Neutrals, connecting all branch circuits neutrals together

[OldYeller]

I have an electrician in my dept. working on another shift that does some work that I feel is un acceptable. On a multiple wire 120 volt branch circuit, he ties all of the neutrals together under one nut. And he never grounds the box. I have a problem with tieing all of the neutrals together. If you lock out the circuit you are working on downstream from the first junction box and the other circuit in the run is still live. Is there not potential for injury if a fan or other device is plugged into the circuit that is live and carrying voltage back to the neutral on the circuit you are working on. I can't find a code that says in black and white not to do this. He is a person that has to be proven wrong to get him to do things differently. Need some help.

Allen

 

[infinity]

What he has done is put all of the neutrals in parallel creating parallel conductors. The minimum size parallel conductors permitted is #1/0. Look at 310.4.

 

[charlie b]

I don?t quite understand the question. A multi-wire branch circuit uses a single neutral conductor from the panel, run with the two (or three) phase conductors, to supply a number of loads. At some point at or near each load, the load?s neutral wire will have to connect to the branch circuit?s one and only neutral wire. That is not a parallel connection, since there is only one wire going all the way back to the panel.

Can you clarify your description? At what point are these neutrals being tied together? Or are you talking about tying neutral conductors to equipment grounding conductors?

 

[petersonra]

I have an electrician in my dept. working on another shift that does some work that I feel is un acceptable. On a multiple wire 120 volt branch circuit, he ties all of the neutrals together under one nut. And he never grounds the box. I have a problem with tieing all of the neutrals together. If you lock out the circuit you are working on downstream from the first junction box and the other circuit in the run is still live. Is there not potential for injury if a fan or other device is plugged into the circuit that is live and carrying voltage back to the neutral on the circuit you are working on. I can't find a code that says in black and white not to do this. He is a person that has to be proven wrong to get him to do things differently. Need some help.

Allen

I don't have a problem with tying multiple neutrals together in a junction box and running back a single, properly sized neutral, if that is what you are describing.

Normally when you lockout a 120V circuit the neutral is not disconnected anyway. it is not required that a grounded conductor be disconnected by the disconnecting means.

 

[realolman]

I think maybe he's talking about more than one circuit.

2 multi wire circuits run in the same conduit would have two neutrals.
I don't think those two should be tied together. I think they should be identified some how to keep them with their respective circuits.

 

[infinity]

I think maybe he's talking about more than one circuit.

2 multi wire circuits run in the same conduit would have two neutrals.
I don't think those two should be tied together. I think they should be identified some how to keep them with their respective circuits.

That is what I assumed, maybe a conduit with several MWBC's. I have seen an electrician take a bunch of neutrals from MWBC's and splice them all together in a homerun box.

 

[petersonra]

I think maybe he's talking about more than one circuit.

2 multi wire circuits run in the same conduit would have two neutrals.
I don't think those two should be tied together. I think they should be identified some how to keep them with their respective circuits.

Why? It is the same point electrically back at the neutral bar.

 

[realolman]

actually, I'm not sure why. Maybe it's not necessary. It just seems like something you ought to do.

Are you saying it would be ok to run 3 or 4 20 a. multiwire circuits in the same conduit and only have one #12 neutral wire? I suppose the wire could handle it allright, it just seems to me if you de-energize the phase you should de energize the neutral also.

I have run separate neutrals to motor starters in a cabinet if they are fed from different control power fuses, just so you can change them ( the starters ) without interfering with the other starters.

maybe you don't have to ...I don't know.

Old Yeller also mentioned grounding the box. If you were to run an EGC in conduit, are you supposed to connect it to every junction box as well?

 

[winnie]

Bob,

If you are thinking about a "common neutral" conductor, then I agree, there is no problem.

However my hunch is that the original poster is describing a situation in which multiple circuits, with multiple separate neutrals, have all the neutrals tied together in a junction box. In this case the electrician would have created 'conductors in parallel', connected electrically at the same point in the panel and at the wire nut. 310.4 makes this perfectly reasonable.... if the conductors are size 1/0 or larger

(Aside: common neutral circuits have been debated to great length in other threads, and I don't intend to re-open this debate here. As a summary: common neutral circuits have a grounded conductor that is sized for the maximum unbalanced load of all the associated ungrounded conductors. They are explicitly described in 225.7(B) for _outside_ branch circuits and feeders for lighting, and common neutral feeders are described and limited in 215.4. Common neutral circuits are _not_ mentioned in article 210, either to permit or to prohibit them. Multiwire circuits could be considered a special case of common neutral circuits. Some would argue that since multiwire circuits are permitted, this is an implicit prohibition against other common neutral circuits, others would argue that since common neutral circuits are not prohibited, then they are allowed. Search for the other thread for more details.)

-Jon

 

[iwire]

Why? It is the same point electrically back at the neutral bar.

Other than being a violation of 310.4 I can't think of any real issues that will become of it.

 

[charlie b]

Why? It is the same point electrically back at the neutral bar.

So too is the equipment grounding bar - it's electrically the same point as the neutral, when you are inside the main panel. But that does not make it safe to connect ground to neutral anywhere downstream.

The neutral of a MWBC will carry the same current as a phase conductor, if there are no loads running off the other phase(s). Suppose you have two MWBCs in the same conduit from the main panel to some junction box. Suppose you connect the neutrals of the two separate MWBC to each other. Suppose the only load running is a single phase load from Phase A of one of the two MWBCs. Then the current returning to the service panel via one neutral will be shared by the other neutral. That puts a voltage drop, a small voltage drop, on a conductor that should have none. If you are working on a load related to the other circuit, and you turn off the breaker and open up the equipment, the neutral point within the equipment will have current running through it. I don't know if it will be enough to cause a shock, but it should not be allowed to happen.

