Cable and plug types for stage jumpers

[Mayhem]

Holy crap 8O Now that it a list of books. I am going to check out if the local library holds any of those and have a look at them.

Sorry for the misspelling of your name Ship.

Cheers,

[ship]

No problem, such things should be in the personal information settings but are not yet.

As for the books: Those with a * I read at least most of, those with a + are reviews on what other people think of them which I did not read yet. Than it's based on my own ratings system for how much value I believe they would be if of any help in how many +++/*** I give them.

[Nephilim]

I finally managed to locate the marking on the cable. Ignoring the code requirement for clearly visible markings (they're *just* readable at the moment), is there a problem, code-wise or safety-wise with our vast inventory of SJTW cords (aside from the fact that they're Edison and bright orange)?

[ship]

What type of cable, plug how it's marked and used is very dependant upon your local interpitation and implimentation of the NEC for what classification of places of assembly you qualify for or comply with. Your TD is responsible for what's used as with the school. You can ask the TD if it's the proper type, gauge and grade of cable to be using, but only with tact and at the proper time. Once you get your answer or intent with it that's it because it's their responsibility not yours. It might be that this cable is approved for your application or that it's already known about and being worked on fixing. But don't push it or make a sour face about it. If they don't know you can mention your heard some stuff but because I am not there nor know what your local code is much less what classification of assembly hall or theater it is I cannot say what specifically is required or not. I know what is smart and it's not cheap.

In general a orange "Edison" extension cord is going to be 16 ga wire which is rated for 1,300 Watts new and no more than 1,000 Watts after it's broken in before you factor in voltage drop. In general unless your dimmers are rated and protected for 10 amp loads, it will be very easy to overload and possibly cause a fire with this cable by up to a 2,000 Watt load drawn by it before the breaker will trip. Actually it's 127% over rated amperage for a period of time stamped on the circuit breaker for most thermal homeline like circuit breakers and dependant upon how old and warn that breaker is, given it's not a instantanious draw of current. In some cases that circuit breaker just does not trip. Been there, the conduit and wire melted into the palm of my hands and across the building the people on stage were wondering why the stage lights suddenly started to brown out. That much current, it's not as simple as just letting go either.

Get the main problem with using cable that's rated for less than half what will be protected by the overcurrent device?

Someone does not think about or know what the rated load is on the extension cord, and that cord can pull the current for a while up until the point it melts thru its insulation and causes a fire or shorts - sometimes long after it's powered up. It takes a while for insulation/resistance to get hot enough to melt the insulation. All cable has a safety factor in it thus only pulling 1,000 Watts off something that's really rated for at least 1,300 Watts if not more. Nothing would be rated for 100% plus it's intended load.

If your Orange extension cords are 14/3, they are rated for 1,800 Watts. This would be the more expensive "Orange" shop cords. I don't mind use of 14/3 wire in general as much even if 16/3 by code is the minimum wire size jumper allowed to be used officially. Given this there is some exceptions in the NEC also. You might find some 12/3 shop cords but they cost about as much money as a black one so why bother at that point. I suspect the people buying your cords are buying whats on sale and don't realize the NEC requirements for their use on stage. Tactfully inquire but be very careful with teaching the teacher that is not open to learning. That if necessary is the role of other teachers and parents - still with tact. Perhaps one of the parents is a contractor that knows the NEC, this would be the best person for an asside on what's required if the TD is not really open to discussion on the subject. Remember that it might be that the problem is already known about and it either complies somehow or is in the works to be fixed. As long as it's properly used and in good condition it is not overtly unsafe.

There is some good about molded plugs on cords that has an advantage. For the most part you don't have to worry about strain reliefs clamping down onto conductors or loose terminals causing resistance. Plus they will be installed properly at the factory. That's security and tamper proof. Unfortunately such plugs are only designed for a 1800 Watt load, so even if you have a 12ga wire on it, the plug possibly will fail given a 2,400 Watt load or more being drawn from it' 1,800 Watt rated plug. It is 12/3 for voltage drop and motor usage not 20 amp loads. Store bought commercial grade plugs on the other hand will be constructed the same as a 20 amp plug of the same type. They for the most part can draw the 20 amp load given the same construction different layout of the neutral position. However on stage there might be a 15 amp requirement of any parallel blade plug. Details stick in my head at times without remembering the entire part of what's said about it.

Such plugs as with the cable are not designed for the extra special hard usage as implied on stage thus I suspect why you should not be using the orange cords or Edison. Again, it's dependant upon your schools interpitation of the local code and the local codes interpitation of the NEC or school distract's observance of it - which ever is the governing body for the school.

There is nothing absolutely unsafe about using orange extension cords, or Edison plugs, even using 16/3 wire as long as you are careful. No it's a junior insulated jacket thus not compliant in that way when over 3' in length, and in general the wire is not going to last as long as a good thick SOOW, but that is besides the point. It works for now as long as you are careful.

Perhaps make up some gaffers tape flags for the receptaple end of the cable, and write on them the wire gauge and type while you can still see it, and the maximum rated draw in amperage and wattage for the cable. This way those about to plug too much draw into the cable will at least have a chance to correct themselfs and learn about wire amperage ratings. Say 16/3 at 25' for a maximum of 1,200 W, 16/3 at 50' for 1,000W, at 100' for 600W would be a very leanant way of rating it for normal fixtures. For 14/3, 1800W for 25 to 50', and 1,200W for 100'. Sound fair? On 12/3 wire and given I have not done the actual voltage drop calculation, I would say 2,000W not 2,400W would be fair.


After you finish marking your cable, perhaps get them to budget into next years budget say a 500' spool of proper 12/3 SO cable and cut it into say two 100' lengths, four 50' lengths, and four 25' lengths as a start. If you don't use 100' lengths, perhaps one or none. Use the proper SO wire were ever it will be on the stage floor and as such subject to more abuse. Or as the primary cable on all large loads. If possible perhaps buy 1,000 feet and bulk up on more 25' and less lengths, than only use the orange stuff when you run out of good cable or for small loads when you know you are going to run out. Segrigate it to second class cable and work within the budget to rotate it out of stock. Perhaps all you can afford is 250' next year. It's a start. While doing this, since it's expensive, put your theater name plus it's phone number on it, perhaps a drama department symbol on it and cover it in heat shrink. This way the floor cleaning guy will be much less sucessful in swipping it for the buffer.

For note, you can purchase from many theater suppliers stage rated cable with pre-molded ends and heat shrink on them for much less money than buying the cable and seperate plugs will cost. I would recommend looking into that.


If necessary do some kind of fund raising campaign amongst local electrical contractors, parents etc. than get the school to pony up and match what budget is raised for the project. Make it cute for the electricians and electrical supply shops to put a fund raising can on the counter and directly contact others especially those that do the work on the school. Do something like a tin can on the counter with a poster saying something like "help the school buy stage rated cable, donate here" perhaps even frame the sign in some trashed orange extension cord. "We want 12/3 SOOW as required, help please." Cute fund raising cans, with examples that gain attention are good ways of raising funds and give you a better chance of the store owners letting you do fund raising at their store. Note your TD would have to approve in a big way and probably do the approaches to the contractors and stores. Just an idea at least, realistically doing a fund raising campaign is very risky and hard to do politically - the school board might not like to see any such thing.

For now and even with the proper wire type, stay Edison, should you go stage pin at some point, it would be easy enough to cut off the Edison plugs and install new stage pin ones.

Any help? I worked at quite a few little theaters that were Edison. They did not listen to the NEC or did not need to comply with the same classification as a real theater. Depends upon how many seats etc. Bars have audiences yet are not considered stages either. Your school board might not consider the theater to be a theater proper by their interpitation of it thus the orange cords. Or more likely, nobody has thought about it yet.

