Earthing and bonding question.

[DetlefSchmitz]

If the pipe to the outbuilding travels underground, I suppose the outbuilding will already be effectively "TTd", whether one likes/wants it or not!

For the record, buried oil pipe is usually plastic covered.

 

[Risteard]

If the pipe to the outbuilding travels underground, I suppose the outbuilding will already be effectively "TTd", whether one likes/wants it or not!

Having an extraneous-conductive-part does not make it TT or otherwise.

TN-C-S systems have the extraneous-conductive-parts bonded and that doesn't make them TT in any sense.

Much of the world uses a TN-C-S system with an actual Earth electrode and this still doesn't make them TT in any sense.

 

[JohnW2]

For the record, buried oil pipe is usually plastic covered.

I agree that most is, but I've seen some that isn't.

If it were deemed to be, and one was confident that it would remain, effectively insulated throughout its underground route (can one ever be confident about that?), then it wouldn't constitute an extraneous-c-p either at house or outbuilding, and therefore would not, per se, need bonding at either end. However, as I've said, if it were earthed and/or bonded at one end, then that would mean that it would be an extraneous-c-p (requiring bonding to whatever was the local earthing system) at the other end.

Kind Regards, John

 

[EFLImpudence]

Pipe goes under ground and the first place I can see it appear is behind the floor mounted boiler so in theory I guess that is where it enters the property.

Ok.

I just wasn't sure if you were referring to the plumbers' favourite 'cross-bonding'.

 

[JohnW2]

Having an extraneous-conductive-part does not make it TT or otherwise. TN-C-S systems have the extraneous-conductive-parts bonded and that doesn't make them TT in any sense. Much of the world uses a TN-C-S system with an actual Earth electrode and this still doesn't make them TT in any sense.

All agreed, but when I talked about 'already effectively TTd' what I meant was that if a pipe is in contact with earth, then adding a bond from it to a TT earth would make no conceptual difference (only a small reduction in the resistance/impedance to earth).