how to troubleshoot multi-wire circuit?

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Old 05-26-18, 03:36 PM
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how to troubleshoot multi-wire circuit?

I know enough not to open neutral connections with only one of the two circuits off.

However, with a dual breaker, I am assuming if you wanted to open neutral connections with one side of the shared circuit still hot, you would disconnect one side of the dual breaker and then it would be like a normal branch circuit. Is this the correct procedure?

btw: no issues just interested in learning!
 
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Old 05-26-18, 03:50 PM
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No..... the neutral is shared. If either of the breakers is on.... the neutral is in use.
You need to shut off both breakers before opening the neutral.
 
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Old 05-26-18, 04:37 PM
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Yes of course, im confusing myself.

Let me know if this makes sense:

If the hot is interrupted in one of the circuits then the other would then act as a normal branch circuit? (as long as the neutral isnt disconnected)
 
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Old 05-26-18, 05:33 PM
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Yes..... that is correct.
 
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Old 05-27-18, 07:47 AM
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Say I wanted to install another neutral back to the panel to make these standard circuits. If your looking for the box where the neutral is split between the two circuits, what would I be looking for?

In one box in particular in my house, im finding one circuit hot is ran uninterupted thru the box, it does not have a neutral wire with it. Then I have a 4 wire splice of hots from the other circuit and a 3 wire splice of neutral wires.

Im assuming that is the point where the circuit splits the neutral conductor.

Hope I am making sense.
 
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Old 05-27-18, 09:51 PM
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You cannot run just a neutral back to the panel. You'd need to run a complete cable.

The point where the MWBC splits is not always easy to find.
Typically you will find 240vac between the red and black at the split point.
 
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Old 05-28-18, 06:38 AM
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You cannot run just a neutral back to the panel. You'd need to run a complete cable.
The point where the MWBC splits is not always easy to find.
Typically you will find 240vac between the red and black at the split point. ]
PJ -

I should have mentioned this is in conduit. So just running a single nuetral wire back is possible , correct?

I think this would be the box where they split:

One circuit hot red is used. The other black is used
There are 4 hot (black) spliced
There are 3 neutral (white) spliced
Then in one conduit there is a red(hot) and white(neutral) that passes thru the box not spliced.

Does this appear wrong because there is only 3 neutrals as opposed to 4 hots?
Or does that indicate the spot where they are sharing since there is one less neutral?

There are a few boxes between this box i am describing and the panel.

Would it be more likely the point where thy spilt would be at the first box after the panel?
 
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Old 05-28-18, 12:41 PM
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Things are different in a conduit. Yes.... you can run a neutral.
You could find multiple taps in a MWBC in conduit.

You have to identify everything on both circuits.
Everything on the black circuit gets put on one neutral and everything on the red circuit gets put on the other neutral. This is important if you are splitting the circuits up.
 
 

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