Options for Multi-Outlet AC Power Cords

Stevens R. Miller

Well-Known Member
In another thread, we've been discussing safety issues (which is a very good idea, imho!), and that's made me curious about one related to the original topic. I've got a few LED lights that, when set to full power, draw about 460mA. Let's call that half an amp. Lots of modern gear has "feed through" or "daisy chain" connections, like this fine product:

proxy.php


But the lights I have don't provide for that. Instead, their AC cords are integrated into the housing, with no socket for anything else to plug into:

proxy.php


This is doubly annoying, since they do have two DMX jacks for daisy chaining, so it's not like the designers didn't know how to do it.

So I am wondering about safe options for providing power. Obviously, if I am hanging (say) a dozen lights, I would rather not run a dozen power cords. At half an amp each, one cord could take the six amps necessary to power them all. But what's a safe way to do it?

One option is the Caldwell Bennett MOXB12-50. That looks good, but I have never seen such a thing before and would like to know what people with more experience think of it.

Alternatively, as a ham radio operator for the last 40+ years, I am always willing to make things myself, if that's a reasonable choice. An option there might be based on something like thie OA Windsor 3-TD box. But I don't know if that's any better and, even if it is, I doubt that a fire marshall would be very approving of a stage festooned with a lot of my home-brew power cords.

What I certainly do not want to do is see power strips dangling from the pipes over the stage, plugged into each other or at the ends of a lot of extension cords, as a few of my well-intentioned colleagues might be prone to using if confronted with lights that don't have pass-through connectors.

As these lights draw such low current, I'm thinking that running several of them on a single line is safe, but I'd be grateful for any advice on what kind of line that should be.
 
@Stevens R. Miller , the product you originally linked doesn't say anything about whether or not it is extra-hard usage cable or SO or anything. To my eye, they look like SJ cables which would be a no go. The cord that @SteveB linked is marketed as Extra Hard Usage Cable and that would be perfect for use on a stage.

If you are going to home-brew your own cables, make sure you're using SO jacketed cables and label them as being for LED use only so they don't get re purposed for regular par cans somewhere down the road.
 
As TheaterEd mentioned, the use of 'extra-hard usage cable' is not just a good idea, it is generally the Law. Portable cordage used near stage lighting is required to be this class in the NEC (NFPA 70 National Electric Code), Articles 5.20 and 5.30. If you are doing stage lighting, you should have a copy of the NEC with you and understand it. Lightweight 'big box store' extension cords, zip cord, and other melt-able cables should not be used around hot theatre lights (the NEC does not yet acknowledge the low heat emissions of LED type fixtures). If the cable jacket melts it can connect the chassis of the lights to the 'hot'/'line' conductor inside the jacket and energize the whole rig. Other good reasons for using the 'extra hard usage' cables are that scraping melted orange, yellow, blue, or green plastic off of the light fixtures is generally not fun or productive use of time. The high durability of the 'extra hard usage' cables also means that they are less prone to having the jackets split or cut-open and exposing the inner conductors.
 
As TheaterEd mentioned, the use of 'extra-hard usage cable' is not just a good idea, it is generally the Law. Portable cordage used near stage lighting is required to be this class in the NEC (NFPA 70 National Electric Code), Articles 5.20 and 5.30. If you are doing stage lighting, you should have a copy of the NEC with you and understand it. Lightweight 'big box store' extension cords, zip cord, and other melt-able cables should not be used around hot theatre lights (the NEC does not yet acknowledge the low heat emissions of LED type fixtures). If the cable jacket melts it can connect the chassis of the lights to the 'hot'/'line' conductor inside the jacket and energize the whole rig. Other good reasons for using the 'extra hard usage' cables are that scraping melted orange, yellow, blue, or green plastic off of the light fixtures is generally not fun or productive use of time. The high durability of the 'extra hard usage' cables also means that they are less prone to having the jackets split or cut-open and exposing the inner conductors.

It's important to keep all of this in mind, and important to follow the rules. That being said, it says a lot to me that the standards for the cables actually attached to the fixtures have a lower standard of cabling than the extensions attached to them (See seachangers, for example--I feel like melting the power cord of a seachanger to it's attached fixture is almost a right of passage when working with them). The cord attached to the LED being discussed is clearly not SO either. As with everything, it's more important to understand why the NEC specifies various requirements, and to take those requirements and restrictions into consideration, than it is to follow the code to the letter of the law.
 
In general, the NEC applicable codes for entertainment use allows SJ cable in certain applications, such as two-fers, adapters, breakouts, and as attached to scenic elements where they are not exposed to getting run over, etc... inside overhead trusses as example. SO for all other uses.

One reason that fixture cable is not SJ or SO typically is the need to terminate the cable inside the fixture, where the heat rating of SJ and SO means it cannot be used. Thus specially rated wiring and covering for fixture wire.

Exceptions exist. Mole Richardson film and TV fixtures often have long cables attached that is SJ, but there’s usually an external connection box provided on the fixture to splice the heat rated fixture wire to the longer SJ.

LED and ML’s using Power-Con connections don’t have the SO or SJ cables terminate inside the fixture.

I believe as well that the NEC is re-visiting the whole issue of fixture wire, jumpers, and use of SJ in general.
 
In the SO vs SJ debate, where does STW come into play. That is what the Lex E-strings use.
 