[Nephilim]

THanks for the info. I'll check the gauge on those cords. We rarely are loading them with more than a 575W HPL; however I realise shorts etc can be an issue.

[STEVETERRY]

You said:
"Type SJ. You are allowed to use junior jacketed cable on stage but only in lengths three feet and under such as in a twofer or distribution tail. This cable however is allowed to be used with truss supporting it in temporary entertainment wiring such as for rock concerts, so it gets a bit grey with what type of cable you need to use in an assembly hall, stage, verses concert hall or convention center. This in addition to specific uses of each where SO wire is required over SJ."

This is not quite correct.

Article 520 of the NEC (Theatres, Audience Areas of Motion Picture Studios, and Similar Locations) requires the use of Extra Hard Usage cable. This would be type S, SO,SOO, ST, STO and silmilar types.

Junior Hard Service Cord (SJ, SJO, SJT, etc) is only allowed as follows:

Breakout assemblies 20' or less in length where they are supported by a pipe, truss or similar structure and not lying on the ground. A breakout assembly is a multiconductor connector on one end and two or more single-circuit connectors on the other end. An example would be a Socapex male to 6 female 2P&G pin plugs.

Twofers not more than 3' in length.

Special high temperature applications on connector strips or fixtures where the 60 or 90 degree C temperature rating of normal cord is too low for the application.

Steve Terry

[ship]

Noting the changes over the years to the code because I also remember a cable drop concept to this original code designation of what type SJ is not servicable for also written in. Still it’s not much changes in difference for stage or correction.

Major difference perhaps I have simplified is the 20' verses 3' for SJ in general.

Still I stand corrected in what’s current code and acceptable and what in concept is acceptable for use. Intent and major emphisis still is that type SJ cable is not to be used as jumpers for stage lighting on stage.

Still given the valid code stipulation, what the intent was in intent still remains.

[STEVETERRY]

Originally Posted by ship

Intent and major emphisis still is that type SJ cable is not to be used as jumpers for stage lighting on stage.

That is the key point that readers need to follow. But not just "on stage"--in any location where Article 520 applies.

Other than twofers or breakouts, anything but extra hard usage cable is verboten.

Also in looking at my previous post, I might have implied that SJ is allowed in special high temp applications. That is not so. These applications release the requirement for extra hard usage cable, but require special high temperature assemblies that become aprt of the UL listing of the fixture, usually made of fiberglass sleeving and teflon wire.

ST

[gafftaper]

Is SJ allowed on just the split end of the two-fer or is allowed on the single line side of the two-fer as well. That seems like a bad idea if it is. True it's only a couple feet of SJ, but it's only a matter of time until somebody's going to run 12 gauge lines 25 feet in opposite directions and try to burn the place down with a couple of 1000 watt fresnels.


Has someone cleaned up this thread and put it in the Wiki yet? There are at least three different topics that should be in there.

[Sean]

Originally Posted by gafftaper

Is SJ allowed on just the split end of the two-fer or is allowed on the single line side of the two-fer as well. That seems like a bad idea if it is. True it's only a couple feet of SJ, but it's only a matter of time until somebody's going to run 12 gauge lines 25 feet in opposite directions and try to burn the place down with a couple of 1000 watt fresnels.
Has someone cleaned up this thread and put it in the Wiki yet? There are at least three different topics that should be in there.

The three-foot limitation is from male connector to female connector. It doesn't matter if it's a "Y" style or a "V" style.

Incidently, the requirement for SO over SJ isn't about ampacity--it's about the ability of the cable jacket to stand up to the PHYSICAL abuse in a performance environment. Electrically, there isn't anything wrong with "somebody's going to run 12 gauge lines 25 feet in opposite directions and try to burn the place down with a couple of 1000 watt fresnels." Two 1000w loads could be safely carried by 12/3 SJOOW.

--Sean