Multi-Wire branch circuit related question

Reply

  #1  
Old 12-05-14, 04:07 PM
Member
Thread Starter
Join Date: Oct 2014
Location: USA
Posts: 21
Upvotes: 0
Received 0 Votes on 0 Posts
Multi-Wire branch circuit related question

My son bought a house in Orlando, FL that was built in 1987. Wow! Have I learned a lot about multi-brach wire circuits. This forum has helped me correct some anomalies associated with them.

I understand that the NEC specifies that you must use pigtails for outlets as you cannot rely on a device to provide continuity for a neutral. Today I went through every single outlet on any relevant circuits and added pigtails in cases where both outlet screws were used to continue the neutral.

One final mystery showed up in one of the outlet boxes: there were three cables feeding in, two 14-2's and one 14-3. All three black wires were wired nutted together and a pig tail went to the outlet. OK. Two of the white wires went to each screw on the outlet. Way in the back of the box was another wire nut that connected the third white wire to the red wire of the 14-3.

I can't wrap my mind around any circumstance where a red would be connected to a white. I'm showing my lack of knowledge here, but I just want to do things right. And for now, I just wirenutted the two whites together with a pigtail to the outlet. I left the red/white alone, but am suspecting they should be joined with the other whites. Correct? Thank you!
 
Sponsored Links
  #2  
Old 12-05-14, 05:15 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,597
Upvotes: 0
Received 13 Votes on 11 Posts
What's on the other end of the 3-conductor cable?
 
  #3  
Old 12-05-14, 06:10 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 51,892
Received 256 Votes on 241 Posts
That is not a multiwire branch circuit setup. That would appear to be a switch loop setup.

My spin.....
The power leaves on the black of a two wire cable and comes back on the white wire that is connected to the red.

You would have to use a voltmeter to check the wiring for power. Locating the other end of the three wire cable would be a plus but may not be easy.
 
  #4  
Old 12-05-14, 06:31 PM
Member
Thread Starter
Join Date: Oct 2014
Location: USA
Posts: 21
Upvotes: 0
Received 0 Votes on 0 Posts
To respond, I am uncertain what is on the other end. I have become VERY familar with the workings of many of the circuits at this house (been in the attic A LOT), but this threw me entirely. There is a switch that controls a lower half of an outlet on a different wall (via a red wire) but that should have no bearing on this, I wouldn't think. I am eager to find where it goes. Switch loop? Could be.

For the record, the circuit is surely part of a multi-branch and most importantly I'd like to know if I should add the red/white to the other two whites for safety's sake.
 
  #5  
Old 12-05-14, 06:40 PM
Geochurchi's Avatar
Member
Join Date: Nov 2012
Location: USA
Posts: 3,956
Received 15 Votes on 15 Posts
If you can pull the red and white out and remove the wire nut and open the splice I will bet that other 1/2 out goes dead,don't make any change to that splice or you will create a short.
How did you determined it is a Multi wire branch?
Geo
 
  #6  
Old 12-05-14, 06:49 PM
Handyone's Avatar
Member
Join Date: Aug 2000
Location: U.S.
Posts: 5,451
Upvotes: 0
Received 0 Votes on 0 Posts
I left the red/white alone, but am suspecting they should be joined with the other whites. Correct?
No. The red/white should not be joined with other whites.
As PJ said, this sounds like a switch loop, but one of the toughest I've ever seen or heard of.

I am very interested in how this will come out.
 
  #7  
Old 12-05-14, 06:54 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 51,892
Received 256 Votes on 241 Posts
A multiwire branch circuit is two circuits on two breakers fed with a three wire cable. In that scenario... white would NEVER be connected to a color.

There is a switch that controls a lower half of an outlet on a different wall (via a red wire) but that should have no bearing on this, I wouldn't think.
That is probably what you need to investigate.

When you see a white wire connected to a normally hot/current carrying conductor...... you should immediately think of switch loop.
 
  #8  
Old 12-05-14, 07:05 PM
Handyone's Avatar
Member
Join Date: Aug 2000
Location: U.S.
Posts: 5,451
Upvotes: 0
Received 0 Votes on 0 Posts
Look at Geo and PJ posts.
In your familiarity with the house wiring, you may have overlooked something.
There is a saying, "white down and black up". Meaning if a white wire carries power, it should go towards a switch (feed it), not to the switched device. For example, if you were to wire a simple ceiling fixture (switched), you would expect black to go to light black, not white.
 
  #9  
Old 12-05-14, 07:40 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,597
Upvotes: 0
Received 13 Votes on 11 Posts
With red and white separated you could, using a multimeter, check voltage white to ground and red to ground.
 
  #10  
Old 12-06-14, 08:59 AM
Member
Thread Starter
Join Date: Oct 2014
Location: USA
Posts: 21
Upvotes: 0
Received 0 Votes on 0 Posts
In response to how I know it's a multi-branch circuit, this goes back to when I first looked at the panel. Some circuit breakers had a red wire coming off them. Never saw that before. Thus began my education.

