code question

[Aman121]

Hey CB.

I am currently helping to hang another area schools plot for their musical, and I came to a bit of a problem. We usually hang a few extra lights from tormentors that do not have circuits close to them. We end up running several runs of cable from a small touring rack they have up the tormentor to the lights. Since a few lights are gonna be circuited together at the dimmer rack anyway, the TD asked me why we didn't just run one line of cable for both lights and put a two-fer on the end. I have never heard of this being done, and I have no idea if its code compliant or even safe, so I thought id ask here before I light myself or the building up. My understanding is that since this is a temporary install the runs of flexible cable are allowed as long as they aren't going through doors or walls(which they are not), but I don't know if there's a rule against putting a two-fer on the end.

Thanks

 

[techieman33]

I can't comment on code. But I wouldn't hesitate to do it as long as you weren't drawing more power than the cord was rated for over the distance between the rack and the fixtures.

 

[chausman]

I'm no code expert, but I can't see where this becomes any more dangerous then a twofer in a raceway.

 

[MisterTim]

but I don't know if there's a rule against putting a two-fer on the end.

No, there isn't any rule against that. We put two-fers all over the place. Now, your cable and twofer must meet code and be sufficient for the breaker to which the lights are attached, but that's a different story (which I hope you've already checked).

 

[Aman121]

No, there isn't any rule against that. We put two-fers all over the place. Now, your cable and twofer must meet code and be sufficient for the breaker to which the lights are attached, but that's a different story (which I hope you've already checked).

Yep, 2 750s on a 2.4k dimmer and 20 amp cable, roughly a 30 foot run, should be fine there.

Ok thats great to hear that its fine to do that. It just seemed kinda weird to me for some reason and I thought it better to ask.

 

[MisterTim]

Yep, 2 750s on a 2.4k dimmer and 20 amp cable, roughly a 30 foot run, should be fine there.

Ok thats great to hear that its fine to do that. It just seemed kinda weird to me for some reason and I thought it better to ask.

Well hey, if you wanna be really code compliant, it's gotta be extra hard usage cable, not just 20-amp-rated flexible cable. (also, read section 520 for theater, not 590 for temporary, even though this usage is temporary).

 

[MNicolai]

I believe what your TD was getting at is that what you gain from running two cables ordinarily is that you can hook each instrument up to their own dimmers and have more flexibility in how you control your instruments. If you're going to tie them together onto the same dimmer in the rack anyway, there is no practical reason to run two cables if you have the two-fers to spare and your cables are of sufficient wire gauge to support the load.

I see it too frequently where someone hangs a plot, then runs out of cable because they cabled inefficiently, and then to finish circuiting they have to go back through the plot and start recabling instruments because they had previously been using two cables where they could've used one, or 50' cables where a 25' cable would've sufficed.

Running cables isn't like building a bridge. When building a bridge, you get an increased amount of safety using two bolts instead of one, or larger bolts than the minimum size required. When running cables, you get trip hazards and tangled messes running more or longer cables than are necessary.

 

[Aman121]

Im pretty sure it is the hard usage stuff, they bought it from a theater supplier for this very purpose and I would assume that they sold them the correct cable. Ill have to take a closer look at it when im in next week.

Thanks for all the help guys, I simply haven't really worked with a cabling situation like this and its all a bit new to me.

 

[derekleffew]

Im pretty sure it is the hard usage stuff, ...

Not hard usage (junior hard service), extra-hard usage, i.e., there can't be any "J" in the initials. 12/3 SOOW is the most common acceptable stage cable type. Hopefully that's what you were sold.

To me it's a no-brainer to tufer two lights if they're going into the same dimmer. But it's more of a procedural, ME question than a code issue. The NEC does not address many of the procedures that we as entertainment electricians regularly undertake (nor should it). Codes are great, until they're not. OSHA says one can't plug an RPT into an extension cord. So I guess that would mean running two cables.

Also, some designers will specify in their notes on the light plot "All units must be single-circuited." or "Do not two-fer." even when the fixtures will end up in the same channel. Saves time later if/when they change their mind and want to use the two lights independently.