Forum Discussion
RustyJC
Jul 30, 2015Explorer
Sport45 wrote:taken wrote:
I had a hard time following how you messed up the adapter. However, to clarify, the 50 AMP cord that RV's with 50 AMP service use as well as it's corresponding outlet is indeed 220V. 220V comes into the RV as the two hot legs are on opposite phases.
50 AMP Service Explained.
That's probably the most-used configuration, but do the two 110 feeds have to be opposite legs? Seems it would work just as well if they came off the same bus. Might work even better as an open neutral condition couldn't put 220V across anything. Of course no 220V appliance in the RV would work...
If the two hot legs are in phase as you describe, there's a real risk of overloading the neutral conductor in your shore power cord. Neutral leg current is the sum of the hot leg currents, but because "proper" 120/240VAC split phase center tap neutral 50A service has the two hot legs 180* out of phase, one leg is mathematically assigned a minus (-) sign. Thus, in a "proper" 50A setup, if both legs were drawing 50 amps, the neutral current would be 50 + (-50) = 0 amps. If it were wired in phase as you describe, then neutral leg current would be 50 + 50 = 100 amps; the neutral conductor is sized for 50 amps, so the potential problem is obvious.
Besides, most power management systems look for 240VAC across L1 and L2 as an indicator that 50A service is available. If they see 0VAC across L1 and L2, they default to 30A service - that's what my system does. By doing so, it prevents the overloaded neutral conductor situation described above.
Rusty
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