Power Delivery... Need Advice

TNasty

Active Member
So right now I'm working on designing a power cord of sorts for running fixtures, since all the fixtures I'm setting up next week lack powercon, and there's only static/relay'd power on the stage left end of each batten. Here's a picture to show what I'm thinking:
Electrical chain.png


So here's the idea. There's the three sets of receptacles, which will be evenly spaced over the stage, which should be sufficient for now and any small fixture upgrades in the future. I like that with this design I can replace the standard 120v receptacles with powercon ones down the line if need be.

I'm currently planning on using this 14/3 cable for the wire. I would have opted for a heavier gauge, but I don't see there being a need for a whole lot of current capacity, as the only two non-LED fixtures that'll be running off of one of these don't use over 300 watts. (The cable's ideal max is 120 volts * 5.9 amps = 708 watts, so I'm trying to limit it to 650 continuous)

Each junction box will be steel, partly for durability reasons, but if I remember correctly it's code to have a metal box if it's not being flush mounted (which happens to be the case here).

I'm also making sure to get all the strain reliefs needed going in and out of the boxes, along with other odds and ends such as the faceplates.

I've got two main questions here, and one small one. I'm considering adding GFCI protection to these guys. I feel like it's a good idea from a safety standpoint being around a stage and such, but I'm sure one of you guys can tell me if it's a good idea or not, and whether I should just use a GFCI receptacle or one of those GFCI plugs.

The second question is about circuit breaking. You probably noticed that I left a blank gang on the first junction box. I'm wondering if there's a way to put a breaker or something like a breaker there to prevent overloading the cable. (Bringing this up reminds me that I could also go for a GFCI breaker for the previous question).

One last question. Is there any apparatus I can integrate into these things to add some degree of surge protection? Just erring on the side of caution here, and I also wouldn't need to plug into a random power strip if I was running directly out of the wall instead of a relay on the dimmer rack.

As a side note, I'm trying to keep the total cost for all three units under $200.
 
I did something similar, but used a string of metal boxes and flex metal conduit. I ran my own 14 guage stranded wire down the flex. Much harder for someone to accidentally breach the line than romex. The conduit connectors take care of any strain worries. Mine are just zip tied to a batten. They run off a stage plug that has a true relay rather than dimmer up in the dimmer rack, and it has a breaker, but a 15 amp breaker wouldn't be a bad idea for the unit itself (14 guage) Even without a breaker, this is a better solution than a spaghetti of extension cords. GFI in theory yes... but when it trips 16 feet above stage during a performance, you will wish it wasn't there... and it WILL trip at some point, as GFI seems to err on the side of caution, and will trip with little inductive voltage spikes etc.
 
I did something similar, but used a string of metal boxes and flex metal conduit. I ran my own 14 guage stranded wire down the flex. Much harder for someone to accidentally breach the line than romex. The conduit connectors take care of any strain worries. Mine are just zip tied to a batten. They run off a stage plug that has a true relay rather than dimmer up in the dimmer rack, and it has a breaker, but a 15 amp breaker wouldn't be a bad idea for the unit itself (14 guage) Even without a breaker, this is a better solution than a spaghetti of extension cords. GFI in theory yes... but when it trips 16 feet above stage during a performance, you will wish it wasn't there... and it WILL trip at some point, as GFI seems to err on the side of caution, and will trip with little inductive voltage spikes etc.
The wire I'm looking at isn't Romex, it's pretty much just an extension cable without the plugs all wrapped up. Here's the stuff I'm looking at.
Good point about accessibility when using GFCI. Can't believe I didn't think of that when I realized that the GFCI plug would be nice because you could see if it was working from the ground. I suppose I could look into having those weather resistant covers, at lest they'll protect closed outlets.
That's exactly what I was thinking when I had the breaker idea. It's probably a good idea if I don't rely on the relay's breaker... It's easier to replace a $15 or so breaker than a $400 relay unit if the breaker jams up.

I've also dealt with the Flying Spaghetti Monster you mentioned. It's bad enough with two fixtures.
 
