# Reverse polarity (again, sorry...)



## Rosbotham (May 4, 2008)

Hi all

We're off to the continent in a couple of months, so starting to put together the extra kit I need.

On the issue of hookups, my intention had been to get a Euro adaptor (short lead converting Euro plug-CE socket, same as the one I use to hook up my MH to mains supply at home, but with a European plug rather than 3 pin UK plug), and also to cope with reverse polarity to wire up a short lead with CE at each end reversing the live/neutral, obviously suitably marked.

Went to our local dealer last week (well one of them, lucky enough to have Discover, Campbells, Todds & Riversway within 10-15 min drive from home), and when I was buying the bits to make up the cross-polarity lead, was persuaded to take another route. Rather than having the CE-CE cross-over, dealer advised me to buy two Euro leads & take one apart to wire as a cross-over.

This means that I can cope with reverse polarity on a bollard that has a Euro socket, but not with reverse polarity on a more modern CE socket bollard. 

Am I missing a lead, or is this a combination that never / extremely seldom happens?

I suppose if it did arise I could either live with reverse polarity (I'm an electronic engineer by trade and I'm not totally sold that it makes a huge difference unless you start to take kit apart), or take my main hookup lead apart to rewire then wire back the right way afterwards (MH is in store this week...not sure if the CE plug/sockets on my 25M cable are sealed or can be taken apart).

Opinions welcome!!


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## 113016 (Jun 5, 2008)

I made up a small reverse polarity jump lead using our standard uk fittings and then all you need is the required fitting to go into the bollard that you intend to use.
Works for me


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## Zebedee (Oct 3, 2007)

Hi Rosbotham

I have a cross-over lead, and would happily give it to you . . . if I could find it! 8O

Does that answer your question?  

I carried one for years, and never used it. 8O :roll:

I do check for an earth connection though, using a little plug-in polarity tester, as this is far more important 8O . I also realise these cheap gadgets don't necessarily indicate the *quality *of the earth connection - but they do at least tell you whether there is one or not.

Can't be bothered with reverse polarity. I would always unplug any item I had to work on anyway - which ever way the polarity was wired. 8O 8O

Hope this helps - I got confirmation of my opinions from a consultant electrical engineer, also a caravanner, and he doesn't possess a cross-over lead!!

Dave


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## karlb (Feb 22, 2009)

Zebedee said:


> Hi Rosbotham
> 
> I have a cross-over lead, and would happily give it to you . . . if I could find it! 8O
> 
> ...


i concur, check the earth connection yes but reverse polarity is not a problem unless working on equipment.


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## 113016 (Jun 5, 2008)

Used mine lots of times and even found different sockets on the same bollard with some reversed and some normal


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## tonyt (May 25, 2005)

If you're worried about reversed polarity and want to knock up a switch over cable then use blue connectors each end then you can use it anywhere. You're going to need a continental adaptor anyway - despite what many say, there are lots of French municipals using old style hook ups (and dodgy eathing!).


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## 113016 (Jun 5, 2008)

I agree, I have found quite a few with bad / no 
earth


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## 113016 (Jun 5, 2008)

By the way, what do you guys do when you get a bad or no earth?


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## karlb (Feb 22, 2009)

can someone explain what bad/dangerous conditions would occur with reverse polarity.


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## 113016 (Jun 5, 2008)

karlb said:


> can someone explain what bad/dangerous conditions would occur with reverse polarity.


 Not 100% sure, however I believe that should a fault occur in an appliance the frame of the appliance could become live.
Maybe someone could expand on this


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## Zebedee (Oct 3, 2007)

Grath said:


> By the way, what do you guys do when you get a bad or no earth?


Tell the management, and wait at the desk until someone comes to fix it . . . then check it again to see if they have done the job. 8O 8O

Or move the hook-up to another bollard, and still tell the management. (They can't mend it if nobody has told them it's bust! :? )

Dave


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## 113016 (Jun 5, 2008)

Zebedee said:


> Grath said:
> 
> 
> > By the way, what do you guys do when you get a bad or no earth?
> ...


I take your point, but easier said than done with some of the smaller French sites as many have a don't care less attitude.
Could you not put your own earth down?


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## Zebedee (Oct 3, 2007)

karlb said:


> can someone explain what bad/dangerous conditions would occur with reverse polarity.


With alternating current, it makes no difference to the use of the appliance which wire is designated "live", because the current reverses its direction 50 times per second. (Frequency changes in some countries, but same principle.)

It's the switch that makes the difference.

It should be connected directly to the *incoming *"live" wire, so that when in the off position no current can even enter the innards of the appliance.

With reversed polarity the switch will (in effect) be positioned at the "exit" of the current, if that makes sense :? . The appliance can still be switched on and off as usual, and will work in precisely the same way, but if you were daft enough to take it apart and shove your hand inside *without removing the plug from the socket* the innards would be "live" even when the switch on the appliance is "off".

