Technical Bulletin March 1999
Subject: Use of Jr. Hard Service Cord in Theatrical & Motion Picture Applications.
(Covered by National Electric Code Articles 520 & 530)
Jr. Hard Service cord is now allowed for Two-fers and Adapters. (1999 Addition)
Article 520-69(c) Conductor Type: Conductors far adapters and two-fers shall be listed, extra-hard usage or listed hard usage (junior hard service) cord. Hard usage (junior hard service) cord shall be restricted in overall length to 3.3 ft. (1m)*
The use of Jr. hard service cord allows the manufacture of two-fers that are smaller, more flexible and more economical than those made of extra-hard usage cord. (See DCA Two-Fer Jr data sheet) The use of glass sleeving and high temp single conductors is no longer allowed based on Article 520-69.
Jr. Hard Service cord is allowed for Breakout assemblies. (1996 Addition)
The use of Jr Hard Service cord for Breakout assemblies not to exceed 20ft. in length was introduced in the 1996 NEC. (See Article 520-68. Conductors for Portables (4) Breakouts for complete definitions and restrictions) The 1999 NEC was revised to more clearly define the application, giving breakouts their own category.
Jr. Hard Service cord is not allowed for general use in Theatrical applications.
Article 520-68. Conductors for Portables. (a) (1) General Flexible conductors, including cable extensions, used to supply portable stage equipment shall be listed extra- hard usage cords or cables. *
Jr. Hard Service cord is allowed in some Motion Picture applications. (Article 530 Motion Picture and Television Studios and Similar Locations.)
Article 530-12. Portable Wiring. The wiring for stage set lighting and other supply wiring not fixed as to location shall be done with fisted hard usage flexible cords and cables. Where subject to physical damage, such wiring shall be listed extra-hard usage cords and cables.*
Extension cords (commonly called "stingers" in motion picture jargon) of junior hard service cord are lighter and slightly less expensive than their extra-hard usage counterparts.
It seems, however, that most motion picture applications involve the potential for physical damage. From our experience, most of the rental houses go with extra-hard usage, regardless of the code ramifications, because the cord will last longer.
Extra-Hard Usage Cord - Portable electrical cord with very thick insulation and jacket to withstand roughest use. (For 12 AWG 3 Conductor extra hard service cord the insulation on the conductors is 60 mils and the jacket is 60 mills. This compares to 30-mill insulation and a 30-mil jacket for 12 AWG 3 Conductor Jr. hard service cord.) Extra-hard service cord is rated 600 Volts. Available in 18 AWG to 2 AWG.
Jr. Hard Service Cord - Portable electrical cord designed to withstand moderate rough use. Jr. hard service cord is rated 300 Volts. Available in 18 AWG to 10 AWG. 2 and 3 conductor versions only.
Two-Fer (National Electric Code Definition). An adapter cable containing one male plug and two female cord connectors used to connect two loads to a branch circuit.*
Breakout Assembly (National Electric Code Definition). An adapter used to connect a multi-pole connector containing two or more branch circuits to multiple individual branch circuit connectors.*
* NFPA 70, The National Electric Code R - The above information is provided for reference. Always check with your local Authority Having Jurisdiction as to what the requirements are in your area.
If there are any questions please email DAN CHUJKO & ASSOCIATES, L.L.C.