520 – Theaters, Audience Areas of Motion Picture and Television Studios, Performance Areas, and Similar Locations
520.25(B) – Dimmers for Theatrical Use
Change at a Glance:
Resistance- and reactor-type dimmers for theatrical use have been deleted as a recognized dimmer option.
520.25 Dimmers. (Theaters, Audience Areas of Motion Picture and Television Studios, Performance Areas, and Similar Locations)
Dimmers shall comply with 520.25(A) through (D).
(A) Disconnection and Overcurrent Protection. (see NEC for complete text) (B) Resistance- or Reactor-Type Dimmers. Resistance- or series reactor-type dimmers shall be permitted to be placed in either the grounded or the ungrounded conductor of the circuit. Where designed to open either the supply circuit to the dimmer or the circuit controlled by it, the dimmer shall then comply with 404.2(B). Resistance- or reactor-type dimmers placed in the grounded neutral conductor of the circuit shall not open the circuit. (C) (B) Autotransformer-Type Dimmers. (see NEC for complete text) (D) (C) Solid-State-Type Dimmers. (see NEC for complete text)
520.68(A)(2) – Listed Hard Usage (Junior Hard Service) Cord or Cable
Change at a Glance:
Listed hard usage cords or cables (rather than extra-hard usage cords or cables) permitted for use with portable stage equipment in protected applications.
520.68 Conductors for Portables. (Theaters, Audience Areas of Motion Picture and Television Studios, Performance Areas, and Similar Locations)
(A) Conductor Type.
(1) General. Flexible conductors, including cable extensions, used to supply portable stage equipment shall be listed extra-hard usage cords or cables.
(2) Protected Applications. Listed, hard usage (junior hard service) cord or cable shall be permitted where all of the following conditions are met:
(1) The cord or cable is protected from physical damage by attachment over its entire length to a pipe, tower, truss, scaffold, or other substantial support structure, or installed in a location that inherently prevents physical damage to the cord.
(2) The cord or cable is connected to a branch circuit protected by an overcurrent protective device rated at not over 20 amperes.
(3) The cord or cable does not exceed 30 m (100 ft) in length. (2) (3) Stand Lamps (3) (4) Luminaire Supply Cords (4) (5) High-Temperature Applications. (5) (6) Breakouts.
(See NEC for complete text)