The stuff you're looking at is designed to be squished a little on the plug end anyway, so I would think you could use the inserts for non metallic cable in the box knockouts and be in pretty good shape.
We squish that stuff in stage plug ends too. That also looks at least as tough as the insulation on our 2fers and extensions. Would probably use the steel face covers instead of plastic though.
 
So what you are building is a stage stringer.
First, metal boxes aren't really the best idea. The trend now is using rubber boxes like the very popular O.A. Windsor or Woodhead. But they are beyond your budget.
Have you considered something like this:
www.lexproducts.com/products/entertainment/powerflex-cable-assemblies/multiple-receptacle-extensions
Here is a price for the smaller one:
http://www.fullcompass.com/prod/229239-Lex-Products-Corp-50123B
Those are exactly what I'm looking for. I guess knowing the name of what you're looking for really helps with finding whatever it is.
I do like those guys, but the only issue is the length. The stage that these'll be going over is a "wide screen" arrangement; the battens are about 60' long.

I'm currently liking my idea, since I'll be able to make it the length I need, but those stringers are pretty enticing.
On the note of the junction boxes and faceplates: Don't worry, I was planning on using steel instead of nylon (that's one of the lessons that stuck with me from that Holmes Inspection series, can't use plastic plates if you don't have it flush). Never knew they made rubber boxes until now; I bet they're a lot like helium hard drives- nothing particularly cool happens when you let go of them.
 
What comes to mind when someone mentions metal boxes, I remember the old way of doing it. Usually it would be a big box store orange extension cord and 1900 boxes and romex connectors. The problem with the conduit boxes is the knockouts, they were designed to be somewhat easily removed which meant they could accidently get bent in and contact a hot wire terminal.
For an idea of a better version take a look at this:
http://www.actlighting.com/ACPower/
Look at the POB series.
Hubbell has a less expensive thermoplastic box.
https://www.zoro.com/hubbell-wiring...utlet-box-500l-277w-430d-hbl3090f/i/G0059136/
 
What comes to mind when someone mentions metal boxes, I remember the old way of doing it. Usually it would be a big box store orange extension cord and 1900 boxes and romex connectors. The problem with the conduit boxes is the knockouts, they were designed to be somewhat easily removed which meant they could accidently get bent in and contact a hot wire terminal.
For an idea of a better version take a look at this:
http://www.actlighting.com/ACPower/
Look at the POB series.
Hubbell has a less expensive thermoplastic box.
https://www.zoro.com/hubbell-wiring...utlet-box-500l-277w-430d-hbl3090f/i/G0059136/
@JohnD Up here in Canada, one of our popular electrical box manufacturers offered a single-gang steel surface mount box designated as their HV, 'High Voltage' model. It only had two knock-outs, one on each end, they were somewhat lighter punched / more difficult to remove and the center to center distance on the two 6-32 holes was slightly different to match 347 VAC rated toggle switches. Up here on my side of our border we jump from 120 / 208 to 347 / 600 where you go to 277 / 480. We only see 277 / 480 in heavy industrial applications. In commercial / strip-mall locations we go straight from 120 / 208 to 347 / 600. It's nasty when you get a bite from it but you can sure run a pile of 4' and 8' fluorescents on a single 15 Amp 600 Volt breaker.
Toodleoo!
Ron Hebbard.
 
I think the code (US National) now states something along the lines of you cannot use devices designed for permanent install (metal boxes) as temporary power devices. There might also be a requirement to use boxes whose receptacles do not face up, but need to be side mounted. And whatever you build with needs to be SO extra hard use cable.

The Woodhead boxes are terrific value (about $75) as they are extraordinarily robust with little maintenance required. Metal boxes have screws and parts that are ALWAYS disassembling themselves.

I built a bunch of these Woodhead boxes, 2 - 20a duplex receptacles, a 6 ft cable with a male 5-15 and a 6” pigtail with a female 5-20. They are useful as they feed thru.

I also use a lot of Lex Product E-Strings, 20ft with 8 receptacles. Well worth the money.

And I would not do GFCI unless you expected to use these cables within 5ft of a wet location, GFCI’s DO NOT LIKE SCR DIMMERS.
 

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All helpful information.

If I weren't to use some sort of plastic box, should I use isolated or self-grounding receptacles? Self-grounding makes sense in the fact that it'd prevent charge from building up on the junction boxes, but that's just me.

