# Mains hookup - earth on your motorhome



## sallytrafic (Jan 17, 2006)

Hi.

On another Forum someone was saying that it was important NOT to earth the chassis of your motor home by connecting it to the earth connection provided by your mains hookup.

That advice is WRONG and contradictory to the 16th edition wiring regulations which apply to motorhomes and caravans and which clearly states and shows that the earth connection should be connected through the connector to the chassis and exposed metal of your van. Several people who posted on that forum did not have that connection made and lo and behold when I went and checked neither did I (Good old Danbury).

So I'm posting here so that you can check too.

There is a simplified version of the relevant regulations HERE and if you look make sure you look at the introduction and also the caravan installation pages 7.9.2. The same advice is also given in the currrent edition of the Caravan Club handbook (p 597).

Regards Frank

Perhaps this could be made a sticky for a while.


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## Scotjimland (May 23, 2005)

A timely warning Frank, 
This is the problem with advice received on forums, it's not always correct and in a case like this downright dangerous.. 
I'm amazed that someone could say that the chassis shouldn't be connected to the supply earth.


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## 88724 (May 9, 2005)

Hi Frank

I have yet to check a Pro van and find that it conforms to regs, even to the point where one manufacturer had bonded earth and neutral in the distribution board.....

Many vans have sockets in obviously dangerous places.

directly above kitchen sink, In splash back area of sink, in the shower room I kid thee not, Mains wiring around the bed (virtually 75% around the bottom edge of the mattress) Be aware that I have recently heard that some of the sockets within a van were wired reverse polarity !! so next time you check internally try every socket.

I have seen vans were an invertor as been wired in to the mains circuit without isolation, now think about this carefully imagine the 16 Amp input unit on the side of your van. can you picture it? there are three exposed pins, these were live when the invertor was on.

also stuff like this on ebay is frightening, he is banking on the site RCD saving his customers, complies with all current regs?????

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=8779822337&category=90870


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## Scotjimland (May 23, 2005)

GeorgeTelford said:


> Many vans have sockets in obviously dangerous places.


Hi George
Very true but how many 'safe' places can you find in a smallish motorhome. Quite a challenge I think..


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## 88724 (May 9, 2005)

Hi Jim

*Quite a challenge I think..*

The shower dude, there is no excuse


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## Brambles (May 12, 2005)

Hi,
Is it so dangerous NOT to earth the Chassis? I think not. Not at all. 
If your mains cable onboard the vehicle is run near the chassis then yes there is a good argumemt to earth the chassis in case the Live cable gets damaged and shorts to the chassis, same applies to converted vans with a metal body, but most Coach built Motorhomes do not have a problem.
There is also an argument not to earth metal van conversions and no doubt you will all prove me wrong now. 
Jon.

P.S. Sorry Sallytraffic, that adVice you refer to is CORRECT.


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## BERTHA (May 21, 2005)

IN my experience a good earth is essential whether that is to ground on the van or through a cable back in to the mains/earth rod in your house.

Further, I would strongly recommend that the mains supply from your house to your van should not only have MCB fuses but also have Earth residual cut off

So should there be an earth leakage then the whole fuse box in the house will be shut off in a fraction of a second.

Every house I have ever moved too, this is often the first thing I change, the fuse box that is, so whatever shape the wiring may or may not be in at least if you have a high level of cover from both the MCB's and Earth Residual breakers.


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## 88724 (May 9, 2005)

Hi Jon

Not sure that I follow your post, on the one hand you argue against earthing the chassis and then you agree with the advice refered to which says you must earth the chassis.

Yes it is dangerous not to earth the chassis, if there is a fault this will then trip the RCD, withour the chassis being earthed someone could cope a belt from the bodywork (you are ten relying on the sites RCD)

We discussed this via PM before Frank posted, on the one and people can misconstrue the "advice" and yet other's who say the reg's are wrong, In some instances there is more than one correct method, but on earthing the Regs are Quite clear chassis must be earthed.


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## 98131 (Mar 14, 2006)

*To earth or not to earth*

Hi
This is not so simple. In Australia the neutral IS connected to the earth in every home .

It will also be affected by the type of protection cct. you use. Is it earth leakage or core balance (the source of another discussion).

