MEXICOWANDERER wrote:
Off Topic but relevant nevertheless
"Why is the neutral wire in a 240 circuit the same gauge as both phases (hot wires). Shouldn't the neutral wire be much larger to carry double the current?"
No.
Current in an AC wire "only flows half the time"
If that current can be "filled up" then the wire will be "full".
The 2nd phase wire wills the neutral wire up with a mirror image filling the sine wave gaps.
Three wire to two wire adapter plug test...
Those little plastic adapter blocks that will allow a grounded three wire plug to connect to a two wire outlet is a great diagnostic tool.
You'll need a non contact AC voltage tester for this...
Unplug ANY metal cased appliance then plug it into the adapter then plug the adapter into a wall socket.
Wave the ac detector over the metal of the appliance. If it sounds off there is a fault inside the appliance.
This is a rare occasion where I will disagree with Mex.
current usually flows all the time in an ac circuit when a load is connected, not just for 1/2 cycle. 120V RMS Voltage goes from about +177 v to -177V each cycle as a sine wave. current likewise goes from positive to negative as a sine wave, not necessarily in phase with the voltage depending on what the load is. resistive is in phase, reactive (inductive or capacitive) is out of phase by some degree with the voltage. Now an exception to sinusoidal continual current flow is switching power supplies, even stranger with non sinusoidal and often non continous current flow.
now in a 120/240 circuit you have two 120v legs relative to the neutral, but they are 180 degrees out of phase. so when one leg goes positive, the other leg is going negative. so when you are connected to the 120V legs if the same current is drawn by both legs, there is no current flowing in the neutral the current from each leg cancels with a resistive load. again the exception being non resisitve loads, but even then it will be close to cancelling. if one leg is drawing rated current, the other no current, then the neutral has rated current flowing in it. anything in between has less current flowing in the neutral than either leg.
If you are connected across the hot side of two 120V legs, you have 240V and when a 240 load is connected all the current flows between the two legs and none through the neutral.
In older 240 V wiring, often the neutral was a smaller guage than either hot leg. the reasoning was the main load was across both legs, and only a minor load was across one leg. Like a dryer, the heating element across both legs, and only the timer across a 120V leg, drawing much less current.
