Connecting an EHU Cable (1 Viewer)

Jan 23, 2016
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Is there a correct way to do this?

Connect the van end first.

Or the supply end first?

My simple thoughts were to connect the van end first because if you connect the supply end first you are walking around with a 'live' cable in your hands.
 
Feb 15, 2016
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You could always press the test button on the RCD to check that it is working, as is often recommended (I have known instances of them having stopped working), then connect the cable up before switching it back on. It wouldn't matter which end you connected first in that case!(y)
 
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Feb 5, 2014
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With regard to the reel wound/unwound question .....

I probably should have paid more attention in my 'A' level Physics lesson that afternoon, but it was the best part of 50 years ago now.

There is the straightforward resistance heating effect that has been referred to already, with the heat being trapped within the reel.

But an alternating current passing through a coil of wire also produces an electromagnetic effect. A coiled mains lead is half of a transformer. And transformers get hot. Does half a transformer get hot, or does it need the other coil to go with it?

I told you I should have paid more attention ....

Perhaps it was me teaching it to you? Pupils always said I talked too much :(.

Seriously though, AND THIS IS NOT A TROLLING SITUATION, I really would like to know if a wound cable gets hot enough to melt insulation, and if so, why? When the Caravan Club recommends that folk don't stay on aires, because they might be robbed (or, dare I say it, gassed), there are lots of contributors keen to de-bunk that advice. ALL that I am trying to do is to establish IF undamaged EHU cables get hot when used in a coil and, if so, WHY? (y)

I don't believe that a "transformer" situation exists, and if a transformer gets hot then it is dealing with a lot of power or it is badly designed: 99% efficiency is a reasonable target. There is a phenomenon called "self-inductance" which could result in a coil effectively magnetising (and demagnetising) itself, but I don't think that the geometries and materials involved here are significant (It's a long time since I did those calculations :rolleyes: )

As far as an inflammatory Henry is concerned, the cable is effectively wound around an iron-filled motor, so "transformer action" could be important AND the motor itself gets hot: hence G_L, you fail to unwind at your peril!

I can accept that unrolling a coil, feeding it through your hands and feeling/looking for damage is a "good thing". However, the more it is coiled/uncoiled then the more likely it is to be damaged and excess metres of cable lying on the ground are more likely to be driven over (not necessarily dangerous ;) ), accidentally cut, etc. thus making it a "bad thing".o_O

I appreciate that this is a way off topic - Gordon

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Oct 15, 2011
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I have the van at home prior to us going away next week and I was ever so careful hooking it up to the mains 5 minutes ago.:rolleyes::rolleyes:
 
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Sep 23, 2013
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Perhaps it was me teaching it to you? Pupils always said I talked too much :(.
Well, if you are now in your late 70s, taught Physics in Market Rasen in the 60s & had/have a seriously gorgeous Welsh wife, then it could be you! I promise not to mention the bald tyres on your car.

By coincidence, one of my 'O' level Physics teachers was called Gordon, but I fear he has been dead for many years. He was Gordon Wild, so known to everyone (unless he was listening) as Oscar. My 'A' level teacher was comparatively youthful and when you are 17, anyone over 25 seems positively ancient.
 
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mustaphapint

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Perhaps it was me teaching it to you? Pupils always said I talked too much :(.

Seriously though, AND THIS IS NOT A TROLLING SITUATION, I really would like to know if a wound cable gets hot enough to melt insulation, and if so, why? When the Caravan Club recommends that folk don't stay on aires, because they might be robbed (or, dare I say it, gassed), there are lots of contributors keen to de-bunk that advice. ALL that I am trying to do is to establish IF undamaged EHU cables get hot when used in a coil and, if so, WHY? (y)

I don't believe that a "transformer" situation exists, and if a transformer gets hot then it is dealing with a lot of power or it is badly designed: 99% efficiency is a reasonable target. There is a phenomenon called "self-inductance" which could result in a coil effectively magnetising (and demagnetising) itself, but I don't think that the geometries and materials involved here are significant (It's a long time since I did those calculations :rolleyes: )

As far as an inflammatory Henry is concerned, the cable is effectively wound around an iron-filled motor, so "transformer action" could be important AND the motor itself gets hot: hence G_L, you fail to unwind at your peril!

