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#8623 - 03/30/02 11:22 AM ground or ground not  
doc  Offline
Member
Joined: Nov 2000
Posts: 119
Texas
this has been gone over a gazillion times I know,but please one more time
A building that is not connected to house no water lines,no phone,nothing connecting it to home
What is the proper way to wire it if there is a sub panel and you run 2 hots a neutral and a ground
would you use another ground rod at building would you tie the neutral and ground on same bar
same set up only no ground wire run to building
would ground rod be installed and would the ground from rod and neutral be placed on same bus or split
What I am trying to understand is an easy way to explain when and when not to use a ground rod and when and when not to keep grounded condutors and grounds apart in the sub panel


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#8624 - 03/30/02 11:35 AM Re: ground or ground not  
GlennH  Offline
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Joined: Nov 2001
Posts: 40
pa.


#8625 - 03/30/02 05:56 PM Re: ground or ground not  
sparky  Offline
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Joined: Oct 2000
Posts: 5,308
Yup, Warren's da man....

2) Grounded Conductor. Where (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 both buildings or structures involved, and (3) ground-fault protection of equipment has not been installed on the common ac service, the grounded circuit conductor run with the supply to the building or structure shall 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. The size of the grounded conductor shall not be smaller than the larger of
(1) That required by 220.22
(2) That required by 250.122

commentary........
Similar to the provisions of 250.30(A)(2), 250.32(B)(2) also eliminates the creation of parallel paths for normal neutral current on grounding conductors, metal raceways, metal piping, and other metal structures. In previous editions of the Code, the grounding electrode conductor and equipment grounding conductors were permitted to be connected to the grounded conductor at a separate building or structure. This multiple-location grounding arrangement could provide parallel paths for neutral current along the electrical system and along other continuous metallic piping and mechanical systems as well. Connection of the grounded conductor to a grounding electrode system at a separate building or structure is permitted only if these parallel paths are not created and if there is no common ground-fault protection of equipment provided at the service where the feeder or branch circuit originates.


Of course any theory here falls into the twilight zone when the POCO does this....
(another lash to the decomposing equestrian..)
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#8626 - 03/31/02 10:16 AM Re: ground or ground not  
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
If you're installing a sub-panel in a detached building, you will always need at least one and probably two ground rods.

The cost of an equipment ground conductor is very small. Unless you're into some really cut-throat low bid situation, just run a 4 wire feed & then the installation will be compliant in the future if someone else runs a metal pipe, etc out to the building.


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#8627 - 04/01/02 08:25 AM Re: ground or ground not  
Redsy  Offline
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Joined: Mar 2001
Posts: 2,056
Bucks County PA
OK, another thread probably, but---
We know that a Grounding Electrode System is required to be established at separate buildings that are supplied by more than one branch ckt.
The question is what purpose does the Grounding Electrode serve if a EGC is run with the feeder/branch ckt conductors?


#8628 - 04/01/02 09:48 AM Re: ground or ground not  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
The grounding electrode limits the potential difference between the grounding conductor and the earth.

The earth's "Voltage" can vary from place to place because of the chemical makeup of the earth in that given spot.

I'm no expert, but this is the way I understand it.

Without the grounding electrode, there could be a potential difference between the equipment metal case and the earth one is standing on.

Sorry, bad grammer, ...upon which one is standing, rather.


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