680.42 (B) (4) - Spa Bonding exception

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Mr. Serious

Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
680.42 (B): equipotential bonding of perimeter surfaces around a spa.
It says the same bonding requirements apply as if the spa were a pool, EXCEPT if all of the following apply:
[conditions (1), (2), (3), and (4)]
The fourth condition is that the top rim of the spa or hot tub has to be at least 28 inches above all perimeter surfaces within 30 inches horizontally from the spa or hot tub.

All surfaces? Or just conductive surfaces? Here's a picture of where they want me to connect the spa:
spa-location.png
Those wooden columns are within 30 inches of the spa, and it would not be possible to move it so they aren't. So, a spa can not be installed there unless the wooden pergola is removed? Or, do the wooden columns not count as surfaces for the purposes of this code section?

Seems like both of the other potential spa locations I've looked at recently also have vertical surfaces next to the spa. The first one had too many other things that were wrong, so I declined to take the job, but I have another job I would like to take, with a wooden fence next to the spa location.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I agree the wooden pergola would make this non compliant but some may disagree. If you could get an equipotential bonding around the perimeter then you could be compliant
 

Mr. Serious

Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
What would I need for equipotential bonding? Seems like I would need at least a solid bare #8 copper wire buried around the perimeter, which would be easy to do on three sides, but on the fourth side, the concrete goes all the way to the house.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Is a post really a "perimeter surface"? I don't see a definition in Article 680, but it doesn't strike me as the sort of thing that 680.26(B)(2) is talking about bonding. In which case it wouldn't be something that needs to comply with the rules in 680.42(B) to use that allowance.

Cheers, Wayne
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
What would I need for equipotential bonding? Seems like I would need at least a solid bare #8 copper wire buried around the perimeter, which would be easy to do on three sides, but on the fourth side, the concrete goes all the way to the house.
This is a choice.... Looks like the 3 sides are more than 2' away from the edge of the tub. I would call the authority having jurisdiction and see if that post is an issue. Since it is connected to the earth and you can reach it from the tub IMO it is an issue and the perimeter bond is necessary

(b) Alternate Means. Where structural reinforcing steel is
not available or is encapsulated in a nonconductive compound,
a copper conductor(s) shall be utilized where the following
requirements are met:
(1) At least one minimum 8 AWG bare solid copper conductor
shall be provided.
(2) The conductors shall follow the contour of the perimeter
surface.
(3) Only listed splices shall be permitted.
(4) The required conductor shall be 450 mm to 600 mm
(18 in. to 24 in.) from the inside walls of the pool.
(5) The required conductor shall be secured within or under
the perimeter surface 100 mm to 150 mm (4 in. to 6 in.)
below the subgrade.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Is a post really a "perimeter surface"? I don't see a definition in Article 680, but it doesn't strike me as the sort of thing that 680.26(B)(2) is talking about bonding. In which case it wouldn't be something that needs to comply with the rules in 680.42(B) to use that allowance.

Cheers, Wayne


The post is a perimeter surface and it can be touch from the tub which is the entire purpose of this section. IMO

It is a surface and it is on the perimeter of the tub
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Reading 680.26(B)(2) in full, it is clear that the "perimeter surfaces" discussed there are horizontal surfaces, not vertical faces. For example, 680.26(B)(2)(b)(5) says "The required conductor shall be secured within or under the perimeter surface 100 mm to 150 mm (4 in. to 6 in.) below the subgrade." That would be nonsensical for a column, you can't bond it by running a conductor underneath it.

Cheers, Wayne
 

Mr. Serious

Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
I should have called the AHJ and asked their interpretation earlier. The phone just goes straight to voicemail now. I'll call whenever they are back at work again.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Reading 680.26(B)(2) in full, it is clear that the "perimeter surfaces" discussed there are horizontal surfaces, not vertical faces. For example, 680.26(B)(2)(b)(5) says "The required conductor shall be secured within or under the perimeter surface 100 mm to 150 mm (4 in. to 6 in.) below the subgrade." That would be nonsensical for a column, you can't bond it by running a conductor underneath it.

Cheers, Wayne


All you are doing is keeping everything in the area at the same potential. If that post is attached to the slab then it is possible for stray voltage to be present in the wood. The wood has a shoe of some sort but if that is metal then imo the wood could be a conductor of stray voltage. What difference does it make if the structure is horizontal or vertical it still can conduct.

I think we will have to disagree on this.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
The wood has a shoe of some sort but if that is metal then imo the wood could be a conductor of stray voltage.
I agree that if the post has a metal shoe that's within 5 ft of the inside walls of the hot tub, then it needs bonding per 680.26(B)(7).

But it still looks to me like 680.26(B)(2) is only talking about bonding the concrete walking surface around the hot tub, and I don't see how the presence or absence of the wood post has any bearing on whether 680.42(B) excludes the hot tub from having to meet 680.26(B)(2). [Code language wise.]

Looking at 680.42(B)(4), you could build a set of wooden (non-conductive) steps to get in and out of the hot tub, and that wouldn't preclude the hot tub from qualifying to the exemption from 680.26(B)(2). Surely the post is no more of a hazard than the wooden steps. [Physics wise]

I'll stick with the idea that "perimeter surfaces" discussed in 680.26(B)(2) are horizontal surfaces.

Cheers, Wayne
 

Another C10

Electrical Contractor 1987 - present
Location
Southern Cal
Occupation
Electrician NEC 2020
Another example of over thinking by the NEC. What ever happened to protecting the water with a GFI secured source.
I suppose if you live in a high lightning strike area one shouldn't be sitting in a pool of water.

Sorry ... just seems so micro managed anymore.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
When did a concrete slab lose its conductive continuity to earth ground, seems to be the whole slab is already grounded.

not directed to you peter, just your keyword.

Yes it is conductive but it won't be at the same voltage potential as the tub water etc. If the slab carries 5 volts and the water has 0 volts then there is a potential difference and you will feel it if you are in the tub and grab the post or if you are stepping out of the tub to the slab when that is possible. That is the reason for that 28" height
 
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