Control/Dimming Extension Cords

[btriple]

First, I want to say thanks for any assistance.

My main question is can I use a 100 ft extension cord to power two Source Four 750 watt? I image it would have to be a 10 gage wire.

Background. I’ve been volunteered to be in charge of setting up lighting every Sunday at a new church that meets in a high school auditorium. We are not allowed to use their light so we bring in our own which consist of 8 Par 56, some LED’s for back wash, and some Source Four for some pattern projection. We use the pars to light the front of the stage which are mounted on some lighting stands and some bases. The problem with that is I can not get the lights high enough to achieve even a 30 degree down angle (I might have about 20) so as you all know the light is not that easy to control and it ends up on the projection screens and running all the way across the stage and hitting the back curtain. What I would like to do is mount a couple of Source Fours up in the “attic” (sorry for the lack of the correct term) where the school has their lights and just run extension cords up to them from a dimmer down below to control them every weekend. Right now I use my computer to control the lights using the pro dongle. If the school does not let me mount the Source Fours up there I’m not sure what to do to fix the problem.

Any ideas?

I’ll post a picture of our layout once I get home this evening.

 

[Footer]

You can get extensions, it just has to be the right cable. Legally, you can not use off the shelf extension cords in a theatre. They are not meant for the abuse that a cable is put through. Beyond that, your extension cable needs to be able to support the same amount of power that the circuit is rated at.

12/3 SOOW cable is the norm in the theatre world. 12/3 Cable is expensive but its worth the money. 100' will set you back about $100.

You can buy it from whomever you purchased your S4's from. If you don't know where your lights came from, here you go....
Stage Cable, 12/3, 600V, 2P&G, 100'

 

[btriple]

I was thinking about some like this. 100-Feet 10/3-Wire Gauge 20-AMP Power Extension Cord

How can you tell if it is legal or not? What portable dimmer can handle a stage pin connection? (man that sounds like a newbie question, oh wait I am a newbie, sorry)

 

[MNicolai]

That's more expensive, and less useful than the SOOW, and you don't need 10/3, you only need 12/3 for that. Plus, do you really want a bright yellow (or orange, for that matter) cord floating around?

The important thing to remember is that you don't need to have 2P&G connectors on the cord. It's the industry standard for incandescent lighting fixtures, but so long as you have the cable, you can put whichever connectors on the ends that you'd like. Within reason...

Your load is presently (2) 750w Source Fours. That's [(750w*2 fixtures)/120volts] = 12.5amps.

According to Table 520.44 of the National Electrical Code, SOOW 12/3 would be allowable for 20A circuits, 14/3 for 15A circuits.

Also note that if you have the wiring to allow up to 20A, but put 5-15 (Edison) connectors on there, those connectors are rated at 15A and you should not use that cable for loads greater than 15A -- the connector serves as a bottleneck.

2P&G connectors are rated to a full 20A, as are the 5-20 connectors (the T-blades). However, I'd venture the guess that no portable dimmer packs have T-blade receptacles on them, partially because those packs are usually not rated for more than a 15A load anyways.

With that said, 12/3 SOOW with 2P&G is the industry standard, but certain situations call for different solutions. The bare minimum you need is 14/3 SOOW with 5-15 connectors, but you had better not go plugging anything else into that cord at the same time! Don't go adding another PAR or Source Four to that load or your extension cord will melt or catch fire. Most people will tell you to go with the 12/3 SOOW anyways such that you never need worry about that happening, but it is not required by code.

And don't worry about having to ask which portable dimmer packs have 2P&G connectors on them - not many do. I have found that these Leprecon ULD packs work pretty nicely, but I've only used them a few times. Be sure to let us know if you have any further questions. Welcome to CB!

 

[derekleffew]

I was thinking about some like this. 100-Feet 10/3-Wire Gauge 20-AMP Power Extension Cord ...

Nope. From the description: "Jacket wire with yellow. cords made of regular SJTW or SJEOW wire types. yellow." NEC Article 520 specifies only extra-hard usage cable (type S and its derivatives), except for very special cases where junior hard usage (type SJ) is permitted. See SJO cable in a theater for more explanation.

As for portable dimmer packs, Leprecon ULD and Lex Products Anaconda are two examples available with 2P&G outlets, but I don't think either comes larger than a 1200W dimmer. Choice of outlet shouldn't be a limiting factor, as 5-15 (Edison) to 2P&G (StagePin) adapters are permissible, and the 2*750W does fit on a 15A connector.

If an outlet is available within a reasonable distance in the "attic" (most would say "FOH position" or "catwalk"), you might consider locating a shoebox dimmer there, near the fixtures, and running DMX cable to and from it. In addition to shortening the power run, you'll also gain individual control of each fixture. Obviously a 4x600W pack wouldn't work for this application.

 

[len]

While a more expensive solution, you might look into a shoebox dimmer up there, with power from an outlet closer to where the lights will live. You can find them with 2P&G, or you can buy them with edison and build some adaptors to get to your lights. Leprecon, Lightronics, Leviton, even Elation make decent dimmer packs. Then you'd just run a data cable up there. Also, you can find inexpensive dmx splitters from Elation, which are decent and under $200. Running power cords all over is usually the last resort.

