Hot tub bonding

[kledford]

What is the correct method to create a equipotential bond for a hot tub on a wood deck (outdoors) that is 8 ft above grade? Each AHJ has a different method.:-?

 

[raider1]

Welcome to the forum.

When you find out the answer to this question please let me know as well.

This is one of the biggest problems with Article 680 in my humble opinion.

Chris

 

[Strife]

What is the correct method to create a equipotential bond for a hot tub on a wood deck (outdoors) that is 8 ft above grade? Each AHJ has a different method.:-?

Equipment ground to pump motor, #8 bonding wire from motor to all metal parts. Continuous.

Probably redundant, but the idea is to create same potential on all metal parts. As voltage is the difference of potential, if water is 120 and the (let's say) handrail is 0, 120-0=120V you get killed. On the other hand if water is 120V potential and the handrail is 120V as well (talking of same phase, same potential) then 120-120=0.
I think there's a lot of miss understanding of this part because a lot of people think in terms of grounding (bringing the potential to 0, or close enough to cause a fault in the breaker), instead of bonding (bringing to same potential). Hence, a lot of people try to come up with creative ideas to create a grounding system.
Haven't checked lately, but I think the code allows some exceptions, like metal drain grills mounted on PVC drains.

 

[raider1]

Equipment ground to pump motor, #8 bonding wire from motor to all metal parts. Continuous.

Probably redundant, but the idea is to create same potential on all metal parts. As voltage is the difference of potential, if water is 120 and the (let's say) handrail is 0, 120-0=120V you get killed. On the other hand if water is 120V potential and the handrail is 120V as well (talking of same phase, same potential) then 120-120=0.
I think there's a lot of miss understanding of this part because a lot of people think in terms of grounding (bringing the potential to 0, or close enough to cause a fault in the breaker), instead of bonding (bringing to same potential). Hence, a lot of people try to come up with creative ideas to create a grounding system.
Haven't checked lately, but I think the code allows some exceptions, like metal drain grills mounted on PVC drains.

I think the OPer is asking about the equipotential bonding grid requirement for outdoor hot tubs installed on an elevated wooden deck.

Chris

 

[KWH]

Bonding

Bonding

I was checking with one local inspector and he stated if hot tub is on a wood deck with at least I believe 3ft extending from edge of tub the ground ring is not required

 

[Dennis Alwon]

I was checking with one local inspector and he stated if hot tub is on a wood deck with at least I believe 3ft extending from edge of tub the ground ring is not required

Great that he said that but the code does not support his argument. If you used the wording of the code the EPB would need to be in the ground below the deck extending 24-30 inches around the perimeter of the tub and 4-6 inches deep.

 

[raider1]

Great that he said that but the code does not support his argument. If you used the wording of the code the EPB would need to be in the ground below the deck extending 24-30 inches around the perimeter of the tub and 4-6 inches deep.

Correct, there is no exception for an elevated above ground wood deck that supports a hot tub.

This really needs to be addressed for future editions of the NEC.

Chris

 

[kledford]

Thanks to all that responded, I agree that this requirement needs further clarification,(maybe in the next code cycle?) This is my first post at this site, looking forward to learning from others. I have been a electrician for 32 years and had my own contracting business for 20 years, my father was also an electrician. Thanks again.

 

[Dennis Alwon]

Thanks to all that responded, I agree that this requirement needs further clarification,(maybe in the next code cycle?) This is my first post at this site, looking forward to learning from others. I have been a electrician for 32 years and had my own contracting business for 20 years, my father was also an electrician. Thanks again.

Welcome to the forum-- just last week I talk with the NC state inspector about this issue. He agrees it stinks but he said what I wrote in my post and added that it would be a good idea to run wiring to the underside of the deck boards as well. When wood is wet it conducts electricity so.....

 

[hurk27]

Well at least Indiana had there head together on this one:grin:

(b) After 680.26(B)(2)(b), insert an exception to read as follows: Exception to (b): The equipotential bonding grid shall not
be required to be installed under pool decks of nonconductive materials. (Fire Prevention and Building Safety Commission; 675 IAC
17-1.8-27; filed Jul 27, 2009, 10:39 a.m.: 20090826-IR-675090140FRA) NOTE: Agency cited as 675 IAC 17-1.8-30, which was
renumbered by the Publisher as 675 IAC 17-1.8-27.

