anesta Posted August 27, 2013 Share Posted August 27, 2013 Hello, Been reading a caravanning handbook to help me get ready for my motorhome arriving in a couple of weeks. Whilst reading about hooking up aboard, I started to read about reverse polarity. I don't understand the physics of what it is but I was very concerned about what was said in the book. The stated things like:- - British people don't hook up when aboard - Some hook up but their appliances stay live :-o and can become damaged It then advises you to buy a 'reversal adaptor' which cannot be bought in a shop but has to be specially made by an electrician. I am now very concerned. I bought my motorhome to drive aboard but does this Reverse Polarity means that every time I hook up aboard I could get Electrocuted??? Will my appliances stay live and damaged??? Do I need to buy specialised equipment??? What equipment do I need to buy??? How will I know if this problem exists when I eventually hook up in my first campsite aboard. Any advice is much appreciated. :-) Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 27, 2013 Share Posted August 27, 2013 In the majority of cases reversed polarity will cause neither you, not any of your electrical equipment, and risk or problem at all. All it means is that the live and neutral wires are reversed in the site supply socket, so what should be the live becomes the neutral, and vice versa. The electricity itself couldn't give a hoot! Contenental wiring practise is different to UK practise, in that their switches generally isolate both poles, whereas ours only isolate the live pole. So, in theory, with a UK switched socket, is is possible for the neutral terminal inside to be live even if the socket is switched off. You will need to get a continental adaptor to be able to plug into quite a few continental campsite suplies where the older two pin plugs are still used. Any caravan/motorhome accessories shop should have these in stock. While getting that, just get a W4 (or similar) mains tester plug, which will tell you if the polarity is reversed, and also, and much more importantly, whether the earth connection is good. If the concept of reversed polarity concerns you, all you need is about a foot of mains hook up cable and one each of the blue electrical hook-up (EHU) sockets and plugs. You wire the plug to the short cable as normal, but when wiring the socket to the other end of the cable, you deliberately connect the brown wire to the terminal marked - or neg, and the blue to the terminal marked + or pos, so reversing its polarity. But, above all, make certain to connect the yellow/green earth wire to the earth terminal of both plug and socket. It really is no more difficult than wiring a plug. Then, if the tester indicates reversed polarity when you first conect to the site supply, simply disconnect the EHU cable from (preferably) the supply point, connect the short cable with the reverse wired socket to the EHU cable, and then plug that into the supply point. If you are using the adaptor plug because the supply is two pin, just put the short cable between the adaptor and the EHU cable. You should then see that the tester no longer indicates reversed polarity. However, if you can say what van you have, and how old, it is probable that the electrics installed in the van are "polarity neutral", in the same way as continental electrics are, and you do not need any more than the just adaptor for those supplies still with two pin plugs. But, the tester would still be agoood idea to check that the earth is good. Link to comment Share on other sites More sharing options...
Mickt Posted August 28, 2013 Share Posted August 28, 2013 They have mains tester plugs in Aldi at the moment Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 28, 2013 Share Posted August 28, 2013 Brian Kirby - 2013-08-27 11:56 PM However, if you can say what van you have, and how old, it is probable that the electrics installed in the van are "polarity neutral", in the same way as continental electrics are, and you do not need any more than the just adaptor for those supplies still with two pin plugs. But, the tester would still be agoood idea to check that the earth is good. Anesta's motorhome is a 2007 Hymer Camp 622 CL (presumably in RHD UK specification with UK-norm 3-pin mains sockets). It is possible to obtain a ready-made reverse-polarity adapter http://tinyurl.com/pg7l5p5 and I suspect that the overall cost of around £12.50 makes it not worthwhile to DIY. But, if a DIY approach is preferred, this may be of interest. http://www.practicalcaravan.com/advice/reverse-polarity-how-cope-tour I'm not sure what "polarity neutral" electrics in a motorhome are, but it should be anticipated that, if the power-supply reaching the motorhome is ' polarity reversed', it will be 'reversed' throughout the vehicle. My Hobby has its original Germany-norm mains sockets that are 'polarity neutral'. As I know what I'll be plugging into those sockets and that reversed-polarity won't be an issue, I'm not concerned about reverse polarity and, although I have a reversing-adapter, I never use it. However (as Brian advises) I do use a tester to ensure that there's nothing really odd (like no earth) about the EHU power-supply. Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 28, 2013 Share Posted August 28, 2013 Derek Uzzell - 2013-08-28 8:47 AM................I'm not sure what "polarity neutral" electrics in a motorhome are, but it should be anticipated that, if the power-supply reaching the motorhome is ' polarity reversed', it will be 'reversed' throughout the vehicle............... Just a bit of perhaps overly crude terminology invention! If the mains "consumer unit" in the van has a double pole RCD or RCBO as its main switch (as I believe all now do), and has double pole MCBs (as I believe most now will, including your Hobby), it is pretty much irrelevant which way the electricity flows round the circuits. That is what I was trying to capture by calling it "polarity neutral", without indulging in too much technicality! The point is that an earth fault or an overload will trigger either the RCD/RCBO in the first instance, or one of the MCBs in the other instance, to isolate both live and neutral simultaneously, either on the whole van, or on the overloaded circuit. So in either event it fails safe, and will remain safe so long as the fault is rectified, or the overload removed, before power is reinstated. I agree about the cost of that polarity revrsing cable being so low it is hardly worth DIYing. Good find - though the cable looks a bit "light" for the full 16A theoretical rating! But, since most continental sites don't supply over 10A, it is probably perfactly adequate. Just don't pack a 3kW electric kettle (don't in any case - as it will almost invariably trip the site supply as soon as you switch on)! Link to comment Share on other sites More sharing options...
anesta Posted August 29, 2013 Author Share Posted August 29, 2013 Derek Uzzell - 2013-08-28 8:47 AM Brian Kirby - 2013-08-27 11:56 PM However, if you can say what van you have, and how old, it is probable that the electrics installed in the van are "polarity neutral", in the same way as continental electrics are, and you do not need any more than the just adaptor for those supplies still with two pin plugs. But, the tester would still be agoood idea to check that the earth is good. Anesta's motorhome is a 2007 Hymer Camp 622 CL (presumably in RHD UK specification with UK-norm 3-pin mains sockets). It is possible to obtain a ready-made reverse-polarity adapter http://tinyurl.com/pg7l5p5 and I suspect that the overall cost of around £12.50 makes it not worthwhile to DIY. But, if a DIY approach is preferred, this may be of interest. http://www.practicalcaravan.com/advice/reverse-polarity-how-cope-tour I'm not sure what "polarity neutral" electrics in a motorhome are, but it should be anticipated that, if the power-supply reaching the motorhome is ' polarity reversed', it will be 'reversed' throughout the vehicle. My Hobby has its original Germany-norm mains sockets that are 'polarity neutral'. As I know what I'll be plugging into those sockets and that reversed-polarity won't be an issue, I'm not concerned about reverse polarity and, although I have a reversing-adapter, I never use it. However (as Brian advises) I do use a tester to ensure that there's nothing really odd (like no earth) about the EHU power-supply. I have just bought this off ebay - it looks exact what I need. Thanks to everyone that helped :-D Link to comment Share on other sites More sharing options...
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