Over thinking

[keith gigabyte]

Simple question yet difficult answer. Single phase residential load centers.
100 amp 150 amp 200 amp main breakers.
I understand load calculation and figuring i.e.: 38,000va..240 v service would be 158 amps so 200 amp panel.
my confusion is if you really look at the way resi single pahse works..each "leg" is 180 out with each other to ground 120v . That being said while one is on the other is off.
so the real question. Let's argue for a moment I was to pull 200 amps on one leg would it trip or am I only able to pull 100 amps per leg. Please explain reasoning in your answer
hope I'm not too confusing
thanks

 

[jumper]

It is 200A per leg, but note it is the same 200A flowing on each leg.

See if this pic helps. Imbalance would just flow on the noodle and back through the windings.

View attachment 16694

 

[jumper]

Another way to see it is like this.

you can have 200A x 120V x 2

or

200A x 240V x 1

or what is more common, a mixture if both types of loads. Say a load of 100A on each 120V leg and a 100A load at 240V.

Your kVA is the same no matter what.

 

[jumper]

Good site to learn about this stuff in nice simple terms.

http://www.allaboutcircuits.com/textbook/alternating-current/chpt-10/single-phase-power-systems/

 

[JFletcher]

Simple question yet difficult answer. Single phase residential load centers.
100 amp 150 amp 200 amp main breakers.
I understand load calculation and figuring i.e.: 38,000va..240 v service would be 158 amps so 200 amp panel.
my confusion is if you really look at the way resi single phase works..each "leg" is 180 out with each other to ground 120v . That being said while one is on the other is off.
so the real question. Let's argue for a moment I was to pull 200 amps on one leg would it trip or am I only able to pull 100 amps per leg. Please explain reasoning in your answer
hope I'm not too confusing
thanks

200A main is good for 200A on each leg. Think of it as 2 single pole 200A breakers sharing a case. If you were pulling 200A on one leg and 0 on the other (a statistical improbability to say the least), there isn't 100A going thru each side, it's 200/0, and the service neutral would be carrying 200A. If you had 200A on each side, it would be 200/200 and the service neutral would see no current at all.

 

[ggunn]

my confusion is if you really look at the way resi single pahse works..each "leg" is 180 out with each other to ground 120v . That being said while one is on the other is off.

Not so. When one leg is at its maximum positive voltage, the other is at its maximum negative voltage. They are both "off" (at zero volts relative to neutral) at the same time.

 

[jumper]

Not so. When one leg is at its maximum positive voltage, the other is at its maximum negative voltage. They are both "off" (at zero volts relative to neutral) at the same time.

Have a pic with your post:

View attachment 16695

Stupid thumbnails always get small and ya gotta click on them.