12/3 SO in a plenum

[jhochb]

Good Morning All
I have an associate working with a small theatre, 100 seats or so.
He is having the theatre install two new circuits, one front of house. The FOH circuit will feed a 4x1K shoe box dimmer. He needs to get power to the SHOEBOX for an upcoming show.
This show will run for three weeks.
The service is above a drop ceiling which is part of the A/C return system ( a plenum).
The question is Can he run 10’ of SO cable to feed the dimmer?
Thanks in advance
and HAPPY NEW YEAR TO ALL

 

[MNicolai]

We can have a long discussion about electrical codes and fire marshals, but the summary of what I have to say is: I wouldn't sweat it.

It's temporary and it's one cable. I know a lot of the administrative team at our local fire department really well, and if I had them come inspect and approve the use of a single cable for a few weeks, everyone could agree that it's a waste of their time and that everyone involved has more important matters to tend to.

Now there were fifteen cables hanging out of our ceiling and were going to be used regularly, we'd have something to talk about.

For that matter -- if this is something he'll see himself using regularly, he might as well pay an electrician to install a receptacle flush-mount in the ceiling panels. It'd take maybe all of an hour and half's worth of work, not very much in materials, and most of the time would be spent getting a couple ladders set up.

 

[JD]

The use of SO in a plenum space is more of a fire code issue as compared to an electrical code issue. I suspect your local fire marshal will say no. The concern is what gasses it will give off if it is burning as these will be recirculated in the building through the system. Plastic cable can be the worst as far as toxins go. Rubber cable (like SO) generally just stinks a lot!

Probably worth giving them a phone call. He might say yes. The 30 day rule is aimed at electrical issues, so this is a little something different. Make sure you indicate the time span, it may help your case.

Get a good guy in a good mood and he may just blow it off as a temp, too much of a bother to make the trip out.

 

[Wood4321]

I agree with John,
I wouldn't try it without asking permission from the fire marshal.

 

[jhochb]

Good Morning all
I hope your head hertz less than mine.

Thanks for your input, all of your answers came up in our disccusions here. I think 1 cable should be fine too.
We sugested they ask the electrician to mount the new circuit below the drop cieling if its not too late.

 

[derekleffew]

...The service is above a drop ceiling which is part of the A/C return system ( a plenum).
The question is Can he run 10’ of SO cable to feed the dimmer? ...

I think this is on-point; from Code Quandaries: Stumped by the Code? November 2011 :

Q. Does the Code allow the installation of cord-connected equipment above a suspended ceiling?

A. Unless specifically permitted in 400.7, flexible cords must not be concealed by walls, floors, or ceilings, or located above suspended or dropped ceilings [400.8(5)]. Flexible cords are permitted under a raised floor (with removable panels) used for environmental air, because this area isn’t considered a concealed space. See the definition of “Exposed” in Art. 100.

Receptacles are permitted above a suspended ceiling, but a flexible cord isn’t. Why install a receptacle above a ceiling if the flexible cord isn’t permitted in this space? Because the receptacle can be used for portable tools; it just can’t be used for cord- and plug-connected equipment fastened in place, such as a projector.

 

[museav]

If the circuit and service are being added just for this purpose then can't you get the Electrical Contractor/Electrician installing it to terminate it where you need it?

 

[MNicolai]

If the circuit and service are being added just for this purpose then can't you get the Electrical Contractor/Electrician installing it to terminate it where you need it?

My interpretation was that they already existed for this purpose. Provided there's nothing else trying to eat up the power on the circuit, it'd be easy to branch off from that circuit and land a second receptacle flush-mount with the ceiling, similar to how most ceiling-mounted projectors get their power.

Suppose it begs the question, has this guy done the math to ensure adding a dimmer pack to this circuit isn't going to cause it to trip with any other loads that may be on that circuit already?

 

[museav]

My interpretation was that they already existed for this purpose. Provided there's nothing else trying to eat up the power on the circuit, it'd be easy to branch off from that circuit and land a second receptacle flush-mount with the ceiling, similar to how most ceiling-mounted projectors get their power.

Suppose it begs the question, has this guy done the math to ensure adding a dimmer pack to this circuit isn't going to cause it to trip with any other loads that may be on that circuit already?

I interpreted "He is having the theatre install two new circuits, one front of house." to indicate that the related circuit and termination were being added just for this purpose. If so, it would seem to make sense to have it installed to terminate where and how you need it to terminate.

I admit to not being clear on who is doing what, but I hope that the party doing any installation is properly qualified and has performed any related design or calculations.

 

[MNicolai]

I interpreted "He is having the theatre install two new circuits, one front of house." to indicate that the related circuit and termination were being added just for this purpose. If so, it would seem to make sense to have it installed to terminate where and how you need it to terminate.

I admit to not being clear on who is doing what, but I hope that the party doing any installation is properly qualified and has performed any related design or calculations.

Rereading it now, I agree with your interpretation. Originally, I read it as the circuit was originally installed for the A/C return system, but that was the load center.

By the time an electrician (presuming that a licensed electrician is doing the install) is on-site and high up on a ladder or scaffolding, the cost of having them install the receptacles somewhere more convenient than above the ceiling isn't much greater.

I framed my original post around the idea the receptacles already existed, but since they do not, I'd advise strongly against going any route that has extension cables in the ceiling. It might be worth asking AHJ for permission the circuit already existed, but since the circuit is being installed anew, I would consider it disingenuous to ask for an exemption.

For this show, it's temporary -- until the next show when someone says "That was a good idea to put lights there -- Let's do it again!"

As a general rule, it's naive to assume that anything being installed permanently for temporary usage will only be used once in a blue moon. As theatres grow, designers get more creative, and clients' expectations go up, facilities see further and further deviation from what they were originally intended to be used for. As a result, things that were temporary solutions and worked well frequently turn into permanent ones until an even better solution comes along.

We see the electricians, architects, and consultants from our theatre regularly; even just three years after opening, we hear a lot of "Well, that's not how we intended the theatre to be used" when we talk to them about how we've adapted to use the space and what have been obstacles for us. It's the nature of the business.

 

[STEVETERRY]

Good Morning All
I have an associate working with a small theatre, 100 seats or so.
He is having the theatre install two new circuits, one front of house. The FOH circuit will feed a 4x1K shoe box dimmer. He needs to get power to the SHOEBOX for an upcoming show.
This show will run for three weeks.
The service is above a drop ceiling which is part of the A/C return system ( a plenum).
The question is Can he run 10’ of SO cable to feed the dimmer?
Thanks in advance
and HAPPY NEW YEAR TO ALL

This is why you can't do it, per the 2011 NEC:

400.8 Uses Not Permitted.

Unless specifically permitted in 400.7, flexible cords and cables shall not be used for the following:

(1) As a substitute for the fixed wiring of a structure

(2) Where run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings, or floors

(3) Where run through doorways, windows, or similar openings

(4) Where attached to building surfaces

Exception to (4): Flexible cord and cable shall be permitted to be attached to building surfaces in accordance with the provisions of 368.56(B)

(5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings

(6) Where installed in raceways, except as otherwise permitted in this Code

(7) Where subject to physical damage

ST

 

[ScottT]

Does 400.8 apply to all cables or just those for power?

 

[STEVETERRY]

Does 400.8 apply to all cables or just those for power?

Article 400 covers Flexible Cords and cables for power applications.

ST

 

[jhochb]

Good Morning all

Thank you all for chiming in on this subject. The NEC info was what I was hoping for.
I know it was in there somewhere but I don't have access to the code book

All your opinions are also helpful and I thank you for your input.

 

[MNicolai]

Good Morning all

Thank you all for chiming in on this subject. The NEC info was what I was hoping for.
I know it was in there somewhere but I don't have access to the code book

All your opinions are also helpful and I thank you for your input.

Visit the NFPA website. I believe you have to register for an account, but anyone can view the electrical and life safety codes for free. You only have to pay money if you want a physical book to hold in your hand.

 

[museav]

We see the electricians, architects, and consultants from our theatre regularly; even just three years after opening, we hear a lot of "Well, that's not how we intended the theatre to be used" when we talk to them about how we've adapted to use the space and what have been obstacles for us. It's the nature of the business.

Three years? I've had projects that the use changed dramatically before the venue even opened.

I remember one project where the TD could not wait for us to sign off on the installation so he could start revising and rewiring things as soon as we had reviewed them. He had not been on staff when the systems were defined and seemed to have goals that differed significantly from what the school representatives had previously identified they desired. I really wish he had waited until the actual use and needs had been better established before changing things since his immediately altering the systems negated any related system warranties. However, many of the changes I noted actually seemed intended greatly to justify his position, e.g. eliminating elements intended to simplify operation for some school uses to create systems that required his involvement for even the simplest events and allowed him to control who could operate the venue.

 

[MNicolai]

Three years? I've had projects that the use changed dramatically before the venue even opened.

I remember one project where the TD could not wait for us to sign off on the installation so he could start revising and rewiring things as soon as we had reviewed them. He had not been on staff when the systems were defined and seemed to have goals that differed significantly from what the school representatives had previously identified they desired. I really wish he had waited until the actual use and needs had been better established before changing things since his immediately altering the systems negated any related system warranties. However, many of the changes I noted actually seemed intended greatly to justify his position, e.g. eliminating elements intended to simplify operation for some school uses to create systems that required his involvement for even the simplest events and allowed him to control who could operate the venue.

We tore apart and re-rigged our catwalk after the first 9 months, among other big projects we did.

We've also done some reworking of systems intended to simplify the theatre operations -- mainly because the affect those systems had only complicated operations. We haven't removed any systems entirely, but there are certain things we avoid using if at all possible despite how "simple" they were supposed to be to use. As the experienced stagehand, I know I'm not the intended audience for some of these things (they were installed for ease-of-use for teachers, faculty, etc.), but if I'm not satisfied with them, I'm not comfortable teaching other people how to use them -- and therefore don't. I'll find them a better solution.

It's a lot less about having job security, and a lot more about ensuring a certain standard of quality for the events the venue produces.

 

[museav]

It's a lot less about having job security, and a lot more about ensuring a certain standard of quality for the events the venue produces.

And that is true for most venues, but for the situation I was referencing it was a bit different. It was a somewhat unusual situation as it was a venue that was initially for just the school and was publicly funded, but then via private funding was expanded in size and scope to also serve the larger community. So it was essentially defined to be a school theatre that could also be used for local and regional touring performances. The TD, who was hired not long before the venue opened, made it very clear to us that their focus was on the touring house aspect and to minimize, if not eliminate, the school use to the point that they were avoiding training any students. To give some perspective, the venue opened 7 years ago and the venue Director, Event and Box Office Coordinator, etc. all still have school e-mail accounts while the TD has a gmail account.

As an example of the issues we encountered, we had a few wireless mics in a booth rack that were split to the console and to an automixer with a "lecture/performance" mode switch that switched the matrix DSP between the automixer output and the console outputs, the concept being that they could handle a simple lecture, panel discussion, emcee or similar without needing to use the main board or a trained operator. For productions requiring a large number of wireless mics it was envisioned that they would rent the microphones, or purchase them if they were used often, and have a portable wireless rack the stage, we located a large number of inputs stage left and right on the upstage side of the proscenium wall for that purpose.

Before we had even left the building the TD had pulled all of the wireless microphone receivers out of the rack, abandoned the installed remote antennas and moved all the receivers to a portable rack. As a result, no event using a wireless mic could be handled without having to pull out the wireless rack, connect it to the stage inputs and use the main mixer. The TD knew that even the simplest of events requiring their presence was exactly what the school had wanted to avoid, but they, who worked for a management company hired by the private investors, clearly wanted to discourage school use.

 

[mstaylor]

And that is true for most venues, but for the situation I was referencing it was a bit different. It was a somewhat unusual situation as it was a venue that was initially for just the school and was publicly funded, but then via private funding was expanded in size and scope to also serve the larger community. So it was essentially defined to be a school theatre that could also be used for local and regional touring performances. The TD, who was hired not long before the venue opened, made it very clear to us that their focus was on the touring house aspect and to minimize, if not eliminate, the school use to the point that they were avoiding training any students. To give some perspective, the venue opened 7 years ago and the venue Director, Event and Box Office Coordinator, etc. all still have school e-mail accounts while the TD has a gmail account.

As an example of the issues we encountered, we had a few wireless mics in a booth rack that were split to the console and to an automixer with a "lecture/performance" mode switch that switched the matrix DSP between the automixer output and the console outputs, the concept being that they could handle a simple lecture, panel discussion, emcee or similar without needing to use the main board or a trained operator. For productions requiring a large number of wireless mics it was envisioned that they would rent the microphones, or purchase them if they were used often, and have a portable wireless rack the stage, we located a large number of inputs stage left and right on the upstage side of the proscenium wall for that purpose.

Before we had even left the building the TD had pulled all of the wireless microphone receivers out of the rack, abandoned the installed remote antennas and moved all the receivers to a portable rack. As a result, no event using a wireless mic could be handled without having to pull out the wireless rack, connect it to the stage inputs and use the main mixer. The TD knew that even the simplest of events requiring their presence was exactly what the school had wanted to avoid, but they, who worked for a management company hired by the private investors, clearly wanted to discourage school use.

That is an absolute shame to have a nice facility and not train the kids to use the equipment at some level.

 

[zmb]

Before we had even left the building the TD had pulled all of the wireless microphone receivers out of the rack, abandoned the installed remote antennas and moved all the receivers to a portable rack. As a result, no event using a wireless mic could be handled without having to pull out the wireless rack, connect it to the stage inputs and use the main mixer. The TD knew that even the simplest of events requiring their presence was exactly what the school had wanted to avoid, but they, who worked for a management company hired by the private investors, clearly wanted to discourage school use.

That sounds like crony something trying to make it so that the crew can get paid for as many hours as possible.