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Old 05-23-2009, 03:47 PM   #1
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Sub Panel Grounding bar


Are the grounding wires and the neutral wires connected to the same bar in a sub panel?

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Old 05-23-2009, 03:51 PM   #2
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Sub Panel Grounding bar


No you need a separate ground bar.

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Old 05-23-2009, 04:02 PM   #3
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Sub Panel Grounding bar


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No you need a separate ground bar.
It's that easy.
True, with most installations the grounds and neutrals are kept separate, but in some cases a sub-panel in a detached structure have the neutrals and grounds bonded.
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Old 05-23-2009, 04:31 PM   #4
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Sub Panel Grounding bar


thanks guys. I thought that was the case. But I looked in my detached cottage behind my house and it has the neutral and ground wires on the same bar. But I think that's the only situation where it is allowed - a detached structure.
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Old 05-23-2009, 04:36 PM   #5
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Sub Panel Grounding bar


Only if there are no other metallic paths between the structure with the service equipment and the detached structure (like a metal water pipe or data/phone lines) and only if your area is on a code cycle prior to 2008.
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Old 05-23-2009, 06:45 PM   #6
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Sub Panel Grounding bar


I was assuming same structure and with a ground to the sub (my bad on the assuming part)
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Old 05-23-2009, 10:30 PM   #7
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Only if there are no other metallic paths between the structure with the service equipment and the detached structure (like a metal water pipe or data/phone lines) and only if your area is on a code cycle prior to 2008.
Yup. That's the "some cases" I was talking about.
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Old 05-23-2009, 10:38 PM   #8
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yea agreed. you got it spot on...

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Old 05-24-2009, 12:55 AM   #9
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Sub Panel Grounding bar


It's not to be taken lightly. (separation of ground and neutral conductors in subpanel)! I've seen subpanels where the ground and neutral conductors were not separated, especially on non-linear loads, like computers and electronic copiers that the panel and breakers were hot to the touch and there was vibration, like a hum or buzzzzzzzzzzz...!
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Old 05-24-2009, 08:30 AM   #10
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It's not to be taken lightly. (separation of ground and neutral conductors in subpanel)!
Spark, did you even read any of the other replies? Are you familiar with NEC 250.32(B)?



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I've seen subpanels where the ground and neutral conductors were not separated, especially on non-linear loads, like computers and electronic copiers that the panel and breakers were hot to the touch and there was vibration, like a hum or buzzzzzzzzzzz...!
I for one sure would like an explanation of how this has anything to do with having the ground and neutral on the same bar in cases where the neutral is also used as the grounding conductor.
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Old 05-24-2009, 08:50 AM   #11
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Sub Panel Grounding bar


I can only offer what I have read about this subject. I have read that the ground and neutral can only be bonded at the main panel and nowhere else. I have also read differing views on grounding a subpanel. What I have read is that if the conduit is all metal (continuous grounding path or a separate ground wire is run from the main panel to the subpanel ground bar, then that is acceptable. Also, a separate grounding electrode for the subpanel is acceptable. In no instance, however, are the neutral and ground ever bonded together except at the main panel.

If this is incorrect, I am sure someone will point it out. A quick search of the Internet revealed this interesting document concerning grounding a subpanel.

http://www.co.shasta.ca.us/Departmen...Structures.pdf
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Old 05-24-2009, 11:29 AM   #12
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Well, some is true, some is hearsay, some is a vague generalization. I'll admit, this is typical information you might find on the interweb.


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Originally Posted by Bigplanz View Post
I can only offer what I have read about this subject.
The NEC (or local codes) are the ONLY reading that really matter.


Quote:
Originally Posted by Bigplanz View Post
I have read that the ground and neutral can only be bonded at the main panel and nowhere else.
Not true.


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Originally Posted by Bigplanz View Post
I have also read differing views on grounding a subpanel. What I have read is that if the conduit is all metal (continuous grounding path or a separate ground wire is run from the main panel to the subpanel ground bar, then that is acceptable.
Yes, a metallic conduit system is an acceptable grounding conductor.


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Also, a separate grounding electrode for the subpanel is acceptable.
A grounding electrode is NOT at all related to the equipment ground run with a feeder or branch circuit. A grounding electrode will NEVER replace or substitute an equipment ground.
However, a grounding electrode is ALWAYS required for a detached structure with a feeder and sub-panel, but it serves a very different purpose than the equipment ground. Confusing as that is.


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Originally Posted by Bigplanz View Post
In no instance, however, are the neutral and ground ever bonded together except at the main panel.
Wrong. See NEC 250.32(B) as referenced above.

Here, I will give you the section. Keep in mind, this is from the 2008 NEC. Prior to this there was no "exception" to (B) below. It was expressly allowed in prior versions. This was changed in 2008 and made into the exception you see below.

250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).

(B) Grounded Systems.

For a grounded system at the separate building or structure, an equipment grounding conductor as described in 250.118 shall be run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).


Exception: For existing premises wiring systems only, the grounded conductor run with the supply to the building or structure shall be permitted to be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded where all the requirements of (1), (2), and (3) are met:

(1) An equipment grounding conductor is not run with the supply to the building or structure.
(2) There are no continuous metallic paths bonded to the grounding system in each building or structure involved.
(3) Ground-fault protection of equipment has not been installed on the supply side of the feeder(s).



For clarity, the grounded conductor is the neutral and the grounding conductor is the equipment ground.
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Old 05-24-2009, 03:07 PM   #13
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Sub Panel Grounding bar


Quote:
Originally Posted by Speedy Petey View Post
Well, some is true, some is hearsay, some is a vague generalization. I'll admit, this is typical information you might find on the interweb.


The NEC (or local codes) are the ONLY reading that really matter.


Not true.


Yes, a metallic conduit system is an acceptable grounding conductor.


A grounding electrode is NOT at all related to the equipment ground run with a feeder or branch circuit. A grounding electrode will NEVER replace or substitute an equipment ground.
However, a grounding electrode is ALWAYS required for a detached structure with a feeder and sub-panel, but it serves a very different purpose than the equipment ground. Confusing as that is.


Wrong. See NEC 250.32(B) as referenced above.

Here, I will give you the section. Keep in mind, this is from the 2008 NEC. Prior to this there was no "exception" to (B) below. It was expressly allowed in prior versions. This was changed in 2008 and made into the exception you see below.

250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).

(B) Grounded Systems.

For a grounded system at the separate building or structure, an equipment grounding conductor as described in 250.118 shall be run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).


Exception: For existing premises wiring systems only, the grounded conductor run with the supply to the building or structure shall be permitted to be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded where all the requirements of (1), (2), and (3) are met:

(1) An equipment grounding conductor is not run with the supply to the building or structure.
(2) There are no continuous metallic paths bonded to the grounding system in each building or structure involved.
(3) Ground-fault protection of equipment has not been installed on the supply side of the feeder(s).



For clarity, the grounded conductor is the neutral and the grounding conductor is the equipment ground.
Thanks again for your detailed answer. To make things even more confusing, local jurisdictions have their own 'home rules' that may not be in the NEC at all. Louisville, I am discovering, has several such local rules. I suppose the requirements from Shasta, CA are also their 'local rules.'

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