Polarity

To save buying, making and carrying a 'polarity swapper' you can always whip the plug off your EHU lead and swap the L & N wires if you can't find a correctly wired outlet, just remember to swap them back when you leave.  My caravanning on the continent is limited but all three sites I have used had correctly wired EHU (with the 'normal' 16A plug as well).

Power goes in to a socket via the live and out via the neutral.  The switch "breaks" the power at the live inlet, result an "empty" socket that is not live.  In reversed polarity power goes in via the neutral and out via the live but the switch still "breaks" the power on the live side which is now the outlet, result a "full" socket that is live.  As others have said, buy a polarity tester (they are cheap) and keep a short length of cable made up with live and neutral reversed.  Many people say there is no danger if unwittingly using a reversed polarity circuit - they may be right as I'm no expert.  But why take the chance when the problem is easily overcome?  On a few occasions we found French sites with polarity reversed so the problem definitely exists.

Please explain how that works on an AC (alternating current) system. 

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It works because in the power station the generator has three live elements (phases) all of which rise and fall between +240 and-240 volts relative to a common centre tap which is neutral. Neutral is permanently connected to the physical Earth at the power and substations, which is why you can get an electric shock just by touching a single live wire. It matters not to your body which which half of the 50Hz cycle you connect with, it'll still hurt. In practice with 50 reversals (as the generator rotates)  you'll feel both. Touching neutral while standing on the ground at a substation where it is grounded won't hurt, but the neutral voltage rises on the distribution to your house/ caravan, despite a metal neutral feed because the ground has resistance. Out of interest, defining the direction of current flow was done before atomic theory identified that the electron flow was the reverse of what we thought. That doesn't change meter readings or measured polarity, it's just a fact of interest to scientists working at atomic levels. In summary - don't touch a live wire.

For the sake of about £10.  For an extension plug, socket and a piece of 16A cable.   Making a polarity reverser is a no brainer really.    I've got no plans on going to the continent, but decided today to make a polarity reverser just in case the wiring on a UK campsite is done wrong.    I'd rather have this tool and never need it hook up to a site and have problems, took me about 30 mins to make one up. 

When you plug in a caravan you're putting a potentially injurious voltage into an environment which comes into contact with the elements, and there are therefore hazards present. You mitigate the risks by having a tester and keeping it to hand. 

If the polarity is reversed does this adversely affect the functioning of the RCD, an essential safety system; how will it be if you stand on wet grass and touch a conducting part of the caravan's structure; how strong and healthy does a person have to be not to be injured by a shock; does any system contain semiconductors? Not sure about stuff like this? - buy the kit. On our first caravan trip across the channel this summer 2 out of the 5 sites we used had reversed polarity. Five minutes with a small screwdriver sorted it (but remember to change the wires back afterwards!).

"On our first caravan trip across the channel this summer 2 out of the 5 sites we used had reversed polarity. Five minutes with a small screwdriver sorted it (but remember to change the wires back afterwards!)."

if you make up a short 'reverse polarity cable' with a male and female connectors (as described many times, no doubt) you will only need to spend the five minutes with the screw driver once, and no remembering to change it back afterwards

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We too have the Tester Plug used every time we visit a site and Lead but don't find many sites we visit with reversed polarity.

DianneT

 

 ..... On our first caravan trip across the channel this summer 2 out of the 5 sites we used had reversed polarity. Five minutes with a small screwdriver sorted it (but remember to change the wires back afterwards!).

Is your caravan fuse box double pole isolation? The French don't care whether it's reversed or not as they have double pole circuit breakers

"If the polarity is reversed does this adversely affect the functioning of the RCD, an essential safety system; how will it be if you stand on wet grass and touch a conducting part of the caravan's structure?"

Just make sure you have an earth connection: your RCD compares the 'live' and 'neutral' current, which should be equal, and trips when there's an inbalance due to any fault leaking current to the earthed chassis. In your house, the 'earth' connection is made via the neutral wire, and any metal sheath on the cable. It's earthed at regular points along its length. On campsites, a  different set of rules apply and each Electric Hook-Up point must have a local earth spike to which the user's earth wire must be connected via the socket.

In several continental countries, housholders have to supply their own earth points, usually a metal rod in the cellar.

If your mains tester says there's no earth then don't use the supply!

"If the polarity is reversed does this adversely affect the functioning of the RCD, an essential safety system; how will it be if you stand on wet grass and touch a conducting part of the caravan's structure?"

Just make sure you have an earth connection: your RCD compares the 'live' and 'neutral' current, which should be equal, and trips when there's an inbalance due to any fault leaking current to the earthed chassis. In your house, the 'earth' connection is made via the neutral wire, and any metal sheath on the cable. It's earthed at regular points along its length. On campsites, a  different set of rules apply and each Electric Hook-Up point must have a local earth spike to which the user's earth wire must be connected via the socket.

In several continental countries, housholders have to supply their own earth points, usually a metal rod in the cellar.

If your mains tester says there's no earth then don't use the supply!

Reverse polarity is still quite common on the continent, even on sites with quite new installations. We experienced it a couple of times this year. I just ignore it but for anybody uncomfortable with this then do as advised in this thread. It is rare to have no earth and that is potentially far more dangerous. I was not aware that a local earth spike was required at each EHU. I have never seen one but it is certainly important to get a good connection to earth and the tester socket will show this. In that situation it would certainly be sensible not to use the supply.

Concerning households with an earth connection in the cellar, this is not relevant as it would probably be what's known as a PME installation (Protective Multiple Earthing). This is not allowed on a camp site, however, if you are paranoid there is nothing to sop you creating a better earth by anchoring the caravan chassis to an earth spike. Some people do it apparently.

Just to make things even more complicated, you may get false tester readings in Spain due to the occasional use of phase to phase transformers where the neutral floats. Not necessarily dangerous but confusing!