Eddy currents

[MiElectrician]

I was pulling 6 circuits into a pipe today. One from leg 1, 3 from leg 2 and, 2 from leg 3. All 120v receptacle with their own neutrals. I thought they were supposed to be evenly spread between the legs to prevent eddy currents and asked my foreman about it. He had never heard of eddy currents. I found 300.20 but it looks like you just have to have the neutral in with the hot.
My question is, can I run a pipe full of circuits off leg 1 like 2, 8, 14 and also is eddy currents in the nec and where can I find more info.

Thanks all

Mi electrician

 

[gadfly56]

I was pulling 6 circuits into a pipe today. One from leg 1, 3 from leg 2 and, 2 from leg 3. All 120v receptacle with their own neutrals. I thought they were supposed to be evenly spread between the legs to prevent eddy currents and asked my foreman about it. He had never heard of eddy currents. I found 300.20 but it looks like you just have to have the neutral in with the hot.
My question is, can I run a pipe full of circuits off leg 1 like 2, 8, 14 and also is eddy currents in the nec and where can I find more info.

Thanks all

Mi electrician

1. Yes
2. Google is your friend. You won't find a detailed technical discussion of eddy currents in the NEC, although there might be some in the various handbooks.

 

[GoldDigger]

One place where conductor separation is mentioned in the NEC is the requirement that all current carrying conductors of a circuit must pass through the same hole in a ferrous metal enclosure.
The problem in this case is NOT eddy currents but rather the magnetic field itself causing hysteresis heating.
The rule states that you either use a non-ferro-magnetic plate (aluminum, brass, hard plastic, etc.) to support the raceway penetrations or you cut slots between the individual holes, in effect making them one large but funny shaped hole.

Eddy currents are the electrical currents induced into any conductive material, not just ferromagnetic, by the changing net magnetic field of the wires involved linking with a loop of conductive material. This can cause resistive heating.

To limit stray magnetic fields which may induce voltages (noise) into other conductors the NEC requires that all phases and the neutral, if any, of the same circuit must occupy a single raceway except in the case of non-metallic underground ducts.
For parallel conductors the same restriction applies. You can have two parallel sets of wires in two parallel raceways as long as each raceway has all phases and each raceway holds the same number of parallel sets.