Speaker Wiring

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JOHNNIEB

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We Have A Light Pole And It Has A Speaker In The Bottom. Our Inspector Will Not Allow Us To Have The Speaker Wire And 277volts In The Pole Together. What Can We Do To Resolve This And Where In The Code Book Can I Find The Answer.
 

charlie b

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The answer lies in 300.3(C)(1). You can do it if, and only if, the insulation system of the speaker wire is rated for at least 277 volts. I don't happen to know if that is the case.
 

HighWirey

Senior Member
charlie b said:
The answer lies in 300.3(C)(1). You can do it if, and only if, the insulation system of the speaker wire is rated for at least 277 volts. I don't happen to know if that is the case.

A lot of speaker wire, especially from a quality vendor, is 300 volt rated. Just review the specs before you purchase the wire.

Best Wishes
 
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don_resqcapt19

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Charlie,
The answer lies in 300.3(C)(1). You can do it if, and only if, the insulation system of the speaker wire is rated for at least 277 volts. I don't happen to know if that is the case.

I don't agree...the speaker wiring is covered by Article 725 and you would have to comply with 725.55. There is a FPN after the section that you have cited that directs you to see 725.55(A).
Don
 

charlie b

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OK, thanks Don. I now infer that it would be OK if you put a barrier between the speaker wire and the 277 volt lighting conductors. How you would accomplish that, if the two run togther within the pole, eludes me. But if it is just at the bottom of the pole that the two run close together, then perhaps a barrier would do the trick.

My basic problem with this, however, is that I have never found a definition, or even a simple explanation, of what is meant by "Class 1, Class 2, and Class 3." 725.2 defines "Class 2 circuit" in the context of wires powered via a Class 2 power source. 725.41(A) tells me that if I wish to design a Class 2 power source, one option is to use a Class 2 transformer. This is even less useful than a "circular definition"; it tells me nothing about what "Class 2" means.

I did not pay attention to the FPN under 300.3(C)(1), for the simple reason that I had no way of knowing that speaker wire was either Class 1, or Class 2, or Class 3, or neither. I infer from your comment that it must be Class 2 or 3, but I couldn't prove it, if I were called upon to do so. Can you show me how I can tell whether speaker wire falls into 725 at all? :-?
 

don_resqcapt19

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Charlie,
There are Class 1 sound systems. As far as applying Article 725, it is my opinion that it is the only Article that fits sound systems and many sound system amplifiers have markings on the back as to the Class.
You can look to Chapter 9, Table 11 for more information on Class 2 and 3 power supplies.
I think that this installation would fall under 725.55(J), and that should be easy to comply with.
Don
 

ryan_618

Senior Member
Charlie, next time you watch Forresst Gump, look closely at the part when he is speaking at the Lincoln Memorial. When he is going to the stage, it shows some of the equipment, and it looked to me like it was probably Class 1.

Class 1 sound systems are pretty rare when compared to Class 2 and Class 3, but if the sound system is very large (such as for outdoor speaking events) it is not uncommon to see Class 1.
 

nakulak

Senior Member
seems like you could use a suitable barrier by using fmc in the pole down to a box, likewise, you can simply use the properly insulated cable as stated and change your system to a class 1 by simply crossing out the label on the transformer and re-labelling it as "Class 1" (300.3 C 1) ( I don't see where in 450 it says you can relabel a transformer, but it doesn't say that you can't. However, on one of my mike holt dvds for masters exam prep he says you can do this exact thing)
 
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iwire

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nakulak said:
use the properly insulated cable as stated and change your system to a class 1 by simply crossing out the label on the transformer and re-labelling it as "Class 1"

If you where to go that route all other speaker wiring connected to that same system would have to be treated as class 1, and then of course there would be the issue of the original class 2 or 3 open terminals now being required to be enclosed.
 

cowboyjwc

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Simi Valley, CA
I would agree with Bob. 725.55(A) tells us we can't do it, but at least 300.3(C)(1) allows you an option that's better than a seperate conduit or barrier.
 

tom baker

First Chief Moderator
Staff member
Seperation in a lighting pole is pretty easy, you can run NM LT or smurf tube inside the luminare pole
300.3(C)(1) is the most misunderstood and misquoted section in the NEC.
My other comment is we need to get away from using the term Low Voltage.
Look at the titles of these three low voltage articles:
411
720
725
 
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