Could someone please explain

[karter]

I was in a mates garage the other day and noticed his nice new hagar consumer unit.The main earth from the earth block to the C.U. was in 16mm and the M.E.B. to the gas and water was in 10mm. OK so far but here is my querie the supply earth was T.N.S. with just a few strands, at a guess no more in total than a C.S.A. of say 4 or 6 mm going from the outer sheeve of the incomming supply cable to the earth block,therefor why use 16mm for the main earth,or should 16mm be somehow attached to the main sheeve of the supply. Please lets have your thought I am very interested. Many thanks

 

[nozspark]

First off I we are on hte same lines then that bit is owned by the DNO and as such shouldn't be tampered with...

You could contact the DNO and ask them to upgrade your earth, but I very much doubt that they will do anything about it.

Just make sure that your side complies with BS7671...

 

[333rocky333]

The consumers Earth and bonding and tails have increased sizes over the years.
Most of them supply earths were installed in the days of smaller tails and 6mm earth bonding or before, theres probably still too many in use to replace them all.

The live and neutral supply cores are also most likely well smaller than the 25mm meter tails used nowadays.

 

[karter]

Thanks Nozspark and Rocky333. I understand the points you have made.I am not an electrician, but am I right to assume that if my mates C.U. installing sparks did all the checks and found that Ze for T.N.S. was within the 0.8 limit that this old small link to earth is perfectly safe and acceptable.

 

[RF Lighting]

Yep, as long as the Ze checks out alright, I wouldn't be too concerned.

It is normally a bare conductor aswell, so the adiabatic equation would allow a smaller CSA I'd expect.

 

[electronicsuk]

Thanks Nozspark and Rocky333. I understand the points you have made.I am not an electrician, but am I right to assume that if my mates C.U. installing sparks did all the checks and found that Ze for T.N.S. was within the 0.8 limit that this old small link to earth is perfectly safe and acceptable.

I'd say it's acceptable under BS7671, as the installing spark isn't responsible for the DNOs side of the installation, so all he can do is ensure that Ze is within limits and his work is compliant. However, that doesn't necessarily mean the DNO earth is adequate.

 

[333rocky333]

Yes it is usually ok to leave it as it is usually soldered on.
Theres been a few pics on here lately of a 16mm bodged on the supply cable with jubilee clips.
DO NOT attempt that.
There are also roll springs used to secure one on.
However the existing one is proberly superior to anything you could do yourself, as it is soldered on.

Therefore if it looks secure and readings are ok, leave it be.

 

[ban-all-sheds]

And of course there's always the TT-opt-out solution....

 

[karter]

B.A.S. by your comment ( TT opt out solution ) does that mean that if the suppliers earthing was when tested found to be inadequat that it could be disconected and a correctly installed full TT system applied.Am I right in assuming that you could not leave the TNS connected if you just added an earth rod or a full TT system. Also would would the sevice provider object to there TNS being dispensed with and prefer just to upgrade it to make good By the way the suppliers earth did test out ok, my mates electrician is dropping him a copy of the cert, my friend,dopey s-d lost his.

 

[ban-all-sheds]

Even when they are obliged to make an earth terminal available, you aren't obliged to use it.

Getting the DNO to resolve the situation is the best option.