@SteveB the cable I'm looking at is SOOW. That's acceptable since it's a higher certification than just SO, right? Or is it a hard set SO and nothing else requirement?
 
All helpful information.

If I weren't to use some sort of plastic box, should I use isolated or self-grounding receptacles? Self-grounding makes sense in the fact that it'd prevent charge from building up on the junction boxes, but that's just me.

@SteveB the cable I'm looking at is SOOW. That's acceptable since it's a higher certification than just SO, right? Or is it a hard set SO and nothing else requirement?

SOOW is the newest version of plain old SO. I think any SO variation is acceptable in entertainment applications, just not SJ unless in certain restricted uses.

Not sure what plastic box you are looking at. The construction trade blue boxes designed for in wall useage, typically can only provide strain relief to NNC (Romex) cable.

The Lex Product E-String 23ft/8 outlet stringer is $85 at Full Compass.
http://www.fullcompass.com/prod/201978-Lex-Products-Corp-E-String-Orchestra
 
Not sure what plastic box you are looking at. The construction trade blue boxes designed for in wall useage, typically can only provide strain relief to NNC (Romex) cable.

The Lex Product E-String 23ft/8 outlet stringer is $85 at FuLL Compass. Might do the shop and be cleaner

http://www.fullcompass.com/prod/201978-Lex-Products-Corp-E-String-Orchestra
I was talking about the more expensive ones from the likes of Woodhead and Hubell, rest assured I was not talking about those cheapo blue guys.

I was starting to think the premade option is better. I'm probably just going to need to get a couple shorter extensions as well in order to get the stringers relatively centered over the stage. I could also get twist-lock adapters so I don't need to run a stringer, but I don't trust people to realize the importance of dimmed vs. undimmed power feeds.
 
Probably still out of your budget, but the first thing that came to mind are these: At least it might give you an idea if you want to make your own
http://www.lexproducts.com/content/upload_products/Datasheet-TRUE1-THREADED_INSERT_-_Rev._000.pdf
I was looking at changing to these when I do my next upgrade, then make custom whips between each box for the spacing I need.
I have several of the LEX Stingers on my batons for constant power distro on each pipe. Also have some in the pit for stand lights.
 
My 2 cents worth-

First it's a Code violation to use a "wiring device" in a manner it is not Listed for, and metal junction/outlet boxes are NOT listed for use as temporary power distribution with Romex strain reliefs on flexible cords. That *should* be the end of the story but I've seen some clever folks use plastic cable glands (the kind used on the Woodhead or OA Windsor boxes), but using those glands with the knockout holes in the metal boxes doesn't meet Code, either.

Also metal boxes and face plates must be connected to ground via more than just the mechanical assembly of the box, outlets and face plate; i.e. the box must have an exothermically welded ground wire or other approved and Listed means of connection to the green wire (ground). A current-carrying conductor termination or insulation failure can potentially energize the metal box and anything it touches (like a pipe batten), so this path to ground helps insure the circuit breaker will trip should the neutral fail for any reason.

Note that Holmes on Homes is a Canadian production and the Code requirements in Canada, although very similar, are different than the model NFPA70 Codes in the USA. Also, like here in the Colonies, Canadian provinces are largely free to adopt Code as they see fit, so what is okay in Saskatchewan might not fly in Ontario.
 
I have a feeling the Northern Tools cable type is not in the "extra hard usage" category but a great find and sure feels better than some of the homemade solutions above.
 
NT does not indicate if it is an S type cable (SO, ST, etc.) but I suspect it is not. The gauge is not as important as the S classification (qualifier ahead!) It needs to be of sufficient gauge for the expected load, and some venues have house rules with regard to using 12/3, but you want a UL approved cable/plug system that is "Extra Heavy Duty", type S, SO, ST for use on stage. (No on SJ)
 
Yeah. I'm pretty sure that cable does not meet NEC requirements for stages but, as far as violations of the NEC go, this one seems not as bad as a lot I see. Still a violation, but then I walk onto a stage and see a rats nest of zip cord. I guess you have to ask yourself if one can be a "little bit pregnant" versus "very pregnant".
 

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