Wild generators are the same - there are situations where the earthing can change safe to more dangerous.

The bottom line is that when dealing with high power, be it main, invertor or or 120A from an alternator it demands a great deal of respect!
david..


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## 88724 (May 9, 2005)

Hi Dave

its the same in UK earth neutral bonding is normal, but its done by the supply company under electrical supply regs, not on the property. Subtle but important difference


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## sallytrafic (Jan 17, 2006)

Brambles said:


> Hi,
> Is it so dangerous NOT to earth the Chassis? I think not. Not at all.
> If your mains cable onboard the vehicle is run near the chassis then yes there is a good argumemt to earth the chassis in case the Live cable gets damaged and shorts to the chassis, same applies to converted vans with a metal body, but most Coach built Motorhomes do not have a problem.
> There is also an argument not to earth metal van conversions and no doubt you will all prove me wrong now.
> ...


I'm sorry Like George I don't understand your PS, would you care to elaborate.

If you are saying don't earth then you are going against the BS and the wiring regulations. If you are saying that then in my opinion you are seriously misguided. Are you ready to defend your advice if someone follows it? The wiring regulations are a good deal less prescriptive than they once were allowing electrical designers to come up with their own solutions but if they say 'earth' it is a brave electrical designer who ignores that. Are you advocating the concept of a double insulated van? Although I agree that fixed wiring kept to the 'plastic' part of the van is relatively safe at the time of initial build what about what is added later. What about 230V electrical equipment that is connected via or referenced to the negative terminal of the battery system and therefore to chassis what if that develops a short circuit?

Regards SallyTrafic


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## sallytrafic (Jan 17, 2006)

*Re: To earth or not to earth*



dmws said:


> Hi
> This is not so simple. In Australia the neutral IS connected to the earth in every home .
> 
> It will also be affected by the type of protection cct. you use. Is it earth leakage or core balance (the source of another discussion).
> ...


To be safe then in Australia you need your own earth rod whether at the van or at the supply outlet. Is that correct? Some vans arrange this in a subtle way by having their steadying legs connected electrically to the chassis I'm not sure I would rely on that myself especially on a hard standing.

I agree with you about protection circuits we all bandy the abbreviations about but there are differing types even within one country and if you go to more than one, well..... In UK now all RCDs that I am aware of work on the principle of comparing line and neutral currents the difference between the two being the residual current this imbalance may be amplified or even delayed. I understand that Earth leakage types were removed from our wiring regulations in the 1980s but still may be encountered in installations.

Regards Frank


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## Brambles (May 12, 2005)

HI George and all. 
As always more than one answer. In the UK all site installations have to tested and checked, therefore shoud be corrctly wired, RCB fitted etc. But as you have mentioned... should we rely on the site RCB. Not at all is my answer, but equally we should not rely on there being a good earth.
On may sites standards are not so good, especially in Europe and say for example the earth connection was to become live on the site. Now we have the situation your Motorhome Chassis is live and the soil round about is not at the same potential. Step out of cab and you get a shock.
In an ideal world the chassis would be earthed but equally you would have an earth stake.
Also bear in mind eathing regs for homes (houses) keep changing and there are differing opinions as to whether everything should be tied back to one main earth point or just cross bond in every room.
Then there are arguments over cross bonding negative to earth at the distribution box, or using a earth running back to the transformer and having a floating earth system. All depends on what the policy is by local supply companies. 
A worse scenario is you are on a pitch when there is a major electrical fault with a power line or underground cable , say a 30,000 volt one. The ground around could quite conceivably have quite a large voltage potential between two points, being your motorhome and the sites earth point. If your chassis is connected to the supply earth and you are leaning against your cab standing on the ground you could be , well , not driving home again!!! 

There are arguments both ways and you have to look at all the possible risks and types of faults that can occur be in in the van and external to the van. 

Look at it another way. You are using a mains powered portable appliance, an electric drill for example, and you are drilling a hole in a metal fence.
Do you need to make sure the fence railings are properly grounded as well. NO, just the drill. What about the car sitting on your drive you are leaning aginst as you drill the holes for whatever reason, should you earth the car. Now you decide to take the extentiom lead and plug in a vacuum cleaner to clean up the mess, I shall do the car at the same time. Ah!! Must earth the car 1st as I now have a mains powered item sitting on the seat while I do the footwells. DO you need to earth the car? NO! Thats all your Motor home is. A lump of material with some mains powerd equipment inside and majority of material around the wiring is insulating. Fibre class body, internal wall panels, lino floor, wooden cuboards etc. 