 

[petersonra]

Other than being a violation of 310.4 I can't think of any real issues that will become of it.

how do you figure running a single wire back to the PB creates parallel conductors?

 

[iwire]

how do you figure running a single wire back to the PB creates parallel conductors?

I don't

I figure mutilple common neutrals tied together at each box creates parallel neutrals.

 

[George Stolz]

Are you saying it would be ok to run 3 or 4 20 a. multiwire circuits in the same conduit and only have one #12 neutral wire? I suppose the wire could handle it allright, it just seems to me if you de-energize the phase you should de energize the neutral also.

If you have more than one conductor on the same phase supplying a single neutral, then the neutral is being made to return twice the current. So, two 20A circuits on the same phase returning on a single neutral could put 40A onto that neutral. The neutral would need to be sized accordingly.

If you were to run an EGC in conduit, are you supposed to connect it to every junction box as well?

See 250.148. When splices are made, all EGCs associated with the circuits spliced are to be connected to each other and the box.

If no splices are made, then the metallic conduit may be used to bond the box if it provides an effective fault current path. If it does not provide an effective path, then the box must be bonded somehow.

 

[dsteves]

Other than being a violation of 310.4 I can't think of any real issues that will become of it.

There is a certain part of my cerebellum which tells me to flight rather than fight on this one, but what the heck? I think by now the players on the forum know me well enough to know that is not in my composure.

The concept here is to avoid creating electromagnetic fields that are not cancelled by conductors carrying the counter field from any particular utilization equipment.

Specifically, the idea is that if you have a current supplying a load, you want the return path (all of it) to be as close to the conductor supplying the load on the line side as possible.

Footnote: EC&M has an article in a recent issue regarding theories that EMF (electromagnetic fields) may be causing some forms of cancer in younger folks' bloodstreams.

That said, NFPA 70 insists that current to any load must be returned to the source via conductors in the same conduit or cable supplying the load.

Forgive me if I get up on a soap box on this one. The problem arises if either the line or the neutral has more than one path from service to load, or if either conductor is separated from the other by some nontrivial distance. The concept is that the electromagnetic field generated by the current to the load should neutralize itself by virtue of the fact that all conductors serving the load shall be contained in the same cable or raceway.

Regardless of any anomalous behavior of the load, the net magnetic field around the branch circuit conductors must always be zero.

One of the typical violations of this arrangement is to provide two or more branch circuits from the service panel to a multigang box next to, say, a front door. The box has branch circuit conductors for the front porch lights, the living room receptacles, and a chandelier, for example. The electrician decides to tie all of the whites together with a gray wire nut. The box has a 14-2 feed from the panelboard for the lighting circuit, and a 12-2 feed for the split receptacles in the adjacent living room.

Dan

 

[George Stolz]

I think they should be identified some how to keep them with their respective circuits.

Why? It is the same point electrically back at the neutral bar.

We recently had a very weird (to me) predicament. We had three sets of two-circuit track lighting, which meant that we needed six hots for the three sets.

With the 120/208 three-phase available, two "boats" were pulled: 32, 34, 36, 38, 40, 42.
Instinctively, two neutrals were used, as that's all two boats would require: 32, 34, 36 on one neutral, 38, 40, 42 on the other.

However, due to the two-circuit track, the circuits were split like this:
32, 34 ... 36, 38 ... 40, 42.
Therefore, we needed a third neutral for the circuits.

Labeling was crucial; even though they all end up at the panel, as circuits are shed along the way away from the panel, it's important to keep track of which neutral is with which circuit. Otherwise, we could inadvertently overload a neutral.

 

[dsteves]

Di! Ecce hora! Uxor mea me necabit!
Translated to English:
God, look at the time! My wife will kill me!

 

[iwire]

The concept here is to avoid creating electromagnetic fields that are not cancelled by conductors carrying the counter field from any particular utilization equipment.

In the example given in this thread presumably all these neutrals are in the same raceway once they become paralleled, that being the case the there will be no electromagnetic field problem.

Also interesting to note that for better or worse the NEC does not seem that concerned with electromagnetic fields as long as they are not causing heating.

If you use non-metallic wiring methods you can pretty much ignore 300.3(B).

 

[iwire]

Labeling was crucial; even though they all end up at the panel, as circuits are shed along the way away from the panel, it's important to keep track of which neutral is with which circuit. Otherwise, we could inadvertently overload a neutral.

Yes, if this gets goofed up it can be a real pain to sort it out after.

This is one of the many reasons I try not deviate from the circuit numbers shown on the print. It makes it easier to keep track of the neutrals.

To speed things we typically only label the neutral with the phase A number.....White 1 goes with 1, 3, 5 etc.

It gets messy if you jump around the panel 1, 4, 41, than you have to put all those numbers on the neutrals.

That is probably coming to an end though via handle ties.

 

[dsteves]

In the example given in this thread presumably all these neutrals are in the same raceway once they become paralleled, that being the case the there will be no electromagnetic field problem.

Also interesting to note that for better or worse the NEC does not seem that concerned with electromagnetic fields as long as they are not causing heating.

If you use non-metallic wiring methods you can pretty much ignore 300.3(B).

Hi there, iwire. It's always a pleasure to fence with you.
I'm gonna sachay over to my code book after a stop at the refrigerator. I'll leave the interpretation of my refrigerator visit to the reader.

Pardon me while I whip this out! (Blazing saddles, 1974)


I'll get back to you on this. Have a good evening.

Dan
Latin language lesson:
Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam.
I have a catapult. Give me all your money, or I will fling an enormous rock at your head.