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I was working on the wiring in an outlet of a home from the mid 1950s. This kitchen outlet connects a switch to the garbage disposal. I connected the live wire from the circuit breaker directly to the wire leading to the appliance and then had the circuit breaker switched back on. At that instant, the wires physically moved a noticeable amount. I repeated this, and the result was the same.

What explanation can there be for the wires moving when the power at the breaker was applied? (Because of how the wires are routed, I don't think the disposal torque pulled the wires, but I could be wrong.)

While I am an electrical engineer, and can sort out connections fairly easily, this has me concerned.

  • ever hear of eddy currents? Many recycling facilities say "throw it all in one bin and let us separate it at our facility" ... look at how they separate non-ferrous metals. That's the effect at work. That's also why Code requires currents be equal in every cable or conduit (i.e. neutrals return alongside their hots), and why current should never travel in a circle around anything (unless it's laminated). – Harper Jul 17 '18 at 5:32
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Is the disposal starting? If the disposal is stuck it could be drawing locked rotor current many times the circuit breaker rating causing the wires to jump even if it is starting a motor normally draws 3-5× its FLA or full load amperage for a fully functional motor. This combined with possibly a longer than normal length distance to the first staple it could be somewhat normal. If you hacer ever watch welding leads jump my big welder when on high the leads may jump a couple of inches with a heavy or thick rod. To further explain your home circuit breakers are inverse time they will hold 10x there rating for a very short time 150 -200 amps in that 14 or 12 awg wire will cause to jump. Hope this helps.

  • Yes, it starts and runs smoothly. I'm just skittish about this old house and its wiring. – Jim Jul 16 '18 at 22:16
  • Cloth braid? Cloth has less resistance to movement than today's NMB thermo plastic with 3 wires. Since you have a breaker panel the only thing that would concern me would be if it is a federal Pacific (FPE) stablock panel, I know of some problems with zinsco I installed one in my moms house in the 70's. And it is fine but I have seen others that had buss damage. – Ed Beal Jul 16 '18 at 22:19
  • It's plastic insulation. I can only see the individual wires, though. I am guessing that individual wires were pulled through metal conduit on this house, but I couldn't be sure. – Jim Jul 16 '18 at 22:22
  • I don't think I would not be two worried with much more modern wiring and a newer panel breakers did not become a standard until later but I am not sure of When they were required and that would depend on your state and when they adopted the NEC national electric code. – Ed Beal Jul 16 '18 at 22:28

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