R5 iirac
Years ago the topic of 12-3 Romex using Black @20 Amps, Red @20 Amps, BUT White, common for each seeming to handle 40 Amps.
The explanation I recall was that in such circuits, the energy is -spent- at the appliance, so a full 40 Amp capacity isn't needed.
That explanation might seem to apply to A/C & D/C as well. BUT !
I found this explanation which seems a little more reassuring.
The term for what you're describing is a "multi-wire branch circuit", so if you want to read more, that's the term to search for.
Alternating Current (AC) power operates by generating "waves" of voltage. In a normal North American residential system, the voltage will alternate from +120V to -120V (relative to neutral) 60 times per second. However, the power is supplied to your house in two legs, which have their alternations offset in time such that whenever Leg A is at +120V, Leg B is at -120V and vice-versa.
This is how we get 240V power in our houses. While each leg is 120V relative to neutral, they are 240V relative to each other, so if you put a load between the two legs, it experiences a 240V potential difference.
And that's also how two wires can share a neutral. If the black wire is drawing 20A at -120V and the red wire is drawing 20A at +120V, the neutral carries no current. You can think of this like destructive interference of the waves. If the loads on the two wires are mismatched, the neutral will carry only the imbalance between them, but that imbalance can't be any larger than 20A, since neither circuit can be less than 0A or greater than 20A.
Some of the details I recalled for the premise may be off. But I thought you might find this explanation interesting. AND !!
While the prior explanation might apply to both A/C & D/C this reddit explanation only applies to A/C.
Years ago the topic of 12-3 Romex using Black @20 Amps, Red @20 Amps, BUT White, common for each seeming to handle 40 Amps.
The explanation I recall was that in such circuits, the energy is -spent- at the appliance, so a full 40 Amp capacity isn't needed.
That explanation might seem to apply to A/C & D/C as well. BUT !
I found this explanation which seems a little more reassuring.
The term for what you're describing is a "multi-wire branch circuit", so if you want to read more, that's the term to search for.
Alternating Current (AC) power operates by generating "waves" of voltage. In a normal North American residential system, the voltage will alternate from +120V to -120V (relative to neutral) 60 times per second. However, the power is supplied to your house in two legs, which have their alternations offset in time such that whenever Leg A is at +120V, Leg B is at -120V and vice-versa.
This is how we get 240V power in our houses. While each leg is 120V relative to neutral, they are 240V relative to each other, so if you put a load between the two legs, it experiences a 240V potential difference.
And that's also how two wires can share a neutral. If the black wire is drawing 20A at -120V and the red wire is drawing 20A at +120V, the neutral carries no current. You can think of this like destructive interference of the waves. If the loads on the two wires are mismatched, the neutral will carry only the imbalance between them, but that imbalance can't be any larger than 20A, since neither circuit can be less than 0A or greater than 20A.
Some of the details I recalled for the premise may be off. But I thought you might find this explanation interesting. AND !!
While the prior explanation might apply to both A/C & D/C this reddit explanation only applies to A/C.