Wiring confusion

Reply

  #1  
Old 02-13-17, 07:44 AM
Member
Thread Starter
Join Date: Feb 2017
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
Wiring confusion

I am working on wiring in a house that built around 1910 but appears to have been rewired in the 1970's. There are two 15a breakers in the panel that have me confused. One has the black wire attached and the other has the red wire attached both of which come out in a box on the other side of them room with the white wire. I assumed that this was done so that there would be two separate power sources to the box. What I find is that both are hot when either one of the breakers is in the ON position.
 
Sponsored Links
  #2  
Old 02-13-17, 07:53 AM
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,182
Received 25 Votes on 20 Posts
Sounds like it was wired to be a multiwire branch circuit, but the breakers are on the same leg in the panel and the red and black are interconnected somewhere along the way. If that's the case then you need to get it corrected. The breakers need to be on opposite legs with a handle tie and the black and red are not to be interconnected because that will create a dead short. The black and red tested across each other should read 240V and each to the neutral should be 120V.
 
  #3  
Old 02-13-17, 09:25 AM
Member
Thread Starter
Join Date: Feb 2017
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
Sounds like this is beyond my elementary electrical skills as I only understood parts of the response. In doing some further research on the terms used in the reply, I am now certain that I need to get a professional to help with this part of the job. Thanks
 
  #4  
Old 02-13-17, 11:22 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 53,522
Received 406 Votes on 382 Posts
Welcome to the forums.

You have a multiwire branch circuit. Two circuits sharing a neutral.
The two breakers in the panel need to be one above the other.
They should have a common tie handle so that they both get turned off at the same time.

If you are using a non contact tester..... then you WILL see power if either breaker is on.
That is perfectly normal. You would need to use an analog meter or probe type voltmeter to see that only the breaker on is live.

Name:  MWBCD.jpg
Views: 238
Size:  18.2 KB
 
  #5  
Old 02-13-17, 12:15 PM
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,182
Received 25 Votes on 20 Posts
Good point on the non contact tester. That is the short coming of using that type of tester.
 
  #6  
Old 02-13-17, 02:27 PM
Member
Thread Starter
Join Date: Feb 2017
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
Thanks. That was a very helpful further explanation. I was using a non contact tester which is what gave me the confusing reading. The diagram helps as well. I may be able to work with this after all.
 
  #7  
Old 02-13-17, 03:27 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
I was using a non contact tester which is what gave me the confusing reading.
Give it to your kid to play with. You should be using a multimeter, preferably analog because ocasional a digital can give an erroneous reading due to induced voltage. An $8-$15 analog multimeter will do a good job.
 
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: