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Old 10-13-2008, 06:57 PM   #1
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Equipotential grid for hot tub


A question for the electricians out there. How do you all handle the equipontential grid requirements for a outdoor hot tub sitting on grade (either on a concrete pad or pavers)? Does the 2008 NEC allow for a single uninsulated conductor to be ran around the perimeter bonded to the metallic equipment?

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Old 10-13-2008, 10:52 PM   #2
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Equipotential grid for hot tub


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Originally Posted by jerryh3 View Post
A question for the electricians out there. How do you all handle the equipontential grid requirements for a outdoor hot tub sitting on grade (either on a concrete pad or pavers)? Does the 2008 NEC allow for a single uninsulated conductor to be ran around the perimeter bonded to the metallic equipment?
I believe, and I don't have my code book handy, so someone will chime in I'm sure, that all you have to do is bond the rebar and metallic parts of the tub, support frame and pump, with at least a #8. And I believe it has to extend 3 ft horizontally from the edge. It doesn't have to connect to a panel ground.

There is also a rule concerning an emergency disconnect for hot tubs and spas, but I can't think of the specifics.

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Old 10-14-2008, 08:41 AM   #3
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Equipotential grid for hot tub


Yes, a #8AWG copper bare wire and listed must bond the following together in a hot tub installation. It can be one continuous wire or a number of wires properly connected to a common wire...
  • All metallic parts of pool, spa, and hot tub structures. This includes reinforcement in the patio the hot tub sits on, if any.
  • All metal fittings attached to the structure (ladders, etc).
  • Metal parts of the circulating/pump system (motor housings have lugs on them)
  • Metal sheathed cables, raceways, piping, and fixed metal parts within 5' horizontally of the inside of the tub wall and 12' above the water level or any elevated platform or surface you can stand on.
The code says that conductive surfaces not likely to become energized, such as towel bars, mirror frames, and air and water jets and drain fittings that are not connected to metallic piping are not required to be bonded.

Don't make the mistake of connecting the bonding grid to the grounding system of the house. Doing so is pointless, and can actually raise the potential for hazards.
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Old 10-14-2008, 08:42 AM   #4
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Equipotential grid for hot tub


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There is also a rule concerning an emergency disconnect for hot tubs and spas, but I can't think of the specifics.
Correct. It must be within sight of the hot tub but cannot be within 5' of it.
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Old 10-14-2008, 10:08 AM   #5
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Equipotential grid for hot tub


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Correct. It must be within sight of the hot tub but cannot be within 5' of it.
I believe that code refers to the maintenance disconnect and not an emergency shutoff which is not required for a single family dwelling.
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Old 10-14-2008, 10:18 AM   #6
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Equipotential grid for hot tub


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Originally Posted by thekctermite View Post
Yes, a #8AWG copper bare wire and listed must bond the following together in a hot tub installation. It can be one continuous wire or a number of wires properly connected to a common wire...
  • All metallic parts of pool, spa, and hot tub structures. This includes reinforcement in the patio the hot tub sits on, if any.
  • All metal fittings attached to the structure (ladders, etc).
  • Metal parts of the circulating/pump system (motor housings have lugs on them)
  • Metal sheathed cables, raceways, piping, and fixed metal parts within 5' horizontally of the inside of the tub wall and 12' above the water level or any elevated platform or surface you can stand on.
The code says that conductive surfaces not likely to become energized, such as towel bars, mirror frames, and air and water jets and drain fittings that are not connected to metallic piping are not required to be bonded.

Don't make the mistake of connecting the bonding grid to the grounding system of the house. Doing so is pointless, and can actually raise the potential for hazards.
My question really refers to the requirement of a stray voltage grid buried below a packaged hot tub(fiberglass tub sitting on pavers) and the surrounding area (three feet out) bonded to the control box and pump motors.
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Old 10-14-2008, 10:18 AM   #7
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Equipotential grid for hot tub


Small clarification... the 'emergency shutoff switch' required in NEC 680.41 is not mandated for a spa or hot tub installed for a single family dwelling only for commercial spas.....however a maintenance disconnect NEC 680.12 is required. Only difference is one must be clearly labeled Emergency Shutoff. My opinion is that labeling the disconnect as an emergency shutoff no matter the application is'nt a bad idea. The ones you see that are at public spas are disconnect switches generally in the form of a large red push button. At any rate I always refer customers to this site for review with their families before using the spa. This is also the site that was used by the nec cmp for article 680 with concerns for safety such as the disconnects.


http://www.cpsc.gov/cpscpub/pubs/chdrown.html
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Old 10-14-2008, 10:33 AM   #8
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Equipotential grid for hot tub


All requirements of a equipotential bonding grid NEC 680.26 (B)(2) under the hot tub are required unless amended by 680.42 (B). You are allowed to use the alternative method of at least one single #8 copper wire or larger around the perimeter buried in the concrete or in the earth below the material the spa sets on within 18 to 24 inches of the inside wall of the spa. This copper wire(s) cannot be deeper than 4 to 6 inches below the subgrade. You must connect this wire(s) to the spa bonding grid from 4 evenly spaced points around the perimeter. However is is very important to check with the local requirements as they often amend the NEC.

Last edited by Stubbie; 10-14-2008 at 10:48 AM. Reason: underlined 'at least one'
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Old 10-14-2008, 10:51 AM   #9
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Equipotential grid for hot tub


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Small clarification... the 'emergency shutoff switch' required in NEC 680.41 is not mandated for a spa or hot tub installed for a single family dwelling only for commercial spas.....however a maintenance disconnect NEC 680.12 is required. Only difference is one must be clearly labeled Emergency Shutoff. My opinion is that labeling the disconnect as an emergency shutoff no matter the application is'nt a bad idea. The ones you see that are at public spas are disconnect switches generally in the form of a large red push button.
Agreed, it isn't for emergency purposes. But the requirement for it to be within sight lends it to that purpose very well.
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Old 10-14-2008, 11:16 AM   #10
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Equipotential grid for hot tub


Yep no disagreement there....just trying to keep the code police off our backs....
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Old 10-14-2008, 12:14 PM   #11
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Equipotential grid for hot tub


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Yep no disagreement there....just trying to keep the code police off our backs....
What changes if any, that the tub is above grade sitting on a wood deck specifically built for the tub. A factory contained unit with no metal ladders ect..? Would the EGC, combination disco and recept in site meet the spec? Thanks
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Old 10-14-2008, 03:09 PM   #12
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Equipotential grid for hot tub


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All requirements of a equipotential bonding grid NEC 680.26 (B)(2) under the hot tub are required unless amended by 680.42 (B). You are allowed to use the alternative method of at least one single #8 copper wire or larger around the perimeter buried in the concrete or in the earth below the material the spa sets on within 18 to 24 inches of the inside wall of the spa. This copper wire(s) cannot be deeper than 4 to 6 inches below the subgrade. You must connect this wire(s) to the spa bonding grid from 4 evenly spaced points around the perimeter. However is is very important to check with the local requirements as they often amend the NEC.
So what are your choices if you place the hot tub on an existing concrete/paver patio, someplace where you can't bury the wire?
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Old 10-14-2008, 03:34 PM   #13
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Equipotential grid for hot tub


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So what are your choices if you place the hot tub on an existing concrete/paver patio, someplace where you can't bury the wire?
That's what I'm getting at. The way I'm reading the code, the patio would have to come up and the bonding grid installed.
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Old 10-14-2008, 03:52 PM   #14
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Equipotential grid for hot tub


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That's what I'm getting at. The way I'm reading the code, the patio would have to come up and the bonding grid installed.
I agree.
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Old 10-14-2008, 03:57 PM   #15
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I agree.
I was hoping you would disagree and prove me wrong.

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