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Polarity Tester/Reverser


snobbyafghan

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I keep reading about these devices without which no English Gentleman should venture over the Channel. Not wishing to venture abroad without such important parts of the vanner's armoury, I went looking online for them. Can't find any.

 

Could anyone suggest an online source?

 

Doug

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I may well be contradicted here (so be it) but my neighbour is both a caravanner and a very highly qualified electrician. He says reverse polarity isn't as potentially dangerous as many people imagine - it just means that the appliance remains live within its casing even when switched off using its own built-in switch.

 

As he says, you are in no danger unless you intend to open the casing and firtle about inside without removing the plug from the mains!! The appliance is obviously live within its casing when in use, so assuming it is safe to touch then it will still be just as safe to touch when switched off. The 100% safe alternative is to switch off at the mains and unplug of course.

 

Having said all that he did think it was wiser to have one, but said not to worry if I couldn't find one before we went.

 

If you can't find a polarity reverser, which is only a plug and socket on a short lead, buy an ordinary English or Continental one (depending on which type of plug you prefer) and reverse the live and neutral wires at one end only. Cost about £6 to £7.

 

I've also got a polarity checker - again on my neighbour's advice. They look similar to an ordinary plug and are only about £7 or £8 from most caravan accessory shops. They have a chart on the front to tell you what each combination of little neon lights indicate.

 

They are far more useful (in terms of personal safety) than the polarity reverser because they will test the earth connection as well. If that is indicated as "dodgy" unplug quick and move somewhere else or get the supply fixed before you use any appliance. A poor or non-existent earth connection really is serious.

 

If I am contradicted by a qualified electrician, take his word for it as I could just possibly have got the wrong impression from my neighbour. You don't muck about with electricity - - - well, only once!

 

P.S. Just noticed Olley's post. It's the Mains Socket Tester you need, not the Polarity Checker lower down the page.

 

Thanks Olley - didn't know Maplin's did them and another friend wants one.

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Just to add to the theme of "Old Gits" reply, I would have expected to see quite a few continentals on foreign camp sites (maybe a few in the UK) with frizzled hair and burnt fingers.

 

Compared with the UK, there does seem to be a more laid back attitude to connecting up to the mains , ( maybe a few other things as well !)

 

Rgds

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as I have been led to believe the continental "off" switch switches off pos and neg connections where ours sitches off only the pos connection

 

Don't shout me down on this it wasn't my idea just what I was told.

 

Either way I have experienced no problems but do have a test plug, have yet to find any reverse wireing either here or in Europe

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Olley

 

Thanks for that; I had looked on Maplins but because I was looking for a polarity tester and the only one they had was for 12v, I thought they didn't have what I wanted. A bit confusing of them to call it something different but that isn't unusual with anything vaguely technical. Anyway, the local branch has got one so I'm sorted.

 

Thanks for the other comments as well - interesting stuff.

 

Doug

 

 

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Syd - 2007-08-30 4:16 PM

 

as I have been led to believe the continental "off" switch switches off pos and neg connections where ours sitches off only the pos connection

 

Don't shout me down on this it wasn't my idea just what I was told.

 

Either way I have experienced no problems but do have a test plug, have yet to find any reverse wireing either here or in Europe

 

Wouldn't dream of shouting you down Syd.

 

You may well be right - my electrician friend is back from Spain this weekend so if nobody else has sent in the answer by then I'll ask him and let you know.

 

I have found reverse wiring in both France and Belgium, but didn't lie awake worrying about it. Come to think of it I didn't use the polarity reverser either, although I had it with us. What a plonker!!

 

I'm only really concerned about the earth connection as mentioned before, and have never come across a bad one.

 

Cheers

 

 

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If you have a modern motorhome it will be equipped with an earth leakage current detecting main circuit breaker. These breakers do this by accurately comparing the current flowing in the NEUTRAL wire with that flowing in the LIVE wire. If these currents are not almost identical (because some has flowed elswehere - like via earth back to the transformer) then the trip will operate disconnecting both LIVE and NEUTRAL connections.

 

If you have an appliance with an earth leakage fault and the Mains hookup is connected correctly then the earth leakage trip will operate when you switch on that appliances ON/OFF switch.

