I searched and didn't find a similar thread. I don't intend to duplicate.
I'm wiring a 220v 3ph lathe, and would like to wire in a 110v machine light without stretching any copper not needed.
Is it correct that I should be able to connect 1leg of the 110v light to one leg of the 220v wires, after I ensure that it is not the leg off the RPC?
However, the second leg would require additional copper wired normally to the panel, because wiring to the ground seems like a bad idea.
Is this accurate?
Are there better/different/safer options?
Thanks,
Daryl
MN[/QUOTE
With "real" 3 phase power the voltage usually is 208 Volts rather than 220 Volts, but often it is called 220, and the difference is trivial. In that case the voltage measured between any two of the three hot wires will be 208 Volts, and the voltage from any hot wire to ground or common in a 5 wire system, will measure 120 Volts (maybe 117). Both the ground and common (neutral) wires are attached together and to a metal rod driven into the earth at the breaker panel where power comes into the building so they are electrically the same thing. Due to resistance in any wire, if there is a current flowing in the wire, there will be a voltage produced due to Ohms law V = I*R, and ideally any wire carrying a current should be attached to the common (also called neutral) wire which then may have a small voltage above ground due to the current and resistance. In an ideal world, the ground wire will not have any current flowing in it, and therefore will not have a voltage difference measured to the earth ground. Pulling a small current from a lamp will have negligible effect on this.
The lamp therefore can be wired between any one of the three hot wires on the RPC and neutral or ground and should work just fine.