Reverse polarity... Does it matter ? (1 Viewer)

[Rob e Lee]

Thanks.... At last an explanation.

If I was at home and wired a plug up wrong IE the neutral to live what would happen ?
This is why I asked. If I didn't ask and had left it alone and buggered something up like say an appliance or even someone got a shock I would look pretty silly. Not quite as silly as some of the replies above but I can try harder..

We are in France for the person that asked.

I guessed you might be

 

[Bailey58]

If you are feeling bored you can search on here for the numerous times this has been discussed.

The answer is: "it depends".

With a modern vehicle you should be fine, less so with older MHs, especially UK ones.

Well you must have been bored to answer ?? But thanks all the same ..

Being a member since May maybe Charlie hasn't seen the many threads on this subject hence @DBK 's answer which I thought useful.

 

[Steve101uk]

My understanding is that the campers internal trip switch will not work when using RP. I made up a reverse cable anyway just so I feel better as I don't understand electrics at all.

^{_{Subscribers  do not see these advertisements}}

 

[chaser]

This crops up loads, and yet I have friends in France doing up old properties , and the regs are quite strict it all has to be in singles in plastic conduit, and checked before they will connect you to the supply, but saying that once they have connected you , you can do what you like

 

[vwalan]

My understanding is that the campers internal trip switch will not work when using RP. I made up a reverse cable anyway just so I feel better as I don't understand electrics at all.

i fitted ehu 15 yr ago never used it .
last winter just before i left for my travels i decided to cool the fridge down on ehu. here at home .
i used a two pin euro lead and adaptor . the fridge wouldnt work. after lots of playing around i found that if i unplugged the euro lead and plugged it in the other way round all was ok. so i agree with your statement . the trip box just wouldnt let anything through . it does the right way round .
mind doubt i shall ever use it again .

 

[andy63]

My understanding is that the campers internal trip switch will not work when using RP. I made up a reverse cable anyway just so I feel better as I don't understand electrics at all.

Hi. I'm not an electrician but my understanding is that the earth leakage circuit breaker will still work on reverse polarity. .. It just detects any imbalance of current in the lines so no reason for it not to work..
Hope that's right but someone who knows will confirm this or tell me I'm wrong lol..
Ta andy

^{_{Subscribers  do not see these advertisements}}

 

[Derbyshire wanderer]

Hi. I'm not an electrician but my understanding is that the earth leakage circuit breaker will still work on reverse polarity. .. It just detects any imbalance of current in the lines so no reason for it not to work..
Hope that's right but someone who knows will confirm this or tell me I'm wrong lol..
Ta andy

Yes as you say it will work.
The problems as said earlier are only relevant if a fault develops.

 

[DBK]

I think the main danger, as raised above, is in the protection components. Of which there are two main sorts. Earth Leakage Circuit Breaker (ELCB) which are voltage operated and Residual Current Devices (RCD) which are current operated but confusingly they are also know as current operated ELCBs, and just to add further Fun to the mix you can get them in different sensitivities.

As an example, we had a new kitchen fitted recently and the electrician to keep things legal had to change the circuit breakers to ones which complied with the latest legislation. Unfortunately, one kept tripping several times a day. Further investigation revealed a fault elsewhere in the house where there was a direct short between live and neutral.

The sobering thing was the house was only re-wired ten years ago and the correct circuit breakers for the time fitted but the short between live and neutral didn't trip them. It was only when the later more sensitive circuit breakers were fitted did the problem come to light.

Now image your MH has circuit breakers like our old ones and you have a neutral to earth short circuit. Nothing will happen and you wont know you have a fault until you connect to a reverse polarity supply at which point something somewhere will get hot very quickly as the live goes straight to earth. Hopefully, the protection device will trip but what happens if there is no earth supply either, which does happen. Suddenly your microwave metal casing is live. Of course whether you would get a shock from it is a moot point when you are standing in the vehicle but it sure ain't a desirable situation.

It is also worth noting operating the press to test button doesn't prove there are no faults in your wiring, it only shows that the device is working - and working within its design limitations which may mean there could still be a fault somewhere.

 

[mitzimad]

all the neons on our switched spurs glow dimly if we are on reversed polarity why i still carry a tester i dont know i suppose it does check for earth as well

^{_{Subscribers  do not see these advertisements}}

 

[Dorwyn]

DP sockets are readily available, if you change over to those inside the van would it negate the need for changing the polarity?

