# Phasing.



## stepps110 (Jan 20, 2008)

Just back from europe and stayed on aires and at stellplatz but I did not use any hook ups.
I did meet people from UK who seemed paranoid about these continentals getting the phase and neutral mixed up.

My question is, if all these Motorhomes (european) use these supplies without any apparent damage what is the likelihood of any damage happening to a UK owned 'van.

What actually happens if the phase and neutral are the wrong way round?
I would have thought a possible breaker trip at most.
I know a lot of electronic equipment is polarity sensitive but the supplies are usually transformed and rectified before use.
So is the fear justified?


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## tony645 (Sep 26, 2010)

Dunno, we`re just back and just plugged in when available, didnt make any difference to anything. The amount of times I`ve seen 3 pin plugs wired up wrongly over the years and everything still works!


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## Penquin (Oct 15, 2007)

What concerns people is the worry that the "live" and "neutral" which in the UK are connected in a very specific manner, are not in Europe.

There are several reasons for this - all of which have been discussed on MHF before by very well qualified people. My understanding is based on what they have written and what I have been able to find out.....

"Live" and "neutral" are terms which we apply in the UK but are not really correct; the electrical supply is AC not DC, if it was DC then the terms could be correctly applied (it all depends on the direction of flow of electrons.....), but in AC the polarity (live and neutral) are reversed 50 times per second (= 50Hz). As such what may be "live" for one fraction of a second is "neutral" 0.02 of a second later and so on.

In the UK we have fuses and simple single pole switches i.e. when we turn an appliance off at the switch we break ONE of the two wires (nominally the "live" one).

In Europe such things do not exist - their switches are double pole i.e. they break both feeds (live and neutral) so that there is nothing flowing through. (Which in the UK would happen if you connect the "neutral" to the earth......)

So they are not concerned in the same way that we are.

As regards most electrical equipment it does not matter as the AC current effectively reverses itself 50 times per second so items will function. Some equipment requires specific polarity (all low voltage DC motors for instance), if the polarity is reversed the motor may run in the opposite direction.

The worry is that if we only have a single pole switch and there is a fault we could still receive an electric shock - in the same way that if "neutral" is connected to earth a current will flow. 

Apparently the only equipment that might suffer is some types of fridge (compressor operated), and some items with cooling fans at low voltage.

So generally we do not have to worry but many people carry and use a "polarity tester" - which also detects other connection faults such as faulty earth connection, and many carry a simple reversing cable which "corrects" the "live/neutral" reversal.

I hope that helps, we have carried those items for years, used the polarity tester frequently and the reversing connection rarely - there generally does not seem to be such a widespread problem now from our experience.

Dave


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## johnthompson (Jul 29, 2010)

Alternating current (AC) does just that, changes (cycles) 50 times a second, between live and nutral.

I was brought up in a house that had two wire AC for everything no earths. We had no problems in 30 years. AC will throw you off, DC will not.

Some appliances can remain live if the UK switching system is used as that only breaks one wire. Continental switches break both wires when in the off position. This presents no real problem unless you start dismantling electricals without unplugging them or the van from the hookup.

Remember, its Volts that jolts, but its amps that cramp.


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## Rosbotham (May 4, 2008)

Of 8 sites I stayed at on my recent break, all but one had reverse polarity.



Penquin said:


> As regards most electrical equipment it does not matter as the AC current effectively reverses itself 50 times per second so items will function. Some equipment requires specific polarity (all low voltage DC motors for instance), if the polarity is reversed the motor may run in the opposite direction.


But DC supply will inherently have been rectified from AC so that won't happen.



Penquin said:


> The worry is that if we only have a single pole switch and there is a fault we could still receive an electric shock - in the same way that if "neutral" is connected to earth a current will flow.


That's the key. You'd be extremely unwise to carry out any kind of electrical work without disconnecting the hookup, and within that I include changing light bulbs. Otherwise, though, so long as none of your equipment malfunctions, you'd be fine.

I have heard it said that because few things are uniquely made for the UK market, everything is dual pole switched nowadays so no problem at all. This is wrong...for "everything" possibly read "most things"...but when on a reverse polarity the "oven on" light on my cooker lit permanently, and even did so when the switch on the 240V plug it's wired through was turned off. Strange really...implies the on light must have been wired between the switched live & earth rather than across the switched live & neutral supply - it did definitively show that the oven switch worked only on the live supply though, and did not disconnect the neutral. Suffice to say I unplugged that as we weren't using the oven anyway.

I don't have a polarity changing lead, but I do make a point of disconnecting any 240V appliances that aren't in use when on a hookup that's got reverse polarity.


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## Exu (Nov 21, 2010)

It is NOT TRUE that phase (live) and neutral swap over 50 times a second.

