Why 2m max from EHU to the consumer unit?

[Nedge68]

Found it…
Sections 708 & 721 of the wiring regulations BS7671:2018
708 for Sites
721 for Motohomes

 

[Nedge68]

Having managed to read Section 721, I didn’t see any mention of the length of cables from the inlet socket to the Consumer Unit. There are specifics about cable protection and mechanical security, i.e. distance between clips should not be more than 0.4m horizontally and 0.25m vertically.
There is separate appendix that deals with DC.

 

[the1andonly]

Can you point me to this as I'd like to buy a deadly tea cosy for someone and want to get the right one!

try the assassins teapot instead.

 

[Reallyretired]

A chap removing a wheel from my motorhome on a site complained of getting a shock from the wheel, not a serious one but enough to feel. By the time he'd finished panicking and demanding an electrician I had found the problem a disconnected earth in the ehu plug.
It was obviously a low voltage shock and presumably was between neutral and earth, where unless they are bonded there may be a small voltage. In this case the earth was disconnected so the usual bonding didn't apply.

 

[Gromett]

A chap removing a wheel from my motorhome on a site complained of getting a shock from the wheel, not a serious one but enough to feel. By the time he'd finished panicking and demanding an electrician I had found the problem a disconnected earth in the ehu plug.
It was obviously a low voltage shock and presumably was between neutral and earth, where unless they are bonded there may be a small voltage. In this case the earth was disconnected so the usual bonding didn't apply.

Sounds like your neutral was bonded to earth?? But "EHU earth" not connected so neutral was floating the chassis voltage up.

That raises questions for me. If the Neutral is bonded to earth before the RCD then that would explain why he got his shocks and the RCD didn't trip. If it was bonded after the RCD why didn't the RCD trip?
Should the earth/neutral even be bonded at all in a mobile application? Or should the bond happen before AND after the RCD to prevent issues like this and also ensure the RCD operates correctly?

I suspect and I may be wrong on this that bonding the neutral to earth inside the vehicle should be avoided except in particular circumstances?

Wissel This is why I couldn't answer your questions definitively.

This thread really is making me think back to my training and perhaps too much time has passed now and I have spent too much time doing other stuff.

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[Hoovie]

There is sometimes a mixing up of terms with electrics. quite a lot of people use the term "Neutral" when they mean either "0V" or "-VE" on a DC system. And people also use Earth when they mean "0V" or "-VE" on the DC system. Mixing terminology can lead to a lot of confusion.
And of course there is no "earth" on a vehicle unless it is connected via EHU to a supply with a ground/earth connection. "Chassis" would be the term for a bonded connection on a vehicle.

Certainly it is common to connect the PE (Protective Earth) connection on a AC EHU plug to the vehicle chassis. And also to connect -VE on the DC system to the vehicle chassis. And with the typical Consumer Unit, the PE on the EHU is also physically continued to all the AC circuits.

But I can't imagine anyone connecting a Neutral (i.e. Neutral on an AC system) to a Bonded (i.e. Chassis) point. That seems like a very odd thing to do.

 

[Gromett]

But I can't imagine anyone connecting a Neutral (i.e. Neutral on an AC system) to a Bonded (i.e. Chassis) point. That seems like a very odd thing to do.

Victron Multiplus do this bonding when EHU is connected. See section 7.4

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

I can't understand why you would do it to be honest which I why I said this.

I suspect and I may be wrong on this that bonding the neutral to earth inside the vehicle should be avoided except in particular circumstances?

 

[rod_vw]

There is sometimes a mixing up of terms with electrics. quite a lot of people use the term "Neutral" when they mean either "0V" or "-VE" on a DC system. And people also use Earth when they mean "0V" or "-VE" on the DC system. Mixing terminology can lead to a lot of confusion.
And of course there is no "earth" on a vehicle unless it is connected via EHU to a supply with a ground/earth connection. "Chassis" would be the term for a bonded connection on a vehicle.

Certainly it is common to connect the PE (Protective Earth) connection on a AC EHU plug to the vehicle chassis. And also to connect -VE on the DC system to the vehicle chassis. And with the typical Consumer Unit, the PE on the EHU is also physically continued to all the AC circuits.

But I can't imagine anyone connecting a Neutral (i.e. Neutral on an AC system) to a Bonded (i.e. Chassis) point. That seems like a very odd thing to do.

And to add more confusion with wires, services and colours.

The incoming EHU Earth is coloured Green/Yellow and Live is Brown.

The 12v -ve (terminals numbered 31) in DIN standard automotive wire colour is Brown!

To those who are not aware of this they could assume that the EHU Live was bonded to the Earth.

 

[Lenny HB]

Victron Multiplus do this bonding when EHU is connected. See section 7.4

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

I can't understand why you would do it to be honest which I why I said this.

I was just thinking about the Multiplus there is a link in them that bonds neutral to earth to enable an RCD to work on the inverter I see from that info there is a relay that disconnects the bond when on the grid and it then relies on the grid bonding.

 

[Hoovie]

And to add more confusion with wires, services and colours.

The incoming EHU Earth is coloured Green/Yellow and Live is Brown.

The 12v -ve (terminals numbered 31) in DIN standard automotive wire colour is Brown!

To those who are not aware of this they could assume that the EHU Live was bonded to the Earth.

This is why I hate seeing mains flex used on DC circuits. I don't understand why so many dealers use it when adding circuits such as Solar.

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[enark]

My point was RCD'S do not guarantee safety, a little common sense has to be used. Unless you have other problems a240v shock won't kill. My wife recently had a severe shock when an expensive RCD shorted to earth, the earth stakes were dry and the taps were live. They were live because the regulators say taps must be earthed for safety even when the pipes are plastic. For safety I did away with the RCD.

