New rules for Type SJ in 2020 NEC

[Jammer]

The powercon...If it had just an ever so slight modification I probably wouldn't have even posted. The SO 12/3 I have is from Royal/Southwire and is 15.11mm OD so .11mm over the design limit for powercon. I tried one and it does begrudgingly fit, so maybe that's the way to go. Frustrating thing is runs for everything else, e.g. mains amps, lighting trusses, trees etc are all easily done with 12/3 SO from protected breaker, FOH runs use 12/3 SJ in cable ramps, it is just this last part of providing service for the stage that seems the toughest to figure out.

 

[STEVETERRY]

We use these: https://www.temporarypowerbydesign.com/portfolio-view/standard-doghouse/

They make a single phase variety. Ours have L5-20 in and thru and 3x duplex outlets. TMB, Lex, Motion Labs, and the rest of the power distro houses all have something similar. I know the boxes you have, they are quality units. Only downside to them is the jr cable thing. It really is unfortunate that the connector of choice we've landed up for this kind of distribution won't take SO cable. I'm still blown away Neutrik hasn't done anything about that yet.

I believe Amphenol makes a plug-compatible version of the PowerCon with a larger cable entry. The "black chuck clamp" is what you want.

https://www.amphenolaudio.com/wp-content/uploads/2018/11/HP-Series-Standard-Data-181107.pdf

https://www.amphenol-industrial.de/en/Power-Connectors

ST

 

[Jammer]

Steve,
Those seem to be the same spec as the Neutrik, at least on the black chuck, 15mm limit, unless I overlooked a different product. Spent some more time working it and looks like I can/will get the 12/3 SO to work. That said, thank you and everyone else for the input/comments. It's one thing to surf around the net for answers, input etc....completely different to have access to someone who is involved in writing the code and people who work in the industry daily. Not lost on me for a second. This stage, theater, live event stuff is tougher than shifting from ships power to shore power on a Navy Destroyer, no variables or maybe's on that one : )

 

[FMEng]

Unless I'm missing something, just use 14 AWG cable. Backline isn't likely to be using 20 amps. I don't see any requirement that the ampacity of the cable has to match that of the circuit feeding it. I can properly use an 18 AWG extension cord in a home or business without any special over-current protection for it. Is this any different, other the requirement for extra damage resistance of the cable?

 

[STEVETERRY]

Unless I'm missing something, just use 14 AWG cable. Backline isn't likely to be using 20 amps. I don't see any requirement that the ampacity of the cable has to match that of the circuit feeding it. I can properly use an 18 AWG extension cord in a home or business without any special over-current protection for it. Is this any different, other the requirement for extra damage resistance of the cable?

That is true for Listed extension cords, where the maximum size of the branch circuit overcurrent protective device is described in the Listing and product marking. However, for a field-assembled extension cord (which would also include extension cords assembled out of Listed connectors and cable by a manufacturer--but not Listed as a complete assembly), the requirements are a bit different, and contained in NEC sections 520.68(C) and 240.5:


520.68(C) Overcurrent Protection.
Overcurrent protection of conductors for portables shall comply with 240.5.

240.5(B) Branch-Circuit Overcurrent Device.
Flexible cord shall be protected, where supplied by a branch circuit, in accordance with one of the methods described in 240.5(B)(1), (B)(3), or (B)(4). Fixture wire shall be protected, where supplied by a branch circuit, in accordance with 240.5(B)(2).

240.5(B)(1) Supply Cord of Listed Appliance or Luminaire.
Where flexible cord or tinsel cord is approved for and used with a specific listed appliance or luminaire, it shall be considered to be protected when applied within the appliance or luminaire listing requirements. For the purposes of this section, a luminaire may be either portable or permanent.
240.5(B)(2) Fixture Wire.
Fixture wire shall be permitted to be tapped to the branch-circuit conductor of a branch circuit in accordance with the following:
(1) 15- or 20-ampere circuits — 18 AWG, up to 15 m (50 ft) of run length
(2)15- or 20-ampere circuits — 16 AWG, up to 30 m (100 ft) of run length
(3)20-ampere circuits — 14 AWG and larger
(4)30-ampere circuits — 14 AWG and larger
(5)40-ampere circuits — 12 AWG and larger
(6)50-ampere circuits — 12 AWG and larger

240.5(B)(3) Extension Cord Sets.
Flexible cord used in listed extension cord sets shall be considered to be protected when applied within the extension cord listing requirements.

