Old 3-wire Feed to Garage in Rigid Metallic Conduit?

[Bbradyc5]

Switching out an old glass fuse sub panel in a garage that has a 3 wire feed from the house via underground metallic conduit. The new sub panel is directly attached to the conduit but the conduit at the house terminates into an old junction box right near the service entrance. Can this conduit be used as the ground by bonding a jumper between the conduit and the main breaker panel (i.e. In essence creating a 4 wire feed to the sub panel)? Or will the original 3 wire feed be "grandfathered" and as long as sub panel has grounding electrode (new ground rod) and neutrals isolated it should be accpetable to inspector? I always see mention of where "no metallic path exists between the two structures" but in this scenario I believe the underground conduit would be in conflict with this clause. I've yet to see what the requirement is when this condition exists.

 

[Little Bill]

I am closing this thread, in accordance with the Forum Rules.

This site is designed for:

• Contractors
• Electricians
• Engineers
• Inspectors
• Instructors
• Other electrically related individuals

* This NEC Forum is for those in the electrical and related industries. Questions of a "How-To" nature by persons not involved in the electrical industry will be removed without notice.

If you feel this action to be in error, feel free to contact me via PM to explain.

A reminder to all members, if you see a questionable post, feel free to report it by clicking the

button at the bottom left corner of the post.