NEC 2005: New Code Clarifies Water Installations

10/05/2005


Editor’s Note: This is the seventh in a bimonthly column that covers significant new issues raised by the 2005 Edition of the National Electrical Code.

Nothing quite transforms the landscape like water.

NEC 2005 Article 682, Natural and Artificially Made Bodies of Water, was created to address installation requirements of electrical wiring and equipment in and adjacent to natural or artificially made bodies of water not covered by other articles in the Code. Prior to Article 682, electrical installations in areas such as aeration ponds, fish farm ponds, storm retention basins, treatment ponds, irrigation (channels) facilities, lakes, streams or rivers presented a problem as to which sections of the NEC covered them. The scope of Article 680, which continues to govern electrical installations involving swimming pools and “similar” facilities, was insufficient for covering such bodies of water. This new article clarifies these particular installations with a uniform standard.

Article 682 uses a term new to the NEC and most likely unfamiliar to electrical engineers and their work—electrical datum plane—which is based on the highest expected water level. Electrical connections below that plane must be suitable for submergence. When the water level rises to that plane, “service equipment must disconnect.”

Electrical datum plane addresses four different locations, depending upon the situation.

1. In land areas subject to tidal fluctuation, the electrical datum plane is a horizontal plane 600 mm (2 ft.) above the highest tide (water) level for the area occurring under normal circumstances %%MDASSML%% highest tide.

2. In land areas not subject to tidal fluctuation, the electrical datum plane is a horizontal plane 600 mm (2 ft.) above the highest tide (water) level for the area occurring under normal circumstances.

3. In land areas subject to flooding or storm runoff, the electrical datum plane based on item (1) or (2) above is a horizontal plane 600 mm (2 ft.) above the point identified as the prevailing high water mark or an equivalent benchmark based on seasonal- or storm-driven flooding from the authority having jurisdiction.

4. The electrical datum plane for floating structures and landing stages (floating docks) that are installed to permit rise and fall response to water level, without lateral movement, and that are so equipped that they can rise to the datum plane established for item (1) and (2) above, is a horizontal plane 750 mm (30 in.) above the water level at the floating structure or landing stage and a minimum 300 mm (12 in.) above the level of the deck.

Before the requirements of this article can be applied, the electrical datum plane must be determined for the specific situation. In the case of tidal fluctuations or storm water runoff, other professionals or the Army Core of Engineers can help in determining these levels. In storm water retention basins or other bodies of water subject to seasonal fluctuation or in lakes, overflow spillways should also be taken into account when considering these levels.

Once the electrical datum plane is determined, the requirements of the rest of Article 682 can be applied. Most provisions of Article 682 concern ground fault protection, electrical services, and disconnecting means.

Electrical equipment and transformers, including their enclosures not approved for operation when submerged, cannot be installed below the electrical datum plane. Electrical service equipment can be located no closer than 1.5 m (5 ft.) horizontally from the shoreline and live parts elevated at least 300 mm (12 in.) above the electrical datum plane. This service equipment is required to disconnect once the water level reaches the height of the established electrical datum plane. Utility equipment is governed by this code and should be addressed with the local power on an individual case basis.

A disconnecting means must be located on land within 750 mm (30 in.) from the structure or equipment connection and within sight of, but not closer than 1.5 m (5 ft.) horizontally from the edge of the shoreline. Live parts must be elevated at least 300 mm (12 in.) above the electrical datum plane. GFCI protection is required for 20-ampere single-phase, 125-volt through 250-volt receptacles installed outdoors and in or on floating buildings or structures within the electrical datum plane area that are used for storage, maintenance or repair where portable electrical hand tools, electrical diagnostic equipment or portable lighting equipment are used. The GFCI must be located not less than 300 mm (12 in.) above the electrical datum plane.

Grounding and bonding is similar to what is required in Articles 250, 553 and 555 of the NEC. However, one variance to keep in mind is the requirement of installing an equipotential plane adjacent to all outdoor service equipment or disconnecting means that control equipment in or on the water and that have metallic enclosures and controls accessible to personnel, and that are likely to become energized.





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