Multi wire branch circuits, all neutrals tied together in junction box

[Ryan902]

Hello there, I recieved a call about lights that were not working in a theater that I service. I went over and noticed that there were two rows of LED lights, both fed from one breaker, but they were on seperate switches. The odd thing was, was that one strip was working fine and the other strip was burnt but (not completely, every one had a couple of flickering leds).

First thing I confirmed was that I was receiving proper voltage to all three phases and that I had no loose neutrals. Voltage to ground and the neutral bus bar were 120. (it's a 120/208v 3phase 4 wire panel).

Everything seemed fine. So I went to the first jbox and noticed they had shared neutrals for each 3 phase group (and some groups of 2 ungrounded) but all the neutrals in this jbox went to a common, giant splice of neutrals. I know normally you keep your neutrals seperate back to the neutral bus bar to avoid a shared neutrals between ungrounded ungrounded conductors on the same phase. But could this cause other problems? Especially when you're switching some lights off at the switch, creating an unintended path through the shared neutrals?

My guess is that either we had a surge of some sort, or there was some issue with these shared neutrals.

The panel was installed 7 years ago with no issues. My plan is to do the unfortunate task of seperating all mwbc neutrals back to the neutral bus bar.

Anyone ever encounter anything like this before? Thanks for your time.

 

[ramsy]

Since cold lighting filaments can provide their own return continuity path thru the fixture, especially with magnetic ballasts, how would you identify true neutrals from other white wires in the junction box?

 

[infinity]

If this system were wired 7 years ago and worked fine until now then I doubt that the bundle of neutrals spliced together caused the problem. You're right that it needs to be corrected.

 

[Ryan902]

Since cold lighting filaments can provide their own return continuity path thru the fixture, especially with magnetic ballasts, how would you identify true neutrals from other white wires in the junction box?

I Identified the true neutrals from the identified conductors by following them through their respective conduits, which had 2-3 ungrounded conductors along with a single neutral, mainly these were for receptacle circuits throughout the theater, so certainly there would be an unbalanced load on some of these neutrals. This J-box (20x20) had all the circuits from the panel stubbed into it so there were at least 20 white wires tied together in the first J-box, some neutrals, some identified conductors.

It's weird because I was there a couple weeks ago and all the lights worked, and then overnight one half stopped working, but all seem to have the same problem that only a few led's on the assembly are illuminated. I'm assuming they had one switch off when the issue happened. (The switch that now only has working lights on it now)

 

[ptonsparky]

How do you tie 20 whites together? Not very easily, or welI. I suspect you lost neutral connection(s) in that cluster. You would not necessarily see evidence other than the resultant damage.

 

[Ryan902]

How do you tie 20 whites together? Not very easily, or welI. I suspect you lost neutral connection(s) in that cluster. You would not necessarily see evidence other than the resultant damage.

They used a very large 3m marrette, and did a poor job of it at that. That's a good point. I plan to rip it all apart and trying to start identifying each grouping to give each neutral a separate path back to the neutral bus bar, but maybe there's one not making good connection.

Thanks

 

[ramsy]

I Identified the true neutrals from the identified conductors by following them through their respective conduits,

Nice work

overnight one half stopped working,

Are LED's under warranty for failing with normal voltage, or did you replicate the over-voltage issue?

 

[Ryan902]

Not sure exactly what you mean about replicating an over-voltage issue, but I just came in to discover half the lights burnt out and the only thing out of the ordinary was the incorrect wiring of the neutrals. The fixtures are also well out of warranty unfortunately.

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[ramsy]

If possible I prefer to demonstrate the problem to the client, before I fix it.

 

[Tulsa Electrician]

I have, we called it a JD special.
There was a contractor that tied every grounded conductor and neutral toghter in every box he did for many many years. Yes he was a contractor. We, all contractors / electricians spent years undoing his work once the AHJ change the rules on having the inside of every box open for an inspection. Mainly due to his work. Yep name was JD. It was not uncommon for six or more ungrounded tied to four grounded/ neutrals.
Very sad.

 

[Ryan902]

I have also seen it before in other people's wiring. Often I see people who modify commercial panels, switch breakers around when there's mwbc's and end up putting 2 circuits sharing a neutral on the same phase. One time it resulted in a pretty crispy neutral.

I guess what I'm wondering, is that if you have a situation like this with all your grounded/neutral conductors combined like this, can it cause issues in over-voltage scenarios? (not just too much ampacity on the conductors themselves) Like I know if you have your neutral and bonding conductors in contact at more than one location in your system it can cause problems with clearing a ground fault. Does anyone know if any issues in clearing faults when your neutrals/groundeds are connected in this manner. It's an interesting thought either way.

Thanks for the replies.

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[roger]

In reality tying all the neutrals together would result in less of a chance for over voltage but more of a chance for elevated EMF in some areas

Roger

 

[synchro]

On noticing the location of the OP, Ryan902, I'd like to take this opportunity to remember and appreciate the hospitality and kindness the people of Halifax extended to thousands of stranded airline passengers 20 years ago on 9-11.

 

[Ryan902]

On noticing the location of the OP, Ryan902, I'd like to take this opportunity to remember and appreciate the hospitality and kindness the people of Halifax extended to thousands of stranded airline passengers 20 years ago on 9-11.

Wow! This brings back memories.

I was in junior high at the time, but I remember all of our local schools, rec centers, arenas etc were used to house the stranded people who were flying over the Atlantic at the time. I'm glad my community was able to contribute in that.

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[ptonsparky]

Wow! This brings back memories.

I was in junior high at the time, but I remember all of our local schools, rec centers, arenas etc were used to house the stranded people who were flying over the Atlantic at the time. I'm glad my community was able to contribute in that.

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Thank you!

 

[jmellc]

Wow! This brings back memories.

I was in junior high at the time, but I remember all of our local schools, rec centers, arenas etc were used to house the stranded people who were flying over the Atlantic at the time. I'm glad my community was able to contribute in that.

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Heroes for sure.

 

[romex jockey]

Anyone ever encounter anything like this before?

manufactured homes.......

~RJ~