EHU quandary - Polarity (1 Viewer)

[Dave and Ginny]

Bit of an odd one.

I'm a bit of a stickler for checking the polarity before plugging into the EHU into the van. Just an old habit, like to see there is at least an earth available. Now I know with a Schaudt Elektroblock that I shouldn't need to worry about polarity, but I've come to the conclusion that the van must be wired with it in reverse!

Used to it being wrong on overseas sites I was correcting an incorrect polarity using my short lead adapter that many of us carry when it's been incorrect at the EHU outlet. But I now realise it's then wrong in the van! If I have reversed polarity at the EHU box but don't correct it with my short lead, it's then correct in the van! So I've come to the conclusion that the van is wrong...maybe always or after some work being done?

So, do I correct it by simply reversing it between EHU input and trip...or just leave it alone!

Cheers Dave

 

[pappajohn]

Let's make it simple......

We expect live to be on the right but on European posts it can be on the left (our neutral side)

Let's say incorrect live is on the left and neutral is on the right.
correct is live right, neutral left.

Plug in your short lead to correct it and that takes the posts neutral (left, which is actually live) and transfers it to the vans live(right).

Nothing wrong with your van unless you reverse an already correct supply which will then make it reversed.

But why anyone bothers is beyond me.
Ever wondered why so many European posts are reversed... .because it doesn't matter and they don't care.

 

[MillieMoocher]

Gotta say I just don’t bother...if everything works as it should. I wouldn’t ever dabble with an electrical item unless it was unplugged so don’t perceive any risk.

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[2657]

The first thing that I would check is the wiring on your short 'correcting' lead.

I bought one a few years ago and reversed the wires to, in theory make a correcting lead, took me quite a while to figure out that the lead was actually wired incorrectly from new and in reversing the live and neutral I had actually put the lead into the correct unreversed polarity, of course this had the effect you describe when connecting to a reversed polarity socket.

 

[scotjimland]

Have you checked the connections are the correct polarity on your EHU lead.. both plug and socket ?

 

[andy63]

I found out that the erberspacher combitronic control unit that i installed in my self build will not allow heating or hot water to work on electric if the polarity is reversed... so it is possible with some electronics that it can matter..
I checked with the manufacturer when i got home and they confirmed that the unit had to see posotive on the correct pin to know mains was available... which obviously doesnt happen if the polarity is reversed..
Andy.

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[Dave and Ginny]

The first thing that I would check is the wiring on your short 'correcting' lead.

Good point, but I made it up myself and it’s been used on my previous van so I know it to be correctly wired.

 

[scotjimland]

I found out that the erberspacher combitronic control unit that i installed in my self build will not allow heating or hot water to work on electric if the polarity is reversed... so it is possible with some electronics that it can matter..
I checked with the manufacturer when i got home and they confirmed that the unit had to see posotive on the correct pin to know mains was available... which obviously doesnt happen if the polarity is reversed..
Andy.

I've never come across electronics fed directly with 240vac, it is always via a step down transformer and rectified to for example, 12, 9, or 5v DC ..
AC does not have polarity , only Live and Neutral , the "polarity' changes 50 times per second .. ie 50Hz , the 240vac 'polarity' doesn't matter

the electronics will certainly require the correct 12vdc polarity .. and the positive on the correct pin..

 

[Dave and Ginny]

Have you checked the connections are the correct polarity on your EHU lead.. both plug and socket ?

Good point, just checked that and it’s correct.

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[ukbill]

I never bothered with polarity,but after killing 2 laptop mains charger,(UK)plug,I always check,my Spanish charger,np,but UK no

 

[2657]

Good point, but I made it up myself and it’s been used on my previous van so I know it to be correctly wired.

I made mine up myself and it took me a long time to realise that the new one that I had purchased was incorrectly wired in the first place and by reversing the connections I had corrected the manufacturers error.

Did you actually test the polarity at the sockets inside your previous van?

 

[scotjimland]

Dave, While polarity 'doesn't matter' , it is better to have it correct in the van..

I would have it checked and tested by a competent electrician and re-certified when you get back to the UK .. peace of mind and you know it's correct

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[Dave and Ginny]

I made mine up myself and it took me a long time to realise that the new one that I had purchased was incorrectly wired in the first place and by reversing the connections I had corrected the manufacturers error.