240.5(B)(4) Field Assembled Extension Cord Sets.
Flexible cord used in extension cords made with separately listed and installed components shall be permitted to be supplied by a branch circuit in accordance with the following:
20-ampere circuits — 16 AWG and larger


ST

 

[brucek]

The 2020 NEC is now published. One of the most important changes of interest to the entertainment industry is new 520.68(A)(2) covering allowable cable types for portable equipment in theatres and similar locations:

520.68 Conductors for Portables.

520.68(A)(2) Protected Applications.

Listed, hard usage (junior hard service) cord or cable shall be permitted where all of the following conditions are met:

(1) The cord or cable is protected from physical damage by attachment over its entire length to a pipe, tower, truss, scaffold, or other substantial support structure, or installed in a location that inherently prevents physical damage to the cord.
(2) The cord or cable is connected to a branch circuit protected by an overcurrent protective device rated at not over 20 amperes.
(3)The cord or cable does not exceed 30 m (100 ft) in length.


ST

Do you know the reasoning behind the 100' limit? Am I allowed to chain cords to get longer than 100'?
Bruce

 

[ship]

In unsupported cable between fly pipe or truss sections for temporary install... What is the maximum un-supported distance in doing SJ between points supported from?

 

[STEVETERRY]

Do you know the reasoning behind the 100' limit? Am I allowed to chain cords to get longer than 100'?
Bruce

100' seemed like a plausible limit to stand a chance of getting approval for the change. The NEC is currently silent on your daisy-chain question--but my personal opinion would be No.

ST

 

[STEVETERRY]

In unsupported cable between fly pipe or truss sections for temporary install... What is the maximum un-supported distance in doing SJ between points supported from?

The intent of what constitutes a "protected application" is pretty clear:

520.68(A)(2) Protected Applications.

Listed, hard usage (junior hard service) cord or cable shall be permitted where all of the following conditions are met:
(1) The cord or cable is protected from physical damage by attachment over its entire length to a pipe, tower, truss, scaffold, or other substantial support structure, or installed in a location that inherently prevents physical damage to the cord.
(2)The cord or cable is connected to a branch circuit protected by an overcurrent protective device rated at not over 20 amperes.
(3)The cord or cable does not exceed 30 m (100 ft) in length.

Therefore, the answer to your question is that SJ cannot be used in the application you describe.

ST

 

[ship]

Thanks, but does bring up the question of in avoved... say a 5' jumper between pipes in a fly system... is the copper strionger between such a 5' connection in difference between SJ and SO cable? Certainly the rubber isn't stronger in possible tension.
But as long as it's on a 20 amp breaker... the SO cableis only ok? Because it's in the air.. so a scrim might hit it?
And by the way, I very much appreciate your time, help and guidance. Just asking questions.

 

[TimMc]

Thanks, but does bring up the question of in avoved... say a 5' jumper between pipes in a fly system... is the copper strionger between such a 5' connection in difference between SJ and SO cable? Certainly the rubber isn't stronger in possible tension.
But as long as it's on a 20 amp breaker... the SO cableis only ok? Because it's in the air.. so a scrim might hit it?
And by the way, I very much appreciate your time, help and guidance. Just asking questions.

Is the wire installed in a location that inherently prevents physical damage? Other battens, cables or wires, hard scenic elements? Impact, tension, abrasion?

This is but one micro-example where there is currently no other object or process that could act upon the wire, but adding or moving anything to the flys means there is no *inherency* to whatever protection might currently exist.

 

[STEVETERRY]

Thanks, but does bring up the question of in avoved... say a 5' jumper between pipes in a fly system... is the copper strionger between such a 5' connection in difference between SJ and SO cable? Certainly the rubber isn't stronger in possible tension.
But as long as it's on a 20 amp breaker... the SO cableis only ok? Because it's in the air.. so a scrim might hit it?
And by the way, I very much appreciate your time, help and guidance. Just asking questions.