I hope that makes sense. 

It's a simple concept but quite difficult to explain. :?

The bottom line (_IMHO - covers tracks carefully_ 8O 8O ) is, don't worry about it unless you intend to dismantle your appliances while they are still plugged in at the socket. 

And if you plan to do that, you are certifiable anyway!! 8O :lol: :lol: :lol:

Dave


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## pejoy (Sep 14, 2008)

:? I'm geting more confused by the minut! So what do you do if you find a poor or no earth situation?

And have i got this bit right, i dont need wory about reverse polarity unles i'm going to take an apkliance apart, and then it should be unpluged.


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## karlb (Feb 22, 2009)

Zebedee said:


> karlb said:
> 
> 
> > can someone explain what bad/dangerous conditions would occur with reverse polarity.
> ...


thanks, that is my understanding as i am a tv engineer and electrician i was just checking and also to see why people worry.


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## Zebedee (Oct 3, 2007)

Grath said:


> I take your point, but easier said than done with some of the smaller French sites as many have a don't care less attitude.
> Could you not put your own earth down?


I take your point as well.  We've all been to a few of those. :roll: :roll:

You *could *put down your own earth, but I would most certainly advise against it unless you really know what you are doing. 8O 8O

It's not as easy as banging a copper stake into the ground and connecting a bit of wire, and I would certainly not bother - even though I know how, and might even have the equipment with me to do it.

If I couldn't find a bollard with an earth, and the management refused to fix it, I would move on. It just isn't worth the risk.

There *should *never be a problem, but who can guarantee that every appliance in their van, both built-in and portable, has been correctly assembled . . . possibly by some spotty youth somewhere doing his (or her) first one without direct supervision?? 8O 8O :roll:

Dave


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## karlb (Feb 22, 2009)

pejoy said:


> :? I'm geting more confused by the minut! So what do you do if you find a poor or no earth situation?


if you were camping with a generator what earth would you have then?


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## 113016 (Jun 5, 2008)

karlb said:


> pejoy said:
> 
> 
> > :? I'm geting more confused by the minut! So what do you do if you find a poor or no earth situation?
> ...


 Good point


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## Zebedee (Oct 3, 2007)

Can't answer that. Never used one so not qualified to comment.

Have to wait for someone who knows about them. :? 

Dave


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## 113016 (Jun 5, 2008)

We were on an Aire with free electricity and of course we plugged in and tested and everything was ok  
We went for a walk and on our return, we found that a French guy had unplugged us, put in his adaptor (as they do) and plugged his m/h in and this then gave us no earth. :x 
I soon sorted it out by moving his again


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## twinky (Aug 11, 2008)

karlb said:


> can someone explain what bad/dangerous conditions would occur with reverse polarity.


The on/off switches would be 'downstream' of the current and although everything would function correctly the power to the appliance would still potentially be present.

Polarity is especially dangerous with Edison Screw lamps because the outer screw of the lamp is a contact. When polarity is correct the flow of current is from the centre pin of the lamp through the filament to the outer screw.

Assume the bulb had blown and the polarity is reversed. You would reach down to unscrew the bulb and very possibly touch the outer screw. Then you would be touching a live part of the circuit.

I also posted a query before about the possibility of the RCD, present in every mh, not functioning correctly but apparently they are designed to work with the supply either way round.

A good earth is vital for the safe speedy operation of the breakers under fault conditions.

I might test this one day, but having sold my multifunction tester recently, will have to borrow one from a mate


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## Tinyk (Mar 18, 2009)

Grath said:


> We were on an Aire with free electricity and of course we plugged in and tested and everything was ok
> We went for a walk and on our return, we found that a French guy had unplugged us, put in his adaptor (as they do) and plugged his m/h in and this then gave us no earth. :x
> I soon sorted it out by moving his again


Sounds handy, so i shall add to my continental pack, rubber gloves (electrical insulated) and pair of wire cutters to deal with French motor homers who nick the socket LOL

Nice discussion I certainly never understood what the reversed polarity meant or did.

Ayone with a good link to the correct tester to take with you?

Thanks

Kevin


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## Zebedee (Oct 3, 2007)

Tinyk said:


> Anyone with a good link to the correct tester to take with you?
> Thanks
> Kevin


Hi Kevin

Unless you know how to use the fancy, and very expensive testers, they are a waste of time - by definition I guess!! :roll:

One of >> these << or maybe >> this one << but it's bulkier and does the same job.

I included the second one to answer Karlb's question when he said, _"i was just checking and also to see why people worry."_

This extract from the website selling the second tester is the answer I think Karl . . . scaremongering to get a sale.

"An absolute must in the caravan! You should always check the polarity of the on site electrics before you connect your appliances to them. Why? 
Because if it's reversed you could easily be eletrocuted!"

