Electronics > Beginners
How is Neutral Wire Neutral in Mains Electricity?
Monkeh:
--- Quote from: IDEngineer on January 20, 2020, 09:31:45 pm ---
--- Quote from: Monkeh on January 20, 2020, 06:44:02 pm ---Did you verify the loop impedance of your earth rod?
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Do you think the Inspectors measure the loop impedance? Do you think the Inspectors even understand the concept of loop impedance? I can guarantee you this one didn't, and none of the others I've worked with over the years did either. Some of them have been very good and very well informed, but the heart of their knowledge is the code - not pure electrical theory.
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I.. don't care if they do or not, they didn't install the system, and they're not the ones responsible for it..
--- Quote ---Think about how power wiring works. In the original house, a three wire connection came into the panel (two phases and neutral). The earth reference came from a copper rod in the ground next to the house, which is bonded to neutral at the breaker panel.
What I did for his standalone garage was EXACTLY the same thing. We brought a three wire connection into the panel (two phases and neutral) and the earth reference came from a copper rod in the ground next to the garage, bonded to neutral at the breaker panel.
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Ah, I see how the edit has changed the story.
You took it upon yourself to run a CNE to an outbuilding from an installation where it's already been split, and then split it again.. Now I don't know your regs, but things are done in specific ways for good reasons, and you thought you'd just figure it out for yourself.
--- Quote ---Breaker operation is not affected by the earth reference. Even the most recent AFCI/GFCI breakers do not have a connection to earth - only to neutral. And while neutral is bonded to the earth reference at the panel, that is outside the circuit being monitored by the breaker.
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If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.
IDEngineer:
--- Quote from: Monkeh on January 20, 2020, 09:38:33 pm ---If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.
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Why would a similar rod, at the other end of 100 feet of copper wire, be an improvement over a much closer rod at the end of a much shorter run of wire? That's what you're advocating. This is not an academic question, I sincerely want to know why introducing 100 feet of copper wire is safer or better.
As you prepare your response, remember that same "much closer rod at the end of a much shorter wire" was deemed good enough for the first building. If a neighbor built a new house next door, perhaps even closer than this garage, they'd do exactly the same thing as we did in the garage. Why does electricity behave differently just because it's on a different side of a human-created property line?
IDEngineer:
--- Quote from: Monkeh on January 20, 2020, 09:38:33 pm ---If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.
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Actually, not. Again, breakers do not work from an earth reference. See my added discussion of the three types of breakers above. For your example of a "fault to earth", you'll have either 1) excessive current (in which case the overcurrent aspect of all breakers will trip) or 2) imbalanced current, the exact situation a GFCI is meant to detect and defeat. And by the way, that's an excellent example of why GFCI's are a good idea (because a traditional breaker will not detect all such "fault to earth" conditions).
None of the breakers are affected by the system's earth reference. If you doubt that, ask yourself if the breakers would operate correctly if the fault occurred with a two-wire appliance, or one where the user had cut off the ground lug on its cord. The answer is yes, all breaker types would still correctly detect their fault conditions and operate properly.
Monkeh:
--- Quote from: IDEngineer on January 20, 2020, 09:54:11 pm ---
--- Quote from: Monkeh on January 20, 2020, 09:38:33 pm ---If you have a fault to earth and your only earth connection to the source (as you were unclear in your post) is a rod.. yes, it's very much affected by how good that rod is.
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For your example of a "fault to earth", you'll have either 1) excessive current (in which case the overcurrent aspect of all breakers will trip)
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And if the impedance of your earth rod is too high for excessive current to flow...
Again, you initially did not mention connecting the neutral to your local rod - creating a TT system in which your earth is extremely poor.
IDEngineer:
--- Quote from: Monkeh on January 20, 2020, 09:59:06 pm ---And if the impedance of your earth rod is too high for excessive current to flow...
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...then 1) you're not getting the protection you expect from your earth ground system, which is its own separate problem; and 2) if an imbalanced current is flowing, then it's finding a separate path which is the exact situation a GFCI is intended to detect, so you are still being protected. Again, consider the case of a two-wire appliance with no earth reference at all.
--- Quote ---Again, you initially did not mention connecting the neutral to your local rod
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Neutral and earth are supposed to be bonded in the panel. That's what existed in the original structure. That's what a neighbor would do if they built ten feet away (five foot setbacks on either side of the property line). That's what we did for the garage, too, which was more than ten feet away.
I'm still waiting to hear how a more distant earth reference is somehow better and safer.
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