# Reverse Polarity



## esperelda (Sep 17, 2010)

Hi, himself would like to understand more about reverse polarity - can anyone explain it please? what happens if you don't realise that it's reversed polarity? Many thanks in advance


----------



## Techno100 (May 8, 2010)

http://www.motorhomefacts.com/ftopict-102298-.html


----------



## barryd (May 9, 2008)

At least two motorhome electrical engineers have told me it is simply not an issue unless your van is ancient. I have a tester and a reverse polarity lead but I never use the lead and I have never had a problem. I think your system in the van protects your appliences and you.

Its a can of worms though. Someone will be along in a minute to argue the opposite. I just speak from experience. No problems (so far)


----------



## teemyob (Nov 22, 2005)

*simply*

Put Simply

There are 3 wires in your Mains 240v

one is live
one is Neutral 
One is Earth (Just another Neutral Really (but let us not complicate matters))

Main Danger is if the polarity is reversed, that is Live Wired to Neutral and vis-versa. If the power outlet is switched off on the single pole switch, the appliance is still LIVE! As only the Neutral has been disconnected.

TM


----------



## teemyob (Nov 22, 2005)

*wrong*



barryd said:


> At least two motorhome electrical engineers have told me it is simply not an issue unless your van is ancient. I have a tester and a reverse polarity lead but I never use the lead and I have never had a problem. I think your system in the van protects your appliences and you.
> 
> Its a can of worms though. Someone will be along in a minute to argue the opposite. I just speak from experience. No problems (so far)


"At least two motorhome electrical engineers have told me it is simply not an issue unless your van is ancient."

It is an issue regardless of van age.

TM


----------



## midlifecrisismil (Sep 27, 2009)

Techno100 said:


> http://www.motorhomefacts.com/ftopict-102298-.html


Thanks for the link techno but I have read the whole of that thread and to be honest it is as clear to me as nuclear physics.

I think all I want to know is how do you know if what you are plugging into has reverse polarity. Do I need to check on every site I visit abroad. And what happens if I don't.

In words that even a dummy can understand :roll: :roll:

Thanks

Milly


----------



## Techno100 (May 8, 2010)

Unless your van does not have an RCD mainswitch you will be safe as long as you test that YOUR RCD works with the test button provided on the front of it when hooked up. If your RCD does not operate under "test" then the supply has not got a functioning earth.
An RCD for this purpose is rated at 30milliamps. This means it will disconnect if 30ma fault current is detected. It takes 50ma or more to addle your brain enough to interfere with your heart.


----------



## barryd (May 9, 2008)

*Re: wrong*



teemyob said:


> barryd said:
> 
> 
> > At least two motorhome electrical engineers have told me it is simply not an issue unless your van is ancient. I have a tester and a reverse polarity lead but I never use the lead and I have never had a problem. I think your system in the van protects your appliences and you.
> ...


Why is it an issue?

So an appliance might still be live even if its switched off. Its only going to be an issue if you decide to take it to bits whilst it is plugged in then

Two specialist dealers who are frequently mentioned on here tell me its safe and I havent had a problem and nor do I know anyone who has had a problem. So please explain based on that why it is an issue.


----------



## lucy2 (Jun 27, 2007)

esperelda said:


> Hi, himself would like to understand more about reverse polarity - can anyone explain it please? what happens if you don't realise that it's reversed polarity? Many thanks in advance


I always test the site outlet prior to hooking up with a tester as not only does it tell you reverse polarity but if the earth is disconnected or other wires are reversed or disconnected as well.


----------



## teemyob (Nov 22, 2005)

*brain*



Techno100 said:


> Unless your van does not have an RCD mainswitch you will be safe as long as you test that YOUR RCD works with the test button provided on the front of it when hooked up. If your RCD does not operate under "test" then the supply has not got a functioning earth.
> An RCD for this purpose is rated at 30milliamps. This means it will disconnect if 30ma fault current is detected. It takes 50ma or more to addle your brain enough to interfere with your heart.


