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  1. #1
    Jerome W. Young's Avatar
    Jerome W. Young Guest

    Default dual gas water heaters/ same flue

    i am not sure where to start with this.
    My questions: can you connect these two flues and still get the proper exhaust?;
    note the a/c return in the garage (unit is only syupplying garage, but worried about flame roll out etc?);
    the tpr piping is also connected to each other for a single termination.

    Is this flue connection improper?

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  2. #2
    Join Date
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    Default Re: dual gas water heaters/ same flue

    The "vent connectors" are fine. (The flue is the space inside a vent or chimney flue liner. If connecting to a chimney, and you really wanted to be anal, they'd be called chimney connectors)

    TPR valves should have dedicated extensions and the return is too close. The return only services the garage?? If it has any connection to the interior rooms it should have no presence in the garage.

    Eric Barker, ACI
    Lake Barrington, IL

  3. #3
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: dual gas water heaters/ same flue

    The vent has got to go no matter what it is supplying. To have that vent there is about as unsafe as it gets. Whether it be a supply or return


  4. #4
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    Default Re: dual gas water heaters/ same flue

    Quote Originally Posted by Jerome W. Young View Post
    i am not sure where to start with this.
    My questions: can you connect these two flues and still get the proper exhaust?;
    note the a/c return in the garage (unit is only syupplying garage, but worried about flame roll out etc?); the tpr piping is also connected to each other for a single termination. Is this flue connection improper?
    Foil tape is not approved for flue pipes, ducting only. Should be mechanically fastened.

    There is a dedicated heater for the garage? I doubt that is OK. Not sure that a return air would cause flame rollout, but it is likely to cause backdrafting.

    Dedicated dischage lines for the T/P valves.

    Department of Redundancy Department
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  5. #5
    Join Date
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    Default Re: dual gas water heaters/ same flue

    Pipe insulation too close to draft hoods.
    Shouldn't there be support for those flue pipes where they change direction?


  6. #6
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    Default Re: dual gas water heaters/ same flue

    Quote Originally Posted by Jerome W. Young View Post
    note the a/c return in the garage (unit is only syupplying garage,
    Quote Originally Posted by Gunnar Alquist View Post
    There is a dedicated heater for the garage? I doubt that is OK. Not sure that a return air would cause flame rollout, but it is likely to cause backdrafting.
    The garage is allowed to have a separate system, it just is not allowed to be connected to the living space system.

    However, that return needs to be 10 feet from the draft hood or burner, as I recall.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  7. #7
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    Exclamation Re: dual gas water heaters/ same flue

    -WHs have to be raised 18"/ protected from cars
    -need draft hood connectors on B-vent to WH and lose foil tape
    -would need to size both the common vent for both and the connectors individually
    -need to support B-vent
    -watch clearance on the pipe insulation
    -we cannot see the ceiling firestop. Is it listed?
    -do you have adequate makeup air? If both WHs are 40K BTUs, then you would need at least 4000 cubic feet of garage or additional MUA.
    -return ducts must be sealed at least 10ft back from air handler but practically, all ducts should be sealed with duct mastic.
    -separate TPR drains per code
    -adequate gas supply for both WHs and full house load
    -seismic straps?
    -water pipe penetrations properly sealed to maintain integrity of wall
    -requisite clearance around both WHs per mfr.?
    -pulling return air from garage into home not allowed and stupid. Should be closed system

    Keep the fire in the fireplace.

  8. #8
    Join Date
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    Default Re: dual gas water heaters/ same flue

    [quote=Bob Harper;60744-pulling return air from garage into home not allowed and stupid. Should be closed system[/quote]

    Bob,

    It is a closed system. Jerome said the system was for the garage only.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  9. #9
    Join Date
    May 2007
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    Frankfort, KY
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    Default Re: dual gas water heaters/ same flue

    The only way to know if it's going to work is to test it.

    There's already two things going against the installation, draft hoods and common venting.
    Both of them combined usually make for an installation that doesn't work properly.

    Since the HVAC system seems to be in question performing draft interference testing would rule out what type of an influence any air moving devices are going to have on the draft.

    Just because it's a system dedicated to a garage doesn't mean that duct leakage and building defects won't influence room pressures.

    It only takes a room depressurization of 3 pascals to create a rollout condition, high draft in the flue can do this also.

    Measured Performance more than just a buzzword

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