Connecting neutral wires of different circuits

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jeff48356

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I've seen it a few times where someone, who didn't know what he was doing, connected all the neutrals together in a multi-gang switch box, even though the switches aren't all on the same circuit in that box. I realize this is very poor practice, and I would never do this in the field, but is there an actual NEC Code reference addressing this? The grounding conductors all go together regardless of circuit, but the neutrals need to be separated.
 
jeff48356 said:
I've seen it a few times where someone, who didn't know what he was doing, connected all the neutrals together in a multi-gang switch box, even though the switches aren't all on the same circuit in that box. I realize this is very poor practice, and I would never do this in the field, but is there an actual NEC Code reference addressing this? The grounding conductors all go together regardless of circuit, but the neutrals need to be separated.
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This puts all the neutrals in parallel and 310.10(H) would be your article. Regardless of code violations it also creates EMF issues throughout the paths of these neutrals.

Roger
 
I've seen it done and was told it's OK because they all go back to the same place in the panel. :slaphead:

Could be hazardous to someone working on a circuit that they have de-energized not knowing that the neutral is carrying current from another circuit further upstream.
 
infinity said:
I've seen it done and was told it's OK because they all go back to the same place in the panel. :slaphead:

Could be hazardous to someone working on a circuit that they have de-energized not knowing that the neutral is carrying current from another circuit further upstream.
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Heard that before.... "they all go back to the same place...what's the problem?"

What about if one circuit lost the neutral back to the panel so the current took another parallel path which could overload another neutral.
 
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I addition to the code violation and danger to doing this as already mentioned, any AFCI's that have GF as part of their design or GFCI's are not going to work.
 
texie said:
I addition to the code violation and danger to doing this as already mentioned, any AFCI's that have GF as part of their design or GFCI's are not going to work.
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With the information given, what danger or code violations are we talking about?

If this is a MWBC that comes into the switch box and the rules are met for disconnecting means, grouping, and the like, what is the danger or NEC rule have they violated?

We would also need to clarify AFCI and GF "Breakers" may not work if a neutral is being shared, but, if we are talking "Devices" and where they might be located in the circuit, then there may be no issues at all.


JAP>
 
The simplest and most obvious danger if sharing neutrals is that turning off only the one supply circuit breaker corresponding to a particular neutral wire can leave it carrying current from another circuit and one side going to the full voltage of that circuit if it is interrupted.
If instead of two circuits sharing a single return path you put the two neutrals in parallel, violating code and bringing the chance if one of them carrying double its rated current if the other is compromised.

Sent from my XT1585 using Tapatalk
 
GoldDigger said:
The simplest and most obvious danger if sharing neutrals is that turning off only the one supply circuit breaker corresponding to a particular neutral wire can leave it carrying current from another circuit and one side going to the full voltage of that circuit if it is interrupted.
If instead of two circuits sharing a single return path you put the two neutrals in parallel, violating code and bringing the chance if one of them carrying double its rated current if the other is compromised.

Sent from my XT1585 using Tapatalk
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Hence my previous statement which included "proper grouping and disconnecting means" which in a MWBC is allowed by code and no more dangerous than every day electricity.

JAP>
 
jap said:
With the information given, what danger or code violations are we talking about?
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The OP said "not on the same circuit" so the dangers and articles already mentioned would be your answer.

jap said:
If this is a MWBC that comes into the switch box and the rules are met for disconnecting means, grouping, and the like, what is the danger or NEC rule have they violated?
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A MWBC is only one circuit and only has one neutral so that is not what is being disscussed, it doesn't matter where or how many times it splits into different directions it only has one neutral.

Roger
 
roger said:
The OP said "not on the same circuit" so the dangers and articles already mentioned would be your answer.

A MWBC is only one circuit and only has one neutral so that is not what is being disscussed, it doesn't matter where or how many times it splits into different directions it only has one neutral.

Roger
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So if I bring circuits 1,3 and 5 and a shared neutral into a box as a multi wire branch circuit, I only have (1) Circuit? .... Hmmm...... I beg to differ.

JAP>
 
jap said:
So if I bring circuits 1,3 and 5 and a shared neutral into a box as a multi wire branch circuit, I only have (1) Circuit?
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Yes

jap said:
.... Hmmm...... I beg to differ.

JAP>
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Besides the actual characteristics which makes A MWBC a single circuit read the second sentence of 210.4(A), you're allowed to consider it "multiple circuits" but it is in fact a single circuit.

Roger
 
roger said:
Yes

Besides the actual characteristics which makes A MWBC a single circuit read the second sentence of 210.4(A), you're allowed to consider it "multiple circuits" but it is in fact a single circuit.

Roger
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You can read it all you want but the fact is that if a "Single" circuit could have handled the load in the switch box, there would not have been the need for any additional circuits.

The additional circuits in the box constitute more than 1 circuit therefore I use my right to consider it "multiple circuits".

Just because there are multiple circuits in the switch box, and, all of the Neutrals are tied together, that does not mean that there is a danger or a violation.

And there's no way of knowing that right now.

Not by what the OP originally stated anyway.



JAP>
 
donselectric said:
every ark fault would trip if you did that
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Only if your talking about Arc Fault or GFI "Breakers" installed "ahead" of the mixed neutrals that is.
They wouldn't trip , due to mixed neutrals, if Arc Fault (even though uncommon) or a Ground Fault "Devices" were installed on the load side of the mixed neutral situation.

Let's be sure to clarify.

JAP>
 
jap said:
You can read it all you want but the fact is that if a "Single" circuit could have handled the load in the switch box, there would not have been the need for any additional circuits.

The additional circuits in the box constitute more than 1 circuit therefore I use my right to consider it "multiple circuits".

Just because there are multiple circuits in the switch box, and, all of the Neutrals are tied together, that does not mean that there is a danger or a violation.

And there's no way of knowing that right now.

Not by what the OP originally stated anyway.



JAP>
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Paralleled neutrals as roger said in post #2.
 
jap said:
Possibly, but not if its actually a MWBC in the switch box , which is not indicated in post #1.


JAP>
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Yes, it is. He specifically said there were multiple neutrals from multiple circuits. An MWBC has one neutral.
 
If I had a MWBC in that switch box consisting of 3 circuits with a shared neutral, all of the neutrals would be tied together in a cobbled up mess just like if there were multiple circuits with multiple neutrals and there would still be no danger or violation.

Until there is something determines this is "not" a MWBC then everything after post #1 is speculation.

JAP>
 
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