Separate grounding electrode bus bar rules

[Caligula]

I have confused myself 'checking' my knowledge to the point that now I've confused myself totally.

You have a service entrance panel with a separate bus bar installed in the room to land all the GECs. When you have a subpanel, do you pull your ground from the ground bar in the main panel, or do you take it back to the separate grounding electrode ground bar? Is either acceptable?

 

[augie47]

IMO, the "ground" to your sub-panel is an equipment grounding conductor and should return to the grounding bar in the main panel.

 

[Smart $]

I have confused myself 'checking' my knowledge to the point that now I've confused myself totally.

You have a service entrance panel with a separate bus bar installed in the room to land all the GECs. When you have a subpanel, do you pull your ground from the ground bar in the main panel, or do you take it back to the separate grounding electrode ground bar? Is either acceptable?

While a room busbar is a popular grounding means in industrial, some commercial facilities, it is not a recognized means of electrode or equipment grounding connection. About the only thing they can be used for in an NEC-compliant installation is for equipment bonding jumpers.

JMO

 

[augie47]

WE may be playing semantics, but I assumed the OP was referring to a common electrode busbar as described in 250.64(D)

 

[Smart $]

WE may be playing semantics, but I assumed the OP was referring to a common electrode busbar as described in 250.64(D)

No semantics. Common GEC busbar is one possibility I didn't include in my comment.

In most environs where these busbars are installed, seldom are there multiple supply (service or feeder) disconnecting means enclosures.

 

[Caligula]

To clarify, I wasn't referring to multiple disconnects under 250.64(D), I was thinking something more like this: http://ecmweb.com/site-files/ecmweb.com/files/archive/ecmweb.com/mag/507ecm1702.jpg only next to the meter you would have a switchboard. I have always returned downstream panels to the ground bar in the main switchboard ( or other service equipment) but started to question that perhaps I could land it on the exterior busbar. I see augie47 agrees. Thanks for your help.

 

[electricalist]

I see this in most of the commercial bldg s around here .

 

[augie47]

The way 250.130 is worded a case could be made for terminating at the grounding electrode buss but I don't think that's the intent.

 

[Dennis Alwon]

I think the op is talking about the grounding electrode conductor from the sub panel. If so you do not need a grounding electrode conductor to a subpanel.

 

[Smart $]

I think the op is talking about the grounding electrode conductor from the sub panel. If so you do not need a grounding electrode conductor to a subpanel.

...unless it's at another building or structure. Then he would need an entirely different electrode system.

 

[Dennis Alwon]

...unless it's at another building or structure. Then he would need an entirely different electrode system.

That is true and I almost mentioned that but didn't. It would seem odd if he was talking about an equipment grounding conductor and taking from the main panel to the grounding electrode conductor buss, I am pretty sure that is not what he means but hey, who knows what is in the minds of others.

 

[augie47]

................., who knows what is in the minds of others.

The shadow knows ! (That REALLY shows my age)

(Brief history of The Shadow:
The Shadow is a fictional crime fighter from the 1930s pulp magazines.In print,The Shadow's real name is Kent Allard; in film, Lamont Cranston.Kent Allard was a renowned World War 1 aviator.)

 

[electrofelon]

Hold on a sec, I am confused here:
1) doesnt 300.3 disallow the proposal in the OP? (Augie mentioned but didnt give code reference). OR maybe he is proposing to follow conductors back to their supply then continue to the GEC busbar?
2) doesnt the "common GEC busbar" (250.64(D)(1)) only apply to installations with multiple service enclosures, that is I cant use this method where there is one service disconnect?

 

[electricalist]

The illustration shows 1 service disconnect and the gec bus bar as a common bonding point. Realistically disconnects won't have enough lugs for that many bonds.
The last paragraph of the op I think is the actual question. From sub panel back to mdp e.g. bar then to gec bus.
It is unnecessary. That bond connection was made already.

 

[electricalist]

I read it wrong.. The egc goes to the mdp not to gec. If it was ok you could get your equipment ground from any gec point. Bldg steel on the other side of the bldg.

 

[Smart $]

...
2) doesnt the "common GEC busbar" (250.64(D)(1)) only apply to installations with multiple service enclosures, that is I cant use this method where there is one service disconnect?

That's how I look at it. IOW, the depiction in the graphic is non-compliant.

 

[electricalist]

the depiction in the graphic is non-compliant.

Thats not good....How would we know what is right..M.H. enterprises on ec&m or years of understanding?

 

[electrofelon]

the depiction in the graphic is non-compliant.

Thats not good....How would we know what is right..M.H. enterprises on ec&m or years of understanding?

Mike Holt is human , not a god.

 

[tom baker]

One reason you are confused is by not using code terms. Ground is not defined in the NEC.
Draw a picture. What color is the wire and what does it do?

 

[electricalist]

One reason you are confused is by not using code terms. Ground is not defined in the NEC.
Draw a picture. What color is the wire and what does it do?

For the record it would make more sense if the grounding conductor was called a ground and the grounded conductor was called a neutral,,,,or whatever you choose to identify them as other than almost the same thing. S o if i say ground its not cause i dont understand what i meant .