Reverse polarity

telekitr · #1 (**permalink**) 11-29-2007

We currently have our Passport 40 on the hard in the back of the shop awaiting her final winter cover. My issue is that I have plugged her in to building AC 120 via an adaptor and yellow shore power cord. The first few times that I went aboard to turn on the systems, all worked well. Of late, I am getting the "Reverse Polarity" light coming on and no systems are working. Does anyone know what might be causing this sporatic RP warning? Nothing has changed in the outlet in the shop....must be something along the line...but what?? Thanks in advance for your reply's.

trantor12020 · #2 (**permalink**) 11-29-2007

check your shorepower cables plugs for loose terminations.

hellosailor · #3 (**permalink**) 11-29-2007

The "reverse polarity" light on WHAT?

There have been some discussions about RP lights on chargers and inverters coming on (and some systems will shut themselves down) because there are different schemes for grounding the AC side of systems. You might be able to turn up some of the older threads on that. My vague memory is that some equipment wants to see a real third wire ground, while some tries to use the neutral wire, and in the process, things can get into conflict between the equipment.

chuckjohansen · #4 (**permalink**) 11-29-2007

You may also want to check the AC pannel for loose wires. Check the grounding lugs on the pannel. Interesting, let us know what you find.

Chuck J.

telekitr · #5 (**permalink**) 11-29-2007

thanks guys for your suggestions. The RP light is the one on the AC panel itself. I will check for loose connections as suggested. Right now however, it looks like we are going to have a whopper of a winter storm here in New England late this weekend so I'll not likely get the opportunity to check things until next week. Have to get the cover on now.....thanks again.

jerryrlitton · #6 (**permalink**) 11-29-2007

All I know is Jordi (The new Star Trek) uses it on everything from tractor beams to fixing the toilet on the Enterprise. It very seldom works.

sailingdog · #7 (**permalink**) 11-30-2007

RP can also be caused by another boat on the same AC line having a faulty setup. That is most likely the case here, since you said it was previously fine. One of the boats or pieces of equipment that has been added recently to the line is causing the RP fault.

thekeip · #8 (**permalink**) 11-30-2007

'Normal' polarity is that condition in which AC voltage is measured between the 'hot' (black) conductor and neutral (white) conductor. You should be able to measure that same voltage between hot and ground too, if all is well...that is, if the neutral and ground are connected together AT THE DOCK, NOT THE BOAT. A little Neon indicator will glow if connected between the hot and ground.
On the other hand, it may be that the black conductor and the white are swapped somewhere down the line. You'll still be able to measure the AC between the hot and neutral as before, only this time the indicator will glow if connected across the neutral and ground...that's what the RP indicator does.
'Older' boats and marinas rarely exhibit reverse polarity...that's because if the condition ever existed at all, it most likely has been corrected.
Howard Keiper
Sea Quest
Berkeley

SEMIJim · #9 (**permalink**) 11-30-2007

Everybody that owns something that's got 125VAC distribution (home, sufficiently large boat, etc.) should have one of these: Ground Fault Indicator Tester. (Tho mine doesn't have the button for testing GFCIs.) It'll tell you if hot, neutral and ground are all present and connected to the right points. The one referenced, with the GFCI test button, will test the GFCI circuit, independently of the GFCI's own, built-in tester, as well.

When I bought our house I checked every outlet in the place. Good thing I did, too, being as, for example, the outdoor outlet (had to be that one, of all of 'em, eh?) had ground and neutral reversed. That was an electrocution waiting to happen. (It's got a GFCI outlet there, now.)

Jim

telekitr · #10 (**permalink**) 11-30-2007

Quote:

Originally Posted by sailingdog

RP can also be caused by another boat on the same AC line having a faulty setup. That is most likely the case here, since you said it was previously fine. One of the boats or pieces of equipment that has been added recently to the line is causing the RP fault.

SD.....mine is the only boat that is connected on this outlet. The shore power cord comes out of the cockpit recepitcal and down inside the garage of my shop and plugs into a short adaptor which allows me to plug it into a normal AC outlet.