Copper can oxidize as well.
If you're this concerned about the quality of a ground-fault path, install 3 or 4 methods. No skin off my nose, and you'll out-price yourself for any job you bid on.
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Copper can oxidize as well.
If you're this concerned about the quality of a ground-fault path, install 3 or 4 methods. No skin off my nose, and you'll out-price yourself for any job you bid on.
mbrooke
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Correct, copper can oxide. However, I see a splice or screw termination as a cold weld whereby the electrical to electrical (R1+R2+R3+R4) contact surface area is protected from oxidation or corrosion. Conduit on the other hand is subject to expansion and contraction whereby its movement within fittings repeatedly breaks any original metal to metal compression such that two long term oxidized surfaces can make contact.
IMHO, conduit expansion and contraction, along with the use of expansion joints is under emphasized.
IMO, the quality of the ground fault loop is thee most essential part of any electrical system.
mbrooke
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That would work.
Don't forget to use PVC-coated rigid. Wrap every raceway with fiberglass, then slop on some roofing tar, then add spray foam, and top it off with rubber tape.
mbrooke
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Don't see the added benefit :/
That will make it hermetically sealed. So,.... no corrosion.
mbrooke
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I would not be worried about that if say threaded GRC was used. The threads prevent pulling in and out. The surface an oxidize, but in theory the threads are locked solid.
Natfuelbilll
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We need to consider that there is a parallel path - one is the low impedance copper path and the other is the higher impedance steel path - both paths in parallel. The low impedance path will initially carry more destructive current, adding to its weakening and until the time the of its failure.
mbrooke
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The breaker should open before the low impedance path weakens, which requires current to do so.
Natfuelbilll
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Other than physically inspecting EACH metal raceway connection does anyone know of any other means to inspect raceway built EGC?
Natfuelbilll
Senior Member
Key word "should"
mbrooke
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Of course, which is why you have to make sure the loop impedance is low enough.
kwired
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I would think if you pass a fixed current through it and check temperature at each fitting, any fittings hotter than the others are the ones that need attention. That may not always be simple or practical though.
mbrooke
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kwired
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I see a locknut that wasn't tight enough.
Can have similar failure if you have someone trying to put several green conductors into a wire nut and one isn't really in there that good.
Schtuff happens.
mbrooke
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Right, but how do we know this didn't get loose over time? Plus how do you even tighten that locknut correctly?
kwired
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Screwdriver and 3 pound hammer
Natfuelbilll
Senior Member
How about 30 or 40 years?
I don’t have it but what does NFPA 70B say about grounding maintenance?
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