Originally Posted by Steve29rlx
How is 100 amps possible with a 50 amp breaker? If you tried to se 100 amps wouldn't the breaker trip?
A 120/240 volt split phase service is really simple once you understand it, but it can take a bit to get your head wrapped around it. The biggest confusion is people thinking that 120/240 split phase works like 120 volt single phase.....which it doesn't.
The main thing to understand is that a 50 amp service is 50 amps at 240 volts or 100 amps at 120 volts. Both produce 12000 watts. Watts= amps X volts
A double pole 50 amp circuit breaker grabs 50 amps from one pole/leg (L1) at 120 volts and another 50 amps from another pole/leg (L2) at 120 volts.
To get 240 volts, you have to have an item connected to both L1 and L2.
The RV doesn't have items connected to both L1 and L2...but instead uses the L1 and L2 separately, so L1 provides 50 amps at 120 volts and L2 provides another 50 amps at 120 volts....... for a total of 100 amps at 120 volts.
Now the L1 and L2 share a common neutral wire (you have to have a neutral when using 120 volts), which is also only rated to carry 50 amps. However, the way the split phase service works is called load balancing as power shuttles back and forth between L1 and L2. The neutral only carries the imbalance.
If you are using 45 amps on L1 and 40 amps on L2...then the imbalance is 5 amps, and this is what the neutral wire carries.
At the extreme, say you are using the max on L1 of 50 amps (as per its circuit breaker max). Then say you are using 0 amps on L2. Then the neutral carries the imbalance of 50 amps (which it is rated for). If something were to happen on either L1 or the L2 and the amps were exceeded on either, then since a double pole breaker is in essence two breakers tied together, if one side trips, then the other side has to trip too. This also protects the shared neutral wire so neither L1 or L2 can make it carry any possible imbalance of over 50 amps.
It's explained a lot better in this link. it takes a little to wrap your head around it, but you will.
Electrical Tutorial - Chapter 3 - 30 Amp versus 50 Amp