Electricians: can neutral be anything but white?

LD1 · Jul 20, 2015

Thanks for taking the time to do a test.

Now you understand why there is no danger of over-current on the neutral. Now if you were to switch the hot leads around so they were pulling from the same phase (line), then you would see 1.0A on a shared neutral and that wouldnt be good.

COASTBUSTER · Jul 20, 2015

Do you have 3 phase power available? Most commercial shops do. In that case you can run 3 hots with a neutral and use the pipe for the bonding conductor. Also in my 38 years of doing elec. installs,the most common type of conduit is the 3/4" emt. Then using 3 hots and a neutral ,there is no derating factor. Use 1 -3/4 for 3 circuits. Clean and neat installation. Use a 3 pole - 20 amp tie handle breaker with #12 thhn copper wire. Normal colors for a 3 phase wye configuration system is Blue-Black-Red-White. 1/2" conduit is normally used for 1 circuit or many low voltage applications. Depending on the # of bends it is hard to pull wires through and any considerable distance. Use 3/4"

buickanddeere · Jul 20, 2015

1/2 pipe or conduit can be bent in a 3/4 bender for a larger radius. I never used the 1/2 GreenLee unless a tight radius was required for clearance.

Fawken · Jul 20, 2015

We have 3 phase at the trailer shop, but we also have plenty of copper wire. Thanks for the tip though. On another note I just got home from re-wiring a National Guard trailer and now I need to go help my son. So, I suppose the noise test can wait til manana. I'm going to use a clean, 9v DC power supply and watch for induced noise on the flat line of the DC signal. Doing it that way because one poster suggested the noise would be canceled out by such a typical DC source.

Fawken · Jul 22, 2015

Here is the noise test as promised: Used a 9v DC power supply to monitor the flat line signal looking for spikes and anomalies. The other appliance is an old craftsman hammer drill running in reverse.

Here is the layout showing a clean signal without the drill on any circuit:

Here is the signal with drill running on another circuit from same breaker box:

Here is with the drill in the shared neutral circuit at start up:

Here is the Display with the drill just running (shared neutral:

Conclusion: There seems to be significantly more noise induced onto the other leg of a shared neutral circuit when a noisy appliance is paired with a DC output device.