Control/Dimming Shared Neutral

Dover said:

Both building wire and portable cord are actually described the same way.

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Perhaps but cable assemblies like Romex (NM in the code) and BX (AC in the code) seem to always include a bare ground and portable assemblies like SO seem to never include a bare ground. That the applications are nearly mutual exclusive makes it moot.

Dover said:

Both building wire and portable cord are actually described the same way. The leading numbers refer to the gauge and number of full voltage insulated conductors in the assembly, the suffix "w/ ground" denotes the inclusion of an un-insulated non-voltage rated grounding wire of adequate size for the maximum current of the insulated wires. The description "12/3 SOOW" only states that there are 3 12ga voltage rated wires in the cable, it does not guarantee that one of the wires is green, the reverse is also true for Romex, 12/3 Romex could be describing a cable with black, white and green.
There are exceptions in the code that would allow for a cable with out a ground or for the green wire to be used as a current carrying wire but these generally only apply to industrial machinery and none are not applicable here.

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I’ve never seen a green insulated cable in NM. Ground is always bare, conductors can be black, red, blue, white or white with red stripe, also known as (12) - 2- 2.

Haven't seen green in "Romex" either. Just bare or paper wrapped. BX (or whatever the newfangled name is these days) has the green for ground, unless it is REAL old! Some of that had a bare in it. (early 1960's or before)

Romex is now just NM (as it always was), BX is AC, though I don't know if that was also the original name.

Jay Ashworth said:

Romex is now just NM (as it always was), BX is AC, though I don't know if that was also the original name.

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BX and Romex are actually trade names for Armored Cable and Non-Metalic cable. I actually never knew that about BX.

http://www.ncwhomeinspections.com/BX+Cables+on+exterior+installations

https://en.m.wikipedia.org/wiki/Thermoplastic-sheathed_cable

I knew Romex was a brandname (which didn't stop my tech high school electicity instructor from calling it that), but I didn't realize BX was a trademark either.

Dover said:

Both building wire and portable cord are actually described the same way. The leading numbers refer to the gauge and number of full voltage insulated conductors in the assembly, the suffix "w/ ground" denotes the inclusion of an un-insulated non-voltage rated grounding wire of adequate size for the maximum current of the insulated wires. The description "12/3 SOOW" only states that there are 3 12ga voltage rated wires in the cable, it does not guarantee that one of the wires is green, the reverse is also true for Romex, 12/3 Romex could be describing a cable with black, white and green.
There are exceptions in the code that would allow for a cable with out a ground or for the green wire to be used as a current carrying wire but these generally only apply to industrial machinery and none are not applicable here.

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This is not the case, as a quick trip to any home supply store will prove. In portable cord, the grounding wire (green) is counted - e.g. 12/3 SOOW has 3 12-ga conductors - black, white, and green. The analogous NM cord is 12-2, where the grounding conductor is not counted - 12-2 NM has three conductors - black, white, and bare. 12-3 NM has four conductors - black, red, white, and bare.

Aaron S. said:

Good morning everyone. Let me ask an opinion and advice.

I'm working a show set in an apartment on a turn table. We have practicals throughout the house. Wall sconces, recessed lighting, and wall outlets.

I have soca running to the turntable that powers some lepi packs.

My main issue right now is this: The wall outlets want to be 2 cir each. Top and Bottom. The shop that built the set only ran 1 - 12/3 cable through the walls. Some of the outlets want both of the cir to go to the lepi packs, while others want 1 cir to a lepi pack and the 2nd to a Non dim.

Can I/is there a better solution - Have 2 hots running through the 12/3 and share the neutral? If so, what would that look like at the lepi pack side? Would I just "2-fer" the neutral between the 2 connectors going into the dimmer pack?

I know this will leave me with ungrounded circuits. I'm just not seeing another option at this point.

Thanks for your help.

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I highly doubt you will get an inspector to sign off on using two circuits on a 3-conductor SOOW assembly, even if in some circumstances the grounding conductor isn't needed. There is material risk of someone coming after you and making presumptions that the assembly is wired to code, and finding out that it isn't in a painful or damaging way.

On a related note, you cannot terminate a multi-wire branch circuit assembly to single-pole male receptacles. It would probably be OK if a 12-4 SOOW cord (not what you currently have) was hard-wired to a dimmer and it would definitely be OK if you used a single male plug such as a NEMA L14-20 to power the entire assembly, but it isn't going to be OK to feed your assembly with a pair of standard Edison male plugs. There are two reasons:

1 - the interior conductors of SO-type cord are not rated to be exposed to the environment - they lack the mechanical protection of the outer jacket. As such, you can't just peel off one conductor to go to a different plug.
2 - if one of the male plugs is energized and the other is disconnected, a multi-wire system may have the potential to make the disconnected male plug hot due to power flowing through your load. This can happen if the neutral wire is compromised or if there is a fault across the two hot legs.

You need to either rewire your set to be code compliant or you need to simplify your lighting needs to function with what you have. Sorry.

TJCornish said:

This is not the case, as a quick trip to any home supply store will prove. In portable cord, the grounding wire (green) is counted - e.g. 12/3 SOOW has 3 12-ga conductors - black, white, and green. The analogous NM cord is 12-2, where the grounding conductor is not counted - 12-2 NM has three conductors - black, white, and bare. 12-3 NM has four conductors - black, red, white, and bare.

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TJ, I think you and Dover said the same thing:

Count the insulated connectors, whether they're grounding or not.

No?

Jay Ashworth said:

TJ, I think you and Dover said the same thing:

Count the insulated connectors, whether they're grounding or not.

No?

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After reading it for the third time you may be right, however in any practical sense applicable in ControlBooth land, green better be ground, therefore the analog of 12/3 SO cord is 12/2 NM (not that I can think of many circumstances where it's OK to use NM cable in theater or production).

Sure. But we were having the academic conversation about how different types of cable are designated, at that point in time...

TJCornish said:

however in any practical sense applicable in ControlBooth land, green better be ground,

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True if control booth land were limited to just AC or to just North America but its not.

Not sure what the power is for but you might look into ETCs dimmer doubling products if desparate to use the 3 conductors.

We should know that AS has been absent from this thread with any commentary since the first post. 12/22 or so.