New Home Wiring

Reply

  #1  
Old 10-29-01, 11:19 AM
atwoodkid
Visiting Guest
Posts: n/a
I recently purchased a new home and had the developer (this is a production home) add three 20amp dedicated circuits to my basement. The electrician tied each off into a box for me to tie into. Now I've opened one up and am a bit curious as to what to do. The wire going into the box has three wires plus the ground, a red wire, a black wire and a white wire then the electrian exits the box with a two wire deal (no black) to another box. So I want to start setting up some switches and outlets from these boxes but the three wire deal is a bit confusing. ANy thoughts, thanks.
 
Sponsored Links
  #2  
Old 10-29-01, 04:33 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
What you have is called a "3-wire circuit" or a "multiwire circuit" or a "shared-neutral circuit". It is a way to get two 120-volt circuits in one cable. The black and white form one circuit, and the red and white form the other circuit. You can see that the white wire is "shared". This is allowed because the black and red are 180 degrees out of phase (they are on opposite bus bars at the panel), and thus the neutral only carries the difference of the two circuits, not the sum. The two circuits will be on a double-pole breaker back at the panel (one circuit on one leg, and one circuit on the other).

So the 12/2 cable (or individual strands -- you didn't say if this house uses Romex or not) that carries the red and white to another box is one of the two circuits. You can add your own 12/2 cable to carry the black and white from here too.

This accounts for two of your 20-amp circuits. I'm not sure where your third is.

By the way, it's very probably that the code would have required two spare circuits (for a future basement finish) anyway, so I hope you only paid extra for the third.
 
  #3  
Old 10-31-01, 08:14 AM
atwoodkid
Visiting Guest
Posts: n/a
Thanks I think that makes sense. So if I understand correctly, then I could run a 12/2 cable from the box to say an outlet or two. I would connect black to black and then white to white. Then I could run another 12/2 from that box to other outlets and switches by connecting the red to the black and then connecting the white to to the other two whites. Correct? Does that mean I really have two 20amp circuits? still trying to figure this out before I zap myself. Thanks again.
 
  #4  
Old 10-31-01, 09:53 AM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
Yes, that is all correct. And yes, you really have two 20-amp circuits. If you find where this ends at your panel, you'll find two breakers (hopefully with one common trip bar).
 
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
 
Ask a Question
Question Title:
Description:
Your question will be posted in: