Originally Posted By: SecondMonkey
Oddly enough, the "220v" outlet reads 230v exactly...which should make each leg 115v, wouldn't it?
Not necessarily.
Picture a Y with equal length and spacing of the three "legs" of the Y.
Picture the center of this Y as grounded and connected to the neutral at the main service panel.
Let each one of these legs from the center out to its end represent one secondary winding of the power transformer(s) supplying this panel.
Now, Picture the voltage coming out of the transformer on each of these legs being 120 volts AC from the tip of the leg to the grounded center.
All these legs can have 120 volts to the center, but they are timed--or "phased"--so that the instantaneous voltage peak (either positive or negative, pick one) occurs at, say the top right one, as the bottom one has already peaked and is heading toward 0 volts. At this moment, the upper left leg has passed 0 volts and is heading back toward its peak voltage of the opposite polarity.
This is three phase--120 degrees of rotation apart.
A motor wired to all three legs will see a rotating current on its windings and want to turn. But if you only want a single phase 120 volt outlet, it would be wired between any one of the leg tips and the grounded (neutral) center of the Y.
OK. Back to voltage. Even though there is 120 volts on each leg to center, there would normally be 208 volts AC between
any two outer tips of the Y legs...because they are not at peak opposite voltages at the same time...not maximum push/pull elecron force at the same time.
The math factor is the square root of three. Approximately 1.732.
208 volts (tip to tip) devided by 1.732 is 120 volts (any tip to center).
This is a typical and most common commercial system:
208/120, 3 phase.
If someone wire this for a 240 volt delta system (triangle, not Y--which we won't get into) Then you have 240 volts devided by 1.732 = 138 volts. That is what you are measuring on your receptacles, apparently.
These are just the general principles. You should get an electrician now.