means a comparable venting system in SS will generally have a higher stack temp., which leads to a stronger draft pressure at a given input rate and dilution air. Everyone has been trained like seals to use B-vent for connectors to push the charts for venting. This is all based upon empirical calculations- not actual measurements. It's all theoretical. What they haven't shown you is that using L-vent with its 400 series high nickel ss inner liner will keep stack temps up, minimizing stack losses, last longer and is rated for 20 degrees F higher than B-vent. This is appropriate because FVIR water heaters can run with a stack temp well above the 570F rating of L vent. L vent lasts longer, too.