 

[JD]

The key part of this whole discussion is what kind of covering the cable has. SO is a thick "rubber like" jacket that can be mishandled. Plastic and vinyl jackets can melt if they come in contact with the hot fixture. Although SO can be damaged, it is less likely to melt/short and cause a fire. Cables also tend to get dragged a lot. The jacket on an SO cable is far less likely to be compromised in this area as well. Note: SOOW is a type of SO cable. (look to the first letters)

Also, I'll second the idea of using a shoebox dimmer. Some can be had for under $100, but I would stick with the $200 range like the Elation. This will also give you independent control without having to run a second cable.

 

[btriple]

Thanks guys, I checked for a closer power source with no luck, everything up this all ready hard wire with no power sources so I guess I'm stuck with the extension cords.

So sense I have four 750W (4*750=3000W & 3000W/120=25 amps) I need a dimmer with two 20 amp sources with about 1800W per channel.

 

[Sony]

Thanks guys, I checked for a closer power source with no luck, everything up this all ready hard wire with no power sources so I guess I'm stuck with the extension cords.

So sense I have four 750W (4*750=3000W & 3000W/120=25 amps) I need a dimmer with two 20 amp sources with about 1800W per channel.

Yes, 750w * 2 = 1500w so two 15a (1800w) dimmers would work just fine!

 

[BillESC]

Leviton's N600P-20 features two 20amp service cords and would give you four channels of control at 1000w each thus allowing individual control of the four fixtures.

Here's the link:
N600P-20 > DDS 6000 & 6000+ > Satellite Dimmer Packs > Dimmers (commercial) > Lighting Management Systems > All Leviton Products from Leviton Electrical and Electronic Products

 

[mrb]

the anaconda is available with multiple power cords as well.

 

[ship]

This is a "Places of assembly" not a class 1A theater location. While type S cable is not required and SJ of at least 14ga is required for the situation, grade S, SO, SOOW would be preferable still as with the 12/3 in general for next time when someone decides to connect more lights to the dimmer. 14/3 cable is fine no matter the type SJ or SO in this situation but gets you into sticky situations later when people try to pull 20A off a 100' jumper. Better off just maximizing the cable size for a few dollars more.

The 12ga cable is a longer term investment for future needs that 14ga cable in being slightly cheaper will not provide for. Same concept in investment for the future of grade S cable over that of SJ. Average lifespan of a SJ cable is about seven to ten years with use assuming no cuts or other problems. Average lifespan of a SO cable is at a minimum about 15 years and up to 30 I have seen without dry rot. A bit more heavy to carry but in cost effectivenes as with commercial grade plugs your cable won't need to be replaced for a long time. 10ga cable... na not for that load. Large air compressor 25' away sure.


This all given none of us have done the specific voltage drop calculation but its fairly assured that 14/3 at 100' is fine.

Sub note, and past debated with me not finding the NEC reference to prove what I remember reading perhaps on a proposal for change published but still think valid and something I remember as permissible in reading it as permissible. I believe a 15A commercial grade Edison plug for use in entertainment/stage is allowed to be used for 20A loading for stage lighting purposes only as a plug and I would only take that as a given the cable it was wired with was 12ga. It is the exact same plug, just different pin configuration so there is no reason as per stage lighting purposes it should not be allowed. To be very clear, you are not to be using some store bought Eagle yellow and silver type plug or worse some rubber plug anyway for entertainment purposes (I use them at most for an adaptor of plug to different plug type for fixture), such plugs are against code to be using anyway. Assuming a commercial grade plug such as a Leviton #5266-CB or even #5256-CY, it in my opinion but not supported so far by code in debate is permissible. Absolutely no difference between such plugs than than the 20A versions other than hot pin in a different position. But again this is a production use and not a home owner or industrial use difference.

 

[derekleffew]

Good catch, ship. I suppose "a new church that meets in a high school auditorium" would fall under NEC 518 rather than 520. But I agree, better to go with the 12/3 SOxx rather than 14/3 SJxx.

 

[ship]

Good catch, ship. I suppose "a new church that meets in a high school auditorium" would fall under NEC 518 rather than 520. But I agree, better to go with the 12/3 SOxx rather than 14/3 SJxx.

Nope, not so good catch in that I didn't see "church that meets in high school auditorium". That's at least in my book class 1A and needs to be SO which ever the gauge. Some mention I remember about use permissible for SJ unless directly supported by truss/pipe that's negotable that I would hope or more NEC experts and panel members would be able to add to. If school, SO would be my rule.

 

[mrb]

Nope, not so good catch in that I didn't see "church that meets in high school auditorium". That's at least in my book class 1A and needs to be SO which ever the gauge. Some mention I remember about use permissible for SJ unless directly supported by truss/pipe that's negotable that I would hope or more NEC experts and panel members would be able to add to. If school, SO would be my rule.

in nec 520 locations, SJ cable acceptable only in adapters and twofers limited to 3.3ft in length, and to breakout assemblies (soco breakout) where the longest tail is limited to 20ft length, and ONLY where affixed to pipe, truss, or other structure where it is protected from physical damage. Cant have any SJ cables that arent either of the above, even if its only 5ft in length and attached to a pipe.