shortcircuit2
Senior Member
- Location
- South of Bawstin
The TIA is that a 680.26(B)(2)(c) Copper Grid must be used over a 680.26(B)(2)(b) single #8 Copper Ring on inground pools. Structural reinforcing steel per 680.26(B)(2)(a) is still permitted in a concrete deck.
There is an appeal of the TIA with 9 disagree - 5 agree results, that is being looked at by a special task group that will report back to the standards council at the December meeting.
In Massachusetts, the Copper Grid is needed by amendment over the 680.26(B)(2)(b) copper ring with language like the TIA.
Here are some commments by CMP 17 panel members on CAM 70-117
I find the research and testing provided and performed by the Electric Power Research Institute (EPRI) compelling. Installing a single conductor for the perimeter surface of a pool will obviously perform better than not installing one at all. In the same vein, installing a grid of copper conductors will obviously perform better than installing a single conductor, as will installing reinforcing steel such as rebar or steel mesh. These facts are beyond dispute, but determining if the single conductor method is “good enough” is the question. The EPRI research appears to show that the difference in voltage (the voltage gradient) is not reduced to an acceptable level across the pool deck when the single conductor method is used. In my opinion, the research and the science have answered the question of “is a single conductor good enough,” and that answer is “no, it is not.” Pool owners and the public both expect a certain level of safety when using a pool, and the single conductor method does not appear to provide it.
I remember discussing this for a long time at CMP 17 meetings. The NEC has taken a number of protection issues for swimming pools within its jurisdiction. See: https://www.nfpa.org/News-andResear...rnal/2017/May-June-2017/In-Compliance/NFPA-70 I agree that there can be issues in a small number of cases. I would like to see the new EPRI reports referenced in the TIA. I found some inconsistencies in a previous EPRI report conducted on an in ground pool in Massachusetts. This solution would be clearly the optimum solution for the utilities but doesn’t get at the “root cause”. It seems to me the utility industry is trying to get the NEC to solve its problem. The NEC does not “preclude” the installation of a copper grid but the requirement would put both a cost penalty and solve a problem that doesn’t usually exist with the three current solutions in the code. At the CMP 17 meeting it was discussed that areas with “stray currents” and “marsh like” soils could have a local requirement to specify a complete copper grid. I think the National Electrical Safety Code, sponsored by the IEEE, should take up the root causes of “stray currents”. This code governs the utilities design requirements. In my opinion, Public Comment 2058 can be handled, after reviewing the new EPRI reports referenced, in the next code cycle.
