taking earth cable from sockets of lights to earth water pipes in bathroom?

[HappyHippyDad]

I was wondering about earthing and bonding today.

We take a 10mm conductor and connect within 600mm for gas/water/oil etc, but quite often pipes in a bathroom or elsewhere have a bonding clamp on them with a cable taken from lights or sockets. In the case of the lights that probably means they have a connection to earth via a 1mm conductor (lets assume they have plastic pipes along the way somewhere so are not connected to the 10mm). I cant quite see how this is acceptable given that 10mm is required for bonding?

I realise if they are not extraneous and have an RCD then 4mm supplementary bonding is not required, but this is not supplementary bonding, it is a light circuit being used to bond the pipes!!?

Any suggestions?

 

[Darkwood]

It was to regulations before widespread use of rcd's - extraneous metalwork in bathroom needed coupling to the earthing of all circuits within the bathroom so it should be a 4mm if singles on its own but you can imagine the issue of fitting numerous 4mm into say a batten lampholder -gladly them days are done.

 

[Leesparkykent]

Supplementary bonding should connect together the earth connections of exposed conductive parts and extraneous conductive parts together.

 

[HappyHippyDad]

Supplementary bonding should connect together the earth connections of exposed conductive parts and extraneous conductive parts together.

Yes, so as to make sure they are at the same potential. These examples that I come across are simply an earth cable taken from a ceiling rose or light switch to a copper pipe in the bathroom with a bonding clamp on. But as Darkwood said, it looks like this was the practise before RCD's.

 

[Leesparkykent]

Yes, so as to make sure they are at the same potential. These examples that I come across are simply an earth cable taken from a ceiling rose or light switch to a copper pipe in the bathroom with a bonding clamp on. But as Darkwood said, it looks like this was the practise before RCD's.

Yes this changed when the 17th come out. The object is to ensure that potential differences in excess of 50 V between accessible metalwork cannot occur.

 

[GEOFF S]

It ensures that if enough current can flow accross the SBC, disconnection will take place, the touch voltage may exceed 50V.

Cheers

 

[Risteard]

but this is not supplementary bonding

Yes it is.