Remote subpanel wiring

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  #1  
Old 07-31-13, 08:48 PM
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Remote subpanel wiring

What can happen if ground and neutral are connected in remote subpanel?
 
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Old 08-01-13, 12:07 AM
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If neutral and equipment ground is bonded in the sub-panel then neutral currents back to the service (main) panel will divide and travel on BOTH the neutral and equipment ground conductors. This would mean that ANY metallic path connected to the earth (any metallic plumbing) including the metallic cases of appliances with a grounding conductor could become energized.
 
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Old 08-01-13, 02:12 AM
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A friend asked me to take a look at the wiring in his shop that he is remodeling. The subpanel in the shop is fed by a 3 conductor cable (2 hots and a neutral, no ground) approx 75 ft from breaker next to meter loop. The grounds on the romex wires at the subpanel were connected to the neutral bar that was isolated from the subpanel box, so the box itself was not grounded. He drove an 8 ft ground rod and ran a #6 copper wire from ground rod to subpanel and we connected ground to neutral bar and bonded bar to subpanel box. Should i go back and isolate the neutrals from the ground?
 
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Old 08-01-13, 05:10 AM
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Once upon a time a three wire feed was permitted if there were no other metallic pathways such as plumbing or phone line. That is no longer true. A GEC (Grounding Electrode Conductor) can not be substituted for the now always required EGC (Equipment Grounding Conductor). Assuming the neutral is insulated best course of action is to add an EGC to the building. It does not need to be in the same raceway. A ground bar should be added to the panel and the new EGC, GEC, and all B/C grounds connected there. The neutral should be isolated.

Assumes a detached building. Above suggestions only. It is probably grandfathered and okay.
 

Last edited by ray2047; 08-01-13 at 05:48 AM.
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Old 08-01-13, 05:22 AM
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As this is an existing installation, it would be grandfathered in to the code requirements at the time.
The installation is fine as is and you can leave it as it does not pose the issues that Furd mentioned with the 3 wire feeder.

If you/he wishes to being it up to current code, then install the EGC and isolate the grounds and neutrals.
 
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Old 08-01-13, 05:51 AM
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Thanks guys, I was just wanting to make sure there was not a safety hazard.
 
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