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Discussion Starter · #1 ·
I've never been really convinced one way or the other about the real dangers of plugging into a reversed polarity line but for the sake of a tenner for a tester and a tenner for a reversing cable and 2 minutes checking, I've always made the effort to check and switch over if necessary.

I've just spent £4.09 and hopefully eliminated the "risk" completely.

My humble campervan has only one 3 pin socket which I've now replaced with a double pole socket from Screwfix - why didn't I do this before?

I know most more upmarket motorhomes have more than one socket but even so, at £4 a time I reckon it's got to be a good buy.

Anyone want to buy a switch-over cable? :D
 

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i'm not up to speed on rev polarity, but have seen numerous references to it...

can I have an idiots guide please.

if I plug van in to charge batteries whilst in France and it is reverse polarity, will it

a. not work
b. charge battery fine
c. blow up the electrics

thanks

chris
 

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chrisblack said:
i'm not up to speed on rev polarity, but have seen numerous references to it...

can I have an idiots guide please.

if I plug van in to charge batteries whilst in France and it is reverse polarity, will it

a. not work
b. charge battery fine
c. blow up the electrics

thanks

chris
Chris,
Everything will work, it changes the way that items are earthed, but as so many electrical products are no longer earthed back through the plug you are unlikely to notice any difference.
Gerry
 

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GerryD said:
chrisblack said:
i'm not up to speed on rev polarity, but have seen numerous references to it...

can I have an idiots guide please.

if I plug van in to charge batteries whilst in France and it is reverse polarity, will it

a. not work
b. charge battery fine
c. blow up the electrics

thanks

chris
Chris,
Everything will work, it changes the way that items are earthed, but as so many electrical products are no longer earthed back through the plug you are unlikely to notice any difference.
Gerry
Hi Gerry its more to do with the fact that the live is usually switched and if polarity is reversed then it means there is potentially still a live at your appliance

The earth is the same

Alan H
 

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If it matters so much how come it does not effect the rest of Europe on 2 pin plugs do you ever see them check NO.

That's because it does not matter which way round the live is.

All of the appliances you use are the same as you get in the rest of Europe. All are double insulated so no worries.

Andy
 

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Reversed polarity is a UK problem. We use sockets and light switches that are only 'single pole' and are intended to be positioned in the live side of the circuit.
European systems use 'double pole' switches, which operate on both sides of the circuit.
The hazard is that an appliance, or light, can still be 'live' if the single pole switch is in the negative, or return side, of the circuit; and the circuit can be completed through the earth connection if you get fingers/tools etc in the way.
For safety you need to check the polarity on european sites before connecting, and use the appropriate standard, or off-standard wired adaptor to ensure that the live side of the circuit passes through the live side of an MH wired with UK sockets.
I use a 'Martindale' circuit tester that I have had for years. Apart from circuit polarity it also checks for the presence of an 'earth'; and has proved useful on occasions. I once came across a site where there was no earth at all, this was indicated on the tester as 'earth fault'. This meant there was actually no safety protection at all, as circuit breakers need an earth to operate. Technically many work as 'balanced circuit' devices, ie the current through live and neutral is the same, and if a defect occurs and contact is made to 'earth' the circuit goes out of balance and 'trips'.
These devices are very sensitive, if you look at them their 'rating' is printed on the front, and is measured in milliamps ie thousandths of an amp. So 30 mA is 30 milliamps is 3 one hundredths, or 0.03 of an amp;
which gives you an idea of the small amounts of power they can detect.
No earth is the most dangerous situation these days, although years ago many houses did not have any earth to their electrical installation if fed from overhead cables down the street!
If no earth is present you need an earth spike, or complain to the site manager ( if you can speak the local lingo tech style that is).
Earth spikes need to go into the ground sufficiently to give a good low resistance, and may need to be kept damp to work in some soils. You might get away with a robust steel or copper clad spike at least 300mm long; but the more metal in the ground generally the better the earth.
Earthing used to give me all sorts of problems when I was in gainful employment, one site on solid chalk where we had to install some 11000/415 volt transformers we ended up rock drilling 50m deep into the chalk to get the earth reading down to a level that the technical safety trips would work on!!

Hope this explains some of the technical side of 'reverse polatity'.
 

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Hi BJT

We don't have to keep the earth spikes damp any more we use Bentonite (might have spelt it wrong) it gives a lower resistance.

Just must add in this country we must stick to the correct polarity.

