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The other day I had to connect a static caravan so the house holders can live in it while their house is being refurbed, the house is tncs
no I know your not ment to export the earth and I understand why, so I installed a earth rod, 78 ohms.
the main board in the caravan has 30ma rcd, but I could not bring my self not to connect the 3rd core in the swa to bring the earth fom the house also. I know the situation that if the dno's neutral fails this earth could end up running the neutral to the house etc.
but what's worse? This earth, now become neutral burnt in the swa or, some one leaning on the outside of the caravan, which would be at 230v with the dno's neutral fault and stood on the ground, possible wet?
they would then complete the circuit from the bonded caravan through them to ground and back to the supply transformer or dno's next earth spike.
any comments?
 
After thinking about it, I see the error in my thinking, the only reason the caravan body could become live under the fault is because the voltage would be carried up the earth wire. I see now why it's better not to connect the earth and only rely on the earth rod, as this way it'd be separated. This has been a lesson to me and I hope others can learn from it. Sometimes you just need to stand back and think about the wiring system as a whole.
 
Why no reply's is this such an easy situation? I can see the answer now but surely other people have had to think about this and maybe been stuck.
 
You knew you shouldn't have done it..you did it..now you want a pat on the back for informing us ? are you for real ? you seem to be a spark you have the regs book what do you want anyone to say ?..congrats ?

J
 
Ref jimmy, us? What's that all about, is this forum all for you guys that have been on here a while and new people like me are seen as outsiders? I've seen soe of te comments people receive on here and I think it's disgusting. Who do people lie you think you are
 
Everyone take a deep breath and...... Chill:thumbsup

There are various threads discussing the exporting the earth on a tncs and from what I can gather there are many differences of opinions for and against.

Why you have received no comments I am unsure but I have a feeling that this thread will either become closed by the Moderators OR turn into another posting frenzy starting the arguments all over again.
 
I will start by saying don't reply to your own post as people don't comment

And the pme? It says not to export but sparks do it because they can argue it in court if they ever got in there
i like a good reading on the earth so may have done the same, also I've never come across or read about the DNO loosing a neutral. (tin hat on) lol
 
Bs 7671 states that if a TN system is used to supply a caravan it shall be TNS...it also states that the ESQR prohibit the use of a TNCS system to supply a caravan.
It's quite clear in 708.411.4....Therefore if you connected a TNCS earth to a caravan and the unlikely accident occured you would be in deep doo doo.
This has nothing to do with general 'exporting the earth' nonsense which gets spouted as soon as outbuildings are mentioned......TNCS is only prohibited in a few of the special locations listed in section 7.
 
LOL, I like the way you had a little chat with yourself. I do that in my head all the time :)

You need to remember that BS7671 is not a Statutory Instrument, i.e. LAW, however in the event of a problem they will beat you around the head with the book (whoever 'they' are).
ESQCR is a Statutory Instrument. That means it IS LAW. i.e. go against it and you have broken the law and they take your pants down, spank you big time and ride you like a -----!

I only scan read your post and couldn't decide if you had TT'd the install or used the DNO earth. If you did break the law, I wouldn't be shouting about it on an open forum, and in such circumstances good luck with the certificate.
 
I suppose that whole chapter on caravan's in the big green book is just there to pad it out maybe?
 
I suppose that whole chapter on caravan's in the big green book is just there to pad it out maybe?

I must admit, it's one I skip but then again... I don't work on caravans lol

I hope this thread continues nicely as I'm following with a keen eye in the hope that I will learn something new and have a few little chuckles along the way :)

:thumbsup
 
It's dead simple, the OP just needs to follow the Regs in the BGB.
You're not allowed to use the DNO earth on a temporary structure. Separate the two and provide your own means of earthing, n'est pas?
 

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