The NEUTRAL is always within a few volts of earth (if the current drawn in all three phases of the district supply were exactly equal, then the neutral would always be at exactly zero volts relative to earth.)

The LIVE wire on the other hand is positive with respect to earth (on average about 230volts) for 1/100th of a second then negative for the next 1/100th of a second.

UK developed the ring main system to use less copper in house cabling soon after WW2 when copper was in short supply. It therefore has a fuse in the live side of the square 13A plug. If there is an overload fault, this blows, the appliance is disconnected from the live (though still connected to the neutral) so is safe.

If you use UK type square pin sockets and fused plugs on the continent, and have a reverse polarity connection, then if the fuse blows the appliance will be left live and hence potentially dangerous. Likewise if you have a single pole overload trip.

The continental system was developed later when copper was more readily available. Ring main systems are strictly not allowed and all circuits are star-wired back to double pole overload trips. There are no fuses in the plugs and often these are not polarised. Reverse polarity therefore does not matter. 

In addition, on the Continent (and in modern house wiring in UK) you always have a double pole differential circuit breaker. The CURRENT in live and neutral should always be exactly equal (though in opposite directions, it reverses 100 times per second). BUT, if there is a difference, some must be leaking to earth - through a fault or even through YOU if you touch to live. The differential circuit breaker detects this difference and if it is more than 30mA (about 1/33 amps) it disconnects both live and neutral from the supply, thus keeping you completely safe.

Many modern appliances are "double insulated" (e.g. have a plastic case and all the wiring inside is also insulated) so do not need an earth connection. Reversing the supply polarity does not matter.

Even in MODERN appliances that need an earth, reversing the polarity will not damage the appliance (but of course, unlike Rosbthom's oven, they need to have been correctly wired internally). But as explained above, if there is a fuse and it is in the neutral, then if the fuse blows the appliance can, potentially, give you and electric shock. The most potentially dangerous are electric kettles with a metal case.

The best way to keep yourself completely safe your UK van is to fit a double pole differential circuit breaker in the incoming supply. But then always, as has already been said, disconnect from the mains supply before doing any work. (I now live in Spain but never trust the Spanish electricians to have got line and neutral the right way round so always turn off the double pole circuit breaker before changing a light bulb - being Edison screw fittings you could easily touch the outer screw of the bulb.)


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## teemyob (Nov 22, 2005)

*Question*

This subject has been on here many times and still gets the same answers from the experts and the I don't give a monkeys brigade.

There are good reasons why we should get the polarity right. Neglect it at your own risk. But don't risk anyone else's safety along with yours.

Simple.

TM


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## Exu (Nov 21, 2010)

*Re: Question*



teemyob said:


> There are good reasons why we should get the polarity right. Neglect it at your own risk. But don't risk anyone else's safety along with yours.
> TM


Yes if you have a UK caravan or motorhome it will have polarised square pin fused plugs, and so of course you are absolutely right. If you want to stay safe, then with that system polarity does matter. (It is an older system and, unfortunately, leads me to the conclusion that British is not always best.)

When I bought my first (and only) caravan it was German. My motorhome was built in Spain (and Spanish wiring regs are very similar to the German system). Because both these (and my house in Spain where I live) use double pole overload trips and double pole differential safety trips, polarity does not matter. Indeed the 16A round plugs with earth contacts on the side will plug in either way round, as will the two-pin 10A plugs that do not have an earth (and of course no plugs have a fuse in them). When you push these plugs in, you have a 50/50 chance of reversing the polarity. It is therefore very important that all appliances can tolerate reversed polarity without damage.

Strangely enough, the French system uses almost identical 16A round plugs with earth but in their system there is an earth pin protruding from the socket that ensures they ARE polarised. (The French 10A two-pin plugs however are identical and hence are not polarised.) The electric kettle we have in our motorhome has a 16A plug that will go into both the German/Spanish sockets AND the French ones - this is quite common with continental appliances that have a plug moulded onto the cable.


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## charlieshelby (Dec 12, 2010)

thats right Exu


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## stepps110 (Jan 20, 2008)

Thank you Exu, that was exactly what I thought.


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## teemyob (Nov 22, 2005)

But are the european type normally NOT switched sockets?


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## Exu (Nov 21, 2010)

What concerned me was that some seemed to base their arguments on why polarity does not matter, on the misapprehension that line and neutral were identical and simply swap over 100 times per second.

On a conventional 230v AC system that is just not true.

The only systems I have come across where it is true, is so-called 110v AC power tool systems. I say so-called because they are in fact 55-0-55 volts systems that use a tool transformer with an input of 230v AC and a centre tapped output with 110v between line1 and line2 - so although you have 110v AC between the two lines, you only have 55 volts (RMS) between either of the lines and earth. These are therefore so much safer because the voltage between line and earth is only 1/4 of that in a conventional 230v AC supply.


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