 

[dbuckley]

Well at least Indiana had there head together on this one:grin:

Does Indiana think a wooden deck is a non-conductive material? When it's dry wood is non-conductive in most senses of the word, but get some water there, paticularly over a long period of time, add some spa chemicals...

 

[Dennis Alwon]

I agree, Indiana missed it on this one. Deck wood is almost always conductive to some degree. Maybe they meant decks made of that plastic stuff-- when wet it probably is conductive also.

 

[hotwire1955]

Great that he said that but the code does not support his argument. If you used the wording of the code the EPB would need to be in the ground below the deck extending 24-30 inches around the perimeter of the tub and 4-6 inches deep.[/Q

The required conductor 18 to 24 inches from inside wall

 

[hurk27]

Does Indiana think a wooden deck is a non-conductive material? When it's dry wood is non-conductive in most senses of the word, but get some water there, paticularly over a long period of time, add some spa chemicals...

Yes true, but how much effect do you think the Earth would play into bringing the deck down to the 0 volt reference if the hot tub had a way to energize it? those long 4x4 or 6x6 leg's that hold it up to me would not have effect on it, it would be kind of like having an automatic EPBG built right in, if water was to get on the deck, then the same water will also act as a grid bringing the deck area around the hot tub up to the same potential as the hot tub?

Here was one of the reasons given when someone brought up that a person could have a radio on the deck that could energize it? OK true, but if the deck is some how bonded to the hot tub, then a greater potential will exist since the radio would be at 120 volts in reference to the wood deck, this would be the Earth bonding argument all over again. there would never be a low enough resistance even in wet wood to ever open any OCPD, that would be the only method to protect a person on a deck? of course we could place a copper mat covering the whole deck, but I think you would have a very upset home owner, and as the code is written, placing the EPBG bellow a deck will not have much effect upon the surface of the deck.

 

[Volta]

...

Here was one of the reasons given when someone brought up that a person could have a radio on the deck that could energize it? OK true, but if the deck is some how bonded to the hot tub, then a greater potential will exist since the radio would be at 120 volts in reference to the wood deck, this would be the Earth bonding argument all over again. there would never be a low enough resistance even in wet wood to ever open any OCPD, that would be the only method to protect a person on a deck? of course we could place a copper mat covering the whole deck, but I think you would have a very upset home owner, and as the code is written, placing the EPBG bellow a deck will not have much effect upon the surface of the deck.

And here you touch on some of the trouble with the statute you posted. If the deck was fully conductive, no further EP Grid would reasonably be needed, either. Just bond it once. It is only the semi-conductor type surfaces (like the earth) that pose the need for the grid.

 

[hurk27]

And here you touch on some of the trouble with the statute you posted. If the deck was fully conductive, no further EP Grid would reasonably be needed, either. Just bond it once. It is only the semi-conductor type surfaces (like the earth) that pose the need for the grid.

And that is the problem, there is no effective way to bring a wood deck to an equal potential, other then the copper or conductive metal mat. at least with Earth we can bury a grid in the earth that can be effective, but with wood you can't? so how can you adopt a code into law as a requirement that would not be effective, a law can not waste peoples money, there must be a reason for the law and it must be provable by science and testing. I don't see this with this requirment?

 

[Volta]

And that is the problem, there is no effective way to bring a wood deck to an equal potential, other then the copper or conductive metal mat. at least with Earth we can bury a grid in the earth that can be effective, but with wood you can't? so how can you adopt a code into law as a requirement that would not be effective, a law can not waste peoples money, there must be a reason for the law and it must be provable by science and testing. I don't see this with this requirment?

I agree. And maybe a grid on the underside of the wood planks would be effective, but that is just conjecture, not Code, and not science either .

 

[hurk27]

I agree. And maybe a grid on the underside of the wood planks would be effective, but that is just conjecture, not Code, and not science either .

So in essences this was the reason it was removed. you can't have a law if you can't prove a reason for it, Like Charlie Eldrige always says, show me the bodies:grin:

 

[electricguy61]

Does not the double pole GFCI protect against the problems listed?

 

[Volta]

Does not the double pole GFCI protect against the problems listed?

Sometimes. But the current can also be flowing from a circuit other than the one supplying power to the hot tub. Whether another from the same premises, a neighbor, or from the utility.