Sub-panel Neutral and Ground

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#1

Originally Posted By: sbelanger
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OK you electrical guys, I know that the neutral should not be grounded in a sub-panel. Can anyone tell me why or what the difference is since they are mechanically bonded in the main panel? Thanks.

#2

Originally Posted By: bking
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120v current flows on neutrals. If the neutral is bonded to ground in the sub panel, the current can travel on the grounds to many places, especially during abnormal conditions like a loose neutral connection.


If you had 2 problems present it would be very likely that a metal cabinet or box could become energized.

#3

Originally Posted By: rcooke
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sbelanger wrote:
OK you electrical guys, I know that the neutral should not be grounded in a sub-panel. Can anyone tell me why or what the difference is since they are mechanically bonded in the main panel? Thanks.

The neutral carries the unbalanced portion of the load .
Example why the neutral should not be grounded at a pony panel .
Lets say the sub panel is in the horse barn and the neutral is conected to the ground at the sub panel .
Electricity is going to take the easiest rout home .
Part of the load could travel in the earth .
There has been cases where horses that obviously very sensitve to some things would not go into some areas because of what they could feel .
In one case they refused to go to a water trough that they had used for years.
This was after some new electrical work had been done in the barn .
They shut of the power and now the horses would again walk through the area that they had refused a few minutes ago.
It took some very sensitive equipment to discover why .
I am going from memory of many years ago but have heard of many similar happenings .

In Canada the neutral and ground are only joined at the primary panel .

Every thing down stream is isolated from each other.

You must carry a separate neutral and ground through the whole system .

Roy sr
#4

Originally Posted By: ddelaney
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I believe the main reasoning for this in the NEC is due to potential difference. Subpanels cannot be regrounded, due to the initial point of service being the main grounding point. If the grounded conductor (white-neutral) is not isolated downstream, the potential difference of the grounded conductor is the same as the grounding conductor.


That is just way to much jargon!!! Just don't let it happen.....LOL

#5

Originally Posted By: pabernathy
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ok…here is a link to a nice summary of detached garages and so on I though you all might fine helpful.


http://www.selfhelpandmore.com/homewiringusa/2002/accessory/detgarage/index.htm


Enjoy !

--
Paul W. Abernathy- NACHI Certified
Electrical Service Specialists
Licensed Master Electrician
Electrical Contractor
President of NACHI Central Virginia Chapter
NEC Instructor
Moderator @ Doityourself.com
Visit our website- www.electrical-ess.com

#6

Originally Posted By: djames2
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Thanks Paul, all NACHI sparky are the greatest