However there is that argument than a cable somewhere could short to the chassis and it becomes live. While you are in the vehicle, no problem, but on stepping out you could get a shock, but then the van's RCB will trip, so again no problem. So to summarise, it is better not to have the chassis earthed, but have a working RCB and have it tested every year.

I am quite happy to be proved wrong and apologies for my french above (10 sentances when a word would have sufficed!!)

Jon.


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## 88724 (May 9, 2005)

Hi Brambles

_say for example the earth connection was to become live on the site. Now we have the situation your Motorhome Chassis is live and the soil round about is not at the same potential. Step out of cab and you get a shock._ 

Say this happened, if the earth was tied to Van chassis the onboard RCD would trip instantly due to current leakage to earth, this shows why the chassis should be tied to the earth wiring.

_
*In an ideal world the chassis would be earthed but equally you would have an earth stake. 
Also bear in mind eathing regs for homes (houses) keep changing and there are differing opinions as to whether everything should be tied back to one main earth point or just cross bond in every room. *_

The 16th Edition regs cover all the earthing types and have not changed for quite a while now. All are discussed in the regs and where each can and cannot be used,although there are still some choices. In a van there is only one acceptable method. An earth stake is likely to cause more problems, a difference in potential which could actually prove fatal, unless you can test and be sure that the Ground earth is at same potential as the mains earth its safer to do without.

_*Then there are arguments over cross bonding negative to earth at the distribution box, or using a earth running back to the transformer and having a floating earth system.*_

Cross bonding at the distro box is specifically prohibited in the 16th edition regs. All bonding should be done by the supply company under the electricty supply regs.

_*A worse scenario is you are on a pitch when there is a major electrical fault with a power line or underground cable , say a 30,000 volt one.*_

I cannot see this being possible, it would blow instantly, when I was young I saw the effects of a chap pick axing a mains cable, it was awsome to behold, flash melted Pick axe and one very shocked (not electrically) road worker.

Re the motorhome large lump of metal I do get what you are saying and if everything was double insulated it might work, but (you knew this was coming didnt ya?) if you do not earth the chassis it may become live and then if you were to contact neutral booosh your one dead MH'r

Live neutral shorts do not pop an RCD and you are relying on the (mcb) unfortunately Fractions of an amp can kill you by the time a 5 amp mcb pops you are probably an ex MH'r

Contrast this with an earthed chassis, live to chassis fault RCD pops.

You know it makes sense.


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## Brambles (May 12, 2005)

Hi SallyTraffic.

"If you are saying don't earth then you are going against the BS and the wiring regulations."
YES! Sounds like it to me!!
A European built mororhome MUST conform to EU regulations, and British built to both EU and BS standards for installations n MOtorhomes, and biuld type vehicles can be used in any european country. Hence most British built homes will probably have chassis bonded to earth, but all comes down the the electrical designer. He could choose to follow the EU regulations and due to harmonisation across Europe can do so. His choice. 

"If you are saying that then in my opinion you are seriously misguided. Are you ready to defend your advice if someone follows it?"
I am not misguided and I don't expect anyone to follow my advice, I offer no advice, just my understanding and if I am wrong, I am wrong.


"The wiring regulations are a good deal less prescriptive than they once were allowing electrical designers to come up with their own solutions but if they say 'earth' it is a brave electrical designer who ignores that."
They are less desriptive because through professional and experience emgineers debating safety, they realised thr old regulations where flawed.
They appropriate bodies still realise their are flaws in any one method chosen and have changed the regulations to minimise danger. Mimimise, not remove all danger.

" Are you advocating the concept of a double insulated van? "
Yep!

"Although I agree that fixed wiring kept to the 'plastic' part of the van is relatively safe at the time of initial build what about what is added later. What about 230V electrical equipment that is connected via or referenced to the negative terminal of the battery system and therefore to chassis what if that develops a short circuit? " 

So the chassis becomes live, so what, If your RCD is working you are protected. You have to balance the risks of that happening with the risks of exteral faults to the van.

