2005 NEC Swimming Pool Bonding

[inspectorsparky]

Understanding the necessity of the equipotential bonding grid, under 2005 NEC, should the electrical contractor and inspector ensure that the concrete company has the individual squares of reinforcing steel tied with tie wires at all corners, or is the common practice of skipping around to every third or fourth square acceptable to maintain the integrity of the equipotential plane?
In another post with the question of " are chairs required to bring the steel a minimum of 2" above the earth" such as with a CEE, an engineer stated that as long as the concrete is touching the steel the integrity of the bond is not lost.

 

[RUWired]

Understanding the necessity of the equipotential bonding grid, under 2005 NEC, should the electrical contractor and inspector ensure that the concrete company has the individual squares of reinforcing steel tied with tie wires at all corners, or is the common practice of skipping around to every third or fourth square acceptable to maintain the integrity of the equipotential plane?
In another post with the question of " are chairs required to bring the steel a minimum of 2" above the earth" such as with a CEE, an engineer stated that as long as the concrete is touching the steel the integrity of the bond is not lost.

IMO, It is up to the electrical contractor to inform the concrete installer that the reinforcing rods need to be all bonded together and its up to the electrical contractor to inspect it prior to calling the inspector in. This is all before the cement truck gets there.

Article 680.26(B)1 (2005 version) states that all metallic parts including reinforcing rods shall be bonded. If you run a common # 8 awg and hit each square, that would be acceptable also.

Rick

 

[Cavie]

Understanding the necessity of the equipotential bonding grid, under 2005 NEC, should the electrical contractor and inspector ensure that the concrete company has the individual squares of reinforcing steel tied with tie wires at all corners, or is the common practice of skipping around to every third or fourth square acceptable to maintain the integrity of the equipotential plane?
In another post with the question of " are chairs required to bring the steel a minimum of 2" above the earth" such as with a CEE, an engineer stated that as long as the concrete is touching the steel the integrity of the bond is not lost.

There is no requirement that every square be tied at every corner. It is up to the structural inspector to inspect the steel reinforcing bares or wire mesh an see that it is up to code.. It is up to the structural inspector to inspect the chairs. The steel cannot be in or touching the dirt. It is required that the EC hit the grid in at least 4 places around the perimeter of the pool with the #8. This is what the electric inspector will look at.

 

[mweaver]

I would agree with Cavie in that “There is no requirement that every square be tied at every corner.” The 2005 NEC informs that: “The usual steel tie wires shall be considered suitable for bonding the reinforcing steel together, and welding or special clamping shall not be required. How the steel is tied with said tie wires (other than tight…) and how often is not addressed in the NEC and (I believe, as Cavie does) this is a structural issue not relevant to the NEC.

Technically, (it appears to me) if each reinforcing bar is connected to another reinforcing bar with only a single usual steel tie wire made up tight, it has met the requirements of the 05 NEC… (I seriously doubt, but don’t really know, either… that this would be adequate from a structural standpoint…) This appears to be adequate from the 05 NEC’s standpoint.


I would have to disagree with Cavie in his statement of: “It is required that the EC hit the grid in at least 4 places around the perimeter of the pool with the #8.”
… (it just doesn’t seem to say that , to me…)

While I will agree that this is what the inspector will be looking for, the 2005 NEC seems to permit much less for compliance.

My understanding is:
2005 NEC Section 680.26(C) informs that a single #8 solid (or rigid metal conduit of brass or other identified corrosion-resistant metal conduit) is all that is necessary to bond the items noted in Sections 680.26(B) to the grid. The grid itself can be comprised of the elements in 680.26(C)(1) or (C)(2) or (C)(3).

The structural reinforcing steel of a concrete pool, once bonded together with the usual steel tie wires, is one option permitted to comprise the equipotential bonding grid (in the 05 NEC) and the pool shell can be bonded to the deck with structural reinforcing steel tied together with the usual steel tie wires (or other permissible methods…).

Once the grid is established, each list item in Sections 680.26(B)(1) through (B)(5) need only be connected to the grid with a single #8 solid [connections accomplished to meet requirements in Section 680.26(D)]. A ladder's mounting brackets could be bonded to the grid in one corner and the pool equipment could be bonded to the grid at the opposite corner. They are bonded together through the grid and the #8 does not need to: “hit the grid in at least 4 places around the perimeter of the pool”.

…While I would certainly do more equipotential bonding than this (and my experience is that most do considerably more…), it seems to me this is all that is required in the 05 NEC.

If I am misinterpreting this, please let me know. This is my understanding…

I am just trying to be accurate… for accuracies’ sake.

…,Personally I believe you cannot do enough equipotential bonding in and around pools. This is a safety requirement to "reduce" voltage gradients and is expected to accomplish the performance requirements of Section 680.26(A) for the life of the pool…

… That being said, I believe it is extremely helpful to understand what the minimum requirements are so one can perform said bonding to a much higher level… In addition, each installation brings with it unique situations which seem to require additional review of what those minimum requirements are…

mweaver

 

[RUWired]

?There is no requirement that every square be tied at every corner.?

There is no requirement that every square be tied at every corner.

