Equipotential bonding adjustments for pools in the 2008 NEC
Since there seemed to be so much controversy about equipotential bonding for swimming pools [Section 680.26 of the 2005 National Electrical Code (NEC)], my May 2005 and November 2005 ELECTRICAL CONTRACTOR articles were devoted to this issue. As they explained, there were major changes in the 2005 NEC involving swimming pool bonding and grounding. Check the Electrical Contractor archives right here on www.ECmag.com for those articles.
As the 2005 NEC has been adopted, phone calls and e-mails have been circulating on this issue from the many electrical contractors and general contractors involved in swimming pool construction. These contractors are searching for further explanations and answers to the methods of grounding and bonding required for pools. Based on the actions that occurred at the 2008 NEC Report on Proposals (ROP) meeting and the 2008 NEC Report on Comments (ROC) meeting, this controversy will continue into the 2008 NEC cycle.
The proposed text for the 2008 NEC covering bonding of pools is located in 680.26 and is divided into two subsections. Section 680.26(B) covers the bonding of the various metal parts of the pool and is composed of seven subsections with the main text in (B) as an introduction to the seven subsections as follows:
“The parts specified in 680.26(B)(1) through (B)(7) shall be bonded together using solid copper conductors, insulated, covered, or bare, not smaller than 8 AWG or with rigid metal conduit of brass or other identified corrosion-resistant metal. Connections to bonded parts shall be made in accordance with 250.8. An 8 AWG or larger solid copper bonding conductor provided to reduce voltage gradients in the pool area shall not be required to be extended or attached to any remote panelboard, to service equipment, or electrodes.”
Conductive pool shells are covered in (B)(1) with a further subdivision of this section into two subsections, (B)(1)(a) and (B)(1)(b) as follows (text in quotes is the actual text, and the text without the quotes is explanatory information not in the NEC):
“(1) Conductive Pool Shells. Bonding to conductive pool shells shall be provided as specified in 680.26(B)(1)(a) or 680.26(B)(1)(b). Poured concrete, pneumatically applied or sprayed concrete, and concrete block with painted or plastered coatings shall all be considered conductive materials due to water permeability and porosity. Vinyl liners and fiberglass composite shells shall be considered to be non-conductive materials.
“(a) Structural Reinforcing Steel. Un-encapsulated structural reinforcing steel (rebar) shall be bonded together by steel tie wires or the equivalent. Where structural reinforcing steel is encapsulated in a nonconductive compound, a copper conductor grid shall be installed in accordance with 680.26(B)(1)(b).”
Section 680.26(B)(1)(a) requires “un-encapsulated structural reinforcing steel [steel not epoxy coated] to be bonded together by steel tie wires or the equivalent” wherever the steel crosses each other. Panel 17 deliberately removed the word “rebar” in the above quoted text to clarify that “welded wire mesh” is included in “structural reinforcing steel” but “only where acceptable to the authority having jurisdiction.” This statement, however, only appears in the panel statement in comment 17-92, not in the NEC.
“(b) Copper Conductor Grid. A copper conductor grid shall be provided and shall comply with the following conditions:
“(1) Be constructed of minimum 8 AWG bare solid copper conductors bonded to each other at all points of crossing.
“(2) Conform to the contour of the pool and the pool deck.
“(3) Be arranged in a 300 mm (12 in.) by 300 mm (12 in.) network of conductors in a uniformly spaced perpendicular grid pattern with a tolerance of 100 mm (4 in.).
“(4) Be secured within or under the pool no more than 150 mm (6 in.) from the outer contour of the pool shell.
“(2) Perimeter Surfaces. The perimeter surface shall extend for 1 m (3 ft) horizontally beyond the inside walls of the pool and shall include unpaved surfaces as well as poured concrete and other types of paving. Bonding to perimeter surfaces shall be provided as specified in 680.26(B)(2)(a) or 680.26(B)(2)(b), and shall be attached to the pool reinforcing steel or copper conductor grid at a minimum of four (4) points uniformly spaced around the perimeter of the pool. For non-conductive pool shells, bonding at four points shall not be required.”
As in 680.26(B)(2), perimeter surfaces must connect to the pool reinforcing steel or the copper conductor grid and extend at least three feet horizontally beyond the inside walls of the pool, including unpaved surfaces, poured concrete, as well as other paving. Bonding must be connected to the pool steel or copper grid at least at four points uniformly spaced around the perimeter, but a nonconductive pool shell does not require the bonding at four points. EC
ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at firstname.lastname@example.org.