Continuity of a Grounded Conductor

Merry Christmas
Status
Not open for further replies.
G

Gustavo R

Member
NEC 2008 has a new section (200.2 B) that mentions "The continuity of a grounded conductor shall not depend on a connection to a metallic enclosure, raceway, or cable armor."

To be honest I'm not sure if I'm interpreting this correctly. I know in the past you could use metallic conduits and boxes as your connection to ground. For example, if you had a 120 V circuit in EMT, you could install a live wire, a neutral wire, and use the conduit and box as a ground connection.

Does this new section in NEC 2008 prohibit this practice? What exactly is the change here? The illustrations I see showing the change are not too clear. Any help would be appreciated. Thank you.
 
The grounded conductor is more commonly known as the neutral.

The new rule has nothing to do with grounding conductors.
 
The grounded conductor can be a neutral conductor but can also be a grounding conductor.

Still, what exactly does this rule change?
 
Gustavo R said:
The grounded conductor can be a neutral conductor but can also be a grounding conductor.
Click to expand...

Never for what you described

For example, if you had a 120 V circuit in EMT, you could install a live wire, a neutral wire, and use the conduit and box as a ground connection.
Click to expand...

The rule basically prohibits using an enclosure to carry neutral current as can happen in some service panels.
 
Bob:

Please clarify the term grounded conductor. I always thought it was a term that involved the neutral conductor and the grounding conductor. If the term grounded conductor is used, does it mean only the neutral conductor or can it mean the grounding conductor?

Thank you.
 
Here is the definition of the terms Grounded conductor and Equipment grounding conductor from the 2008 NEC:

Grounded Conductor. A system or circuit conductor that is intentionally grounded.

Grounding Conductor, Equipment (EGC). The conductive path installed to connect normally non?current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.
FPN No. 1: It is recognized that the equipment grounding conductor also performs bonding.
FPN No. 2: See 250.118 for a list of acceptable equipment grounding conductors.

Hope this helps.

Chris
 
Gustavo R said:
Bob:

Please clarify the term grounded conductor. I always thought it was a term that involved the neutral conductor and the grounding conductor.
Click to expand...

For the sake of this conversation, the grounded conductor would be the neutral, the grounding conductor which we should be calling an Equipment Grounding Conductor is a seperate conductor all together.

Gustavo R said:
If the term grounded conductor is used, does it mean only the neutral conductor or can it mean the grounding conductor?
Click to expand...

It would mean only the neutral conductor.

Roger
 
Basically this new section is telling you that you cannot use the metal of the enclosure or a raceway to carry the neutral current. If you had a panel with two neutral bars they must be physically connected together in some way. You cannot simply bolt both of them to the panel enclosure and use the metal enclosure to carry the neutral current between them.
 
Here are a couple of illustrations that might be applicable

Violation

neutral_current_in_enclosure.JPG


Legal

neutal_current_in_jumper.JPG


Roger
 
LarryFine said:
The Emperor's New Images? :grin:
Click to expand...

No, these have been around a couple of years or more, you can find them in other threads if you look hard enough. :grin:

Roger
 
roger said:
Here are a couple of illustrations that might be applicable

Violation

neutral_current_in_enclosure.JPG



Roger
Click to expand...

In this drawing it is still okay to use the bar on the left for ground wires only.
 
roger said:
No, these have been around a couple of years or more, you can find them in other threads if you look hard enough. :grin:
Click to expand...
My comment doesn't make sense now, but when I posted it, your post contained no images, only text. :cool:
 
LarryFine said:
My comment doesn't make sense now, but when I posted it, your post contained no images, only text. :cool:
Click to expand...

Well, now your comment makes sense to me. :)

Roger
 
Excellent. Thank you all for your help. I believe you all have clarified the issue for me.

Now I want to add another question related to this. When do you have to consider the neutral conductor as a current carrying conductor AND give it the same derating factors as ungrounded conductors (or live conductors)? There is a section in the NEC (dont have the number with me at the time) that says that if the neutral conductor is only carrying the unbalance load, you don't have to apply the different derates etc.

Again, thank you all.

Gustavo
 
Status
Not open for further replies.
Top