Flat spots on wires

[JEuriech]

Would the flat spots (indentations) on the neutral wires where they were previously tightened, be an area of concern?

Thank,

Jeff Euriech

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[mjr6550]

Yes. The wires will probably carry current ok, but they are weakened and could break if disturbed. The fix is simple.

[Jim Katen]

Yes. An electrician should clean up that mess.

[rjbrown2]

Actually when you cold work soft copper, you raise its tensile strength but lower its ductility. The problem it would face is vibration or frequent handling over some period could further work the interface between the soft and hardened sections leading to a brittle failure there. This seems low probability in a residential situation. An electrical question is that the skin depth of the current for 60Hz is significant. Reducing the cross section of the wire does what in near capacity conducting situations ? Seems like a hot spot is possible. Bare wire in an open area, OK ? Electrical experts please ?

[Marc]

Actually when you cold work soft copper, you raise its tensile strength but lower its ductility. The problem it would face is vibration or frequent handling over some period could further work the interface between the soft and hardened sections leading to a brittle failure there. This seems low probability in a residential situation. An electrical question is that the skin depth of the current for 60Hz is significant. Reducing the cross section of the wire does what in near capacity conducting situations ? Seems like a hot spot is possible. Bare wire in an open area, OK ? Electrical experts please ?

Skin effects are a consideration in some application involving frequencies in the megahertz range. At 60 hertz, it's negligible. Ordinary conductor resistance is a far greater factor.

What Jim K said.

Marc

[rjbrown2]

Marc:

I said it clumsy. Since the skin depth is almost total at 60 Hz (current flows across the whole cross section) that means that conductor resistance is dominant like you said. The resistance of the squashed area is proportionally higher than the wire gauge. Is there (a) NEC citation(s) that back up the need to do anything ?

It looks like ©rap, but absent a 'violation' what ? How do we justify it ?

[Jim Katen]

110.12

[rjbrown2]

Thanks