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Author Topic: Black truss  (Read 11983 times)

Brian Ship

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Re: Correction!
« Reply #10 on: April 21, 2004, 10:57:02 PM »

 Shocked I was hoping to keep it as an off line correction because in general Craig's point was valid.  Keep the Zip cord and Orange extension cords at home.  In general for actual stage type play use in a 100 seat or larger theater, you are not allowed to be using junior jacketed cable no matter the type - SJE, SJ, SJT as most but all orange extension cords are.  The NEC makes (at least under my understanding of it) no separation between the rubber like plastic, the rubberized plastic supplemented and the totally plastic type of wire for use on stage or in amperage rating - much less color.  They are all - no matter the color yellow, green, brown, white, blue, black or what ever banned from proper stage usage in the SJ grade as he referred to.  On the other hand as long as they are type S without the SJ following it, they are all permissible for use on stage in jumper cable types but not single conductor feeder cable which is still required to be type SC or W.  SOOW wire in fluorescent yellow would thus be more proper for use on a actual stage than anything SJOOW much less SJTOW no matter the color on a real stage.

That all said, there is an exception for cable supported by truss in conditions other than theater.  Otherwise the maximum length of SJ type cable no matter the plastic content in them is 3'.  I read about such an exception once but am not an expert on Code thus would rely on others to state the exact exemption for stage usage.  This however controversially would not apply to even in a rock concert to stuff used on stage or dropped down from the truss since it's not supported by the above.  In other words, use of SJ cable in general is a large Gray area and one that to the best of my knowledge is either ignored and broken or there in rock/convention use separates it application to it's use by our stage hand brothers.

In any case, Orange, Black or what ever the color, there is no NEC requirement for color that I can discern for use in our industry.  It's very un-professional to be using orange cords, but nothing electrically wrong with it in general given the plugs are also acceptable for your application which is another area of debate.  In general, he is also right in that the thermoplastic type SJT wire will not hold up as well as other cable.  I differ in that it does not hold up as well by way of abuse - all it takes is one cable loom with a stage hand having other than a hook blade utility knife and that jacket no matter the material will be slit.  I don't differ in that rubberized type SJ, SJO, SJOW or SJOOW wire in being rubberized will react much better to heat than any SJE or SJT type.  Plastic melts and drips away when heated.  While all similar cables above have the same operation temperatures, just touch anything in SJE or SJT to the back of a Leko or moving light and it's going to be much more damaged than any rubberized cable.  Granted the rubber won't be di-electrically as strong, at least it's still a barrier between conductor and short.

SJT type orange plastic/thermoplastic/thermoset type cables on the other hand do have a better abrasion resistance to that of rubberized wire.  It on the other hand is by far harder to bond to a strain relief or twofer junction than rubberized materials supplemented by plastic also to prevent bugs, rot and make it cheap.  They all will cut open very easy in comparison to the "Extra Heavy Duty" thick jacket type S materials such as S, SO, SOO, SOOW or SOW material.  Good stuff, but "Too heavy" as most complain.  When it comes to load rating that weight will add up however.  Expect any SJ type will last three to seven years.  The thick cable is heavy jacket and should last 10 to 20 years.

Craig is right in avoiding the Orange cable given it's SJT type, type stuff will melt down when heated exposing conductors.  It's jacket once it gets really cold or otherwise abused won't last as long in general.  On the other hand some vendors do sell SJT pre-molded Edison type plugged cable in this style - just in black.  On the whole there is nothing wrong with it but it's made to a higher standard or grade in general than your 99 cent home owner grade.  The home owner stuff does fall apart readily.  This while usually Euro with it's own standards is what you might find on your IEC type cable such as you have coming off your computer monitor.  Them things when not abused do last.

The next new thing is SJE which is supple like rubber unlike SJT but still plastic.  Many microphone cables and snakes will be made of a similar material.  The at least electrical contracting industry is very much sold on this stuff.  Any questions, contact your electrical supply house and wait for the next sales pitch for SJE over SJ cable.  For the most part, Coleman makes a very nice SJE cable, but it's still going to melt and not be as easy to work with.  It should take heat and cold conditions a little better, but for general usage, it's crap.  Remember the NEC accepts any of these cables by code for their usage equally so if low on budget, SJE might not be a bad solution.

Grade S cable while not really completely rubber any more is the stuff you want to be using.  It's mostly only available in black as a color but often can be found even in an orange color - even the thick extra hard usage stuff as per proper stage usage - remember it's the construction industry that pushes the market and Orange has a value to them at least.  SJ verses S wire is your choice as long as your local inspector signs off on your usage of it.  I supply in stock both types but my intent is a more strict interpretation of the NEC and it is very much not followed by the end users on shows even where I work.  "It's too heavy."  Thus even on a floor that does not at least have a ramp over it, the SJ - junior jacket cable is used even in doorways that are also against code to string thru.  Get a lot of cut SJ cable that were passed thru doors much less cut themselfs on the corner of a truss.  Since our stock is primarily SJ and black, with orange only occasionally and in limited usage, I see lots more of the black not holding up to utility knives or abuse than any orange cable no matter the grade.  SJ cable might seem thicker in jacket to SJT but in actuality, it's resistance and strength is similar.

Does not matter the color, and at least when temperatures are not factored in, the SJT orange extension cords might even hold up to more abuse than a rubberized cable - at least it's not going to rot in a few years like the other stuff.  I have seen the thick jacket type S cable last over 30 years.  On the other hand, SJ lasts about 15 years in the extreme and if lucky.  Given the cheaper over the life price of the Extra Heavy Duty cable, it's more economical to be using anyway, but at least is required on stage.  For truss, the SJ cable is best for our type of "entertainment usage" as long as any cable is 12 AWG.  I say 12 AWG because given most dimmers are rated for 20 amp, and most stage hands don't know amplification tables for extension cords, much less voltage drop, anything 14/3 at 15 amps/1,800w is very likely to be used for larger loads thus potentially melt down or even explode at times.  Go with at least 12/3 S or SJ for all your cable as a American 120v standard.  Much safer.  The 14/3 much less 16/3 stuff will be overloaded and one of the problems with rubberized cable is that it can become overheated without showing a problem, but still loose it's dielecric strength.  On rubber cable if overheated or over amperaged, it's much more possible you won't notice the problem until it is far too late.  SJE has it's advantages in this case.

Hope it helps describe the three types of cable, NEC requirements as I understand them, and what's best to be using in spite of all being Ok or not Ok for usage.

I became sold on the SJE cable for a while in saving about $0.04 per foot over 1,000 and 2,000 foot spools of it.  Hated wiring with it, and in general the cable did not last as long.  I also frequently get in SJT black cables with pre-molded plugs on them without any identifying marks on them that I'm forced to put into my own stock since I can't send them back.  In my case I have the ability to mark them well.  The SJT and SJE for the most part seem to hold up as well if not better than SJ rubberized wire on the whole as long as they don't touch a fixture.  Economically, the price on pre-molded Edison plugs on SJT wire might be well worth it also given the prices such things sell at.  They won't take the heat thus can be dangerous, but for the most part work just as well all around.  I'm back to normal rubber wire now, the SJE did not hold up as well, nor was it as easy to wire, but there is nothing on the whole wrong with it.  Where possible, especially for adaptors and twofers, you might go with grade S Extra Heavy duty in thickness jacketed cable because it will last longer, but after that for rock it's all good.
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