 

If the mains hookup is connected with reverse polarity and you have an appliance with an earth leakage fault then the trip will operate as soon as you connect your hookup irrespective of the appliances ON/OFF switch.

 

If you have an OVERLOAD situation then the circuit breaker supplying the circuit which has the overload will open irrespective of supply polarity. If this overload is because of an earth fault then the earth leakage trip will operate anyway.

 

So, I would not worry about reverse polarity unduly as faults will get picked up one way or another.

 

But,

The latest Autotrails, Autocruise, Kontiki, Bessacar and Timberland motorhomes include an indicator lamp to warn of reversed mains polarity.

 

 

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Old Git - 2007-08-30 10:13 PM

 

Thanks Clive. Very clearly explained so I won't have to bother my electrician friend after all - who has just returned from Spain and is about to reverse his caravan into the drive as I type. Must dash and see if he needs a hand.

 

As a further point it might be useful to know that I fitted one of these devices about 6/7 years ago. Forgotten the name but it was well promoted in all the mags at the time and cost about £50. When using it in Portugal (probably the first occasion it was needed!) it cut the power off completely and after much trouble shooting the only solution was to remove it from the circuit. Whole thing took about 4 hours mainly in the dark.

 

Although I fully accept Clive's advice I now just take along one of those circuit testers you plug into a 13 amp socket, and a "reverse wired" hook-up plug. Total cost about £10 for added piece of mind for those of us that don't understand this electrical stuff.

 

Vernon

 

 

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I agree to a point with Crinkly, but when a non or low cost hookup is available we take the coffee machine out of its cupboard, switch the water heater to electric and use a small electric kettle for my cuppa.

We havent got a microwave (yet)

 

 

 

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Why don't you just purchase a second European hook up cable, less than a tenner, and reverse the wireing in that, mark it with a coating of red insulating tape so that you dont mix it up with the correct one then rely on your polarity meter to let you know if the wireing is incorrect, if it is then change your European hookup cable for the one that you doctored earlier.

 

Like what I do

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Clive's comforting advice about earth leakage trips has set my mind at rest, though I was really only concerned about the earth connection.

 

I also mentioned it again to my electrician friend. He never gives it a thought, but did wonder how many polarity reversers and testers of varying cost and complexity have been sold as a result of yet another inflated scare story.

 

His words, not mine - but haven't we been there before? Expensive gas detectors for detecting an as yet unidentified gas? (!) (!)

 

Regards

 

Dave

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I don't sell gas detectors because I don't believe there is a true need for them but I do sell polarity changeover switches as I think there is good reason for it. Interestingly Crinkly, as you come from a boating world where 240V and water are frequently in very close proximity, these devices started life aimed at boat owners. In general I would agree that the risk is small as you'd need several faults to occur simultaneously for a real problem to exist but its that small element of risk that is important. Just because the risk is small doesn't means that it will never happen.

 

D.

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crinklystarfish - 2007-09-02 9:23 AM

OG alludes to a compelling trend. Motorhome owners, and I include myself, do seem happy to spend huge amounts of cash on barely-ever-used, or utterly useless tat.

I wonder why?

 

Hi SteveInsert a tiny, niggling little thought into someone's mind, and it won't need any fertiliser. However logically certain you are that a scare story is a load of crap (sorry ladies) it will tend to fester away until you find yourself shelling out "Just in case" or "To set the wife's mind at rest". It's so insidious - I don't believe the gassing stories for a minute, but I still hesitate for a moment before leaving the windows open overnight.As for the "must haves" it's quite clear that the majority of us are susceptible. Advertising is costly, especially on the box, but it is patently very effective or no-one would continue spending the cash.I think another of those little reminder cards is required - next to the crinklies in the wallet.Aaarrrrggghhhhhhh. All these awful puns. :$ :$ :$ :$ Dave
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Dave,

The sensible part of me says you're absolutely right: the cynical part says we're over-regulated, over-cosseted and utterly uncritical. I can't defend the non-purchase of safety related items, so won’t try. I was more alluding to the whistles and bells type of stuff that suddenly becomes ‘essential’; but had never entered your head to buy, before exposure to magazines, shows, or forums!

OG,

Where do you buy those reminder cards?...

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