The difference between hard usage and extra-hard usage cable is simply in the jacket thickness and the conductor insulation thickness. In aggregate, these increased thicknesses provide additional resistance to cuts, abrasion, and flexing damage that might expose the conductor.

Now, you might ask "How much better is extra-hard usage?" That is very hard to quantify, since the UL62 standard for Flexible Cords and Cables does not contain performance standards, only construction standards specifying the thicknesses. A few years ago, I asked UL whether a specific custom 12-conductor flat cable would meet the extra-hard usage performance requirements. They replied that they would be happy to test some extra hard usage cables to failure in order to determine performance, and then see if the flat cable could meet that number of test cycles. If I recall correctly, that was a $50,000 science experiment.

BTW, the end result was this change in the NEC:

520.40 Stage Lighting Hoists.
Where a stage lighting hoist is listed as a complete assembly and contains an integral cable-handling system and cable to connect a moving wiring device to a fixed junction box for connection to permanent wiring, the extra-hard usage requirement of 520.44(C)(1) shall not apply.


ST

 

[RonHebbard]

The difference between hard usage and extra-hard usage able is simply in the jacket thickness and the conductor insulation thickness. In aggregate, these increased thicknesses provide additional resistance to cuts, abrasion, and flexing damage that might expose the conductor.

Now, you might ask "How much better is extra-hard usage?" That is very hard to quantify, since the UL62 standard for Flexible Cords and Cables does not contain performance standards, only construction standards specifying the thicknesses. A few years ago, I asked UL whether a specific custom 12-conductor flat cable would meet the extra-hard usage performance requirements. They replied that they would be happy to test some extra hard usage cables to failure in order to determine performance, and then see if the flat cable could meet that number of test cycles. If I recall correctly, that was a $50,000 science experiment.

BTW, the end result was this change in the NEC:

520.40 Stage Lighting Hoists.
Where a stage lighting hoist is listed as a complete assembly and contains an integral cable-handling system and cable to connect a moving wiring device to a fixed junction box for connection to permanent wiring, the extra-hard usage requirement of 520.44(C)(1) shall not apply.


ST

In the mid 1990's during my automation shop daze, we used yellow jacketed 19 conductor 12 gauge copper festoon cable housed in drag-chain to power dimmer circuits in 6 automated tracks within a touring deck. Within the same drag-chain, we also housed 12 gauge twisted copper 4 or 6 conductor for 3 tiny AC servo motors powering rotators within three of the six tracks along with additional cables for resolvers, hard failsafe limits and spring-activated brakes. Once we received TUV's approval for Offenbach, Germany, the Brit's had no problems approving this for London.
Working in theatre, we were able to find black jacketed festoon cable for applications above deck level.
Toodleoo!
Ron Hebbard
Ron Hebbard

 

[Jay Ashworth]

Reminder: we are connected to a common power grid. Now, explain to me like I'm five years old, why do we need two different electrical codes?

Oooh! Ooooh!! I know; I know!!!

"Because, being promulgated by NFPA, the NEC is mostly about 'not starting fires'." Has little to do with electricity except that it's an energy source.

Why it would be different to Canada I can't address, but it's about insurance and money, not electricity.

 

[sk8rsdad]

Well, one reason we have different codes, even from province to province, is related to geography. Grounding, trenching, insulation, and such tend to vary depending on terrain, climate, proximity to seawater, etc. Codes tend to get tweaked to suit the things the local inspectors care about. Now let's debate the proper orientation of a NEMA 5-15R.

 

[Jay Ashworth]

Ground pin up.

 

[RonHebbard]

Ground pin up.

What if it's mounted horizontal?
Toodleoo!
Ron Hebbard

 

[Jay Ashworth]

Still ground pin up.

 

[danTt]

Well, one reason we have different codes, even from province to province, is related to geography. Grounding, trenching, insulation, and such tend to vary depending on terrain, climate, proximity to seawater, etc. Codes tend to get tweaked to suit the things the local inspectors care about. Now let's debate the proper orientation of a NEMA 5-15R.

Why aren't you installing a 5-20R instead?

 

[Jay Ashworth]

Why aren't you installing a 5-20R instead?

Well, that's a fair question about this fictional installation, Dan.