I purchased a progressive industries portable unit just before a long trip down to LA from our home in Seattle.
While in LA we decided to take the kids to Universal Studios. We stayed at Balboa RV park I plugged in my unit and after a few seconds it showed the code for Phase reversal
I contacted management and let them know. They had just replaced the pedestal and where shocked that I had a unit that could determine this. They said well you still have power because it does not matter which side it comes in on. I mentioned that it will affect the delicate converter in my Earthbound RV
They finally rewired the pedistal and all was good. We ran the air conditioner since it was about 90 degrees that day.
I am glad I had thie progressive industries unit as I could have had some damage to my trailer.
On another note. On our way back home we stopped in Shasta at the KOA and the next day when where leaving I accidentally left the unit plugged in and I drove off.
We called them once on the road and they sent us the unit in the mail.