Do you have any idea how much resistance is typically at the transformer XO? If the GEC ties to an earth electrode at 25 ohms—the max allowed by NEC—what would be usually seen at the transformer ?
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We have to speak in terms of relativity.
Resistance between what points?
If you’re asking X0 to X1/2/3 then it’ll be transformer windings.
If it’s X0 to service grounded point then it would be the value of the cable.
If you wanted to know X0 to ungrounded conductors, you’d have to lift the connections at X1/2/3 then measure.
And I think that 25 ohm value is only applicable when using just 1 rod. If you can’t prove 25 or less you use 2 rods and to my knowledge there’s no further confirmation required.
Also, those testers are not cheap so I think most just drive 2 rods and be done. There was a thread recently talking about that.
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