National Electrical Code Top Ten Tips: Article 520: Theaters and Similar Locations

1. 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.
    
2. 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.
    
3. 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].
    
4. Any branch circuit that supplies receptacles can supply stage set lighting [520.9].
    
5. Portable equipment used outdoors must be supervised by qualified personnel and barriered from access to the public [520.10].
    
6. Stage switchboards must be of the dead-front type [520.21].
    
7. Stage switchboard feeders can be one of the only three types described in 520.7(A).
    
8. Footlights, border lights, and proscenium lights are limited to circuits of 20A or less [520.41(A)].
    
9. A road show connection panel is a type of patch panel, and it must comply with 520.50(A) through (D).
    
10. 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.