Honestly, there are arguments both ways using various examples, but your orininal post implied NOT earthing was WRONG.

"That advice is WRONG and contradictory to the 16th edition wiring regulations which apply to motorhomes and caravans"

That is what I am disagreeing with, the word 'WRONG'. It may be condratictory to the 16th edition regulations but does not mean it is dangerous.

Just because there re regulations does not mean they are 100% correct - if they where why would they get updated.

Equally if your chassis is earthed I am not saying it is dangerous, I for my own technical opinion choose to prefer not to have it grounded.

If anyone wants follow my opinion , then that is entirely up to them, and not me, so lets just pretend the usual disclaimer follows.


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## 88724 (May 9, 2005)

Hi Brambles

The problem is that although in certain cases one can do things differently, you need to be able to show that it would be safe.

At the end of my last post I showed why it would be safer with the Chassis earthed and why it would be more dangerous not earthed.

Get some sleep

Ciao 4 Niao


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## Brambles (May 12, 2005)

Hi George. 


"say for example the earth connection was to become live on the site. Now we have the situation your Motorhome Chassis is live and the soil round about is not at the same potential. Step out of cab and you get a shock.

Say this happened, if the earth was tied to Van chassis the onboard RCD would trip instantly due to current leakage to earth, this shows why the chassis should be tied to the earth wiring. "

----- No it would not trip - its a RCD measuring difference in live and neutral . If it was a earth leakage breaker then it might trip if the tyres conducted to earth or someone touched the chassis and was not insualted to ground/soil. 


"In an ideal world the chassis would be earthed but equally you would have an earth stake. 
Also bear in mind eathing regs for homes (houses) keep changing and there are differing opinions as to whether everything should be tied back to one main earth point or just cross bond in every room. 

The 16th Edition regs cover all the earthing types and have not changed for quite a while now. All are discussed in the regs and where each can and cannot be used,although there are still some choices. In a van there is only one acceptable method. An earth stake is likely to cause more problems, a difference in potential which could actually prove fatal, unless you can test and be sure that the Ground earth is at same potential as the mains earth its safer to do without. "

------ I agree over earth stakes. Not a good idea and every installation of an earth stake needs to be tested.

"Then there are arguments over cross bonding negative to earth at the distribution box, or using a earth running back to the transformer and having a floating earth system. 

Cross bonding at the distro box is specifically prohibited in the 16th edition regs. All bonding should be done by the supply company under the electricty supply regs. "

--- Yes agree, by the wiring installers in the distribution box, and not the supply comany who still cross bond in many areas. I said 'at' which is not very clear but mean where cable coming in is terminated which is usually on the distribution board distribution box is mounted on also. 

"A worse scenario is you are on a pitch when there is a major electrical fault with a power line or underground cable , say a 30,000 volt one. 

I cannot see this being possible, it would blow instantly, when I was young I saw the effects of a chap pick axing a mains cable, it was awsome to behold, flash melted Pick axe and one very shocked (not electrically) road worker. "
------ It happens, and a lot as well where leakage occurs into the ground and is not detected.

"Re the motorhome large lump of metal I do get what you are saying and if everything was double insulated it might work, but (you knew this was coming didnt ya?) if you do not earth the chassis it may become live and then if you were to contact neutral booosh your one dead MH'r 

Live neutral shorts do not pop an RCD and you are relying on the (mcb) unfortunately Fractions of an amp can kill you by the time a 5 amp mcb pops you are probably an ex MH'r "

------- Why would you contact the neutral -- Hmm - see your point there though, but surely equally you could contact the live and neutral by the same means - lets face we have all done it..haven't we and learned not to touch more than one metal thing at time. Ned to think aboutt his one but think to have a fault to chassis and do somethig stupid like stick you finger in a socket has the same chance as touch live and neutral inadvertantly. (Got me thinking on that one George!!)

Contrast this with an earthed chassis, live to chassis fault RCD pops. 

--- IF the earth to the site connection is good. Said in one of my posts there are arguments both ways.

"You know it makes sense."

---Nope, not at this time of night and I am going to bed as it is well past 2.00am

Jon.