Best Regards
Broom
 

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there's an interseting point you make in your posting - you refer to the uk 3 pin socket...

therefore I guess that in imports like mine, fitted with a single european 2 pin socket, then no worries?

chris
 

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No, you are quite right Broom, it is Bentonite. I thought there was enough tech stuff in the post without Bentonite, earth resistivity, copper clad driving rods, null earth balance meters, etc., etc.....
Brain goes into 'tilt' with too much info.
 

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Hi BJT

Going to show my age now, what about me ''bridge megger'' still hung up in the garage.

Just asked the young wiz kids which sit around me about one, all frowned.

I still think that correct polarity should be observed with UK accessories and sites.

Best Regards
Broom
 

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Discussion Starter · #14 ·
chrisblack said:
there's an interseting point you make in your posting - you refer to the uk 3 pin socket...

therefore I guess that in imports like mine, fitted with a single european 2 pin socket, then no worries?

chris
Well that socket should be switched and being continental, the switch will be double pole so you'll be ok.
 

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GerryD said:
chrisblack said:
Chris,
Everything will work, it changes the way that items are earthed, but as so many electrical products are no longer earthed back through the plug you are unlikely to notice any difference.
Gerry
I must disagree most strongly with this statement.

Reversed polarity has nothing whatsoever to do with earthing.

It means that the earth and neutral wires are reversed hence a socket with a single pole switch (the usual type of socket) will have the switch and the fuse in the neutral line. This means that if you switch off the socket or if the fuse blows the item plugged into the socket will remain live even though the current will no longer flow.

Touching a live part of the item will result in a shock though you should still be protected by the rcd.

You can have reversed polarity with and without an earth connected.
 

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This is no criticism of previous posters, but just an opinion. :D :D

The problem with reams of technical jargon is that it often doesn't mean a lot to some folk, and simply serves to make them even more nervous than before. :?

In a nutshell, so long as you disconnect an appliance from the mains socket before poking around inside it you should be safe, whether its polarity is reversed or not!

I know there is always the miniscule chance that a wire will come loose and touch the casing (or something equally unlikely) but that's a risk I'm willing to take if it means I don't have to carry a bundle of three foot copper rods to hammer into the ground on Continental sites!! 8O

(Bundle??? They ain't coming out again easily are they? 8O )

And I make that ridiculous statement quite deliberately, as I was asked exactly that question by a worried Newbie we got chatting to on a French campsite. 8O (You guessed! He had been reading the forums and magazines! :roll: )

It's always better to do things correctly of course, but sometimes the cure is far more problematic than the ailment!! :roll:

Dave

P.S. I do use a plug-in tester, but only to check for an earth connection. I also know they are not completely reliable for this purpose, but a lot better than blind faith because the earth connection most certainly is important.
 

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Reverse Polarity

Hello,

We have had a lot of reverse polarity on mains abroad, mainly France, Italy and Spain.

I was going to consider a switch over unit but noticed on our Frankia the hook-up plug simply twists off and without any tools you can unclip the wires and swap them.

Not sure where you can get the plugs from, cannot seem to find them anywhere.

Trev
 

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[Moderately technical bit follows]

My little Fluke plug-in socket tester states: will only detect missing earth >200KOhms.

Which implies that anything less than that would show as 'OK'.

Those who know what "Zs" is, also presumably know the max for a circuit behind a B10 MCB is 4.6 Ohms.

Assuming that the earth resistance referred to by the socket tester is "R2"; anything more than a couple of ohms is dangerous.

Furthermore, the Fluke one says it can't detect a Neutral / Earth reverse. (can't vouch for other brands products; but Fluke stuff is not 5hite)

[End of moderately technical bit]

OK, plug-in testers; they'll detect L / N reverse, and complete absence of E, but anyone armed with one of these should not be under the impression that it vouches for the safety of a circuit.

Having said that; if I remember, I'll be taking mine with me to Europe in 2wks time, but only out of interest. I'm certainly not taking a thousand pound multifunction tester with me; it's supposed to be a holiday after all!

My advice is not to use appliances in (and especially out of) your motorhomes, which are not "Class 2" = Double Insulated = have a symbol of 2 concentric squares (inside each other) on them;

and of course, don't start tinkering with mains electrical stuff unless you know what the limit of your knowledge is.
 

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If your RCD is double pole (which prety well all of them in motorhomes are) then you have nothing to fear with reversed live and neutral connections at the hookup. Irespective of which one is live any earth fault will unbalance the trip and cause it to open.


C.
 
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