Jump to content

reverse polairty


mids

Recommended Posts

  • Replies 57
  • Created
  • Last Reply

I have motorhomed all over Europe and never once have I been killed by reverse polarity, possibly because I never used an ehu and didn't carry a lead as I found that reduced the risk considerably!

 

If it still worries you that much and you really cannot live without your umbilical cord only ever use plastic double insulated appliances and wear rubber gloves.

Link to comment
Share on other sites

agedone - 2018-01-21 11:28 AM

 

So the fuse in a 13 amp plug to is now redundant? Can I replace with a safety pin as in the old days?

 

The fuse in a BS1363 "13A" plug is for overload protection, and will still function in that capacity regardless of polarity.

 

That being said if live connections were to come into contact with earthed metal enclosures, the fuse should blow because the current returning along the earth wire is sufficient to blow the fuse. This would not happen if the live and neutral connections were reversed. Many appliances now have plastic covers, and are double insulated as denoted by the double concentric square symbol. In use such appliances pose no shock risk regardless of polarity.

 

The main earth fault protection is usually provided by the Residual Currenr Device or RCD. This compares the current flowing in the live and neutral conductors, and if they differ by more than typically 25mA (0.025A) the RCD will trip and disconnect the supply.

 

I regard the reference to a safety pin as irresponsible. It is not wise to joke about electrical safety.

 

Alan

Link to comment
Share on other sites

Alanb - 2018-01-21 12:08 PM

 

agedone - 2018-01-21 11:28 AM

 

So the fuse in a 13 amp plug to is now redundant? Can I replace with a safety pin as in the old days?

 

The fuse in a BS1363 "13A" plug is for overload protection, and will still function in that capacity regardless of polarity.

 

That being said if live connections were to come into contact with earthed metal enclosures, the fuse should blow because the current returning along the earth wire is sufficient to blow the fuse. This would not happen if the live and neutral connections were reversed. Many appliances now have plastic covers, and are double insulated as denoted by the double concentric square symbol. In use such appliances pose no shock risk regardless of polarity.

 

The main earth fault protection is usually provided by the Residual Currenr Device or RCD. This compares the current flowing in the live and neutral conductors, and if they differ by more than typically 25mA (0.025A) the RCD will trip and disconnect the supply.

 

I regard the reference to a safety pin as irresponsible. It is not wise to joke about electrical safety.

 

Alan

 

Yes, it is not wise to joke about electrical safety, sorry. I cannot understand why anyone would take a risk, no matter how small, with electricity. In my youth I took several "hits" and I am still here, however now that I am older and perhaps wiser, I am more careful.

 

I would add that many motor homes are of a vintage that predate RCD's and are therefore not protected against earth faults.

 

It is not difficult to test for reverse polarity, and then correct it. Why would you not?

 

 

 

Link to comment
Share on other sites

In this era of, so called "elf'n'safety" and litigation etc, if "reverse polarity" really did pose a real world danger whilst using ehu in motorhomes/caravans, then surely the manufacturers would by law be routinely fitting techy-gubbins to deal with it?

(..something that either "auto corrected" it or at least, had a warning buzzer and manual "correction"/change over switching..?)

How many,if any, mainstream manufacturers install such things?.....if not many(or none?), then why do we think that is?......

 

(..and as it stands, IF it is supposedly a real danger, then using some £4.99ish tester and then relying on some lead, which had possibly been cobbled together by some well meaning but no less ham-fisted DIYers, hardly sounds ideal anyway... ;-) )

Link to comment
Share on other sites

aandncaravan - 2018-01-16 9:04 PM

 

This webpage it explains the issues. : http://www.aandncaravanservices.co.uk/reverse-polarity.php .

 

Thanks for the link. The article seems to say that reversed polarity shouldn't be a safety issue in day to day use. Also in the vast majority of cases reversed polarity with the functioning of equipment attached to it. However, there MAY be a functionaily issue with some pre- 2002 mains battery chargers and some electronic equipment. Is this correct?

