ID of grounded conductors

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durban1

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Fairly new to NEC, so might be nitpicky question. As I understand it, neutrals shall not be connected to ground in secondary panels. Is there a place that indicates whether they shall still be white or gray colored insulation (200.6), as if they were "grounded conductors", or does common sense take over?
 
zbang said:
In almost all systems, what we commonly call the 'neutral' is the grounded conductor.
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And (for further clarification) is not the Equipment Grounding Conductor (EGC) for which continuity back to the main service must be maintained in complete isolation from the grounded conductor/neutral.
 
Background

Background

Mostly industrial electricity. The reason I ask is that when I moved a residential service for my son-in-law's house addition, the service panel became secondary as it was now inside with a disconnect outside, which made the service a secondary panel. The inspector required me to separate the neutral and ground at the service, which unbeknownst to me, is apparently code. Hence my question. If the neutral and ground are not common, then, apparently, the neutral is not a grounded connector...is it? And I have never had a journeyman or master electrician able to explain the reason for this (separation of neutral and ground on secondary panel. Do you know?

Thanks for replying.
 
The premises neutral (technically: grounded conductor) is only connected (technical term: bonded) to the ground (technically: grounding conductor) at the point of service or first disconnect on any separately derived system.

The grounded conductor and the grounding conductor are maintained separately in any subsequent gear and equipment. This is also our NEC standard practice in the industrial environments where I work. And this is because of the reason that Jim just posted, because he's faster than me. :)
 
Dead horse

Dead horse

Thanks for explanation. We had no "neutrals" in our control circuits in the industrial applications I worked. Both sides of the line fused/hot. But if it "unsafe" or that inefficient, why not require the same (bonded neutral and disconnect) at any service?
 
durban1 said:
Thanks for explanation. We had no "neutrals" in our control circuits in the industrial applications I worked. Both sides of the line fused/hot. But if it "unsafe" or that inefficient, why not require the same (bonded neutral and disconnect) at any service?
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They are required at any service that uses/has a grounded/neutral conductor. I think you may be confusing the terms grounded and grounding. The grounded conductor (neutral) is the conductor that (in many cases) is grounded at the POCO transformer and again at the first OCPD/disconnect. This is tied into the GEC (grounding electrode conductor). This can be a ground rod, water pipe, CCE (grounding electrode encased in concrete) ground ring etc. Actually, the GEC is part of the GES (grounding electrode system) and is the conductor connecting the rod, water pipe, etc to the panel. The neutral (grounded conductor) is landed on the neutral bar in the first OCPD/disconnect, for simplicity's sake, the panel. Then it is bonded to the panel and to the grounding connector. The grounding conductor (EGC) is not the neutral. It is a conductor to protect the equipment from a fault and a low resistance path back to the panel where it can trip a breaker and clear the fault, that is where some people confuse the terms grounded and grounding. These grounded and grounding conductors are only bonded at the panel and no where else downstream. This is to prevent unwanted current on the grounding conductor. If they were bonded anywhere downstream of the panel there would be parallel paths for the neutral (grounded) conductor back to the panel. In other words, you would be putting current on the grounding conductor and could be dangerous should someone come in contact with anything metal along the circuit. Remember, when I'm saying panel, I'm talking about the first OCPD/disconnect. You could, as in your case, have a disconnect and OCPD outside and the panel would then be a sub panel and you would not bond there, only in the disconnect.
I hope I have made this clear as mud!:D
 
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durban1 said:
Thanks for explanation. We had no "neutrals" in our control circuits in the industrial applications I worked. Both sides of the line fused/hot. But if it "unsafe" or that inefficient, why not require the same (bonded neutral and disconnect) at any service?
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Do you only work on power and controls with no neutral loads? A little hard to imagine you do not have any 120/240 or 120/208 at all at your industrial work location. What powers general purpose receptacles in offices, shop, other non production areas, maybe even some lighting? Even if those loads are powered from small transformers near the outlet there are similar rules for the separately derived system.
 
durban1 said:
Do you know?
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250.6 Objectionable current. Fires, shock hazard, improper operation of electronic devices, loss of zero volt reference. The neutral is a current carrying conductor, when a neutral to ground connection is made at a downstream panel, neutral current is on all the metallic paths back to the service. Conduit fittings are not designed to carry neutral current. Open a raceway with neutral current and you could be in series and get a fatal shock.
 
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