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flue damper with horizontal diverter

I do not have enough room between the top of the boiler and the existing penetration in the chimney to use the vertical diverter supplied with the new hw boiler I am installing.If I use a horizontal diverter, can I mount the flue damper on top of the boiler before the diverter. The supplied diverter is 6" but the top of the boiler is 7". The diverter is made to fit the 7" side on top of the boiler and the top of it is 6". Do I go with a 6x7 increaser right on top of the boiler and then the damper and then the horizontal diverter??? HELP !!!!!


  • Tony_8
    Tony_8 Member Posts: 608
    the best thing

    would be to make a new penetration into the chimney and use the supplied diverter. If don't have height available, then I think the diverter should go before the damper. This keeps the chimney from pulling room air all the time, defeating the purpose of the damper.
  • Jack_23
    Jack_23 Member Posts: 153
    Vent connector lay-out...

    is one of the most important aspects of vent system design. I agree that you should make a new chimney penetration. Is this oil or gas? If you check the gas vent tables you will see the affect that vent connector height has on capacities. You need that first few ft of height to get the velocity going before it hits horiz runs. If your appliance is oil fired you can reduce the breaching with Manuf approval.
  • MikeB34
    MikeB34 Member Posts: 155
    Utica boilers

    Look at the Utica boiler. Built in draft divrter. You can 90 it right off the boiler.
  • Boilerpro_3
    Boilerpro_3 Member Posts: 1,231
    Don't change the draft divertor!

    You should use only the divertor that came with the unit! I've seen this done before and the most obvious result was continuous spillage into the boiler room. If you can't fit a boiler using the factory tall draft divertor, use a boiler with a factory low horizontal divertor. All Dunkirk boilers and some Weil-Mclain, Burnhams and Lochinvars have these type of divertors. Don't buy your boiler until you know it fits. I tend to stick with the Dunkirks due to the fact that the low draft hood allows greater installation flexibility and much better venting design (alot more connector height) when used in a common venting system with other equipment.

  • Draft Diverter

    As Dave (BoilerPro) stated, do NOT use an alternate type draft diverter or modify a draft diverter supplied with a new gas boiler. The draft diverter supplied was part of the testing and certification process of the equipment. If the chimney connection is too low, you have three choices.

    1.) Mount the motorized damper on the horizontal directly after an elbow on top of the vertical draft diverter. This will gain you several inches.

    2.) Put a new thimble into the chimney higher to accept the new connector.

    3.) Use an alternate boiler with a draft diverter built into the back of the boiler such as our Independence boiler (configured for water).

    Do NOT put the damper on top of the boiler before the draft diverter. Hope this helps.

    Glenn Stanton

    Manager of Training

    Burnham Hydronics
This discussion has been closed.