The NEC only requires that Extra Hard Usage type S cable be used. S, SO, SOOW STW and ST all qualify, all are type S cables. The same goes for SJ type cable SJO, SJOOW SJT and SJTW are all accepted types of Hard Usage Cable. Most LEDs will come with a SJT cord and almost anything with an IEC plug will come with an SJT cord as well.

Now using a thermoplastic ST or STW cable next to hot lights is not a good idea but it is not against code, likely because leaving them in a position to touch the lights could mean they were "exposed to physical damage" and be in violation from that direction.

The Lex E-Strings are marketed towards use in orchestra pits and convention centers so STW is a fine choice for that use. If you are using them on an all LED pipe or truss then there should be no issues with heat damage to the cable. Using an E-String on a mixed pipe would require care be taken to insure that the cable is not subject to excessive heat.
 
In general, the NEC applicable codes for entertainment use allows SJ cable in certain applications, such as two-fers, adapters, breakouts, and as attached to scenic elements where they are not exposed to getting run over, etc... inside overhead trusses as example. SO for all other uses.

One reason that fixture cable is not SJ or SO typically is the need to terminate the cable inside the fixture, where the heat rating of SJ and SO means it cannot be used. Thus specially rated wiring and covering for fixture wire.

Exceptions exist. Mole Richardson film and TV fixtures often have long cables attached that is SJ, but there’s usually an external connection box provided on the fixture to splice the heat rated fixture wire to the longer SJ.

LED and ML’s using Power-Con connections don’t have the SO or SJ cables terminate inside the fixture.

I believe as well that the NEC is re-visiting the whole issue of fixture wire, jumpers, and use of SJ in general.


Please see 2017 NEC 520.68 Luminaire Supply Cords:

(3) Luminaire Supply Cords. Listed hard usage supply cords
shall be permitted to supply luminaires when all of the following
conditions are met:

(1) The supply cord is not longer than 2.0 m (6.6 ft).
(2) The supply cord is attached at one end to the luminaire
or a luminaire-specific listed connector that mates with a
panel-mounted inlet on the body of the luminaire.
(3) The supply cord is protected by an overcurrent protective
device of not more than 20 amperes.
(4) The luminaire is listed.
(5) The supply cord is not subject to physical damage.

ST
 
Last edited:
The cord attached to the LED being discussed is clearly not SO either.

Maybe, maybe not. Look closely and although it may be skinny, it may still be 90 degree C rated. More importantly, the requirement for the cord on the fixture is different than the requirement for the extension cord, which is what we are talking about. Also, there are a few (rolling eyes) fixtures out there that have bogus (fraudulent) UL / ETL / CE listings, or none at all, so the manufacturer is just ignoring the thermal requirement and the possibility that you might use an LED fixture in close proximity to a conventional (HOT) incandescent fixture. This is an important teaching opportunity for everyone out there - talk abut the fire / electrical hazards of mixed use of LEDs and incandescents when the power cords might come in contact with hot lights. The same concern exists for DMX / Network / speaker / microphone cabling that is used around hot lights. Dress your cables up so they don't touch the hot light parts (regardless of the temperature rating of the cable)!
 
Maybe, maybe not. Look closely and although it may be skinny, it may still be 90 degree C rated. More importantly, the requirement for the cord on the fixture is different than the requirement for the extension cord, which is what we are talking about. Also, there are a few (rolling eyes) fixtures out there that have bogus (fraudulent) UL / ETL / CE listings, or none at all, so the manufacturer is just ignoring the thermal requirement and the possibility that you might use an LED fixture in close proximity to a conventional (HOT) incandescent fixture. This is an important teaching opportunity for everyone out there - talk abut the fire / electrical hazards of mixed use of LEDs and incandescents when the power cords might come in contact with hot lights. The same concern exists for DMX / Network / speaker / microphone cabling that is used around hot lights. Dress your cables up so they don't touch the hot light parts (regardless of the temperature rating of the cable)!


Hi Erich--

We need to differentiate between cable temperature ratings and Hard Usage vs. Extra Hard Usage. There is little difference between a hard usage or an extra-hard usage cable, both with 90 degree C temperature rating, coming into contact with a very hot tungsten luminaire. The difference between S and SJ is all about resistance to physical abuse.

"Dress your cables up" out of the hot zone applies with both type of cable.

Cheers

ST
 
Hi Erich--

We need to differentiate between cable temperature ratings and Hard Usage vs. Extra Hard Usage. There is little difference between a hard usage or an extra-hard usage cable, both with 90 degree C temperature rating, coming into contact with a very hot tungsten luminaire. The difference between S and SJ is all about resistance to physical abuse.

"Dress your cables up" out of the hot zone applies with both type of cable.

Cheers

ST

There is an additional difference - maximum voltage - and it's related to the physical construction of the cable: conductor insulation material, conductor insulation thickness, filler material, and outer jacket thickness. My understanding (which could be wrong) is that the "J" in the designation stands for "Junior" as in junior extra hard service which became "hard service". My copies of the NEC only go back 12 years and I cant' spot when the change was made (TL;DR).

Oh, the max voltage rating? 600v for S, SO, etc and 300v for anything with a "J" in the designation.
 
The stringer cords are great, thats what I'd go with. I might also just daisy chain short SO cables with triple taps but don't tell anyone I do that. ;-)
 

Users who are viewing this thread

Back