# Obtaining an earth on hook up



## grizzlyj (Oct 14, 2008)

Following on from the current () thread on reversed polarity, would anyone suggest trying to earth your van yourself when the hook up doesn't have a decent one as shown by the test plug?

I have seen sparkies putting in earth rods on new properties, and know that sometimes several meter long rods need to be whacked into the ground one after the other before a suitable ground is obtained.

Our camper came with a seperate hook up lead that had the earth wire coming directly from the blue camper end socket, which they connected to a tent peg! 8O 
I have used this a few times (using 2' of copper tube in the ground)without really thinking about it, each time the test plug said I had an earth so no problem???

Any possible reason or situation why its not a good idea? Would it affect the RCD I try to always use at the site end of the hook up lead? 


Incidentally, the test plug seemed to be getting on a bit, so bought a new one which seems to be a great deal more sensitive.


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## raynipper (Aug 4, 2008)

The only reason I can see why not to do this is if you are providing the only way to earth for all the sockets on the site, you could experience a hell of a spark when connecting.

Ray.


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## grizzlyj (Oct 14, 2008)

And how will I know if thats going to happen?!?! 8O  :idea: 

Or will this be relegated to a job for the co-driver? :twisted: 


Cheers

Jason


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## tonyt (May 25, 2005)

If I were on a site and checked for earth and found none, I'd not have much faith in the rest of the site's electric circuitry - I'd either report it and get it fixed or find somewhere else to pitch!

I don't mess with electricity


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## raynipper (Aug 4, 2008)

grizzlyj said:


> And how will I know if thats going to happen?!?! 8O  :idea:
> 
> Or will this be relegated to a job for the co-driver? :twisted: Cheers Jason


Thats the point Jason.
You won't know.

It's OK earthing your own van that you should know has no faults. But as you connect your mains lead to the site, you would be also connecting your earth pin that is now connected down to earth, into the sites earth wire that could have various faults just waiting for you to accommodate them.

In turn this could trip any breakers not 'seeing' an earth before.

Ray.


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## wobby (May 1, 2005)

If there is no earth,-- don't hook-up,-- as the earth is their for your safety. Don't wire an earth that will connect back into the sites system by mean of an earthing rod, you may get more than you bargained for. On some old systems neutral and earth were the same connection!!!

Wobby


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## wobby (May 1, 2005)

Tried to delete this repeat  

Wobby


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## barryd (May 9, 2008)

I have a short length of cable (about 1ft) that plugs into the EHU and on the end it has a 13 amp socket where I plug my tester. I just plug it into every available socket until I get one with an earth. Saves getting your big cable out only to find there is no earth. Im ok with Reverse Polarity as I dont think it is a problem but no earth sounds too scary to risk to me.


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## Chudders (Jul 5, 2008)

You are unlikely to get a 'satisfactory' earth from your tent peg. You may get an indication on a socket tester but that is no indication that the earth is satisfactory to provide the necessary 'automatic disconnection of supply' (ADS). 
All caravan sites are required to provide what is known as a TT system for pitches. That is where an earth spike is used and the earth path back to the transformer is provided through the mass of the earth. 
Other earthing systems such as TNC-S (also known as PME) are not permitted. This is where the earth is connected to neutral at the incoming supply. TT is the only system. To ensure a satisfactory earth you need an Earth Fault Loop Impedence Tester, (or another type of tester that tests the earth) to ensure that the EFLI is not too high. The wiring regs provide the figures for this.
On a TT system of earthing it is not uncommon to drive in several feet of earth rod (or multiple rods) or lay a metal grid in the ground. It all depends on the type of ground in use. 
An RCD is also required with a TT system. (There are a few exceptions but very rare)
I carry out electrical testing on caravan sites and it is surprising how many hook up points are found to be unsatisfactory. 
My advice is to only use a normal hook up point, by all means check for polarity and earth with your socket tester. It is at least an indication. Sites are required to have installations periodically tested. Also test your vehicles RCD,s mechanical operation on a regular basis by pressing the test button. Again you may be surprised at how many RCD,s fail this simple check. If your socket tester does show any faults I recommend you move.
For those that are interested the 17th Edition of wiring Regs includes provisions for caravan sites. Amongst them are, each hook up point should have its own individual 30mA RCD. The connection point should not be more than 20M from the pitch. The hook up cable should be no more than 25M
All sorts of other regulations as well.
Sorry to go on
Regards, Dave
PS The above is my informal comment, I take no responsibility for any inaccuracies, (Cause I aint being paid.)

I am grateful to a member for pointing out that TT is not the ONLY way. A TNS system could be used if circumstances permit but it is in my experience unusual.


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## tonyt (May 25, 2005)

Chudders said:


> You are unlikely to get a 'satisfactory' earth from your tent peg. You may get an indication on a socket tester but that is no indication that the earth is satisfactory to provide the necessary 'automatic disconnection of supply' (ADS).
> All caravan sites are required to provide what is known as a TT system for pitches. That is where an earth spike is used and the earth path back to the transformer is provided through the mass of the earth.
> Other earthing systems such as TNC-S (also known as PME) are not permitted. This is where the earth is connected to neutral at the incoming supply. TT is the only system. To ensure a satisfactory earth you need an Earth Fault Loop Impedence Tester, (or another type of tester that tests the earth) to ensure that the EFLI is not too high. The wiring regs provide the figures for this.
> On a TT system of earthing it is not uncommon to drive in several feet of earth rod (or multiple rods) or lay a metal grid in the ground. It all depends on the type of ground in use.
> ...


Thanks for that Dave - it all helps us lesser mortals to understand the complexities of electricity.

I believe the majority of "dodgy" hook-ups are found in continental sites where I guess these regulations don't apply?


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## grizzlyj (Oct 14, 2008)

Thankyou for an official but unpaid answer!



Chudders said:


> You are unlikely to get a 'satisfactory' earth from your tent peg. You may get an indication on a socket tester but that is no indication that the earth is satisfactory to provide the necessary 'automatic disconnection of supply' (ADS).


That does raise the question why the test plug would show something that the Earth Fault Loop Impedence Tester may say isn't OK?

Or rather, is the test plug saying a hook ups earth is OK to be trusted?


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## Chudders (Jul 5, 2008)

A socket tester is only an indication and it may show that some sort of earth continuity exists. A EFLI tester is a lot more exacting in its testing (And a lot more money)
Indeed even the person testing has to use some experience in interprating the results. For instance you may carry out a test when its been pouring with rain, the ground is wet etc. On a dry day you may get a different reading which could render the test unsatisfactory. 
As I said a socket tester is better than nothing as it may give you an indication that polarity is wrong or the earth is non existant. It wont prove that the earths integrity is sufficient to satisfy the 'Automatic Disconnection of Supply'
That is why sites have to be professionally tested and certified. As users of sites we assume that we can trust the site to have safe electrics conforming to current standards.
Dave


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## gromett (May 9, 2005)

I am doing a self build at the moment and this is one of the things on my list.

I will be installing a DPDT switch (center off) which will allow me to change the polarity of the input literally at the flick of the switch. This switch will be mounted next to a polarity tester permanently fixed in the vehicle. 

I know it's not an option for most people with factory made boxes but it is doable if you are handy and understand electrics.

Karl

PS: The switch I am using is the ML78K from maplins


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## pippin (Nov 15, 2007)

Gromett - I would be interested to know how you are going to do that with just one of those switches.

I have a gut feeling that even though they are rated at 16A they would not really be up to the job.


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