Why 30 amp and not 50 amp

Bobbo wrote:

DrewE wrote:

That's half true; 50A service is 50A, 120/240V service, but it's not in any way a 100A circuit: you cannot connect a single 120V, 100A device to it should that odd need come up. It is correct that it provides a nominal 12 kW rather than 3.6 kW for the 120V, 30A service.

Saying it's a 100A service is about like saying that a semi tractor pulling dual trailers is really travelling at 120 mph, because it's pulling two trailers traveling at 60 mph apiece.

But, it is also true that a 50 amp trailer has access to 100 amps of power. You just have to use two circuits to access it. Sometimes, simplifying a subject can get the concept across even though the technical details are wrong.

I think it is both simpler and more correct to use units of power when comparing power, rather than units of current--doubly so when one of the current values must be incorrectly stated for the comparison to work out. "Amps of power" is a nonsensical phrase, if taken at face value. In the context, it is a shorthand form (or a shorthand way of thinking) based on the assumption that the voltage is invariant, when in fact the different voltages are at the heart of the matter. Similarly, saying that a 50A circuit supplies 100A is also something of an absurdity, and is also forced by incorrect assumptions about the voltages. Comparing power using the proper units--watts or kilowatts--avoids all the confusion.