National Electrical Code Top Ten Tips: Article 520 -- Theaters and Similar Locations
- Article 520 applies to all structures or parts of structures used for presentations and/or performances. Basically, if it has a stage, auditorium, or audience seating area, it's covered by Article 520.
- You can use raceway, Type MI cable, Typle MC cable, or Type AC cable. If you use nonmetallic raceway, it must be encased in at least 2 in. of concrete [520.5(A)], unless it's for Article 640 circuits.
- Article 520 puts a twist on raceway fill. If using a raceway other than an auxiliary gutter (or aux raceway), the normal raceway fill requirements of Table 1, Chapter 9 apply. Otherwise, the sum of the cross-sectional area of all contained conductors at any cross section can't exceed 20% of the interior cross-section of the gutter (but the 30-conductor limit of 366.22 and 376.22 does not apply) [520.6].
- Any branch circuit that supplies receptacles can supply stage set lighting [520.9].
- Portable equipment not identified for outdoor use is permitted for temporary use outdoors if it's supervised by qualified personnel and barriered from access to the public [520.10].
- Fixed stage switchboards must contain overcurrent protection [520.21].
- Stage switchboard feeders can be one of the only three types described in 520.27(A). For example, it can be a single feeder disconnected by a single disconnect device.
- Footlights, border lights, and proscenium lights are limited to circuits of 20A or less [520.41(A)].
- A road show connection panel is a type of patch panel, and it must comply with 520.50(A) through (D). For example, the panel construction must comply with Article 408.
- There are many types of portable stage equipment other than portable switchboards (arc lamps, PDUs, busbars, receptacles, etc.), and these are covered in Part V of Article 520. Requirements address such issues as festoons, conductor types, conductor ampacity, and adapters.