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concentric conundrum

D_Hatina Member Posts: 3
Hoping to get some clarification.

Last week I had my contractor install a Goodman HE furnace and an AO Smith Vertex 100 water heater.  The install so far has been great but I've got some questions about the venting.  The contractor was going to use 4 seperate 2" pipes, 2 supply and 2 exhaust so I asked if we could change the venting to two 2" concentric vents instead...and we checked each appliance's installation manual but got some conflicting info.  The furnace manual says multi-concentric terminations must have a minimum seperation of 12" but the water tank manual calls for maximum of 2",... so which to follow?.  Also, the water heater says only a Bell & Gossett vent kit is certified but I get the feeling my contractor will use whatever is available from his supplier.  Are all PVC concentric kits the same - if not will this be a problem?  Finally I have a dryer vent between the concentrics and my gas meter but not far enough away from either.  Can we split the difference(2' to each) or should it be relocated completely.

Any guidance much appreciated,



  • Charlie from wmass
    Charlie from wmass Member Posts: 4,250
    Move the dryer vent

    the amount of lint it produces will amaze you.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Henry
    Henry Member Posts: 996
    NFPA54 or B149

    Depending where you live, your installer must follow either NFPA 54 in the US or B149 in Canada. Also, he must follow the certified installation manual and use the strictest interpretation of both and the gas code.

    In Canada, we have changed the 2010 B149 to include specific distances for all "moisture ducts" and air inlets for appliances. Try to keep the dryer vent as far as possible from any air inlet! Concentric vents do not work well where one has a lot of snow or if there is an adjacent structure close by. They can block with snow or cause icing on walls.


  • Tim McElwain
    Tim McElwain Member Posts: 4,580
    Manufacturers Instructions

    prevail and must be equal too or exceed NFPA 54 or B149. Most furnace and water heater companies have termination kits available for their equipment. Ask your contractor to go over the options with you.

    I also agree dryer exhaust (they are not classified vents) should be moved as far away as possible from air intakes on other equipment as they exhaust lint, residue from bleaches, and anything else that was in the wash. All of which are highly corrosive to equipment.

    Dryers should not even be in the combustion zone and need make up air for their operation in accordance with code.
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