Split Neutral

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#1

Originally Posted By: rmoore
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I borrowed this photo, with permission, from Bob Sisson over at IN.


![](upload://lYF3RuPERcbKho6CkOjR3SaHvUf.jpeg)

It's the neutral to a 100 amp sub-panel in a 150 amp main (service equipment) panel. The main panel is probably overloaded and of course there are those nice double-taps, but I was hoping our resident electricians could offer their opinion on both the "legality" and practicality of this split neutral conductor.

--
Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com

#2

Originally Posted By: jmyers
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Richard,


You have picked an easy one. Here it goes. The question of legality would be no. Reasoning is that the buss bar that wire is attached to is not rated, UL or otherwise, for that size wire. What would be proper in this case would be to add a lug onto the buss bar which is made for this purpose. You can purchase them separately at most places that sell electrical supplies.

Not sure what you mean by "practical" but I think you are saying would this be ok, splitting the wire into two. Considering this would be illegal, I would have to say it would also not be practical.

In my opinion it would all fall back to the UL rating for the wires and the buss bar, which would be an improper installation, no matter if it was practical or not.

Hope that helps.

Joe Myers

#3

Originally Posted By: rmoore
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Hmmm…maybe “practical” is the wrong word. Perhaps “theoretical” would be better.


No doubt this would not be allowed (at least very little doubt...I'm not afraid to be uncertain of a lot of things ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif) ) and need "repair" but I was trying to get it straight in my head if this split neutral, rather than the bar connections, would cause a problem. It seems that, as all the conductor is in use, any amperage would be shared and should not cause a fire hazard.

I've got the day off and I'm procrastinating on the Honey-Do jobs.

--
Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com

#4

Originally Posted By: lfranklin
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What if the current on that wire did not split when it came to that split.


That's one of the problems I see with that set up.

#5

Originally Posted By: Joey D’Adamo
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do my eyes see goop on that aluminum wire? If so, the installer must’ve known something… but even so, it doesn’t look right.

#6

Originally Posted By: jpope
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Looks like someone installed an equipment panel downstream and got lazy with the neutral (didn’t want to replace the bus in the service panel).


I've seen worse, but it still needs to be corrected.

--
Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738

#7

Originally Posted By: jmyers
This post was automatically imported from our archived forum.


Richard,


Maybe ok from a theoretical standpoint but not from a legal standpoint. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

Joe Myers

#8

Originally Posted By: Blaine Wiley
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IMO not even ok theoretical because neither part of the split is rated to carry the possible load of the whole conductor. eusa_think.gif

#9

Originally Posted By: jmyers
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Blaine,


Oh, no you are wrong. The buss is indeed rated to carry the whole potential load of those conductors and the other conductors that are attached to it. From a theoretical standpoint, the buss could carry the load of the conductors and the other conductors which are attached to it.

It would be illegal from a UL standpoint, since the buss is not rated for that large of a conductor in those terminations. Since the conductors would not be attached in a manner for which the buss bar was UL rated, it would also make it illegal according to the NEC.

Joe Myers

#10

Originally Posted By: Blaine Wiley
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I must have missed something, Joe. The buss is rated for a bunch, but the split portion of the wire is not rated to carry the load that the full wire is rated for. That is what I was speaking of.

#11

Originally Posted By: bbadger
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It is both an NEC and UL issue. icon_cool.gif


The NEC says we must use the terminal per UL labeling. 110.3(B)

That split conductor is installed outside the labeling.

It is also a 310.4 violation (conductors in parallel) but there is no need to try that hard.

--
Bob Badger
Electrical Construction & Maintenance
Moderator at ECN

#12

Originally Posted By: rmoore
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There you are Bob… icon_smile.gif


If we can put aside whether this is allowed or not...obviously it's not...the electrical theory I'm trying to understand is whether the connection as shown would safely handle the full rating of the whole conductor. One earlier post asked "what if the current didn't split", while another pointed out that neither "branch" could handle the rated current. My thinking is that the load would be shared, akin to multiple feeders for a high amperage panel, and, assuming all connections were solid, this wouldn't actually create an overload situation. Am I screwed up here?

As a home inspector, this is probably more info than I need and I too would call this as needing repair, but I also have a curious side that just likes to know this stuff.

--
Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com

#13

Originally Posted By: jpeck
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rmoore wrote:
If we can put aside whether this is allowed or not...obviously it's not...the electrical theory I'm trying to understand is whether the connection as shown would safely handle the full rating of the whole conductor.


Yes, it could.

Quote:
One earlier post asked "what if the current didn't split",


It would.

Quote:
while another pointed out that neither "branch" could handle the rated current.


That's the problem part, IF either terminal was not as good a connection as the other, more current would be forced through the strands in the terminal with the 'good' connection.

Quote:
My thinking is that the load would be shared, akin to multiple feeders for a high amperage panel, and, assuming all connections were solid, this wouldn't actually create an overload situation. Am I screwed up here?


No, you are on the right track, but you are also making a big assumption when you are "assuming all connections were solid".

Neither connection has to fail entirely, just become higher resistive. The higher its resistance, the less current it handles and the more current it forces through the other strands.

But then, a similar thing could happen to the neutral on a multi-wire circuit, turning that multi-wire circuit into a 'floating neutral' circuit, but that risk is acceptable, isn't it?

Strange ...

--
Jerry Peck
South Florida