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I am doing a service upgrade from 100 to 400A. I recently passed the mandrel inspection for the conduit. The power company, PG&E, now wants a meter release from the city. I met with the city Inspector and he said he'll happily do the meter release when I ground the new meter, either with the UFER if my house is new enough to have it, or with the two ground rods.

This is my old (but at this time, what provides power to the house) meter/main combo: Old panel

The ground conductor goes to the UFER I have found inside the garage wall: UFER

This is the new meter/main combo: New panel

By looking at the meter/panel, it appears to me that the ground conductor might have to be pretty big; what size should I reasonably use by the most recent N.E.C. code?

Also, after I have determined the ground conductor size, I will probably enter from the back of the new meter panel; should I just use one of the available knock-outs and install a nipple that allows it to go through the stucco and into the wall???

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    What size is the existing grounding electrode conductor?
    – ThreePhaseEel
    Commented Aug 27, 2023 at 2:50
  • I could try to measure it with a caliper... but in what will that answer my question? It was installed in the 70s. From the pictures, 4 AWG maybe?
    – Alessio Sangalli
    Commented Aug 27, 2023 at 21:01
  • Sizing the existing wire will tell us if it complies with Code for a CEE as-is (which it likely will)
    – ThreePhaseEel
    Commented Aug 28, 2023 at 1:21
  • The current wire is 0.16in in diameter which should correspond to 6AWG. However it is connected "doubled-up" (see photo) meaning two runs of such wire go to the old panel, making it better than a 3 AWG.
    – Alessio Sangalli
    Commented Aug 28, 2023 at 4:55
  • Do you know the route the grounding electrode conductor takes to exit the top of the existing meter-main?
    – ThreePhaseEel
    Commented Aug 29, 2023 at 2:28

1 Answer 1

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As confirmed by the inspector, and according to NEC 250.66(B) The answer is 4AWG wire.

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  • Yeah, the whole "paralleled GEC" situation you had is something the Codes don't account for, but in my research it seemed to be something folks frowned upon all the same
    – ThreePhaseEel
    Commented Aug 31, 2023 at 3:10

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