Err..shore Power Polarity

[tom52]

Well !
I have read all the answers and the doomsday scenarios and now I am confused.
Perhaps some of my confusion comes from not necessarily having read the replies in the right sequence since several discussions/disputes seem to have broken out simultaneously.
So I am in France I have a built in polarity light on the boat and an RCD.
I plug into the shore power the polarity light tells me incorrect polarity. It is the first time I have seen this. All my neighbouring Brit. boats are arriving plugging in without comment ( perhaps because they do not have a polarity warning system ?) and are happily going about their business.
What should I do
1) disconnect and have nothing more to do with shore power at this marina
2) rewire my shore power plug at the boat end to switch the polarity (or use a polarity switching extension if I had one )
3) Ignore the incorrect polarity warning and bash on regardless.

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[halcyon]

Reverse polarity lights are a Marine Projects thing that goes back to tthe dark ages, doubt if they now know why they fit them.
Could be the marina wrong, could be just your socket thats wired wrong, if your stoppng a long time, try someone elses socket, if that's wrong as well it's probably the marina, if ok get them to rewire your socket. Or swop your plug, or make up a polarity swopping lead if your worried.
After all the bottom line is, if you had yacht without a reverse polarity light, would you still be worried.

Brian

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[AlexL]

Try plugging into a different socket in the marina - I was in ostend recently and the shore power post had 6 outlets, the first one I plugged in gave a reverse polarity indication - so i tried another - which was fine!

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[MainlySteam]

I pretty much sympathise with Brian's comment.

I think the only ways (but maybe there are some more) you could come to harm if the polarity is reversed are:

1. If the main breaker on your boat for the shore power inlet is only single pole ie the line only is switched - it should be 2 pole if the boat was wired professionally but may not be if wired by an amateur - as obviously in reverse polarity all your neutral conductors will remain live with the main switch off and a neutral to ground shock is possible even with the main breaker off. Perhaps only likely to be a problem during any servicing of the boat's ac wiring/electrical fittings.

2. All appliances with single pole switching will remain electrically hot when turned off - for a simple example, although one probably hasn't got ac lamps, the neutral terminal in a lamp with the bulb removed would remain live and a neutral to ground shock is possible.

In a properly wired boat I think only 2. applies so the increased risk is not great but I would personally avoid it.

John

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[Alex_Blackwood]

Could be that the marina in question is working BETWEEN PHASES and not PHASE and NUETRAL as is the case with the UK 220 volt system. I don't know as I have never used a continental marina shore supply.
If the above is the case then depending on phase rotation (Which two phases are being used) it MAY or MAY NOT show reverse polarity!
The way to tell is to put a voltmeter between phase and earth and between nuetral and earth, if it is a phase and nuetral system then you will only get 220 volts between phase and earth (also between phase and Nuetral). If the system is between phases you will get half voltage (110 volts) give or take a few volts between both the phase and earth and the "Nuetral" and earth.
A polarity reversing lead will, in that case, be about as much use as a chocolate teapot. The polarity may show correct but you will still have two live wires coming inboard. Hence the importance of a DOUBLE POLE Main Circuit Breaker.
Normal domestic equipment will be OK on this system but should be unpluged if not in use as any swtches fitted will be single pole.
A RCD will work with the between phase system but will only be about 90% effective.
I would suggest that anyone using a strange system checks it to determine the polarity and voltage at the marina socket before pluging in!
Sorry if the above has added to your confusion, hope it just may be of some help!

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[Becky]

Alex, my Partner suggests that you may have this wrong. He suggests that phase to neutral is 230-240 volts, whilst phase to phase is about 315 volts. It is usual to find that circuit breakers are dual pole switches, but I agree with the rest of what you have stated.

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[MainlySteam]

It is a few years since I was last in France but my recollection is that their electrical system is a polarised one like the UK ie nominal 220-230 volts on the line. I think that must be so as if it was working between two phases then the operation of polarity indicators on a visiting boat would always show "incorrect" (sic) polarity as the boats neutral would always have 110 odd volts on it, whereas peple are only reporting random instances of reverse polarity indication.

John

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[Mike21]

As AlexL posted, try a different outlet, if not can swap live and neutral on plug.


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[Alex_Blackwood]

Becky, Yes your Partner is nearly correct for the UK system. This is transformed down from the high voltages of the National grid distribution system and eventually ends up as 415 volts 3 phase and neutral. The 415v is used to supply small industrial units etc. using 3 phase equipment.
The 220-240 supply for domestic use is derived from a single phase and neutral supply, all three phases are used. i.e. 1(or Red) - Nuetral, 2 (or Yellow) - Neutral and 3 (or Blue) - neutral. This accounts for some power cuts only affecting certain houses in a street. (Loss of a single phase).
Some countries will transform down to 220-240 volts between phases giving 110 volts between phase and earth or neutral. I believe that this is the case in the U.S. They use the 240 to drive heavy domestics such as washing machines and a 110 phase and neutral supply for lighting and portable eqipment such as vacuums and drills etc.
Hope the above helps, all figures are approximate!
I would reiterate that I think any one using a strange marina shore power should check voltage and polarity with a meter before connecting. Find out what you are going to get before it gets you!

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