Just quick note on 30 amp systems. our previous coach was 30 amp and we had the Progressive Industries installed protection. We had several expected low voltage protection cutoffs (under 108 v) and that seemed normal and we were glad to be protected. Then in a NY State Park when it cut out I was surprised to see 134 V showing on the monitor. When I checked at the post it was also 134 v. That was only late evening when the air cooled and everyone shut down their ACs.
At another park, in El Paso NM, I plugged the unit in and it would not connect as there was a polarity fault on 30 amp. I got my tester out and found an unused post one site over that tested good. Had the night manager block out that site and report the problem. No telling how many rigs plugged in and hadn't a clue that they might have a hot skin/frame because of that. Might not cause any problem in the coach, but sure would cause an issue to a person standing on damp ground and touching the frame of the coach!