Did you actually test the polarity at the sockets inside your previous van?

Yes, at each of the socket outlets I get the same. If it’s correct at the EHU it’s wrong in the van and visa Versa. It could be that my short lead that I use to test is wrong...I’ll check that out as well.

 

[andy63]

I've never come across electronics fed directly with 240vac, it is always via a step down transformer and rectified to for example, 12 or 9v DC ..
AC does not have polarity , only Live and Neutral , the "polarity' changes 50 times per second .. ie 50Hz , the 240vac 'polarity' doesn't matter

the electronics will certainly require the correct 12vdc polarity .. and the positive on the correct pin..

The 240v is fed into the control unit ... the electronics must monitor that in the fashion i described above .. if it doesnt see the posotive feed on the correct pin it doesnt know the mains are connected and will not allow the system to work on 240v...
When i phoned the lad pointed out that the lightning strike symbol on the pannel would be missing if polarity was reversed and the unit would not allow heating on 240v...
Just thought it worth pointing out that although unusual it can matter because of the control side of things.
Andy.

 

[treetops1]

I just use my plug in tester its just a plug that lights up on the back so you can check all is ok ,if not just turn you plug round at the main supply in Europe ,cost me £2 lol

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[chaser]

Bit of an odd one.

I'm a bit of a stickler for checking the polarity before plugging into the EHU into the van. Just an old habit, like to see there is at least an earth available. Now I know with a Schaudt Elektroblock that I shouldn't need to worry about polarity, but I've come to the conclusion that the van must be wired with it in reverse!

Used to it being wrong on overseas sites I was correcting an incorrect polarity using my short lead adapter that many of us carry when it's been incorrect at the EHU outlet. But I now realise it's then wrong in the van! If I have reversed polarity at the EHU box but don't correct it with my short lead, it's then correct in the van! So I've come to the conclusion that the van is wrong...maybe always or after some work being done?

So, do I correct it by simply reversing it between EHU input and trip...or just leave it alone!

Cheers Dave

i might be reading this wrong, but if you are 'correcting ' it at both ends surely thats putting it back to how its coming out of the hookup point.

 

[two]

I assume that your ‘reversed’ circuit is that to your (UK) sockets?
In that case I’d find where they are fed from and swap the L & N wires there.

 

[two]

Ever wondered why so many European posts are reversed... .because it doesn't matter and they don't care.

because Europeans don’t use as much mains as they can,
… and don’t have toasters

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[ukbill]

I'd leave it all alone,just use ya polarity changer,start messing and normally it's a can of wirms,imho

 

[Lenny HB]

Germans like other countries don't worry about polarity as they either use unswitched sockets, double pole switched sockets and double pole MCB's. However I have noticed in the modern vans they wire them all the same and even the German sockets have a "L" & "N" on them for wiring.
I susspect your sockets are crossed because the loom was already in place when they fitted the UK sockets if they had wired them with live to the live connection the sockets would have probably been upside down. Doesn't matter which way up they fit the German sockets as you can fit the plug either way round.

Doesn't bother me but I've got German sockets anyway.

 

[Minxy]

Whilst some don't worry about it, I'd rather have it 'right' so we do have a reverse polarity correction lead that I made up, however as we rarely use EHU except at home I can't remember the last time I had to test for it!

What concerns me more is if a MH is wired wrongly so that equipment remains 'live' when it has been turned off with a possible risk of electrocution, may be an extremely slight risk but better to be safe.

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[autorouter]

I've never come across electronics fed directly with 240vac, it is always via a step down transformer and rectified to for example, 12, 9, or 5v DC ..

Step-down transformer/bridge rectifier/reservoir capacitor is a bit niche nowadays. Switch-mode power supplies use the 240 volt mains directly, using precision timing to chop the incoming mains wave into suitable bursts to charge a smoothing capacitor to the desired voltage output level.

All the same, I'm a bit mystified why a heater manufacturer would make something dependent on 'polarity' when there seems to me to be no good reason.

 

[two]

I’ve not thought (nor worried) about this before but, if you could get an ‘intermediate switch’ rated at 16A, you could arrange the swap internally and not need a reversing lead.

