Originally Posted by harderd
I do know that when you talk about polarity related to AC you usually think of AC cycles not reverse wiring. I have a friend who is an electrical engineer so I asked him about this and his thought were the same as mine. So my guess is this term is being used in the RV industry for lack of a better term.
You are correct. I hate the word "polarity" when referring to AC power. That's because an AC outlet actually reverses its own polarity 120 times per second for 60 Hz power in the US (it's 50 Hz in much of Europe). But the RV industry uses Reversed Polarity to describe what's actually reversed Hot and Neutral wiring. I think that's because in the 40's and 50's there was something called a non-grounded "polarized plug" on radios and home appliances. And those early appliances lacked input transformers, which bonded the incoming neutral wire directly to the chassis. So if the "polarized plug" was flipped, reversing its "polarity", then the radio chassis was connected directly to the hot wire, which could be lethal.
That's why all modern appliances have some sort of power transformer to isolate their own chassis from the power line. The exception is double insulated power tools and things like hair dryers with GFCI plugs. So with all modern appliances and RVs, it really doesn't matter if the hot and neutral wires are reversed. There are tons of old wives tales that swapped H-N lines somehow burns up on-off switches, or causes an appliance to use more electricity, or hum, or whatever. But that's all incorrect information. The REAL danger is that troubleshooting a system with the neutral wire energized to 120-volts can be deadly to the technician doing the testing.
So why should you care if your RV outlet shows reversed polarity? Well, if you have a second miswiring condition in your RV, specifically an internal Ground-Neutral Bond, it's possible for a reversed H-N outlet to create a hot skin condition. Also, it shows that whoever wired the electrical outlet doesn't know what they're doing and could have made other mistakes. So don't accept reversed Hot-Neutral outlets on a pedestal since it's an obvious mistake that should be corrected.
One of the things I've pitched to the RVIA and various inspection agencies is the idea of a testing RV pedestals for proper grounding and "polarity" yearly or maybe every other year. And I think they should also be retested anytime there's been a repair done on a pedestal. But it's slow going since nobody wants to spend money, even if it is for safety.
BTW: I don't like the term "RV hot-skin" either, since it's really a hot-chassis condition that also spreads to the RV "skin". So a hot-skin condition creates voltage not only on the "skin", but also on the RV's wheels, trailer hitch, the tow vehicle, door handles, metal steps, etc... That's why an RV hot skin is so dangerous.
PS: I thought Mike's write up was great and should be of help in the future.
Thanks very much.
No Shock Zone