 "It takes 50ma or more to addle your brain enough to interfere with your heart"

Is that the same for people with Pacemakers?


----------



## teemyob (Nov 22, 2005)

*Re: wrong*



barryd said:


> teemyob said:
> 
> 
> > barryd said:
> ...


Many Many Reasons.

You do not have to take things apart for them to become dangerous.

What about Children running around cables of double insulated appliances with live cables barefoot?. Oh well I guess it does not matter if they are switched off!.

What if the RCD is Faulty?

In order for RCD's to function correctly they should be tested once a month. How many people lay their vans up over winter or don't use them for several months?.

Our van is a Modern 2007 Build year. But currently there is no RCD Fitted. The Manufacturer did not fit them.

What if the appliance is not earthed? (Worse still the supply to the van!).

Better to be safe than sorry.

That is why we have or should have Good Earths. RCD's and correctly wired and poled outlets.

Only trying to help.

Read the top 3 results in this current google search

8% Failure Rate for RCD's !

TM


----------



## Techno100 (May 8, 2010)

The periodic test of RCD's is only for fixed installations. On a mobile installation you should test it everytime you hook up.

Incorrect polarity will not lessen the protection offered by an RCD

If you don't have an RCD mainswitch I would have that fitted before ANY other extras. Most hook ups have RCD's built in BUT I would not rely on them


----------



## erneboy (Feb 8, 2007)

I must say I agree entirely with Barry on this one. I never think about it. Maybe we could just agree that opinions differ? Alan.


----------



## Techno100 (May 8, 2010)

Techno100 said:


> The periodic test of RCD's is only for fixed installations. On a mobile installation you should test it everytime you hook up.
> 
> Incorrect polarity will not lessen the protection offered by an RCD
> 
> If you don't have an RCD mainswitch I would have that fitted before ANY other extras. Most hook ups have RCD's built in BUT I would not rely on them





> What if the appliance is not earthed? (Worse still the supply to the van!).


most appliances these days only have two core cable NO EARTH. Only protection is YOUR RCD


----------



## karlb (Feb 22, 2009)

many modern appliances are not earthed and in certain circumstances a earth is dangerous.

Today, many modern buildings have plastic pipes and these may make for a safer electrical installation. One reason why bathrooms and kitchens can be dangerous is the presence of earthed metal water pipes. If a person touches a live part and - at the same time - an earthed metal pipe, the result could be fatal. Therefore, the contention is that a home with many earthed metal pipes is potentially less safe than an earth-free environment. This is where plastic pipe installations may lead to greater electrical safety. 

the above is a quote.

the continentals do not concern themselves with polarity and they appear ok, indeed many plugs can be put into sockets both ways!!
if any body cares to take equipment apart they should know what they are doing, so again reverse polarity is not a issue.


----------



## pieterv (Feb 3, 2009)

Many countries have plugs that fit their sockets two ways, so live and neutral get reversed on average half the time an appliance gets plugged in. 

Most appliances nowadays will, I think, have double poled switches which interupt both live and neutral (since appliances get made to be sold in different countries, some of which will not have UK style plugas, that only fit one way). With appliances like that it is no issue.

Pieter


----------



## teemyob (Nov 22, 2005)

*Agree*



erneboy said:


> I must say I agree entirely with Barry on this one. I never think about it. Maybe we could just agree that opinions differ? Alan.


Agree with Barry or what Barry has been told?

I am right!.

Come forward Barry's misinformers.

TM :wink:


----------



## barryd (May 9, 2008)

It does seem strange that we are always so divided on this one. Perhaps ignorance is bliss as I am no expert but go on what I am told by experts. What is worrying is said experts in the trade (and i wont name them) specifically tell me I dont need to worry. Perhaps they meant for my specific van I dunno!

I do test for earth though on EHU points (well abroad mainly) and many are not earthed so I dont use them.

We are never going to agree. Shall I start a Gas Thread?


