Re: Correct Cable For Temporary Use?
Matt,
I'm not specifically trying to single you out, but this seems as good a place in the thread as any to interject the relevant code details, which I put together as boilerplate a while ago. First, the caveat of "I am not a licensed electrician." Everything below hews very closely to the NEC, but when in doubt contact your local Authority Having Jurisdiction as they may have a different local interpretation of the NEC, or the locale may have adopted more, or less, stringent local Code:
For the purposes of show power, the relevant sectionss in the NEC are 200, 300, 400, along with articles 520, 525, 530 (to a lesser extent), and 640. Articles 520 and 525 are especially important. The first one, Article 520 starts on page 70-459 of the 2011 NEC edition.
You should be able to find the NEC locally at the library or electrical supply house to show to the fire inspector, if need be. When indoors, portable power for audio visual falls under NEC 520; while outdoors under NEC 525.
Sections you should read include:
· 520.5(B)
· 520.7
· 520.9-10
· 520.21-24
· 520.27(A)(1)
· 520.27(C)(1)-(3)
· 520.44(B)-520.45
· 520.50-52
· 520.53 (defines portable feeders and switchboards)
· 520.62 (This defines power distribution for non-switchboard units)
· 520.67 (defines multi-pole branch circuit capable conductors - e.g socapex)
· 520.68-69 (defines conductors and adapters)
· 525.10
· 525.20-22
· 525.23 (defines GFCI requirements)
· 525.31 (defines grounding)
The NEC states that entertainment power cords in the traffic path of people, or on the ground, need to be 'hard service' cords with a 600 volt insulation rating - not the 'junior' (J) version with only a 300 volt rating. There is no provision for a SJ-jacketed extension cord of the configuration we normally think of where that cord comes in contact with the ground, or is in the traffic path of people.
NEC 2011 Table 400.4 is the place with allowed cable types. In an attempt to summarize the relevant ones:
• SO and SOO as suitable for "damp locations."
• Note 6 says: "Types G, G-GC, S, SC... SO, SOO... etc. are permitted for use on theater stages in garages and elsewhere were flexible cords are permitted by this Code."
• ST, STO, STOO, STOOW, on "theater stages."
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Now, there is an exception in the NEC 520 that allows the use of SJ rated cable under specific instances. I summarize that exception from the NEC below:
NEC 520.68(A) Exception 4
• 6m maximum link of SJ-derivative cords in the form of breakout.
• Must be supported over entire length off the ground by "pipe, truss, tower, or other substantial support."
• Must connect a single multipole connector containing at least two circuits to multiple two pole, 3 wire connectors.
• Overcurrent device must not exceed 20A.
To my reading this exception probably covers above ground short power breakout stringers, socapex "spider head" breakouts to lighting fixtures, and the terminating power fanout cables into pieces of gear (e.g. moving heads or powered speakers).
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You will therefore find SJ rated cords can be used under specific circumstances. In practice, where cords are in the traffic pattern of people, or used unsupported on the ground, the cables must be SO, SC, or ST rated when indoors.
In my opinion, the most prudent cabling to purchase for distribution is SOOW. It covers your bases in all the portable power distribution contexts you will conceivably face.
