Please explain 725.

[peter]

Yeah, Right... in 25 words or less...
I was reading a security alarm trouble-shooting book the other day and it mentioned that those little transformer cubes that you plug into a wall receptacle to power a calculator or, in this case, an alarm panel produce a Category 2 class.
This reminded me that the Code, in its desire to obfuscate everything, never really differentiates between the three categories. There is a verbal rat's nest of "power limited", VA, maximum volts and such. I have a hunch that these include telephones, data cable, thermostats, stereo speakers, intercoms, maybe TV co-axial cable, security systems and fire alarms, etc.
So please tell me what goes into each category or which is which?
~Peter

 

[Nick]

Re: Please explain 725.

It is defined for you in 725.2

The key to knowing what you are dealing with is knowing what the power supply is. It can?t be a class 2 or class 3 circuit unless it is powered by a listed class 2 or class 3 power supply. If it is not, it?s probably class 1.

 

[tom baker]

Re: Please explain 725.

A very good explaination of Art 725 can be found in Mike Holts Understanding the NEC Volume 2. 725 is hard to understand but this new book makes it much simpler.

 

[peter]

Re: Please explain 725.

Well thanks for the replies so far. I guess everything is Class 1 unless otherwise stated.
I'll put it another way--
Can you give me an example of a Class 3 circuit?

The library doesn't have Mike Holt's book but it does have his Exam preparation guide which I'm using now.

I'm not asking for help on exam questions by the way. I'm just peeved at the Code for obfuscating things. Like why call Romex "non-metalic sheathed cable"? They could have said "non-metalic sheathed cable, such as 'Romex'..." for example. The term for this is "Double speak". Guess what a "Multi-dimensional Impact Director" is?

~Peter

 

[iwire]

Re: Please explain 725.

A Hammer

 

[mikeackley]

Re: Please explain 725.

Peter:

Mike Holt has a book on Low Voltage Wiring that you can download from the website here. Not only is it free, but it's in English. Covers 725 well, plus the other low voltage NEC articles. Go here, http://www.mikeholt.com/freestuff.php?id=freegeneral then scroll down until you see the Low Voltage Book and double click. On my DSL line it only took 15 seconds but if you are on a dial up modem, it could take awhile.

You asked for an example of Class 3 circuit - Some that Mike has in this book are: Nurse Call Stations, Public Address Systems, Background Music, Burglar and Secruity Systems.

Good luck.

[ March 04, 2003, 12:46 PM: Message edited by: mikeackley ]

 

[jtb]

Re: Please explain 725.

Mike, I tried that link, but it said "File not found for ./content/freestuff/freegeneral,.htm"
Was it removed? ~Jim

 

[don_resqcapt19]

Re: Please explain 725.

Peter,

Like why call Romex "non-metalic sheathed cable"? They could have said "non-metalic sheathed cable, such as 'Romex'..." for example.

Romex is a registered trademark and cannot be used in codes. The codes must use generic terms.
Don

 

[charlie]

Re: Please explain 725.

Like why call Romex "non-metallic sheathed cable"? They could have said "non-metallic sheathed cable, such as 'Romex'..."

Peter, before I address this comment, I would like to point out that most people put their thesaurus up while they are posting here.

One of the things I used to do with my classes (I don't teach any more since I am too involved in other things) is to use the correct terminology for everything and insist the students do the same. If an answer contained Romex, Red Head, Greenfield, BX, etc. it was wrong. How do you move from Maine to Florida to Montana to California to Indiana and have the ability to converse with another electrician? How would you answer an apprentice who asked you why they named the cables with type letters except for Romex which is a copyrighted name that is owned by the Rome cable company? What is NMC is that Romex also?

Learn the proper terminology, especially for grounding, and you will be able to converse better . . . anywhere.

 

[mikeackley]

Re: Please explain 725.

Humm....I see what you mean about the busted link.

Try getting to "Free Stuff" this way. Go to Mike Holt's Home Page [scroll up and you'll find a link to Home, upper left hand corner. When at "Home" go to the "Free Stuff" link that should be displayed on the left hand side of the Home Page. Once at "Free Stuff" then scroll down to the Low Voltage Book.

 

[peter]

Re: Please explain 725.

iwire,
You're right. You get 6 stars.

Mike, thanks for the examples.

Don, Sometimes clarity is important. It helps to understand what you are reading about if yu know what you are reading about. I figure that by now, "Romex" has become a general usage term like "Kleenex" or "Xerox". I didn't say replace the term "Non-metalic sheathed cable" with the word "Romex" -- I just suggest that it could be inserted, perhaps in a FPN, to make the Code a little more understandable.

Charlie, I didn't use a thesaurus. Sorry to have strained your brain. I didn't mean to replace the precise terminology "NM-B" with a localism -- just maybe hint that there could be a fine print note "An example of Class 3 wiring would be background music." [But then I like to hook up Muzak systems to 277v. heh heh.]

Now if someone could please give me an example of a Class 1 system?
And what is the telephone system?

~Peter

 

[jmc]

Re: Please explain 725.

Peter: When I worked for NFPA,I added "Romex" to the index because that's what we electricians called it. The manufacturer send us a letter and told us to take it out, it's their trade mark name, the correct terminology is Nonmetallic Sheathed Cable. We had the same problem with "Greenfield". An example of Class 3 circuit is one that comes off the laod-side of a PA system. See the voltage, current, and VA parameters in Table 11(A) and 11(B)Chapter 9 of the 2002 NEC.

 

[peter]

Re: Please explain 725.

jmc,
Thank you for at least trying to make the code understandable.

Now I am starting to wonder about the wisdom of the term "Non-Metalic". Doesn't that mean any sheathe not made of metal. For instance it could include concrete sheathed cable, wood sheathed cable, rock sheahed cable and, best of all, air sheathed cable.

Anyway, I'm still waiting for an example of Class 1.
~Peter

 

[Nick]

Re: Please explain 725.

Example of class 1:
Take a 20A 120V circuit and run it to a motor starter through a series of start stop stations.

This differs from a control circuit tapped from the motor circuit. This is not classified and must comply with part 6 of article 430.