Link to comment
Share on other sites

mids - 2018-01-16 8:31 PM

 

what is the worst case scenario if I ignore it am I worrying for nothing

Travelled in France last Sept/Oct, some of the places we stayed at showed up as reverse polarity, but everything worked as normal.. ours is a 2004 Inca.

 

Oh... and ignore the 'Bear Grills I don't need no electricity' types, do your own thing...

Link to comment
Share on other sites

The danger would be if the outlet is switched with a single pole switch as is current(sorry for term) for UK houses then when switched Off the connection would still be connected and live.

Splashing the lead when refilling the kettle could be fun......

I always check to see if the mains is reversed and check for the earth connection.

A simple mains indicator will show any problems, these can easily be overcome with suitable adaptors, some are needed any way for continental mains connection.

Link to comment
Share on other sites

The electrical systems that mainstream UK motorhome/caravan manufacturers install will very often be based on Sargent equipment, and this equipment will include a light to warn of reversed polarity. It’s then up to the motorhome/caravan user to decide how to react to that warning.

 

There’s also this product

 

https://www.leisureshopdirect.com/electric/230v-equipment/230v-plugs-and-sockets/mains-polarity-changeover-switch

 

that has been available for years, but I don’t think any UK motorhome/caravan manufacturer fits it as standard. As far as I’m aware there is no commercially-available device designed for leisure-vehicles that would detect reversed polarity and automatically ‘correct’ it.

 

I carry a short lead that I can connect to a 230V hook-up outlet and a neon ’socket tester’ that I can plug into the lead. I’ve no real interest in an outlet’s polarity, but I prefer to know if it’s live before I position my motorhome and uncoil the hook-up cable. I won’t use the outlet if there’s no earth, but if its polarity proves to be reversed I don’t bother to correct it. As has been mentioned on this forum in the past there is the possibility that 230v equipment will be polarity sensitive, but there’s nothing in my Rapido that is.

Link to comment
Share on other sites

michaelmorris - 2018-01-21 3:13 PM

 

aandncaravan - 2018-01-16 9:04 PM

 

This webpage it explains the issues. : http://www.aandncaravanservices.co.uk/reverse-polarity.php .

 

Thanks for the link. The article seems to say that reversed polarity shouldn't be a safety issue in day to day use. Also in the vast majority of cases reversed polarity with the functioning of equipment attached to it. However, there MAY be a functionaily issue with some pre- 2002 mains battery chargers and some electronic equipment. Is this correct?

 

 

Yes, that is a fair summary.

 

If I had to fit a new plug to my Toaster in the house and wired it with the neutral to live and vice versa, i.e. Reverse Polarity, the Toaster would be no more dangerous than if it was wired 'correctly'.

It would still blow the fuse if a fault developed and trip out the House RCD as normal.

It would still function normally if not wired to the 'UK Polarity rule' as opposed to the European 'any' Polarity is safe approach.

 

However, if I were to leave it plugged into the wall and then took it apart, slightly more of the cable would be 'live' than if it was wired to the UK Polarity rule.

 

So if someone was stupid enough to poke their fingers into the wiring while it was in pieces and still plugged into a live supply, then they might be electrocuted.

 

But clearly no one is going to do such a thing, making the risk non existent.

 

Those exact same issues apply in a Motorhome. A modern motorhome on a reverse Polarity connection is no more a safety risk than that at home, provided the most basic of common sense is followed.

Much more detail on the webpage detailed above.

 

If anyone tells you that there is a risk with reverse polarity on a modern Motorhome, get them to detail EXACTLY what that risk is and why.

 

The Kettle example above is a Green Pilchard, because to fill a kettle where you let the lead get wet is a danger that would apply with either polarity wiring.

I can't imagine a single scenario of filling a Kettle, while plugged into a live wall socket where reverse polarity makes any difference.

 

In any case someone not taking care to ensure water and electricity don't mix, is not being very sensible.

Secondly modern appliances are double insulated and double pole switched.

 

A Motorhome 13amp socket we recently dismantled was also double pole switched, as are the ones in my house.

 

Most of the scaremongering we hear is based on information 30 years out of date plus poor information from British Motorhome manufacturers, who should have started fitting polarity safe appliances 30 years ago. Just as the Motorhome manufacturers did on the continent.

