dumb question


  #1  
Old 09-21-04, 04:46 PM
G
Member
Thread Starter
Join Date: Apr 2004
Location: Los Angeles
Posts: 42
Upvotes: 0
Received 0 Upvotes on 0 Posts
dumb question

I know the only dumb question is the one you don't ask...

What do the numbers 12/3 12/2 mean? I had assumed the first is the wire gauge, and the second is the number of conductors? But then I looked at the romex I've got in my garage and it says 12/2 on the box, but there are three wires, black, white and ground.

Anyone care to enlighten me?

Thanks.
 
  #2  
Old 09-21-04, 04:53 PM
FireSong
Visiting Guest
Posts: n/a
They are not counting the ground wire (the bare copper one) as the conductor. Most boxes of romex I've seen say either 12/2 or 12/3 and they usually have 'with ground' printed on them.
 
  #3  
Old 09-21-04, 05:20 PM
G
Member
Thread Starter
Join Date: Apr 2004
Location: Los Angeles
Posts: 42
Upvotes: 0
Received 0 Upvotes on 0 Posts
So 12/3 would be for two phases? But don't you want a separate neutral for each phase?
 
  #4  
Old 09-21-04, 05:46 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Upvotes: 0
Received 1 Upvote on 1 Post
There are many different possible applications for the three conductors (not counting ground). Although a shared neutral circuit is possible with 12/3, it is far from the only application of it. If you really want to talk about a shared neutral circuit (officially called a multiwire circuit), we can, but it is a big subject and a lot would need to be written. You can surely find it all simply by searching this forum for "multiwire". It's all been written many times before.

I should note that 12/3 means three conductors plus ground when talking about NM cable. But when referring to other kinds of cable, it can mean two conductors plus ground. Bottom line is that of course, like everything, the devil is in the details and there are very few generalizations you can make without the need to cite exceptions.
 
  #5  
Old 09-22-04, 05:34 AM
R
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,246
Upvotes: 0
Received 0 Upvotes on 0 Posts
As John said, 12/3 could be used for a multiwire circuit, but multiwire circuits are not that common in residences.

More common use of 12/3 in a residence would be for:

Wiring three way and four way switches.
Wiring a ceiling fan where the light and fan are controlled by separate wall switches.
Wiring a switched receptacle where it is also necessary to have unswitched power also available.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: