Reverse Polarity - boat or marina issue?

Halo

Halo

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When I left the marina 2 days ago shore power was fine. I circumnavigated Anglesey and now no power is available at the onboard sockets.
The 240v panel has a red "reverse polarity" light which now lights up together with the green power available light.
Previous threads suggest that reverse polarity means the live and neutral are reversed and that an extension which reverses these can eliminate the problem.
I also found a technical article which says that the reverse polarity detectors used on boats sense any voltage between neutral and earth and isolate the supply if this occurs. so I wonder if it is a stray current.
The marina have a cheapo tester which indicates there is no issue with the supply on the pontoon.
Can anyone suggest what best to do to solve the problem ?
many thanks
Martin
 
Perhaps if you circumnavigate Anglesey in the opposite direction... :)

It's quite plausible that the marina is right with their polarity tester. Do you have your own cheapo tester to double check their results? Have any neighbouring boats experienced problems?

Have you tried a tester on your own boat? Without knowing how your panel works, you don't know what circumstances would cause it to give the reverse polarity result, but unless you know you've done something that risks reversing the polarity a fault of that nature is unlikely to have happened spontaneously.

The cheapo testers usually tell you if something else is wrong e.g. missing earth or neutral (which is much more plausible if there's been a bit of corrosion of the shorepower cable or plug). If you haven't got one, worth getting one of the cheapo testers yourself, or borrow the marina's one to carry out the test on your own boat.
 
Halo said:
When I left the marina 2 days ago shore power was fine. I circumnavigated Anglesey and now no power is available at the onboard sockets.
The 240v panel has a red "reverse polarity" light which now lights up together with the green power available light.
Previous threads suggest that reverse polarity means the live and neutral are reversed and that an extension which reverses these can eliminate the problem.
I also found a technical article which says that the reverse polarity detectors used on boats sense any voltage between neutral and earth and isolate the supply if this occurs. so I wonder if it is a stray current.
The marina have a cheapo tester which indicates there is no issue with the supply on the pontoon.
Can anyone suggest what best to do to solve the problem ?
many thanks
Martin
Click to expand...
M
Do you have a volt meter on board? If so, undo the plug coming on board and see if you have voltage from neutral to earth, if so then the live and neutral have been transposed on the marina side. If not then something has changed on your boat.
S
 
Halo said:
When I left the marina 2 days ago shore power was fine. I circumnavigated Anglesey and now no power is available at the onboard sockets.
The 240v panel has a red "reverse polarity" light which now lights up together with the green power available light.
Previous threads suggest that reverse polarity means the live and neutral are reversed and that an extension which reverses these can eliminate the problem.
I also found a technical article which says that the reverse polarity detectors used on boats sense any voltage between neutral and earth and isolate the supply if this occurs. so I wonder if it is a stray current.
The marina have a cheapo tester which indicates there is no issue with the supply on the pontoon.
Can anyone suggest what best to do to solve the problem ?
many thanks
Martin
Click to expand...

If you are saying you have returned to use the same marina shorepower outlet as you were using two days previously and now experience this lack of power and reverse polarity indication I think you should carefully check out the plug and socket connections at either end of your shorepower lead.
OR
Try another lead if you can.


Is your lack of power due to the RCD having tripped ?

Do you have a link to the info about reverse polarity detectors which isolate the supply if this happens ? I was not aware of them 'til now. All I knew about was a couple of indicator lights.
 
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Halo said:
Hi Vic
I will try another lead next time I go to the boat.
The link you asked for is
http://www.cruisersforum.com/forums/f14/reverse-polarity-ac-1180.html
The RCD has not tripped as it doubles as the main isolator on the panel and the green light indicates some sort of power coming in.
Any further thoughts appreciated
Martin
Click to expand...

Thaks but I dont think the link describes any form of isolator that will operate if reversed polarity is detected. Just reversed polarity indicators (RPI)

I'd expect the RPI to be in the circuit before the RCD and to show a green light even when the RCD is off. Presumably yours is not wired like that?
 
I had exactly this problem a couple of weeks ago. After thinking it must be the marina, I found out it was actually a short in my shore power lead after swopping to a spare lead. I unscrewed the plugs, found the neutral wire had become detached, screwed it up again and all was well.
 
PurpleKate said:
I had exactly this problem a couple of weeks ago. After thinking it must be the marina, I found out it was actually a short in my shore power lead after swopping to a spare lead. I unscrewed the plugs, found the neutral wire had become detached, screwed it up again and all was well.
Click to expand...

Thats the sort of thing I am expecting Halo to find.
 
Many thanks for the insights. I replaced the plug on the bollard end but did not have a spare for the boat end. I have a spare lead and will take that and try it (boat currently 180 miles from home).
Will let you know what happens
Martin
p.s. Vic my mistake - I thought with the references to resistors etc it was talking about a device - did you notice the bit about fresh water eletric leaks stunning swimmers in fresh water and them drowing because they could not use thier muscles. Remind me not to fall into a fresh water marina !!
 
Just to let you know what happened..........
The problem was the actual shore power cable. I tried an old shore power cable (massive 32A one) and it worked fine. Changed both plug and socket on mine but still no good. Replaced actual flex and all well. I expect the cable failed internally due to foot trafiic and marina trolleys.
Thanks for the insights
Martin
 
Halo said:
Just to let you know what happened..........
The problem was the actual shore power cable. I tried an old shore power cable (massive 32A one) and it worked fine. Changed both plug and socket on mine but still no good. Replaced actual flex and all well. I expect the cable failed internally due to foot trafiic and marina trolleys.
Thanks for the insights
Martin
Click to expand...

Thanks for the feedback.

Your experiences underline the advisability of using 2.5mm² cable rather than 1.5mm² and better still to use HO7 cable rather than arctic grade PVC
 
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