 

Talk to a German, Spaniard, Frenchman, etc. about 'reverse Polarity' and they won't have a clue what the fuss is about.

There is no such thing on the continent, their Motorhomes are configured so it's safe wired either way.

 

 

Link to comment
Share on other sites

Personal experience of 'reversed polarity':

 

1) An Eberspächer heater with the mains heater attachment, would not run at all on mains and defaulted to diesel (fitted to an Auto Sleeper Duetto on a 2008 MK 7 Transit)

 

2) A Thetford Caprice cooker showed the mains hotplate light as dimly lit with the hotplate switched off (on a 2014 Auto Sleeper Warwick Duo)

 

Reversed polarity can and does give rise to unpredictable side effects. My solution is to ensure (via a made-up reversal lead) that 'polarity' is always correct. Standards are there for a reason, if you think that you can ignore them with impunity please don't complain if things go wrong for you.

Link to comment
Share on other sites

spospe - 2018-01-22 4:01 PM

 

Personal experience of 'reversed polarity':

 

1) An Eberspächer heater with the mains heater attachment, would not run at all on mains and defaulted to diesel (fitted to an Auto Sleeper Duetto on a 2008 MK 7 Transit)

 

2) A Thetford Caprice cooker showed the mains hotplate light as dimly lit with the hotplate switched off (on a 2014 Auto Sleeper Warwick Duo)

 

Reversed polarity can and does give rise to unpredictable side effects. My solution is to ensure (via a made-up reversal lead) that 'polarity' is always correct. Standards are there for a reason, if you think that you can ignore them with impunity please don't complain if things go wrong for you.

 

I believe that this particular case has been aired before???....it's the only time in the history of caravans and motorhomes that I have actually heard of a specific incident under a reversed polarity situation.....or perhaps I don't read very much? *-) (lol)

Link to comment
Share on other sites

spospe - 2018-01-22 4:01 PM

 

Personal experience of 'reversed polarity':

 

1) An Eberspächer heater with the mains heater attachment, would not run at all on mains and defaulted to diesel (fitted to an Auto Sleeper Duetto on a 2008 MK 7 Transit)

 

2) A Thetford Caprice cooker showed the mains hotplate light as dimly lit with the hotplate switched off (on a 2014 Auto Sleeper Warwick Duo)

 

 

...and the common denominator there is?............(no! not you..(lol) )...begins with *Auto-...

 

(..*and if it wasn't down to them, then presumably all vans with Eberspächer heaters or Thetford Caprice cookers are being affected by it...? ) :-S

Link to comment
Share on other sites

EJB - 2018-01-22 5:32 PM

 

...I believe that this particular case has been aired before???

 

Yes it has...

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Reverse-Polarity/47011/

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Hints-and-Tips/A-couple-of-Reversed-Polarity-points/39946/

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Hints-and-Tips/Reverse-polarity-points/33356/

 

It seems probable (though illogical) that an Eberspacher “Airtronic” heater with the “Airlectric” option will only function on 230V if the polarity of the mains power-supply is to the UK-norm. The only motorhomes that have this appliance seem to be a relatively small number of Auto-Sleepers models and there’s a fairly low chance that their owners will encounter a reverse-polarity 230V supply when the motorhome is used in the UK . Even if an A-S motorhome with Airtronic + Airlectric is used outside the UK, there’s still a 50:50 chance that the polarity of the power-supply the vehicle is connected to will not be reversed, and there’s also the possibility that, even if the supply is reversed, the UK motorcaravanner will notice and ‘correct’ this before switching on the Airlectric heater. So this reverse-polarity oddity will affect only a tiny number of motorcaravanners and only occasionally and, in any case, as long as those affected understand what’s happening, the problem can be sidestepped by ‘correcting’ the supply’s polarity. But the potential problem does exist...

 

Allan says above

 

"So if someone was stupid enough to poke their fingers into the wiring while it was in pieces and still plugged into a live supply, then they might be electrocuted. But clearly no one is going to do such a thing, making the risk non existent.”

