Borrowed earth allowed?

[mmax6870]

Hi All,

As I am about to start my second year on C&G 2330, my knowledge is still very limited. However, I would like to think I can work through a problem and find a solution. I would be very grateful if anyone could clarify the following situation, which I am not sure is acceptable.

As always, as soon as anyone knows you have a little knowledge in a specific area, you are called upon for advice. In this instance a friend of a friend has attempted to replace a light fitting in an old house, only to find that there is no earth present at the fitting or corresponding switch (or any other ones to mention it). Therefore, there question was, can they pick up an earth from a socket which is in the same room?

My thinking was probably no, but I spoke with an ex-electrician who said it was ok.

Can anyone explain why it is ok, or why it is not ok please?

Thanks

 

[sparks1234]

The best solution would be obviously to rewire the circuit, I take it that is not going to happen, next best would probably be to install a seperate earth back to the consumer unit but again that could be a real nightmare depending on the installation etc etc, I would think the easiest way would be to take an earth from a suitable circuit. If that is the only way of going about it then its better than nothing but I would make a note of it on a certificate and also put a label on the consumer unit to say what has been done saying if the other circuit is disconnected then an alternative means of earthing should be carried out.

 

[ajelec10]

Run it in 4mm g+y single from the socket that way is like a supplementary bond and has sufficient mechanical protection.

 

[acvc]

A 4mm plus a 2.5 in a socket terminal. Is that possible?

Also, what about separation of circuits?
Isn't sup bonding meant to be additional protection?

 

[NoSparks]

OK fellas. I did somthing very similar and during my inspectiobn discussed it with my inspector. And did I get a wolloping. No, No, No was his answer for the same reasons given above, that discounection of the second circuit would leave the light fitting unearthed. His instructions to me were to take the whole feed, line nutral and cpc from the alternative supply.

We might also wish to consider the recomendations for replacing a CU where there is no earth to the lights. This has a risk assessment section which just might apply in these circumstances, and would include the fitting of an RCBO to the circuit.

 

[wigan]

Hi mmax6870,

Try 543.1.2 in the big red book. I did it with upstairs lights connected to a shower circuit cpc (10mm T+E) from lights to sockets would say ok [check first] from sockets to lights would presume no unless tests prove otherwise.

Kev

 

[mmax6870]

Thanks to you all. At least I am not alone with the 'what is best practice of borrowed earth' issue!

My gut feeling as mentioned was no, so I think my advice will follow that route and suggest a Line, Neutral and Earth from alternative supply. This would also benefit from the fitting of a 5 amp FCU after supply point would it not? I take the point about 'any earth is better than none' and that notification on the CU to advise of disconnection risk, makes a great deal of sense should there be an issue with the supply end though.

It will be interesting to get the views of my tutor when I return to college in a couple of weeks, so I will let you know what line he takes also.

Thanks again for you help.

 

[ohmeelectrical]

Hope this ESC guide helps