With all power off. I followed each red wire to their entry cable point, found the black from that cable, and then back again to another breaker see which two breakers were involved in that multi-branch circuit. Nothing was indicated on panel description and no handle ties, so I documented everything so someone else would know to shut off BOTH circuit breakers while servicing (e.g. 22 & 24). Found four like that. I know, handle ties are best. It's in the process.

Next trip will go in attic and see if I can find that 14-3 and where it goes. I thank all for their insight. I don't like mysteries and like to understand things. When it comes to electrical, if you weren't the creator of the wiring, it can be a puzzle to unravel the facts (as all of you well understand). Will update when I learn more.
 
  #11  
Old 12-06-14, 09:47 AM
Geochurchi's Avatar
Member
Join Date: Nov 2012
Location: USA
Posts: 3,956
Received 15 Votes on 15 Posts
Have you determined where the red wire spliced to white went?
Just curious.
Geo
 
  #12  
Old 12-06-14, 09:59 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 51,892
Received 256 Votes on 241 Posts
Yes.... you probably have multiwire branch circuits in your house. Most houses have them. However, seeing a red wire in a box doesn't automatically mean it's a part of a MW branch circuit.
 
  #13  
Old 12-06-14, 11:04 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,869
Received 15 Votes on 12 Posts
The neutral only needs to splice where the circuit splits. When you only have one circuit in the box you do not need to splice the neutral.
 
  #14  
Old 12-06-14, 11:46 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,597
Upvotes: 0
Received 13 Votes on 11 Posts
You would not have a white connected to a red in a multiwire circuit. You would have a red connected to a white in a switch loop circuit.
 
  #15  
Old 12-06-14, 03:03 PM
Handyone's Avatar
Member
Join Date: Aug 2000
Location: U.S.
Posts: 5,451
Upvotes: 0
Received 0 Votes on 0 Posts
Next trip will go in attic and see if I can find that 14-3 and where it goes
Two of the white wires went to each screw on the outlet. Way in the back of the box was another wire nut that connected the third white wire to the red wire of the 14-3.
You said you left the red and white that are connected alone for now.....
What cable contains this white that's connected to red? The 14/3? Or one of the 14/2's?
 
  #16  
Old 12-06-14, 03:22 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,869
Received 15 Votes on 12 Posts
Do not go making changes to something that works just because it does not look correct to you. There are often good reasons.
 
  #17  
Old 12-06-14, 03:30 PM
Handyone's Avatar
Member
Join Date: Aug 2000
Location: U.S.
Posts: 5,451
Upvotes: 0
Received 0 Votes on 0 Posts
Thank you pcboss,
I was about to ask that.
Are there any switches that don't work?
Are any outlets not working?
Are there in particular, any three way switches that are not working as expected?

An on-site electrician would be able to explain the reasoning behind this wiring rather quickly.
It's hard to picture thus far.

If it ain't broke, don't fix it.
 
  #18  
Old 12-09-14, 05:04 PM
Member
Thread Starter
Join Date: Oct 2014
Location: USA
Posts: 21
Upvotes: 0
Received 0 Votes on 0 Posts
First, sorry for the delay to those who responded and were interested in what I found. I was not able to return to that home until today.

As usual, you folks were zeroing in on the answer right away (with the switch loop idea). Let me first mention that previously I found three bedrooms and a living area with wall switches that did absolutely nothing. In each case I found an outlet that had one black and one red traveler wire, BUT, the metal piece joining the duplex outlet was still intact. Once I removed that piece the switch controlled the lower half of the outlet as expected. And in three of those cases, a red wire came off the switch.

In the case in question, it was only room that I did not have cause to observe the switch. I just ASSUMED it had the red traveler wire as well. That turned out to be a wrong assumption. The switch had both one black and one white wire.

This tells me that the white goes over to the far outlet on one wall where it was joined the red (and thus created the original question). Then that 14-3 cable goes over to another wall where the red is attached to the lower portion of the outlet and is thus controlled by the switch.

I am uncertain why it was necessary to do this in this manner in the original design of the house, but obviously there must be a reason. The bottom line is that the suggestion of switch loop was spot on and this mystery no longer troubles me. Thank you to all who commented. I very much appreciate the help.
 
  #19  
Old 12-09-14, 05:38 PM
Handyone's Avatar
Member
Join Date: Aug 2000
Location: U.S.
Posts: 5,451
Upvotes: 0
Received 0 Votes on 0 Posts
You have yourself to thank for being able to work through this and understand the wiring.
It helps to remember that a neutral within a circuit will never be broken. So if you see a white wire attached to a switch, you know it is not a neutral. If you see a white wire attached to a black or red wire, you will also know it is not a neutral.
 
  #20  
Old 12-10-14, 06:04 AM
Geochurchi's Avatar
Member
Join Date: Nov 2012
Location: USA
Posts: 3,956
Received 15 Votes on 15 Posts
Code now requires the white wire of a switch leg be identified.
Geo
 
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: