Reverse polarity

[ejostone]

My dismountable camper - which I carry on a Nissan pick-up - has an electrical panel which carries all the fuses, trip switches, pump switch, charger switch etc. It also has a light which shows if the polarity is reversed. I can't understand why, because I thought AC current changes polarity constantly. It obviously shows if the mains current in is wired up with reversed polarity - but this does not seem to cause any problems. The camper battery continues to charge OK and all the systems, both mains and 12 volt work without problems. What danger is there if the polarity is reversed by mistake? Can anyone explain for me? john

 

[Modernelectric]

if polarity is reversed then the fusing would all be in the neutral conductor and if this is isolated then the equipment could become live as it would have no return neutral path and would find the easiest route to earth.