OMG….240 VAC is a lethal voltage and will kill. Do you really know better than the regs? I would suggest for safety you don’t tamper with what you don’t understand.

 

[Lenny HB]

This is why I hate seeing mains flex used on DC circuits. I don't understand why so many dealers use it when adding circuits such as Solar.

Cheap, using 1.25mm2 mains cable will be cheaper than using 4 or 6mm2 auto cable.

 

[Gromett]

This is why I hate seeing mains flex used on DC circuits. I don't understand why so many dealers use it when adding circuits such as Solar.

I agree. I use brown/blue/yellow-green for AC and black/red for DC in my self builds.

Seeing blue and brown for DC is a nightmare in commercial European vehicles especially when they don't seem to be consistent on which should be 12v and 0V

 

[autorouter]

This is why I hate seeing mains flex used on DC circuits. I don't understand why so many dealers use it when adding circuits such as Solar.

I follow the example of my Hymer wiring, which is white 3-core flex for 240V, and black 2-core flex (brown and blue) for 12V DC. Brown is DC negative (chassis).

It is recommended that in a motorhome where 240V and 12V wires coexist, the 12V wiring is insulated to the same standard as 240V wires. Using 240V-rated flex for 12V circuits near to 240V wiring is a good idea, but they must be clearly labelled.

 

[Hoovie]

I follow the example of my Hymer wiring, which is white 3-core flex for 240V, and black 2-core flex (brown and blue) for 12V DC. Brown is DC negative (chassis).

It is recommended that in a motorhome where 240V and 12V wires coexist, the 12V wiring is insulated to the same standard as 240V wires. Using 240V-rated flex for 12V circuits near to 240V wiring is a good idea, but they must be clearly labelled.

lovely idea. Except brown is used for +12V very often as well.

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[ctc]

OMG….240 VAC is a lethal voltage and will kill. Do you really know better than the regs? I would suggest for safety you don’t tamper with what you don’t understand.

It is for some but I've had that many shocks I ceased worrying about it many years ago. If you want to panic about something try drowning, that is 100% lethal.

 

[Hoovie]

Cheap, using 1.25mm2 mains cable will be cheaper than using 4 or 6mm2 auto cable.

you can get Red/Black twin cable in all sizes you might want to use. so no, not cheaper, just lazier

 

[Gromett]

lovely idea. Except brown is used for +12V very often as well.

I have seen them use both blue and brown for +12v in the same vehicle. Hymer was the last one I had this happen on.

 

[Gromett]

you can get Red/Black twin cable in all sizes you might want to use. so no, not cheaper, just lazier

I needed some urgently earlier this month and paid over the odds for it. If you know a cheaper supplier I would be interesting for future reference.

I normally buy singles. But for this particular job a twin made more sense.

 

[autorouter]

lovely idea. Except brown is used for +12V very often as well.

Once when the water pump failed I bought a temporary replacement while in Italy. I had to wire it brown to blue, blue to brown. Never assume anything in a motorhome, always get out your meter and check.

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[Captain Yoghurtpot]

I am finding this thread very interesting and informative.
I have some specific questions relating to my motorhome’s incoming electrics from ehu and will post tomorrow when I have all the relevant details of what is fitted currently and what I would like to fit to the existing set up in a 22 year old van.
Cant post questions now as am too tired and need to be in bed as at work early tomorrow.
Stay tuned

 

[Lenny HB]

Once when the water pump failed I bought a temporary replacement while in Italy. I had to wire it brown to blue, blue to brown. Never assume anything in a motorhome, always get out your meter and check.

Yep, Reich pumps use brown for +ve and blue for - ve the opposite of Hymer.

 

[Gromett]

Yep, Reich pumps use brown for +ve and blue for - ve the opposite of Hymer.

In my Hymer (2005) from memory. The cassette area had brown as + but behind the fridge it was blue as +. It cause a great deal of consternation as the pump I fitted for the water filter tap worked perfectly. But my SOG was blowing inwards. It wasn't until I rechecked the polarity that I found out the colours don't matter in a Hymer

 

[Hoovie]

I could say that is why always stick to black for -ve but that doesn't work either always....

Once when the water pump failed I bought a temporary replacement while in Italy. I had to wire it brown to blue, blue to brown. Never assume anything in a motorhome, always get out your meter and check.

When I cabled up my camper, I decided to use black as -ve and a selection of colours for +ve for identification for cable runs with multiple services (similar to car wiring and all-in-one looms like Sargent).
For the fan I use a white cable plus black -ve. However I fitted the Maxxair fan which is American, and they had a black and white cable there - but black was +ve and white was the -ve.
Added extra labelling to both sides of the connections just to help anyone who may be working on it at some future time.

 

[rod_vw]

This is why I hate seeing mains flex used on DC circuits. I don't understand why so many dealers use it when adding circuits such as Solar.

I didn't mean using mains flex. Brown is the standard colour for negative 12v (chassis ground) in the DIN (German standard) automotive wiring colour which is by the same standard referred to as Terminal 31.

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[Hoovie]

I didn't mean using mains flex. Brown is the standard colour for negative 12v (chassis ground) in the DIN (German standard) automotive wiring colour which is by the same standard referred to as Terminal 31.

maybe you didn't. But dealers DO use mains flex for wiring DC circuits. I am talking about twin-core brown+blue cable, and occasionally you see 3-core flex used and the PE wire cut short. And german standard wiring colours are in the minority anyway. We don't all have Electroblocs or VWs.

TBH, I have myself used 3-core mains flex in a van when wiring up a 2-way lighting circuit as it is hard to find 3-core cable. But I cover the exposed brown and yellow in different colour heat-shrinks so it does not get confused so easily