I’m not trying to be a jerk, but what is the fascination with this 400A @ 120v thing??? So many folks pressure us to say “Yes, it is 400A at 120v.”. It is not.

You are incorrect in your assumptions. In the hypothetical situation you have outlined, (200 amp balanced loads on each of the two legs), you will only measure 200 amps at any point in the system.

Lets follow the electrons. For 1/120th of a second, 200 amps will flow into the panel through Leg A, the same 200 amps will then flow through the 120V loads connected to leg A, the same 200 amps will then flow to the neutral bus, the same 200 amps will then flow through the 120V loads connected to leg B, then the same 200 amps will flow out of the panel through leg B. Then the current reverses and takes the same path backwards. It is all the same electrons.

Thats a good explanation of the actual operation and the reason why AC is used for power distribution instead of DC.

The highest measured current will be 200 but you have 48,000 watts of power dissipated on 120V loads. It takes the equivalent of 400 amps to produce this amount of power on 120V loads.

This “never to be found” setup in residential is best described in watts rather that amps since the voltage on the loads is not 240V.

Your looking at the concept of current, load and A/C incorrectly.

Alternating current A/C is not like DIRECT current or DC… meaning a constantly current level…

I was going to go into a very long explanation on the theory but figured it would be best if Paul Abernathy would explain it …

On a side note, Tangent.

By the way A/C was found to be easier to “transmit” via overhead “High” power lines over great distances. Loss factors are very high that is why we don’t use DC in homes these days. Samuel Insull… He had a HUGE part in it…see…www.geocities.com/WallStreet/Floor/3748/insull.html

245MKV at the towers and 12,500 volts at the wires at very top of the poles around the neighborhoods in my area to transformers 240 volts to the house…

Side note:

What happens to the voltage in the summer time when everyone runs there AC Compressors??

It was a good discussion, also one over at INews, I think most everyone including me learned something and got another angle on it. Sometimes practical explanations and theory will cause differences but the operation from an inspectors view is the same which is what I am trying to point out.

I am in full agreement with you and never intended to indicate that one could measure more than 200 A anywhere in the system.
I very familiar with center tapped transformers which is what a 120/240 V service is being supplied from the POCO transformer.

Not sure where you got the idea that I had incorrect assumptions. Please point it out to me. I imagine its from stating you could have 400A of 120 V loads. It can never be above 200A on either hot leg(for long anyway) as the breaker will trip.