---------- Forwarded message ----------
Date: Sat, 08 Mar 2008 08:18:22 -0500
From: Dale Farmer <dale@...>
To: EntertainmentElectricity@yahoogroups.com
Subject: Re: [EntertainmentElectricity] 120VAC over microphone cable?!?

Ken Porter wrote:
> I've lurked for a while, but I finally have something for which I
> need some more knowledgeable support. This came from a coworker in a
> separate venue, who has a roadshow loading in.
>
> Apparently the tech who came with the show wants to run 120VAC power,
> at 1.1 amps over microphone cable (i.e. 3-pin XLR, typically about 20-
> gauge wire) to run a small motor.
>
> Now my co-worker's, and my instinct is to say "no way". The tech's
> response being "they do it all over the country" and "it's how rental
> gear comes in NY".
>
> There's going to be roughly 100' of this power/control cable, but I'm
> not sure the length is even relevant. Who's bonkers here? If this is
> unacceptable, is it because of the current? the voltage? the distance?
>
> I think the tech may be confused because (I'm led to understand that)
> the equipment in question can be either A) fed 120V @1.1 amp OR B)
> fed a low-voltage control signal separate from 120V power feed. I
> think he's confusing method (B) for method (A).
>
> Can someone point me to some particular pice of NEC code that we can
> show this visiting tech, to put this issue to rest?
>
> thanks,
> - Ken
>

If his cable is rated for the voltage and current, then no problem
with the cable. I don't recall, offhand, what is the voltage rating of
the insulation of microphone cable. I don't think it is the 600 volt
that is usual for SO power cable, or the 300 volt for SJ.
You are in a stage setting, so you are required to be using
entertainment rated cable for power. I doubt that microphone cable
comes in SO or SC insulation.
Plus in the city of boston, the electrical inspectors are not known
for their allowance of variant electrical wiring. Boston inspectors
don't give a hoot how things are done in NYC.

--Dale


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