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I have an outdoor outlet about 60' from my house. It is properly wired using an underground cable with ground. It is in a plastic box with plastic conduit protecting the stub-up. Recently a tree near by it was hit by lightning and one of the paths to ground was back into the house, which did a lot of damage. I have since replaced the ground fault outlet, which was destroyed by the lightning.

My question is whether it would be beneficial or not to drive a grounding rod at the outlet and tie the outlet to both the ground wire from the house and the local ground rod.

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  • Is moving the GFCI to the house from this remote outlet location an option?
    – ThreePhaseEel
    Jul 14, 2019 at 0:03
  • The wire now goes directly into a circuit breaker in the house panel. Are you suggesting placing a GFCI box inside the house before the panel? If yes, what is the benefit?
    – Frank
    Jul 14, 2019 at 0:12
  • The benefit is not having the GFCI in a place where it's exposed to a big ol' ground potential rise from the strike -- what make and model is that panel, and is the breaker in question a full-width breaker or a half-width/tandem (2 handles on the same breaker space)/double-stuff breaker?
    – ThreePhaseEel
    Jul 14, 2019 at 0:21
  • It is a GE Cat No. TLM202C. I don't see a model number. The circuit is a full width, 15A, which tripped from the strike.
    – Frank
    Jul 14, 2019 at 0:29
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    Next time use Rigid conduit last 10 feet and stub-up. Pricey, but comes with a free ground rod lol...
    – Harper - Reinstate Monica
    Jul 14, 2019 at 2:03

1 Answer 1

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Is it practical? I guess the question is, "does lightning strike twice?"

One problem is with near misses. Lightning has so much voltage at biblical amperage, that it creates a voltage gradient across the ground. Earth at your remote outlet could be 20,000 volts hotter than your house. This is what kills animals; the voltage on their front feet is different enough than their back feet that a lethal current can flow through their chest.

Without a ground rod, you hope the PVC and THWN insulation is strong enough to survive a 20,000V differential. With a ground rod, you remove all doubt - you are grounding both ends of the ground wire. That means the ground wire will be participating in this voltage gradient (helping to arrest it also). This has the risk of burning out the ground wire and having this voltage arc internally to the hot and neutral.

So lightning is such a slippery customer that it's hard for me to call it "definitely good". There are outlier conditions in which it could make things worse, as I described. But it's the way to bet IMO.

Of course, since it's not a mandatory ground rod, it doesn't need to meet standards for mandatory ground rods like the 25 ohm impedance test.

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