I can accept that unrolling a coil, feeding it through your hands and feeling/looking for damage is a "good thing". However, the more it is coiled/uncoiled then the more likely it is to be damaged and excess metres of cable lying on the ground are more likely to be driven over (not necessarily dangerous ;) ), accidentally cut, etc. thus making it a "bad thing".o_O

I appreciate that this is a way off topic - Gordon
Maybe this will explain it.
https://uk.answers.yahoo.com/question/index?qid=20100520125802AAs2Ufo

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Apr 27, 2008
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And then there's the sights you see on continental sites. Hardly anyone seems to have a proper EHU lead, usually a supermarket extension reel with an adaptor on one or both ends, usually mainly coiled up. Of course there's usually only 6A available, sometimes only 4A and I wouldn't put any money on there being an RCD either.
 
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Aug 6, 2013
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Inductive effects should be cancelled by an equal and opposite current flowing in each of the conductors. Having said that if you look at any professional source of extension reels (a source that offers a data / safety sheet for them) you will note that if the reel is not fully uncoiled the load carried by the extension cable must be reduced by at least 50%.

I too have noticed the melted snow adjacent to a loaded cable.
 
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sdc77

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Still lucky to be alive.
Van is always plugged in on the drive with an older EHU lead of which most is on a reel.

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sdc77

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Charger obviously ... fridge .. and a oil rad that sits in there when we're not using it. Its warm at the moment so that's probably not on.
 
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Feb 5, 2014
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What I'm asking for are FIGURES supporting the advice. I think 25m of 2.5mm wire should have a resistance of 0.02ohm (but I could be misinterpreting my values). :LOL:

:doh: Now I need to find an icon for "eating humble pie"! :blush:

Getting off my lazy *** I've checked the actual resistance of my cable and it comes in at about 0.2ohms per core. That means that each core will dissipate 20W at 10A and 50W at 16A!!! So we are looking at upto 100W concentrated in the coil of wire if it is not fully unwound.

Hence I FULLY CONCUR with the advice to TOTALLY UNWIND coiled cables :imoutahere: Gordon
 
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Sep 23, 2013
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@Rapido925M I've given that a 'Like', because we can only select one, but it also deserves thanks, was funny, useful & informative.

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Ed-E

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How about your advice/experience on this one, please.
I do not have off road parking, so when out of storage, i park me MH on the road. Obviously this give a potential problem with the EH. I have thought about a rubber tread guard for the part that crosses the pavement and will use an RCD. Thoughts/experiences?
 
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Sep 23, 2013
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I do not have off road parking, so when out of storage, i park me MH on the road.
Mine has to be not just on the road, but across the other side of it (double yellows on our side). That was just one more reason for solar panels.
 
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Ed-E

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Two Weeks :)
Yes, I have Solar but I am very new to all this (great site nd members, btw) but I wanted to give it that little top up before embarking on adventures, if possible.

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DBK

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Yes, I have Solar but I am very new to all this (great site nd members, btw) but I wanted to give it that little top up before embarking on adventures, if possible.
Solar will soon top up your batteries and if you fit a battery master you can top up the vehicle battery as well. A drive of a few hours will further ensure all is bursting with amps. :) I don't think you have anything to worry about.
 
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andy63

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How about your advice/experience on this one, please.
I do not have off road parking, so when out of storage, i park me MH on the road. Obviously this give a potential problem with the EH. I have thought about a rubber tread guard for the part that crosses the pavement and will use an RCD.
Thoughts/experiences?
Having anything crossing the pavement far from ideal especially if there is no one around a lot of the time.
Lad next to me has an rv which I've seen him charging in the street by using an upstairs windows and keeping the cable tight on to the roof, is that a possibility... If you need to charge from house..
Andy

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Jaws

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Really dislike EHU cables on a reel
To easy for people who do not appreciate the danger to not only them selves but others to leave a long cable all rolled up

As a by the by, all those who say plug in the van forst cos you are walking round with a live cable.. Are you telling us you never plug an extension lead in at home and then plug something in to it ?
Cos that is basically exactly the same thing !

( sorry.. came in a bit late so if this has been covered, ignore me.. The wife has been doing it for years so I will not be offended !! LOL !!
 
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OP
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The Old Man
Jan 23, 2016
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Bout time this thread was wound up.

Final question:

Do you think the cable is strong enough to hang myself with?
hanging-smiley-emoticon.gif
 
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