The National Electrical Code (NEC) first introduced swimming pool grounding and bonding in the 1962 edition. In this edition, the code required that all metal objects, including: the steel rebar in concrete (support), metallic conduit, piping systems, pool reinforcing steel, light fixtures, ladders, diving boards and the like, shall be bonded together and grounded to a common ground. A minimum 14 AWG wire was required for this bonding. In the 1965 they increased the bonding wire size from 14 AWG to 8 AWG, and in 1968 they added the 5-ft rule. The 5-ft rule required that every metal object within 5-ft of the pool must be bonded to the same equipotential grounding system.
The pool shell reinforcing steel, including the steel in at least 3’-0” of the perimeter deck, and all metal anchors, inserts, fittings, light niches and equipment in the pool and within 5’-0” of the pools edge, as well as all mechanical equipment in the filter room, must be bonded together per NEC Article 680 to form an “Equipotential bonding grid.” All bonding must be verified prior to the pouring of concrete.
The purpose of the equipotential bonding grid is to electrically connect all metallic components in and around the pool in order to eliminate electrical potentials that could otherwise prove unsafe to bathers.
Typically, the bonding grid is formed by connecting together all the reinforcing steel in the pool and deck to which all other metallic components connect. To achieve this, the reinforcing steel must be tied together to form a conductive whole through which electrical currents can easily pass. Every lane anchor, handrail anchor, diving board support and light niche must connect to this grid with a solid #8 copper conductor, which must then be taken back to the filter room and connected to the mechanical equipment.
For this reason, epoxy coated reinforcing steel should not be used. Epoxy inhibits adequate electrical connections between the various sections of rebar as well as the connections of fittings and equipment to the grid. The result would be an inadequate equipotential bonding grid which could possibly allow differences of electrical potential in the pools fittings and equipment.
Galvanized reinforcing steel is an option if corrosion resistance is a requirement. Zinc is suitably conductive, yet still provides corrosive protection. Galvanized reinforcing steel, however, costs about 3 times as much as uncoated rebar.
Stainless steel pools are themselves conductive, and properly bonded form the major part of the required equipotential bonding grid. As in conventional reinforced concrete pools, 3’-0’ of the perimeter deck reinforcing and all fittings and equipment in the pool and within 5’-0”of the pools edge must still be bonded to the grid, taken back to the filter room and bonded to all the mechanical equipment.
If there is no bonding grid available, and the pool is not lined with an impervious and insulating plastic, vinyl or fiberglass liner, a separate equipotential bonding grid consisting of a matt of #8 copper conductors spaced at 12” on center in both directions placed under and around the pool may be required. Consult the code and the local building departments for specific requirements if this appears to be the case.
Properly bonded, a bather could not become a conductive link between an area of higher electrical potential and a lower because the system bonded together, and any potential would be equal throughout the system. Additionally, because any stray electrical currents in the system would seek the path of least resistance to ground, the equipotential bonding system would tend to disseminate them to ground.
Although the NEC specifically does not require that the equipotential bonding grid be taken to electrical ground, it will be so connected at least indirectly through the equipment grounding systems. That, however, may not be adequate. In pools that may be subject to stray electrical currents, or on which a saline chlorine generation system may be utilized where the electrolyte level in the pool is higher than normal, connection of the pool bonding system to a true, solid, and viable ground is imperative. It is therefore recommended that the building ground system be tested, and its adequacy certified as a condition of acceptance. In rare instances, it is possible that a separate ground will be required to ensure that any stray currents find their way to ground before passing through the pool and its related equipment.
Typically, a minimum of 3 inches of concrete coverage over the reinforcing steel in a pool shell is recommended.
Bonding and grounding requirements should be coordinated with the electrical engineer and should be an item of review during construction. It is recommended that the electrical ground system be tested, determined to be adequate and that a written confirmation of that be provided.
The typical bonding detail should be included on all projects. In addition, notes requiring compliance with NEC 680 should be included on the Drawings, and provisions in the specs should be reviewed and maintained.
In addition to the pool shell and equipment, the stainless steel counters at concession areas, and wherever wet bather may congregate near electrically operated equipment, should be separately bonded and grounded, and GFI protection for all electrical outlets provided.
In 2014, NEC updated their language for bonding. The new code language states the following: “Where none of the bonded parts is in direct connection with the pool water, the pool water shall be in direct contact with an approved corrosion resistant conductive surface that exposes not less than 9 in^2 of surface area to the pool water at all times. The conductive surface shall be located where it is not exposed to physical damage or dislodgement during usually pool activities and it shall be bonded in accordance with 680.26(B).” To satisfy this requirement a bonding device has to be installed at the main drains since the main drains will be in constant contact with the water regardless of water level in the pool. The bonding device must be run above water level and tied to the bonding grid by Electrical.
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