 

One of the Murphy’s laws is "It is impossible to make anything foolproof because fools are so ingenious” and this Wikipedia entry shows that people’s foolhardiness knows no bounds .

 

"In 1983 Jimmy Ferrozzo, a bouncer, died in the Condor Club, San Francisco while having sex with his girlfriend Theresa Hill on a grand piano that was lowered from the ceiling by a hydraulic motor. Ferrozzo accidentally activated the lifting mechanism which pinned him against the ceiling leading to his suffocation. Hill survived the accident."

Link to comment
Share on other sites

Like I said above, some Motorhome builders spend less time and money on making a motorhome reverse polarity proof than others.

Even so neither of the examples above make it unsafe on either polarity, and that was the concern of the OP and the basis of my reply and the more detailed explanation that can be found on our webpages.

 

 

If a toaster is on the 'UK standard'' polarity and plugged into a live mains socket, it won't necessarily make it safe to poke fingers into the wiring.

The mains 230v wiring in most appliances goes to a switch, usually soon after entering the appliance. The wiring to that point will still be live and will electrocute anyone touching it, even if the polarity is to the UK standard.

 

If someone is going to be that silly and ignore Common sense and the stickers on the appliance, then Derek is right, no amount of legislation/standards will protect such a fool.

 

Hence my saying there is no additional risk if the tiniest amount of common sense is applied. I wrote above : -

"A modern motorhome on a reverse Polarity connection is no more a safety risk than that at home, provided the most basic of common sense is followed".

 

 

 

 

 

 

 

 

Link to comment
Share on other sites

There seems to be a little confusion in some of the above posts. Most vans now have two types of safety devices.

 

One is the miniature circuit breaker (MCB) (they have long taken the place of fuses, and are to be found in the consumer unit in the van).

 

Their function is to protect the wiring in a particular circuit from overload, causing it to heat up and possibly catch fire. UK practice is to install these only to the "positive" side of the circuit, placing the MCB between the main switch and any appliance connected to the circuit. If the mains polarity is reversed, the appliance is now placed between the positive feed and the MCB, which is not desirable, and not how the installation is designed to function.

 

Continental practice is to use twinned MCBs, so that both positive and negative wires are protected, and polarity becomes irrelevant. One or other of the MCBs will thus respond to overload, causing both to open.

 

The other safety device is incorporated into the mains switch. This is a residual current device (RCD). Its function is to protect against electrocution. As described above, it does this by monitoring the current flowing into the system against that flowing out. If there is a difference in this current (meaning current is flowing to earth, possibly through a person), the switch instantly opens to cut off the supply to all the circuits. There are variants on this device, one combining the MCB function with that of the RCD (an RCBO), but they function in the same way regarding both overload and earth faults. These devices function irrespective of polarity.

 

The function of the fuse in a BS plug is solely to protect the wiring between the plug and the appliance from overload. This is because the current available at the socket (usually 30A/7kW in UK) greatly exceeds the rating of the appliance and its connecting wiring. In the absence of the fuse, an appliance fault causing a short circuit could draw sufficient current to burn out the appliance wiring and possibly start a fire. Instead, the fuse blows.

Link to comment
Share on other sites

One point to consider, although it will not probably apply to many readers of this Forum, is the action to be taken when faulting apparatus.

 

The only way that much of complex apparatus can be faulted when not working properly, is with the power connected and the case covers off. Imagine trying to trace a fault on a TV; the only way that an oscilloscope can be used to trace a problem, is with the case off and the technician, probes in hand, delving into the innards whilst it is still powered up.

 

In the good old days of valves (when I was new to this sort of work), a colour TV would have voltages in excess of 25,000 volts flying round inside the case. It was possible to 'draw' a spark over an inch long in some cases when faulting on the EHT circuit and this had of course to be done fully powered up.

 

Many time in these reversed polarity discussions people have said that only a fool would go poking around inside live apparatus. Was I a fool? If I was a fool, I am a live fool and I would be a dead fool if I did not check for polarity.

 

Sorry to go on at such length, but a lifetimes caution has a lingering effect and I say again that standards exist for a reason, ignore them at your own risk.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.


×
×
  • Create New...