Do I use 12/3 Romex?

Reply

  #1  
Old 09-12-04, 09:13 AM
jichi
Visiting Guest
Posts: n/a
Do I use 12/3 Romex?

I'm trying to wire a new 20AMP dedicated circuit to the garage and another 20AMP dedicated circuit to a room right next to it. I was told I could use a 3 conductor Romex cable(12/3) and use the red and black wires for the separate circuits, each going back to the breaker box to two separate 20AMP breakers. The neutrals would all be joined near the two rooms, would this work?
 
Sponsored Links
  #2  
Old 09-12-04, 10:31 AM
HandyRon's Avatar
Member
Join Date: Dec 2001
Location: New York
Posts: 1,365
Received 0 Votes on 0 Posts
It would work if done properly. It is called a multiwire circuit. It is generally not advisable for a DIY to use a multiwire circuit due to some of the anomalies that may happen. Just install two 12-2 cables.
 
  #3  
Old 09-12-04, 11:08 AM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
There are at least a dozen special rules for a multiwire circuit, and it limits current and future options, so unless you have a special reason to want one, I strongly agree with Ron that you should probably not do it. The most compelling reasons you might want to use a multiwire circuit are: (1) very long run (at least a 100 feet) and high power needs including motors, such that voltage drop might become significant. (2) very difficult conditions to pull wire, such that pulling one 12/3 is significantly easier than pulling two 12/2. (3) wiring a detached structure without a subpanel.
 
  #4  
Old 09-14-04, 07:37 PM
Member
Join Date: Sep 2003
Posts: 344
Received 0 Votes on 0 Posts
I agree with all that is said about multi-wire. If you follow the rules (NEC article 210 is a good place to start), then you are according to code, but doesn't mean that someone (even you) can't come later and mess it up (boom).

Tag that circuit at every location as "Multiwire". Wrap a sticker/piece of tape around the wires and mark as "Multiwire". A small hangtag is also nice.

Do your best to communicate that those two hot wires have a relationship that must be respected. Tag at every opportunity, ESPECIALLY inside the breaker panel. I also ziptie the two hots together as they exit the two breakers, to reinforce the relationship.

I don't feel comfortable using multiwire for computers or high dollar electronics, they might be at an increased chance for surges/transients.

Multiwire for three-phase circuits is downright confusing.

You may find that the cost-saving isn't there, if you use only a half roll of 12-3, it would be cheaper to use a full roll of 12-2.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


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