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Interpreting swimming pool code requirements
The May 2005 Code Applications column, “Going For a Swim,” contained information on a major change in Article 680 for the 2005 National Electrical Code (NEC) concerning the construction requirements of fiberglass pools, vinyl-lined pools and concrete pools that contain epoxy-coated rebar. The November 2005 Code Applications article covered a Tentative Interim Amendment (TIA) by NEC Panel 17 and processed by the National Fire Protection Association’s (NFPA) Standards Council in its meeting in July 2005. This TIA revised Section 680.26(C) and its requirement for an equipotential bonding grid for all fiberglass pools, vinyl-lined pools and epoxy-coated rebar pools. However, the new wording still left questions for many electrical contractors trying to comply with the requirements in the TIA.
The TIA added the following italicized words to the text to read as follows: “The equipotential bonding grid shall conform to the contours of the pool and shall extend within or under paved walking surfaces for three feet horizontally beyond the inside walls of the pools.”
An exception was added in the TIA that exempted the bonding grid from under the bottom and from the vertical sides of vinyl-lined, fiberglass and epoxy-coated rebar pools. It reads: “Exception: The equipotential bonding grid shall not be required to be installed under the bottom of or vertically along the walls of vinyl-lined polymer wall, fiberglass composite, or other pools constructed of nonconductive materials. Any metal parts of the pool, including metal structural supports, shall be bonded in accordance with 680.26(B). For the purposes of this section, poured concrete, pneumatically applied (sprayed) concrete, and concrete block, with painted or plastered coatings, shall be considered conductive material.”
The exception did not change the requirement to extend the equipotential bonding grid for 3 feet horizontally (measured from the edge of the pool), within or under paved walking surfaces, and the exception applies to all swimming pools without regard to the type of pool construction. The TIA did, however, provide revised requirements in Section 680.26(C)(1), where structural reinforcing steel of either a concrete pool or concrete deck is used as the equipotential bonding grid. The revised text reads as follows: “(1) Structural Reinforcing Steel. The structural reinforcing steel of a concrete pool or deck where the reinforcing rods are bonded together by the usual steel tie wires or the equivalent. Where deck reinforcing steel is not an integral part of the pool, the deck reinforcing steel shall be bonded to other parts of the bonding grid using a minimum 8 AWG solid copper conductor. Connection shall be per 680.26(D.”
The text specifically requires the reinforcing rods from the pool or the deck to be used as the bonding grid but does not permit steel wire mesh in the deck, which was customary in deck installations in the past. This text also does not indicate if all or part of the reinforcing steel from the pool structure must be transitioned into the concrete deck for it to be used as the bonding grid. It does state, however, the deck reinforcing steel must be bonded to other parts of the bonding grid using a minimum 8 AWG solid copper conductor where the deck reinforcing steel is not an integral part of the overall structure of the pool.
The question the text does not answer is: Can steel reinforcing rebar in the deck be used as the bonding grid for a fiberglass swimming pool with all metal parts described in 680.26(B), which are tied to the bonding grid by a No. 8 AWG solid copper conductor or is an additional bonding grid required? Unfortunately, this text does not specify what constitutes the “other parts of the bonding grid.”
Proposal 17-114a for the 2008 NEC consists of a total rewrite of Section 680.26, but seems to have introduced additional questions, rather than answers. For example, the following text is part of 680.26(B), dealing with the area surrounding the pool: “680.26(B)(2) Perimeter Surfaces. Extends for 1 m (3 ft) horizontally beyond the inside walls of the pool. Includes unpaved surfaces as well as poured concrete and other types of paving. Bonding for perimeter surfaces shall be provided as specified in 680.26(B)(2)(a) or 680.26(B)(2)(b), and 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 nonconductive pool shells, bonding at four points shall not be required.” This new text states that paved, concrete and unpaved surfaces extending for 3 feet around the pool must have an equipotential grid. Does this unpaved surface also mean the earth surrounding the pool?
Based on the original text for the 2005 NEC, the TIA for the 2005 NEC and the proposed text for the 2008 NEC, there are many questions that remain unanswered. 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 via e-mail at mark.c.ode@us.ul.com.