Equipotential Bonding and Conduit

[TheOldFellow]

I've buried a meter or so of heavy gauge steel conduit in a brick wall to bring some lighting switch cables to a switch. I had to route them in the back of the wall behind tiles and the accessory isn't visible - it's on the other side of the wall. It's clearly under the tiles in a zone 1 area. Of course this doesn't make it 'in zone 1', but there may be dampness eventually.

1) Do I need to bond this? The plumbing (basin and loo) is going to be plastic.

2) As there isn't anything to bond it to, I'm tempted to connect it to the CPC for the lights. That way any wally drilling through it (by golly this brick is hard!) will have his drill bit earthed before he hits the live. Is this allowed?

R.

[cynic]

Are you inferring that the job is within a room containing a bath or shower? If not zone 1 or bathroom type bonding requirements would not apply.

However as the 17th edition of the wiring regulations are now in force any new work involving buried/plastered in cables requires them to be RCD protected unless more than 50mm deep behind the wall surface, or the cable must be enclosed in earthed metal protection. This would normally be achieved by connecting to the cpc of the circuit.

[TheOldFellow]

Sort of, see below. Walls have two sides!

Thanks, that's what I wanted to know.

The cables are 75mm beneath the wall from one side, and just 20mm from the other. The accessory (switch) is on, and visible from, the 75mm side, but not from the 20mm side - which is a zone 1 area.

Thus, I have enclosed the said cables in a steel conduit, which is now connected to the CPC.=20

R.