Conductors per box -- meaning ?

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mathedman

Member
The code gives a "volume per conductor" for
junction boxes, etc.
Popular do-it-yourself books translate this
to tables of "wires per box" for various common
boxex.
I've been told that a Romex cable counts as a single "conductor" or "wire" for this purpose.
Yet the cable has 2,3 or 4 wires.
What is the correct interpretstion of what a "conductor" is?
 
B

bennie

Esteemed Member
Re: Conductors per box -- meaning ?

Your desire to learn about the electrical trade is respected. Your questions are about the fundamental basics of electrical systems.

It is recommended that your education start with a credible classroom course in electrical technology.

The items of curiousity are trivial and not relevant in the beginning.
 
tom baker

tom baker

First Chief Moderator & NEC Expert
Staff member
Location
Bremerton, Washington
Occupation
Master Electrician
Re: Conductors per box -- meaning ?

A cable is composed of conductors. Box fill is counted using conductors. A cable is a wiring method. Mike Holts excellent text "Understanding the NEC" would be a good reference for you.
 
A

a.wayne3@verizon.net

Guest
Re: Conductors per box -- meaning ?

Although your replies are respected,when did this code forum become a class system as in ancient history.Come on guys this is a legit question from some one who has basic electrical knowledge or so it seems.
I`ll answer the question. Each size conductor has a cu.in. size 2.0,2.5 cu in. etc.these are in direct relation to the capacity a box has 22 cu in etc..in nm the wires are counted as the # of conductors within it. calculating the wires in a box take their gauge cu.in size and multiply by the # of conductors, all grounds count as 1 wire, devices as 2 wires.I assume that since you stated that the box has the # of wires printed this is a nm installation,so deduct 1 wire for the grounds and 2 wires for each device and the rest is simple math just look inside to see the max. allowed
hope this helps
 
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bennie

Esteemed Member
Re: Conductors per box -- meaning ?

I will apologize if it is warranted. I responded in the manner I did, due to the unusual question. You have electrician on your profile, I assumed you were putting us on. :(
 
electricmanscott

electricmanscott

Senior Member
Location
Boston, MA
Re: Conductors per box -- meaning ?

Whay appologize for your opinion Bennie? If that's the way you feel say it. You have ceratainly earned the right to speak your mind and should do so.
 
M

mathedman

Member
Re: Conductors per box -- meaning ?

I asked the question because I had conflicting answers and the code is not clear on this point.
Example: A plastic junction box says 8/12; that
is 8,12-gauge somethings-- (wires or conductors
depending on what I read). It has four openings.
If "conductors" means individual 12 gauge wires
then I can't even branch an AWG 12 2+ ground
in this box (that would mean 9 wires). But the
"electrical guru" at a Lowes store tells me the
Romex AWG 12 2+ground cable is to be counted as
one conductor in these volume per conductor
calculations. And when do I count or not count the grounds as "conductors" ?
 
M

macmikeman

Senior Member
Location
Planet macmikeman
Re: Conductors per box -- meaning ?

If you can find an actual licensed trained electrician working in a hardware for around $6.00 an hour he is not an electrical guru, he is an electrical mystic. or misfit.
 
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bphgravity

Senior Member
Location
Florida
Re: Conductors per box -- meaning ?

Cable assemblies are considered one conductor for the purposes of conduit fill calculations, and not box fill.

In a conduit, the cable will be whole whereas in a box the cable is separated into the individual conductors.

Once you enter a box, the calculation for the individual conductors would be performed the same as any other wiring method with no consideration of the outer sheathing.

Please review 314.16(B) and Table 9 Note 9. :)
 
R

randyo

Member
Location
Maryland
Re: Conductors per box -- meaning ?

As the self apointed "BUY A BOOK" guy....
I would have to agree with the consessus here.

Wire, cable conductor.. ground, grounding and grounding conductor and EGC... all "101" stuff.


But guys!!! when I ask dumb questions I expect smart answers..... with code refs.


His question should be answered in ANY home wireing book... But maybe not the NEC...

So the REAL QUESTION FOR THE MATH MAN IS..???

Where in the NEC does if give you the rules for box fill....
Answer that guys... then he can go look it up....

I have a copy of the 2002 nec.. and I cant go to the index and look up box fill, go to 333.3.a.1.2.(b3) Ex 1.c....... to find the answer....

Its just not that easy!!!!!!! Damm that book anyway...

So as you all did to me many monthes ago when I was new to the fourm....give him enough greif and he will start to ask the right sort of questions!!! in the right way!!!!

and best of luck math man... and remember, electricity kills... It really can ruin your day...
 
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bphgravity

Senior Member
Location
Florida
Re: Conductors per box -- meaning ?

Randyo:

Did you read all the other posts? I did give the code references for box and conduit fill?

:confused: :confused: :confused:
 
H

hbendillo

Senior Member
Location
South carolina
Re: Conductors per box -- meaning ?

I do think people need to lighten up a little on this so called "answering test questions" issue. So what! I realize that we want people to learn how to use the code, but in the early stages of learning the code, it helps to have someone point the way sometimes. I do not think we should question peoples motives for asking a question. We should just be another resource. If you want to answer the question then do so. If on top of that you want to suggest some specific books or resources that may be useful that would be great. If not, just ignore the question and move on.
 
J

jro

Senior Member
Re: Conductors per box -- meaning ?

Is is hbendillo in the room ? Give that man a goldstar, super post h man, I'm with you, this forum in my opinion is to learn, I for one have learned some new things, bhgravity, bennie, don, and others give super informative answers, and no I'm not sucking up to anyone, this is how I expected this forum to be when I first logged on! :D

[ May 27, 2003, 06:29 PM: Message edited by: jro ]
 
electricmanscott

electricmanscott

Senior Member
Location
Boston, MA
Re: Conductors per box -- meaning ?

I'm not! This is not a site for do it your selfers if it was it would say Bob Vila not Mike Holt. As for test questions I prefer to see people learn on their own and if they can't,have their teachers help them. Getting the answers here might make you the teachers pet but it won't help in the field.
 
R

randyo

Member
Location
Maryland
Re: Conductors per box -- meaning ?

No need to be scared Philis!!!!

Just ask good / real / educated questions and all will be forgiven!!!!
Or if you are an answer-er just give it in code!!!!

We all can make a difference, make a stand, say our peice....

Now... why is it called 12-2 if it has three cables in it???? and can 24 awg carry twice move volts than 12 gage????
 
B

bphgravity

Senior Member
Location
Florida
Re: Conductors per box -- meaning ?

Originally posted by randyo:
Now... why is it called 12-2 if it has three cables in it???? and can 24 awg carry twice move volts than 12 gage????
Click to expand...
Its usually called 12/2 w/gr. The 2 represents the ungrounded and grounded conductors present. 12/3 w/gr is 2 ungrounded, 1 grounded, and one equipment grounding (bonding) conductor.

You are backwards on your wire size and current carrying capabilities. Also, current is the issue and not voltage.

A conductors insulation will determine how much voltage it can tolerate. The current carrying capability is based on circular mil size of the conductive material itself and not necessarily the standardized size.

As you count from #1 wire up, the ampacities go smaller. Above #1 or 1/0 you count up for the bigger size. It is a little confusing at first.

See Table 310.16 of the NEC for standardized wire size and respective ampacities. I believe that every time you reduce the conductor size by half, you actuall cut the current carrying capability 4 times. Or something like that. It is not directly proportional.
 
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