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In a secondary panel (not a service panel), the grounded (neutral) bus bar is to be kept isolated from the grounding conductors (250.24(A)(5)). In article 408, the code has this to say...

National Electrical Code 2014

Chapter 4 Equipment for General Use

Article 408 Switchboards, Switchgear, and Panelboards.

408.3 Support and Arrangement of Busbars and Conductors.

(D) Terminals. In switchboards , switchgear and panelboards, load terminals for field wiring, including grounded circuit conductor load terminals and connections to the equipment grounding conductor bus for load equipment grounding conductors, shall be so located that it is not necessary to reach across or beyond an uninsulated ungrounded line bus in order to make connections.

In a panel like the one below, where there's a grounding bus bar on one side of the panel and a grounded (neutral) on the other. It's easy to terminate all the neutrals at one bar, and all the grounds at the other. However, does 408.3(D) mean that there should actually be a grounding and grounded bus bar on each side of the panel?

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Should the panel actually look like this?

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4 Answers 4

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I think you may be over-thinking this. You can make a connection on either bus without reaching across an ungrounded bus in that panel.

The ground and neutral bars are so located as to give you free access to them without have to reach around or near an energized bus. You could stand to the right or left to make your connections without reaching across the phase bus.

In a larger piece of switchgear, the phase conductor bus should be located further in and the ground and neutral bars closer to the access panel not the other way around.

I think that is the intent of the code.

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    Thinking more about it, I think that makes a lot of sense. The NEC is not simply about residential and quasi-residential (like the 120/240 service in our old factory). But I wouldn't know on our 480 delta, because we don't have neutral and ground is in the conduit.
    – Harper - Reinstate Monica
    Jan 28, 2016 at 23:01
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Imagine the panel in your first photo with 78 positions, the main breaker snug against top, and the buses running all the way to the bottom. No headroom to route wires above or below the buses. Every connection must cross the buses with either a neutral or ground. It becomes a well understood convention to put 2 rows of blank covers 1/4 and 3/4 of the way down, and use those blank areas for crossovers. You also find wires between breakers. under breakers. Bare grounds through paper tubes made of rolled up work orders. Bunches of grounds wirenutted together to reduce the crossover wire count because somebody really needed one of those "crossover" slots for a breaker. Grounds attached to the box metal with sheetmetal screws so the left ground can be re-tasked as a neutral and every breaker can be used. THAT. That is my guess.

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I think this is more for larger switchgear, not panels like this. This would prevent a manufacturer from building a cabinet where you have to reach your hand past the hot bus to reach the ground terminals.

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With a sub panel the neutral side is isolated and a new earth ground is needed. The neutral comes from your service panel to tie the 2 together as I believe your photo shows would “create a path for objectionable current flow” this is the reason the neutral in the sub is isolated from the ground. you can have a ground on 1 side and a neutral on the other or if you want you can have both on both sides code only states that the neutral is isolated.On smaller panels I usually remove the shorting bar from the left to the right if one side is isolated.

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    That's not an answer to the question here. He mentions that in the first sentence.
    – TFK
    Jan 28, 2016 at 19:01
  • I'm not asking about isolating the neutral, or grounding the panel. I'm asking specifically about NEC 408.3(D).
    – Tester101
    Jan 28, 2016 at 19:46
  • the code dosent specify a distance other than clearance to live parts that I know of. All the panels I work on even 3 phase are arranged like those you have. as I said above the neutral and ground buss can be on one side or both.
    – Ed Beal
    Jan 28, 2016 at 21:10

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