 

[Lenny HB]

I’ve not thought (nor worried) about this before but, if you could get an ‘intermediate switch’ rated at 16A, you could arrange the swap internally and not need a reversing lead.

In the past you have been able to buy auto changeover boxes.

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[scotjimland]

What concerns me more is if a MH is wired wrongly so that equipment remains 'live' when it has been turned off

That is why continental vans do NOT have switch sockets .. and the CBs are double pole.. but if someone unwittingly adds a single pole 13A SWITCH socket then they have negated the built in safety measures designed to protect and make polarity a non issue .

 

[scotjimland]

Step-down transformer/bridge rectifier/reservoir capacitor is a bit niche nowadays. Switch-mode power supplies use the 240 volt mains directly, using precision timing to chop the incoming mains wave into suitable bursts to charge a smoothing capacitor to the desired voltage output level.

quite so.. but I'm old school, in my apprenticeship days valves were used to do the same job .. the solid state bridge rectifier was 'state of the art' ..

so all things become obsolete and niche eventually .. a bit like old engineers

 

[two]

If a double-pole RCD is present you'll be protected, irrespective of wrongly-placed switches.

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[Minxy]

That is why continental vans do NOT have switch sockets .. and the CBs are double pole.. but if someone unwittingly adds a single pole 13A SWITCH socket then they have negated the built in safety measures designed to protect and make polarity a non issue .

Its a while since I had a UK built MH - do they still have switched mains sockets? I seem to recall our Autocruise Accent 2015 PVC didn't.

 

[Dave and Ginny]

I made mine up myself and it took me a long time to realise that the new one that I had purchased was incorrectly wired in the first place and by reversing the connections I had corrected the manufacturers error.

Did you actually test the polarity at the sockets inside your previous van?

Yes, all show the same.

 

[scotjimland]

Its a while since I had a UK built MH - do they still have switched mains sockets? I seem to recall our Autocruise Accent 2015 PVC didn't.

never had a UK van.. so really can't comment what was or wasn't fitted.. I was thinking on DIY people who don't understand why they shouldn't fit a single pole switch socket, I have seen many fitted in continental vans INCLUDING mine, fitted by previous DIY bodger ..

17th edition regulations have all the latest requirements , extract ..

16.13.2 Requirements for safety

The protective measures of obstacles and placing out of reach are, not surprisingly, precluded by Regulation 721.410.3.5 and, similarly, the protective measures of non-conducting location, earth-free local equipotential bonding are precluded by Regulation 721.410.3.6. The use of the protective measure of electrical separation is not permitted except for shaver socket-outlets, as given in Regulation 721.410.3.3.2.

Regulation 721.411.1 calls for an RCD (see Figure 16.10) where protection by ADS is used (the normal method) with a protective conductor connecting the exposed-conductive-parts of the installation, including socket-outlet protective contacts, with the earthing contact of the caravan inlet plug. The RCD must comply with BS EN 61008-1 or BS EN 61009-1, interrupt all live (line and neutral) conductors and have the characteristics specified in Regulation 415.1.1 (In ≤ 30 mA and operating time ≤ 40 ms at a residual current of 5In).

All extraneous-conductive-parts accessible from within the caravan (or motor caravan) must be bonded with a main protective bonding conductor to the main earthing terminal of the installation in the caravan, as called for in Regulation 721.411.3.1.2. All that will be required, in many cases, will be a ‘main’ bond on to the vehicle chassis.

Regulation 721.43.1 calls for each final circuit to be protected by an overcurrent pro- tective device which disconnects all live (line and neutral) conductors (see Figure 16.10). This will of necessity involve the use of single-pole-and-neutral (SP&N) or double-pole (DP) circuit-breakers. DP devices will detect overcurrent in both line and neutral and interrupt both on operation, whereas SP&N devices detect only overcurrent in one pole (line) but will disconnect both poles on operation.

Where more than one electrically independent installation is present, each will require its own independent inlet plug, as indicated in Regulation 721.510.3.

Any part of the caravan installation operating at extra-low voltage must comply with the requirements of Section 414 (SELV and PELV) and for d.c. be at one of the standard voltages (12, 24 or 48 V). For a.c., permissible standard voltages are 12, 24, 42 and 48 V.

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