0

I have a junction box in the garage that has cables with 12-2 with ground. However, the ground wires were clipped back to the sheathing.

Background: This is an older house with a fair amount of old cabling. As we’ve done projects and replaced fixtures, I’ve updated the cabling and in many cases also fixing circuits that didn’t have a ground.

With that said, why would the ground be cut back? Was this ever standard practice in certain cases? Is there ever a time nowadays that someone would do this?

Thanks in advance.

Improve this question
2
  • if there is gound at the other end of the cable then cutting off the ground would prevent it from mistakenly being used as a ground.
    – Jasen
    Aug 16, 2020 at 3:51
  • @ Jason could you verify I think you meant no ground. I have seen this where 2 wire cloth or k&t was updated possibly diy and the installer cut the ground so the wiring had to be replaced. I think because the person replacing the cable did not understand they just cut the grounds I have seen this a couple of times and that is my best guess.
    – Ed Beal
    Aug 16, 2020 at 4:12

1 Answer 1

Reset to default
2

When you're extending old ungrounded circuits, Just randomly hooking up grounds higgledy-piggledy can create an interesting problem. I call it "Islanded grounds".

When a device has a ground fault, it's going to energize the ground wire. It's trying to return that ground fault to source (the panel and its N-G bond) so it can trip the breaker.

But imagine there is no ground wire back to source. If the ground wire just stops there, then it energizes the chassis of the machine.

But what if all the grounds in a circuit extension are connected to each other (but not the panel)? The "islanded" ground wire carries the ground fault around to all the other devices in the island. So now all their grounds are hazardous, even the cover plate screws on the light switch! That's the very opposite of a safety improvement!

So someone extending a non-grounded circuit might do just what you see. I'd prefer to coil it up and insulate it, myself, for the happy day the original wiring is replaced.

Improve this answer
11
  • This did make sense. So it’s best for the circuit to be all grounded and grounds connected together or if no panel grounding then don’t connect any of them?
    – Valerie
    Aug 16, 2020 at 5:44
  • 1
    @Valerie exactly, don't spread grounds if they're not connected back to the panel. Of course since 2014 they greatly liberalized the rules for retrofitting grounds, so it's a lot easier to get ungrounded places grounded now.
    – Harper - Reinstate Monica
    Aug 16, 2020 at 5:49
  • I’ll have look into that. This house’s electrical work has been frustrating to say the least, wrong gauge wires on 20A breakers, had an illegal tandem breaker, outlet grounds were jumped to neutrals. I’ll have to review my work to make sure I didn’t contribute to any island grounds. Thanks for your advice!
    – Valerie
    Aug 16, 2020 at 5:52
  • 1
    @Valerie -- if you do find an island, take a bare or green copper wire of the appropriate gauge and run it from anywhere on the ground island back to a properly grounded circuit with a same or thicker gauge ground wire, to the electrical panel that islanded circuit came from, or to the grounding electrode conductor (water pipe bond wire, ground rod wire) in your house, if the other two aren't practical (you may need a lay-in-type tap connector to attach to the last one)
    – ThreePhaseEel
    Aug 16, 2020 at 8:04
  • @ThreePhaseEel Thank you for the details that’s very helpful. My problem will be actually finding wiring in the attic (nearest accessible location) that has grounding. I have several (old and newer) cables labeled as having ground wires, but is there a multimeter test I can do to check that it makes it back to the panel. It’s such a mess up there with insulation, etc, not sure I can physically follow it.
    – Valerie
    Aug 16, 2020 at 14:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.