It's not a lie, but is deliberately misleading.

You could indeed easily be eletrocuted (sic 8O ) but only if you were idiot enough to firtle in the innards without unplugging an appliance from the mains.

Edison screw lamps excluded 8O . Good point Twinky, but not a big concern to motorhomers since I don't think they are used - and if they are, forewarned is forearmed. :wink: :wink:

Good discussion indeed - that's what MHF is all about, eh? :lol: :lol: :lol:

Dave


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## tonyt (May 25, 2005)

Picking up from an earlier post in this thread......

How is the mains supply earthed when coming from either an invertor or a generator?


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## Zebedee (Oct 3, 2007)

tonyt said:


> Picking up from an earlier post in this thread......
> 
> How is the mains supply earthed when coming from either an invertor or a generator?


Start a new thread Tony.  

People will ignore this one after a quick glance as the topic comes up so often.

We need a title something like, "Are appliances earthed when using a generator?"

That should attract the right sort of attention. :?

Dave


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## 113016 (Jun 5, 2008)

There is a relevant article in May edition of MMM, page 12/13.
It is mentioned that there is a main earth wire in motorhomes to earth all of the 240V appliances to the chassis and this should be checked periodically.
I do realize that this earth will not pass through the rubber tyres to the ground.
The same writer mentioned that he was on a camp site in Spain with no earth showing on the tester and he put a tent peg into the ground with a wire to the chassis, however the tester still showed no earth.
Maybe a longer rod and a decent size wire would help if you are found in this situation.
Maybe this would help the generator situation?


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## Rosbotham (May 4, 2008)

Thanks for the replies guys...confirms my belief that the whole issue is over-blown.


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## 113016 (Jun 5, 2008)

Grath said:


> There is a relevant article in May edition of MMM, page 12/13.
> It is mentioned that there is a main earth wire in motorhomes to earth all of the 240V appliances to the chassis and this should be checked periodically.
> I do realize that this earth will not pass through the rubber tyres to the ground.
> The same writer mentioned that he was on a camp site in Spain with no earth showing on the tester and he put a tent peg into the ground with a wire to the chassis, however the tester still showed no earth.
> ...


A further point is, don't forget that we are using a moving vehicle (not while using the 240 V) however our vans are subjected to lots of vibrations and strains and therefore wires could become dislodged or broken and then could easily touch the frame of an appliance.


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## Chrisv (Jun 10, 2007)

Hello,
My MH has just had its first habitation service and mysteriously the polarity was reversed (now rectified)- didn't seem to make a difference. Ignorance is bliss! Coincidentally I bought one of those plug in polarity testers last week but haven't used it yet.
Thanks for the explanation Zeb. I'd always thought that it was something terrible to be avoided.

Thanks
Chris


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## karlb (Feb 22, 2009)

tonyt said:


> Picking up from an earlier post in this thread......
> 
> How is the mains supply earthed when coming from either an invertor or a generator?


generators have a "floating earth" which imo means no earth but i stand to be corrected


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## karlb (Feb 22, 2009)

http://www.voltimum.co.uk/news/6514/s/Small-generators-on-construction-sites.html

no earth.......so to the people who check the earth do you use a generator? if you do why do you bother checking the supply on site :roll:


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## Zebedee (Oct 3, 2007)

Good point Karl.

I'll think of an answer - one day - - - perhaps! 8O 8O :roll: 

Dave


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## cronkle (May 1, 2005)

> A further point is, don't forget that we are using a moving vehicle (not while using the 240 V) however our vans are subjected to lots of vibrations and strains and therefore wires could become dislodged or broken and then could easily touch the frame of an appliance.


Which is my concern. It happened to me just before Easter with one of those plug in electrical rings. Something got loose inside the thing and caused it to smoke. Obviously this was not the wire touching the casing but some other component that came loose and overheated, however, in my mind if one component can come loose an electrical one might do as well.

Any way, checking the polarity gives me the chance to play with gadgets  but then again pushing plugs in and out can cause a danger but on balance, as I have the gizmos and wires I will keep using them.


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## rayhook (May 15, 2005)

*Reverse polarity*

The explanation above about switches is how I understand it. Now, Europeans don't suffer from this - you can plug a two pin plug in either way round. The reason? They use double pole switches. So, all you guys who are so worried about reverse polarity (I've got continental sockets in my Chausson), why not change your switched sockets for double pole ones and then just forget about reverse polarity? You can buy switched double pole sockets most anywhere for small change and I'm baffled why (UK) manufacturers don't fit them as standard - extra cost about 30p/socket.

Or am I missing something? In four years with my Chausson (about 12 months in Europe) I've only ever seen Brits checking for reverse polarity and I've never bothered about it myself with no adverse effects.

Ray


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