Outlet wiring, need quick help loose neutrals.

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  #41  
Old 11-20-13, 06:33 PM
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If there was only two white/neutrals connected to the outlet, does that mean that outlet would be the only one "sharing" a neutral?
No. Devices don't "share" neutral any more than they "share" hot. You either have a MWBC, which has two hots sharing one neutral, or you don't.

From your description of the conditions in the first box you worked in, and the TV and computer, you probably do have a MWBC there.

To find out how many MWBCs you have, and what they're supplying, the only sure method is to open the panel and trace all of the wires in it. A MWBC will have two hots and one neutral leaving/entering the panel in the same cable or conduit, with the two hots terminated to two 120V single-pole breakers - not to a 20-pole 240V breaker.

You can turn off the main before doing this, but you'll need a source of work light if you do. And, if the main breaker is in the same panel as the branch circuit breakers, the feeders to it will still be hot.

All MWBCs that you find should be supplied/protected by two vertically adjacent breakers of identical size. The handles of those two breakers should be tied together so that each can trip independently but turning either one off will also turn the other off. "Independent trip, common open" is the typical shorthand for that.
 
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  #42  
Old 11-20-13, 06:37 PM
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There is also a white in the conduit from the panel with the both ungrounded conductors. It is connected to the other neutral that the red wire feeds.
That's a MWBC. The single grounded conductor is serving both of the ungrounded conductors.

The red wire does not feed a neutral.
 
  #43  
Old 11-21-13, 05:11 AM
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Thanks for the clarification.

Nashkat or anyone else following along:

From my description, can you say there are actually two splices of the grounded (white)conductor then to this MWBC?

One in the box I worked in that has the pigtailed outlet. And another presumebly in the ceiling box. Since there are only 2 neutrals in the outlet box I worked in, I am assuming there would be 3 in the ceiling (1 back to panel, 1 for L1 and one for L2)

Again Thank you all for your patience with me.
 
  #44  
Old 11-21-13, 09:06 AM
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From my description, can you say there are actually two splices of the grounded (white)conductor then to this MWBC?

One in the box I worked in that has the pigtailed outlet. And another presumebly in the ceiling box. Since there are only 2 neutrals in the outlet box I worked in, I am assuming there would be 3 in the ceiling (1 back to panel, 1 for L1 and one for L2)
There is only one grounded conductor (aka "neutral") for this MWBC. In the receptacle outlet you found two white wires that appear to function as a feed-in and a feed-out for that conductor. In the ceiling outlet, there may be any number of white wires. If that is where the home run ends, then there should be at least the three you suggest.
 
  #45  
Old 11-21-13, 09:25 AM
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THanks for the explanation.

So once the neutral branches out to each circuit (I will say L1 and L2), for example an outlet on L1 with neutral and hot feeding thru to next outlet, I can treat it like any other neutral (ie: I dont have to pigtail it per code?)??

In other words, breaking the neutral at the outlet in that case, wouldnt put the unbalanced 240 load over the two circuits.

The splice at the box I worked on though, to confirm, if its broken then I would have the unbalanced 240 load over both circuits? If that is the case, I prey the Ideal wirenut (yellow with 3 #14's ) doesnt fail....
 
  #46  
Old 11-21-13, 10:35 AM
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So once the neutral branches out to each circuit (I will say L1 and L2), for example an outlet on L1 with neutral and hot feeding thru to next outlet, I can treat it like any other neutral (ie: I dont have to pigtail it per code?)??
Best practice is to always splice the wiring through and pigtail to the device. Why build the highway through the center of town rather than constructing a bypass with a local road to access it?

In other words, breaking the neutral at the outlet in that case, wouldnt put the unbalanced 240 load over the two circuits.
An open neutral will always create voltage in excess of line voltage. In a MWBC on a 120/240V single-phase service, losing the common neutral will produce voltages greater than 240.

The splice at the box I worked on though, to confirm, if its broken then I would have the unbalanced 240 load over both circuits?
I must not be understanding your question. If what I said above doesn't answer it, maybe another member can help.
 
  #47  
Old 11-21-13, 11:59 AM
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Best practice is to always splice the wiring through and pigtail to the device. Why build the highway through the center of town rather than constructing a bypass with a local road to access it?
Agreed as long as there sufficient room in the box to pigtail. I should have said, if the neutral was broken at that point the circuit just wouldnt work, not send the unbalanced 240 thru it.

In a MWBC on a 120/240V single-phase service, losing the common neutral will produce voltages greater than 240.
Greater than 240?? Please explain.
 
  #48  
Old 11-21-13, 05:50 PM
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If this is where the two circuits split, I believe the NEC requires the neutral conductors to be pigtailed.
Does each outlet on a MWBC, even downstream where the circuits split, need to be pigtailed?

