I recently re wired my AC system and installed new Blue Seas transfer switches and a small panel with a main and two branch breaker for the shore charger and the water
heater. I was very careful, but like you one circuit "seems" to show reverse polarity... some of the time - the water
heater. I say seems to and some of the time because the reverse polarity LED is not very bright and does seem to come and go.
But here's an odd thing. The transfer switch #1481 has a reverse polarity indicator and is "downstream" from the 1402 Main w/ two branch circuit breakers. So if I use shore power
IE outlet receptacles get juice from Main breaker (marina supplied AC) the reverse polarity does not light on the transfer switch. This would seem to indicated that there marina source DOES NOT have reverse polarity. When I close the charger circuit no reverse polarity light. When I close the water heat a faint red shoes on the main (1402) panel which seems to indicate some sort of fault. But the transfer swtich, now in down up stream shows no reverse polarity and I would think that if something in the system had a reverse polarity it too would show it - but it doesn't.
And why if there IS a reverse polarity would the LED not shine as bright as the other ones?
And then of course the 1402 light is very dim and sometimes not on at all. This appears as some sort of intermittent condition and it may be, but the heater seems to work fine. Perhaps the heating
element has a short to ground on the neutral or a bad connection. Since I am not using shore power for water heating
now it's low on my priorities to check it out, but it is an oddity. I emailed Blue Seas and never got a reply.