----------



## Techno100 (May 8, 2010)

> "It takes 50ma or more to addle your brain enough to interfere with your heart"
> 
> Is that the same for people with Pacemakers?


I imagine a pacemaker would be safer?
There are no electrical regulations regarding pacemakers so the same regulations apply


----------



## erneboy (Feb 8, 2007)

OK Trev. There are topics I am sure about too so I know where you are coming from. Still you will never convivce me, Alan.


----------



## Zebedee (Oct 3, 2007)

The only sure way to settle this is for someone to provide *verifiable *statistics of death or injury caused as a *direct *result of using a "reversed polarity" supply.

With heavy emphasis on the words in bold text!

Dave


----------



## Techno100 (May 8, 2010)

Reputable Verifiable Genuine non counterfeit RCD's don't account for 8% of failures(8% quote from earlier post). RCD's are expensive enough for some less than genuine Chinese sources to make products that look like the job but don't do it for long if at all in the first place. Also it is not always the device that is responsible for failure rather than who and how it was installed and initially verified and tested.


----------



## Patrick_Phillips (Aug 17, 2006)

barryd said:


> At least two motorhome electrical engineers have told me it is simply not an issue unless your van is ancient. I have a tester and a reverse polarity lead but I never use the lead and I have never had a problem. I think your system in the van protects your appliences and you.
> 
> Its a can of worms though. Someone will be along in a minute to argue the opposite. I just speak from experience. No problems (so far)


I did the article on this at http://www.motorhomefacts.com/ftoptitle-70164-polarity-testing-and-changeover-cables.html
An interesting exercise because there were many different comments and corrections to my first draft but in the end, we managed to get an article that everybody who read at the time agreed on 8)

I think we are in danger of combining two (related) topics here:
1. (Why) Does reverse polarity matter
2. Should we have an RCD which we know works?

The answer to the first is, of course, maybe! Often not!!
If you have a continental motorhome, almost certainly your switches will be double pole and therefore switch off both poles of your supply.
If it is a UK van, especially older ones, the chances are that it may have single pole switches and so could leave you with live equipment which you might expect to be off!
Sadly, it doesn't follow that equipment will be safe if you have corrected the polarity. In Spain, we stayed on a very large popular site where the power failed at least twice a day and often more. Each time it came back on, there was a 50/50 chance the polarity had changed and often the earth would have vanished
:twisted:

As far as the RCD is concerned, I agree with what has already been said but would point out that a van isn't always "earth free" because it sits in insulating tires.
Remember the leveling jack. Hose pipes pumping water. The foot step.
There are many ways in which that "insulation" can be compromised.

As with all things, caution is always good and paranoia is also dangerous.

Patrick


----------



## Techno100 (May 8, 2010)

That's good Patrick but just to clarify. As far as the RCD goes it only needs an earth TO IT to do it's job (by the nature of how it works). The circuits it is protecting do not need an earth for the device to protect you. 
This is why you are protected outside of your home with a flymo fed in 2 core cable but plugged into an rcd.


----------



## clive1821 (Mar 27, 2010)

Just have in mind that the test button is for testing the RCD and its not an indication that you will protected, to test it correctly you need a RCD tester which puts a test leakage current on the circuit, which will set off the RCD protected circuit under test, if the earth is non existent between the rcd under test and the mains supply to the RCD, you are NOT protected.... how many times I have found this to be the case many times....


----------



## Techno100 (May 8, 2010)

The test button trips by creating an internal leakage to earth so it does confirm it will afford protection. An RCD tester verifies the time it takes to trip at the specified measured amount of leakage.This would form part of initial verification and testing and official periodic testing/inspection.


----------



## barryd (May 9, 2008)

Ah stuff this! Im just going to buy a massive solar panel and never go on EHU again! Most of the ones in France never work anyway.


----------



## esperelda (Sep 17, 2010)

Well, thanks to all who answered my query, we feel safer now with information learned and advice given. It's good to know that there's usually someone out there that's been there and done that, so as to speak.


----------

