sub panel, two ground paths?

lostmotionOctober 1, 2013


I have a sub in an out bldg. The neutral/ground bonding screw was removed with a dedicated grounding strip screwed to the cabinet and cabled to a copper earth stake. My cheapest and safest choice for a 50A service cable was 2-4 Al "mobile home cable." I could not buy 2-3 cable so I had a grounding conductor (green stripe) that I thought was not necessary. Untwisting that strand to get rid of it for over 80' of cable was not an attractive option.

A guy I worked with has a son who is a journeyman electrician so I tapped his brain. He said it is now considered okay to connect the grounding cable between the main breaker and sub cabinets as long as the sub has an earth ground, so that's what I did.

Everything I seen on the subject though forbids a grounding cable between a main and sub. Is there a revision on this?

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It might help to take a look at this URL

You can't bond the neutral bus to the box like you do in a main panel, but its okay to have a ground wire connecting the ground bus on the main to the ground bus on the sub panel. However, the sub-panel in a separate building must also have its own separate grounding rods. The key point is the separation of neutral and ground at the sub panel, and the only place they are connected is at the main panel.


    Bookmark   October 1, 2013 at 8:00PM
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Bruce, That is exactly how I have it wired. Thanks for the confirmation that I have done it right.

    Bookmark   October 1, 2013 at 8:31PM
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"Everything I seen on the subject though forbids a grounding cable between a main and sub. Is there a revision on this? "

Amazing! Then everything you've seen is VERY wrong.
It was NEVER forbidden to run an equipment ground to a sub-panel, and in most cases it is/was required. This goes back as far I have ever known.

Just where are you getting your information from???

In fact, the way you wanted to do it was definitely wrong. A ground rod is NOT a substitute for an equipment grounding conductor. They are two VERY different things.

    Bookmark   October 1, 2013 at 9:00PM
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