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Old 02-01-2008, 02:02 PM   #1
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Grounding electrode at subpanel


Is a grounding electrode required for a 4-wire feed to a subpanel?

The MAIN and the Subpanel will have a metallic bond through only through the grounding wire of the feed. It's in PVC, so there's no other metallic bond.

In the SUB, the NEUTRAL and the GROUND will be isolated. Is a secondary rod required to be attached to this isolated grounding bar? I know it is for a 3-wire installation.

The SUB is about 20 ft. from the MAIN.

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Old 02-01-2008, 02:12 PM   #2
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Grounding electrode at subpanel


Same building?....no


Different building without piping systems in it?....no

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Old 02-01-2008, 02:17 PM   #3
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Grounding electrode at subpanel


Different Building, no metallic bonds other than the grounding conductor....so no?
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Old 02-01-2008, 02:21 PM   #4
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Grounding electrode at subpanel


yes, no

If you have no metal piping (gas/water etc) going to the structure.
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Old 02-01-2008, 02:40 PM   #5
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Grounding electrode at subpanel


duh! O.K.
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Old 02-01-2008, 02:52 PM   #6
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Grounding electrode at subpanel


If it is a subpanel in a detached building, a grounding electrode (rod) is REQUIRED. See NEC 250.32
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Old 02-01-2008, 02:56 PM   #7
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Name:  250.32(A).jpg
Views: 468
Size:  60.2 KBEvery building needs a Grounding Electrode System, take a look at 250.32 (A) & 250.50, Your outbuilding also requires a disconnect...

Last edited by chris75; 02-01-2008 at 03:00 PM.
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Old 02-01-2008, 04:05 PM   #8
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Grounding electrode at subpanel


Same building....no.
Detached structure....YES.


Chris and HH are correct.
A grounding electrode is ALWAYS required for a detached structure supplied with a feeder.
The ONLY exception to this is if the structure is fed by only ONE circuit. 250.32(A)Exception
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Old 02-01-2008, 05:06 PM   #9
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Grounding electrode at subpanel


It is being fed a by a single circuit feeder on #4/3 w/grnd.
There will be a circuit breaker at the main for the disconnect. I have no problem with putting an extra electrode, just checking for safety.

I'll add the electrode. I will also isolate the Neutral and Ground in the SUB. I'll connect the grounding electrode to the isolated grounding bar in the panel with a #8 bare. Sound good?

Last edited by Randell Tarin; 02-01-2008 at 05:09 PM.
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Old 02-01-2008, 05:21 PM   #10
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Grounding electrode at subpanel


Quote:
Originally Posted by Randell Tarin View Post
It is being fed a by a single circuit feeder on #4/3 w/grnd.
There is NO such thing as a "single circuit feeder". It is either a branch circuit or it is a feeder.

Here is the applicable code section:

250.32 Buildings or Structures Supplied by Feeder(s) or Branch Circuit(s)
(A) Grounding Electrode
Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with 250.50. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.
Exception: A grounding electrode shall not be required where only a single branch circuit supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the conductive non–current-carrying parts of equipment. For the purpose of this section, a multiwire branch circuit shall be considered as a single branch circuit.




The grounding electrode conductor (wire from the ground rod) does NOT go to the isolated bar. The isolated bar is for the neutrals. The bar bonded to the panel box is the ground bar.
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Old 02-01-2008, 05:44 PM   #11
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Grounding electrode at subpanel


Quote:
Originally Posted by Speedy Petey View Post
There is NO such thing as a "single circuit feeder". It is either a branch circuit or it is a feeder....

The grounding electrode conductor (wire from the ground rod) does NOT go to the isolated bar. The isolated bar is for the neutrals. The bar bonded to the panel box is the ground bar.

O.K., O.K. so I get my terminology wrong. I'm I doing it right?

I've got one friggin wire going to the sub. Whatever the hell you call the bar that's bonded to the panel is where I attach the ground. The neutral ALWAYS comes isolated unless you bond it to the ground.
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Old 02-01-2008, 05:49 PM   #12
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Grounding electrode at subpanel


I'm not sure why you're getting pissed. I am just trying to make sure you get the right information.
YES, terminology is important. It ensures we are all on the same page.
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Old 02-01-2008, 06:10 PM   #13
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Grounding electrode at subpanel


Randall .... Randall.... again ....
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Old 02-01-2008, 06:45 PM   #14
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Grounding electrode at subpanel


Speedy Petey,

Sorry, I should have put a smiley face by my comment. I'm not pissed.

I just get confused because the "experts" never seem to agree on what everything is called or how it's to be connected etc.

And JGarth, this forum is called "DIY Chatroom" (Do-It-Yourself), NOT degreed engineer's forum. We can't all be as brilliant as you'd wish. I'm here to learn and hopefully wire safely.
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Old 02-01-2008, 06:48 PM   #15
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Grounding electrode at subpanel


Quote:
Originally Posted by Randell Tarin View Post
I just get confused because the "experts" never seem to agree on what everything is called or how it's to be connected etc.
Yup. We all face this all the time.
It's cool.

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