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## 88724 (May 9, 2005)

Hi Brambles

Yes they (rcd) measure the difference between live and neutral, but if its not going back down the neutral line, it must have gone somewhere else thats somewhere else is earth.

Thats why on some invertors the RCD will not ever work because the invertor does not have an earth there is no other potential for the current to escape too.

*It happens, and a lot as well where leakage occurs into the ground and is not detected*.

Or easily detected if you stand under the big pylon power lines with a flourescent tube in your hand Dont try this unless you are really clued up.


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## sallytrafic (Jan 17, 2006)

We can carry on debating this but as the examples we use get more and more involved the layman reading this is going to get confused. 

I have just let my membership of the IEE lapse (I didn't want to pay once I had retired) but there is a forum on their website where these sort of things can be discussed. For lay readers the IEE wrote the Wiring Regulations and it is the body that chartered electrical engineers belong to.

It has been discussed there and members disagree there as well and for much the same reasons that have been discussed here. 

Unfortunately the forum muddies the waters still further as it reveals that some sites are still being found with PME (OK TN-C-S) earthing arrangements. This is clearly dangerous and against regulations.

Lets see if we have and common ground (no pun intended) do we agree on the following statements?

1. The 16th edition calls for chassis of the 'van to be earthed through the hookup cable.

2. There is the possibility (in two fault situations) where this could be dangerous.

3. If you don't earth the van there are situations where this could be dangerous.

4. PME earthing systems are not allowed in the UK for connection to caravan (and construction sites) Situations in other countries are more unclear still. 

It is a great pity that in such an important safety issue that there is no clear unequivocal answer.

For me, personally, I'm going to earth my van but hey I'm a rule follower and I do like one of the posts on the IEE forum 'just think of the van as a bathroom on wheels'  and with the condensation I had before I had the water leaks cured that was just about right.

Supplementary question can anyone with a copy of the regs quote me regulation 608-03-04 (complete with any cross references)

Regards Frank


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## sallytrafic (Jan 17, 2006)

I'm just resurrecting this thread to say that in the April Caravan Club's magazine the advice is given again to earth the incoming supply to vehicle chassis etc etc. 

Regards Frank


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## 88724 (May 9, 2005)

Hi All

Just gave this thread a quick once over and noticed something that I missed before, Brambles thinks that all vans are made to EU or BS standards, this is clearly not true, in fact I would say the opposite, not one motorhome that I have ever checked would pass if it were checked to 16th Edition wiring regs.

The dumbest mistakes are 

1. 240 Socket in the shower room
2. mains cable run through the mattress area on a bed
3. Unbonded metal
4.Sockets directly over sink
5. Socket directly over hob
6. Incorrectly wired live neutral crossover
7. diagonal hidden wiring runs Buried
8. Shared channel for 12v ands mains
9 wiring in gas locker
10. Spur for all sockets, not ringed
11. wire not protected in lockers
12. earth neutral bonded in distribution unit !!!
13. Chassis not earthed
14 Invertor wired permenantly 
15 Cross over units that retained outside earth when on internal power (ie Inverter and Generator
16. not grommeted when passing through bulkheads
17. wires rated lower than the fuse/mcb protecing them
18. Incorrectly secured, not at prescribed intervals
19. wiring running through bathroom, hidden behind plastics but unsheathed.
20. Pendant luminaires without prescribed travel securing device.

I bet If Frank and I went through every motorhome on this forum, we would not find one that conformed to regs.


Frank in point 2. of your post you say that in a double fault situation earthing could be dangerous, how so? (are you looking at lost neutral scenario's?) 

I must have missed that post, which site as been found with PME ? (Protective multiple Earthing)

Sorry keep forgetting to look up that reference.


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## sallytrafic (Jan 17, 2006)

GeorgeTelford said:


> Hi All
> 
> Frank in point 2. of your post you say that in a double fault situation earthing could be dangerous, how so? (are you looking at lost neutral scenario's?)
> 
> ...


No not a loss of Neutral but losing earth in cable or from supply and having live to earth short at van not as far fetched as it might sound as I found exactly that in a building once that was partly wired up with MICC.

I don't know which site it was. It was reported on an IEE forum where the poster was asking if he should write up a code 1 report as previous inspectors had allowed it!

Frank


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