110.31 Enclosure for Electrical Installations
For installations other than equipment as described in 110.31(D), a wall, screen, or fence shall be used to enclose an outdoor electrical installation to deter access by persons who are not qualified. A fence shall not be less than 2.1 m (7 ft) in height or a combination of 1.8 m (6 ft) or more of fence fabric and a 300 mm (1 ft) or more extension utilizing three or more strands of barbed wire or equivalent. The distance from the fence to live parts shall be not less than given in Table 110.31.
Informational Note: See Article 450 for construction requirements for transformer vaults.
|Minimum Distance to Live Parts|
|Note: For clearances of conductors for specific system voltages and typical BIL ratings, see ANSI/IEEE C2-2017, National Electrical Safety Code.|
Exception to (1), (2), and (3): Where the vault is protected with automatic sprinkler, water spray, carbon dioxide, or halon, construction with a 1-hour rating shall be permitted.
Informational Note No. 1: For additional information, see ANSI/ASTM E119-2018a, Method for Fire Tests of Building Construction and Materials, and NFPA 80-2019, Standard for Fire Doors and Other Opening Protectives.
Informational Note No. 2: A typical 3-hour construction is 150 mm (6 in.) thick reinforced concrete.