CDP wrote:
I don't know what the code is for RV site services. A friend of mine ran into this fairly recently after a discussion on electrical services. Just out of curiosity, he checked the service he was plugged into at the time and discovered his two 25A circuits were on the same phase. He had voltage from hot to neutral on both circuits and "0" between the two. Of course you know this must mean they're in phase since any phase difference would show some voltage difference between the two. He didn't look into this any further before they left the next morning, and since it was of no consequence to him at the time anyway. He just thought it odd enough to comment to me during a recent conversation on the same subject.
I don't know how the pedestal in question was wired internally. Nor do I know if others in the same park were like this one. I made an estimate on how it might be wired to get the results of the same phase on both circuits of a 50A service.
Perhaps there have been changes in the code that might allow this, something the park manager did himself without knowing the code, or perhaps an honest error by someone else that should never have been working on a power pedestal. It is only 50A at 120V which really isn't that much for one conductor to the pedestal. I don't know. My friend is a retired Radar Engineer and I trust what he told me to be accurate. He's actually sort of anal that way. He probably took his oscilloscope to the pedestal for a better investigation. lol
There is no such thing as two 25 amp circuits on a 50 Amp pedestal. If you mean he got a reading of zero volts between the hot circuits on a 50 amp pedestal, then yes, the pedestal is incorrectly wired and out of code. Such wiring could lead to the neutral being overloaded, since the neutral in a 50 RV outlet only carries the difference between the usage in the two legs, so the theoretical limit is 50 amps (50 amps one leg, zero amps 2nd leg). For this to actually happen the two legs must be 120 degrees out of phase. If they are both on the same phase, there is no cancelling effect and the neutral will carry the sum of the usage of both legs. That would mean the neutral could theoretically be carrying 100 amps, which would eventually lead to it failing.
All that information is in theory, in practice both legs seldom carry 50 amps each, 50 amp neutrals do not fail instantly fail at 51 amps and most 50 amp RVs have an energy management system that would see zero volts across the two legs and automatically switch to 30 amp mode (since that is what those adapters from 30 amp source to 50 amp RV actually show). So normally no serious threat actually occurs. That being said, if I saw that wiring at a park, I would be wheels a rolling. Who knows what else has been jury-rigged.
