landing neutrals on ground bars

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RustyShackleford

Senior Member
Location
NC
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electrical engineer
Just wondering what peoples' opinions, and experiences with AHJs are, on this topic.

On a residential main load center, which is the first means of disconnect, grounds and neutrals are not separated. Manufacturers typically provide neutral bar(s) which are directly connected to the neutral on the service entrance. One or more ground bars are screwed into the enclosure. A bonding screw connects the neutral bar to the enclosure, so that grounds and neutrals are connected.

Here's the question: when (if ever) is it ok to land neutrals on the ground bars ? The issue is that neutral carries ordinary service currents at full ampacity at any time, whereas ground only carries current during a ground fault (which should hopefully end quite soon). As such, there are very different requirements for size and quality of connection (e.g. ground wires can be #8 on a 100A feeder, and need be connected with only a fine-thread screw into the thin enclosure sheet metal).

This can be overcome by providing a high-current jumper from the neutral bar to any ground bar where one wishes to land neutrals. But does this violate the load center labeling/instructions ? If acceptable, how is the jumper size to be calculated ?
 
Note 200.2(B)
(B) Continuity. The continuity of a grounded conductor shall not depend on a connection to a metallic enclosure, raceway,
or cable armor.
 
Electrically it would only be ok with a jumper between the neutral bar and the ground bar. In short with the jumper, it would be like extending the neutral bar.

But in the real world I doubt any inspector would go along with this and yes it probably would violate the panels instructions.

On top of that there is no good reason to do it and it would be confusing.
 
Two things come to mind.
1.) If there are ground bars in addition to the neutral bars, I see no need in landing neutrals on the ground bar. There shouldn't be that many neutrals anyway. You can double up on the grounds if you need to and move them to the ground bars if any are landed there.

2.) With the plug on neutrals, there should be plenty of room for any other neutral conductors.
 
RustyShackleford said:
...
Here's the question: when (if ever) is it ok to land neutrals on the ground bars ?
Click to expand...

If by ground bar you mean a bar that is only connected to the enclosure, the answer is...
Never.


This can be overcome by providing a high-current jumper from the neutral bar to any ground bar where one wishes to land neutrals.
Click to expand...
Yes, that essentially turns it into a neutral bar.

But does this violate the load center labeling/instructions ?
Click to expand...

Not in my opinion, at least if the labeling isn't very explicit about it.

In panels made in the last 20 or more years I think it is unlikely to be necessary since usually the number of nuetral terminals matches the panel circuit maximum. Maybe the proper solution is to double up the EGCs on the groundbar like Bill said. In older panels I've found it to be a slightly more common problem.

If acceptable, how is the jumper size to be calculated ?
Click to expand...
The calculated neutral load for the loads connected. Conservatively, use the same amps as the main neutral bar.
 
Generally if a panel has a main breaker it ussually only comes with the neutral bars with the green screw. If it fills up I have added grounding bars.
I use an 8 or 6cu as a jumper when I put neutrals on it.
I have always done that even before it was required by 200.2 b
 
Adding a jumper between the official neutral bar and the ground bar is a violation of the NEC as it creates a parallel paths between the jumper and the steel of the panel enclosure. See augie47's answer in post #2.
 
jim dungar said:
Adding a jumper between the official neutral bar and the ground bar is a violation of the NEC as it creates a parallel paths between the jumper and the steel of the panel enclosure. See augie47's answer in post #2.
Click to expand...
I think we've discussed this and not all agree. It's not a violation of 250.142(B) if done at the service equipment. And the enclosure may already be carrying parallel current if something like a meter socket is bonded to the grounded conductor upstream.
 
jaggedben said:
I think we've discussed this and not all agree. It's not a violation of 250.142(B) if done at the service equipment. And the enclosure may already be carrying parallel current if something like a meter socket is bonded to the grounded conductor upstream.
Click to expand...
The enclosure is always a parallel path for neutral current in my town as the only wiring methods permitted for service conductors are RMC and IMC.
 
Up to and including the main service disconnect enclosure, the neutral/grounded conductor and any metallic conduits, enclosures, troughs, other raceways, etc., are considered to be one and the same.

They, along with the grounding electrodes, establish, or re-establish the zero-volts reference point for the service and the premises equipment grounding system. That's "earth" for all intents and purposes.
 
The use of a jumper between the EGC and neutral bus would violate using a single neutral for multiple circuits.
 
infinity said:
The use of a jumper between the EGC and neutral bus would violate using a single neutral for multiple circuits.
Click to expand...
:unsure: Hmmm. Wouldn't that also prohibit every feeder's neutral?

We have been considering such a jumper to be an extension of the neutral or the neutral bus.
 
jaggedben said:
In panels made in the last 20 or more years I think it is unlikely to be necessary since usually the number of nuetral terminals matches the panel circuit maximum.
Click to expand...
Looking at a panel replacement, so have to deal with existing wire lengths. Siemens, in their wisdom, decided not to extend neutral bar the entire height of the columns of breakers.

Of course it's not that hard to extend wires using inline Wagos or the like. Speaking of which, is it ok to extend wires using soldered joints protected by heat shrink ? Wagos are clearly ok and easy, but solder joint seems more electrically "sound" - perhaps an issue for the excessively short neutral wire on a surge supressor such as https://www.eaton.com/us/en-us/skuPage.CHSPT2ULTRA.html given their exhortation to keep the leads as short as possible. (Seems likely it'd be good for the transmission-line characteristics of the wire to be uniform, to prevent reflections and such on the weird transients that might occur in a surge event, and certainly the soldered joint is more like a continuation of the wire than a Wago or a wire nut).
 

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RustyShackleford said:
Looking at a panel replacement, so have to deal with existing wire lengths. Siemens, in their wisdom, decided not to extend neutral bar the entire height of the columns of breakers.
Click to expand...
That's a plug on neutral panel. Any GFCI/AFCI installed will not take up any slots on the neutral bar.
Even if they did, that still looks like enough spaces. Especially with the separate ground bars.
 
RustyShackleford said:
Like I said, the issue is the existing lengths of the neutral conductors for cables entering the cabinet from the bottom (in the picture).
Click to expand...
Well you asked about putting neutrals on the ground bar. The ground bars I see in the pic are higher than the neutral bars. How would you reach the ground bars if they are higher than the neutral bars?

Just splice on some white conductors on the ones that don't reach.
 
RustyShackleford said:
Like I said, the issue is the existing lengths of the neutral conductors for cables entering the cabinet from the bottom (in the picture).
Click to expand...
Grab a bag of wire-nuts and some white, black, and bare wire. Anything more is overkill.

Wait, you're an engineer. I understand. But that's still all you need to do.
 
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