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Thread: Bonding of a recessed hot tub in composite deck.

  1. #1
    Join Date
    Oct 2008
    Location
    Cincinnati, OH
    Posts
    85

    Bonding of a recessed hot tub in composite deck.

    Biding a job for a recessed hot tub that will be sitting on a concrete pad under the deck. Do I bond the concrete pad metal rebar or mesh? I'm running 1 inch pvc with 50 amp GFCI protected wiring from the house disconnect, within site of the tub. If they use metal joist hangers under the deck and they are over 9 sq inches do I have to bond these?

  2. #2
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    32,470
    See 680.42(B)


    If the tub were a packaged unit and sitting on concrete with no raised deck - you typically don't need to bond any perimeter surfaces, but adding a raised deck made of non conductive material (except fasteners and misc hardware) does make for a complicated situation to figure out the intent for perimeter bonding.

  3. #3
    Join Date
    May 2014
    Location
    AZ
    Posts
    1,838
    recessed how? is concrete at grade level and the decking is ~36" off the ground, or maybe just 18" off the ground.

    i suspect whatever decking it is people cannot walk under it.

    to provide additional safety, lay down/loop #14 (if not required by NEC to be bigger) bare copper across the joists about 1ft away from hot tub all the way around the tub, tap the copper into top of joist with hammer but not fully flush because you want the decking planks to crush down onto that wire to make contact (not sure what decking screw system is being used, blind anchors or top screw), then bond that loop down to tub egc. where wire may run parallel to joist, just run wire on top/side edge of joist but provide a few short weaves over the top edge of joist allowing wire to go from one side to the other.

    with plastics, voltage on a plank 10ft away wont really make it to the tub, but wet planks/decking will allow it. with a copper loop under and everything get all wet as folks get out of tub, at least you'll have some additional safety.

    but as noted, you may not need bonding at all. what does your AHJ say? but having a bonded decking near hot tub + gfi is very very very safe
    maybe even put in one 8-10ft ground rod right next to tub (in the slab) and bond decking loop and egc to that. you never know when lightning may strike. ground rods are good

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