I hope you guy's didn't think i meant that every square had to go back to the corners. My point is that for an equipotential grid , all the squares would have to be bonded together otherwise you could have a step potential difference. Either tie the squares together with rebar ( or wire mesh whatever is being used) or run the common # 8.

 

[mweaver]

Ruwired stated:
“I hope you guy's didn't think i meant that every square had to go back to the corners.”

I did not think that…


Ruwired stated:
“My point is that for an equipotential grid , all the squares would have to be bonded together otherwise you could have a step potential difference. Either tie the squares together with rebar ( or wire mesh whatever is being used) or run the common # 8.”

Personally, I believe:
All the squares are bonded together without physically tying all the individual intersections together with the usual steel tie wires (or with #8 and suitable clamps).

I believe:
It is not necessary that each individual intersection be bonded (tied) together with anything.

I do not believe it actually says this is a requirement. [I believe if every individual intersection of structural steel needed to be tied, this fact would have been noted in text, as it is for the alternative method as noted in Section 680.26(C)(3)] … The fact that it is noted for the alternative method and not noted for the structural steel (for me) demonstrates where every point of intersection must be tied and where it is not necessary to tie each intersection… (from an 05 NEC standpoint...)



The reinforcing steel shall be bonded together with the usual steel tie wires. How often and how many intersections is a structural issue, and not an equipotential bonding issue.

It appears as though we read (and or understand) this differently, so I am certainly willing to admit I am not reading this correctly…


Where does it state that each intersection of structural reinforcing steel must be tied (bonded) together? (I could be missing this…)


What it says at the beginning of Section 680.26(B)(1) is: “All metallic parts of the pool structure, including the reinforcing metal of the pool shell, coping stones, and deck, shall be bonded.”

What it says at the beginning of Section 680.26(C)(1) is: “The structural reinforcing steel of a concrete pool where the reinforcing rods are bonded together by the usual steel tie wires or the equivalent”


No additional instruction is provided (… I believe none should be assumed)… For structural steel, this can be accomplished without the bonding (connecting together) of each individual intersection… (...at least as I see it...)



…Tying at each intersection of structural steel is certainly a good idea, but I do not believe it is a requirement in the 05 NEC… (...misconceptions, and they could be mine, abound which is why I believe even more clarity is necessary from the CMP...)

mweaver

 

[mweaver]

05 NEC Section 680.26 TIA

05 NEC Section 680.26 TIA

I am pretty sure this has been noted on this board before and, I do not believe it has any contradictory bearing on this thread up to now. If this thread continues (and I certainly hope it does...) it may have bearing in future posts. (We should all be on the same page here and I for one was not looking at the TIA when I posted in this thread...)

It is probably important to note (again) that Section 680.26(C) in the 05 NEC has been superceeded by a TIA which can be found here:

http://www.nfpa.org/assets/files/PDF/CodesStandards/TIAErrataFI/TIA70-05-2.pdf

If you are under the 05 NEC and have not incorporated this TIA into your verison of the document (your Code book) it would be a good idea, since this is now the language of Sectin 680.26(C) and (C)(1) in the 05 NEC...

mweaver

 

[RUWired]

I'm sorry i had to drag you guy's through this but in my mind, i was thinking of prefab rebar mats that were laid out and not tied together.

Rick

 

[inspectorsparky]

Thank each and everyone of you for your responses. From this information I have surmised: 1) From a structural standpoint the rebar needs to be tied appropriately to ensure proper depth of the reinforcement. 2) The rebar grid shalll have chairs underneath as the safest way to inspect this bonding grid is to consider it a CEE. 3) The #8 connection from the equipment to the bonding mat shall be made with an irreversible ground clamp listed for concrete encasement, or exothermic welding per ART 250.8. We will discuss whether we should require the connection to be accessible.
Please keep any additional thoughts coming. We have alot of pools in Texas.

 

[Cavie]

Thank each and everyone of you for your responses. From this information I have surmised: 1) From a structural standpoint the rebar needs to be tied appropriately to ensure proper depth of the reinforcement. 2) The rebar grid shalll have chairs underneath as the safest way to inspect this bonding grid is to consider it a CEE. 3) The #8 connection from the equipment to the bonding mat shall be made with an irreversible ground clamp listed for concrete encasement, or exothermic welding per ART 250.8. We will discuss whether we should require the connection to be accessible.
Please keep any additional thoughts coming. We have alot of pools in Texas.

The connection of the #8 the the steel is done with a standard j-junior ground clamp with ss screws approved for underground. It does not have to be irreversible or exothermic. It does not have to be accessable, kind of hard to do encased in concrete. Don't make mountians out of mole hills.

 

[inspectorsparky]

The connection of the #8 the the steel is done with a standard j-junior ground clamp with ss screws approved for underground. It does not have to be irreversible or exothermic. It does not have to be accessable, kind of hard to do encased in concrete. Don't make mountians out of mole hills.

Mountains out of molehills? I was just rendering my interpretation of ART 250.8 "listed clamps". In the case of pool bonding I do not believe it is prudent to simply consider as long as the bonding meets the minimum standards of the code then the installation is approved. There are too many variables to consider.