 

[GeriatricWanderer]

One important thing to remember about RP is that it results in bi-negative charging of the poly-ions which, in itself, is not overly dangerous but if it happens in the presence of certain necro gasses, as frequently used by French camping car gassers, could prove fatal. Of course, total protection from both RP and gassing can be guaranteed by wearing a necklace of wet garlic.
Have a nice day - I am

 

[andy63]

DP sockets are readily available, if you change over to those inside the van would it negate the need for changing the polarity?

hi dorwyn, that would ensure that the appliance plugged in was in fact isolated when switched off, but as many have said as long as you are aware of the dangers associated with the polarity been reversed with single pole switches in use, everything should work normally anyway... if you had any 240v lighting (unlikely I know )then the danger would still be present on that circuit unless you did the same there..
if its seen as an issue the simplest solution is to have a short lead wired to reverse it back.. or just reverse the two pin plug on the supply post if that's possible.
I have a combitronic control panel on my diesel heater and its one of the few things I have come across that wont allow me to select heating and hot water using 240v if the polarity is reversed on a hook up, so in some cases it might matter with regards to some functions working especially on modern vans with so much electronic control..

^{_{Subscribers  do not see these advertisements}}

 

[Dorwyn]

I have reversed leads too, I was just wondering .... Point taken about the lights, which I do have. Ta

 

[mexican pete]

Hi, yes it does matter if the polarity is reversed. The Thetford fridge in my Bessacarr 765 will not work if the mains is reversed. I always check the polarity and carry two reversed polarity leads (one 16A and one Euro 2 pin) suitable marked, to get over this problem.

 

[Anthony496]

Forget the fact it works it's not worth the risk if there is a problem; as mentioned above, the live now enters the neutral and the appliance remains live even when switched off.

You are therefore switching the neutral which isn't something you want to do in any domestic wiring situation.

Saying it will be ok is the same as saying just put a nail in the plug instead of the fuse ... No problem, if your happy with that then fine but quickly reversing the polarity on the plug to the MH is the right way.

^{_{Subscribers  do not see these advertisements}}

 

[tonyidle]

It makes no difference to the operation of the appliances. The danger is that should something fail in the appliance when switched off, anything not earthed will be live.
Only an issue if you come into contact with it and become very lively till death!
UK live switching can only be safe if wired correctly.
Just imagine a 240v telly drops on the floor and breaks the casing, switch it off to pick up with the plug still in a it could be half a day out with the undertaker!

Still would reversed or not. Most televisions don't have an earth connection.

 

[Anthony496]

Yes Double insulated appliances don't have earths all modern LCD LED TVs, DVDs, hair driers straightners, kettles etc are double insulated.

Problem would arise with installed items such as fridges, heaters, water pumps etc... let's face it these are the items that are most likely to have wiring issues as they are bespoke to each motorhome and could be subject to dodgy installs or DIY fixes.

 

[Teuchter]

The ELCB/RCD (the electrical protection device) fitted to older Uk manufactured caravans and motor homes just had a single pole trip which interrupted the "Live" wire only hence if it tripped because of a fault and the polarity was reversed then it was the "Neutral" connection which was interrupted not the now "live" wire creating a potentially dangerous situation.
Continental manufactured caravans and motorhomes (and I believe on more modern UK ones) are fitted with a double pole trip which interrupts both Live and Neutral supply therefore making sure all wiring beyond the trip switch is "dead" therefore safe regardless of whether or not the supply polarity is reversed

^{_{Subscribers  do not see these advertisements}}

 

[DBK]

The ELCB/RCD (the electrical protection device) fitted to older Uk manufactured caravans and motor homes just had a single pole trip which interrupted the "Live" wire only hence if it tripped because of a fault and the polarity was reversed then it was the "Neutral" connection which was interrupted not the now "live" wire creating a potentially dangerous situation.
Continental manufactured caravans and motorhomes (and I believe on more modern UK ones) are fitted with a double pole trip which interrupts both Live and Neutral supply therefore making sure all wiring beyond the trip switch is "dead" therefore safe regardless of whether or not the supply polarity is reversed

Correct, but in my post above i described how the ELCB in my house did not trip even with a dead short between neutral and earth. It only did so when it was replaced with a more modern version which had higher sensitivity and could detect the small current leak between neutral and earth.

This experience suggests to me I need to get a tester even though my MH has double pole ELCBs. I used to think I was safe but am not so sure anymore.

 

[Teuchter]

Correct, but in my post above i described how the ELCB in my house did not trip even with a dead short between neutral and earth. It only did so when it was replaced with a more modern version which had higher sensitivity and could detect the small current leak between neutral and earth.

This experience suggests to me I need to get a tester even though my MH has double pole ELCBs. I used to think I was safe but am not so sure anymore.

The "old style" ELCB's were not all that sensitive and operated on a voltage principle and could take up to 40 volts PD (potential difference) across its trip coil to activate it - the more modern RCCB (reverse current cct breaker) or RCD (residual current device) operates when the trip coil senses a difference of 30 or so milliamps of current in the live and neutral wires thus meaning that the "missing" current is going elsewhere - ie to Earth" via something (or someone)

Double poled RCD's are pretty "safe" as tripping at 30 or 40 milliamps does not allow enough current to electrocute a person!

If however due to a faulty RCD they fail to operate within that sensitivity then it matters not whether the polarity is reversed or not