(ps I know what perfered practice is as Nashkat states, but I am curious if feeding thru the outlets using all 4 screws is allowed at all anywhere on the MWBC? ... reason I ask is every other outlet on this circuit is wired like this on the circuit in question. )
 
  #49  
Old 11-21-13, 05:57 PM
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Does each outlet on a MWBC, even downstream where the circuits split, need to be pigtailed?

(ps I know what perfered practice is as Nashkat states, but I am curious if feeding thru the outlets using all 4 screws is allowed at all anywhere on the MWBC?)
Downstream of the split, feeding through the device is perfectly acceptable by code although it is better to pigtail the wires at each and every device. In residential work you don't see that much pigtailing because it becomes labor intensive in a house with 50 or 60 receptacles. That being said, there is nothing wrong with feeding through the devices, it's entirely your preference.
 
  #50  
Old 11-21-13, 08:58 PM
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Greater than 240?? Please explain.
See Open Service Neutral Causes Dangerous Touch Voltage on Metal Parts and Danger of Open Service Neutral. Add up the voltage for 10 ohms of ground resistance in the second reference.

Originally Posted by CasualJoe
In residential work you don't see that much pigtailing because it becomes labor intensive in a house with 50 or 60 receptacles. That being said, there is nothing wrong with feeding through the devices, it's entirely your preference.
It becomes labor intensive in a commercial work with, say, 800 devices in the building. I know, I've done those - by myself.

I pigtail because I've had to troubleshoot and repair circuits that failed at the feed-throughs.
 
  #51  
Old 11-22-13, 04:46 AM
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Downstream of the split is each leg of the MWBC (L1 and L2) and upstream of the split is the return to the panel.

So interupting the neutral in the middle of one of the legs of the MWBC would just stop the circuit to a portion of those outlets.

Where breaking the neutral interupting the other sides or boths return to the panel would send 240 down the other side of the MWBC.

If the neutral to one side was removed at the point they split, as long as the other leg still has a return to the panel then that would be OK (of course the side where it was removed would no longer be a complete circuit).

I think I understand it better now, I was concerned I had to rewire each outlet on one side of my MWBC that uses the screws to feed each outlet....
 
  #52  
Old 11-22-13, 11:42 AM
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Downstream of the split, feeding through the device is perfectly acceptable by code although it is better to pigtail the wires at each and every device. In residential work you don't see that much pigtailing because it becomes labor intensive in a house with 50 or 60 receptacles. That being said, there is nothing wrong with feeding through the devices, it's entirely your preference.
THis makes sense but it is also where I am getting confusion. Everything I read about code requirement to pigtail the neutrals in MWBC simply says "all outlets on a MWBC".

So is it acceptable as stated here or no exceptions in regards to the NEC... "All outlets on a MWBC" is what is throwing me....

Please someone confirm with me either way, per code, so I can rest easy and not worry that my appliances are going to fry if I feed thru outlets like this..... If one of my fed thru outlets on the MWBC fails, am I going to get zapped?
 
  #53  
Old 11-23-13, 06:19 PM
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THis makes sense but it is also where I am getting confusion. Everything I read about code requirement to pigtail the neutrals in MWBC simply says "all outlets on a MWBC".
Where in the NEC did you read that?


Please someone confirm with me either way, per code, so I can rest easy and not worry that my appliances are going to fry if I feed thru outlets like this..... If one of my fed thru outlets on the MWBC fails, am I going to get zapped?
We have already been down that road, the neutrals must be pigtailed where the multiwire branch circuit is split, neutrals after the split can be fed through the device. You always run the risk of being zapped if you were on hot circuits.
 
  #54  
Old 11-25-13, 12:39 PM
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Joe said>
We have already been down that road, the neutrals must be pigtailed where the multiwire branch circuit is split, neutrals after the split can be fed through the device. You always run the risk of being zapped if you were on hot circuits.
OK, thank you for both your explanations and your patience with my inquiries.

I think ideally the neutral, prior to it branching out, should be unbroken (no outlets or splices), taking the overvoltage situation out of the equation.

Is it out of the ordinary having outlets/splices prior to the neutral branching out? Is that a wiring error in my home?

Also, are wirenuts ok to use for splices in MWBC? Should it be something more secure like barrel crimps or something? What would be standard procedure?

Happy Holidays! (and thanks again).
 

Last edited by rards; 11-25-13 at 01:04 PM.
  #55  
Old 11-25-13, 01:11 PM
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Wire nuts are fine for the connection.

This should help, courtesy of Mike Holt.


 

Last edited by pcboss; 11-25-13 at 02:22 PM. Reason: added graphic
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