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#91784 02/04/05 01:13 PM
Joined: Aug 2004
Posts: 54
G
Member
could someone please enlighten me on article 720. more specifically 720.4. doesn't make sense to me. is it an ohm's law issue? could you give an example of an installation?
I did a search for old posts on this without result. thanks in advance for your responses.

2017 / 2014 NEC & Related Books and Study Guides
#91785 02/04/05 01:22 PM
Joined: Feb 2004
Posts: 494
M
Member
Hi,
Where are you supplying 50 volts or less?

Are you talking controls or signals?

regards

Greg

#91786 02/04/05 01:42 PM
Joined: Aug 2003
Posts: 1,374
R
Moderator
Article 720 is basically for the old farms that used (6) six volt batteries.


Ryan Jackson,
Salt Lake City
#91787 02/04/05 02:15 PM
Joined: Jul 2004
Posts: 9,644
G
Member
What is old becomes new again. With all of these alternate energy schemes I expect we may start seeing low voltage high amp circuits in homes.
I have dabbled with 12 volt stuff myself in an attempt to mitigate hurricane blackouts. The RV industry makes 12v consumer technology available and junk cars makes generation cheap. Shock injury is pretty remote with 12v but you are still dealing with currents that make fire a real concern.


Greg Fretwell
#91788 02/04/05 04:00 PM
Joined: Aug 2004
Posts: 54
G
Member
thanks for the replies.
I ran across article 720 while looking for something else. I'm not actually applying this code "out in the field" at this time. just nosing through the book and was wondering "why 12 awg or greater" for less than 50 volts. (ohm's law?) I would imagine that we'd be talking about control curcuits. I've used #12 to jump from the 24 v PLC to the function, but never knew that it was actually a requirement. just did it 'cause #12 was handy.(especially when you look at the rating of a S-valve or whatever, and it's only about 1 amp...

#91789 02/04/05 04:45 PM
Joined: Feb 2004
Posts: 494
M
Member
Hi,
Article 720 applies to ac or dc and is one of the smallest articles in the book!

I do a lot of work on wind turbines that sometimes use pm generators that produce AC but then is rectified to DC. SOmetimes the amps can get on up there.

I prefer 240 vac three phase output for pm generators myself.

A lot of folks do not know about this article.

I am guessing that there is a restriction for this so you dont start seeing a lot of MTW 18, 22 etc in control panels...which I already have seen!

Regards

Greg


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