Earthing & Steel Conduit

[ryanj]

I've been asked to help wire a quite large workshop for one my friends. The workshop is never going to be open to the public and as we live in Scotland, we are currently exempt from this Part P nonsense.

The majority of the installation is going to consist of cables run inside steel conduit buried (some buried in plaster). I'm simplying wondering whether the steel conduit itself is going to be an effective earthing conductor, or there should be a seperate earthing conductor ran inside the conduit?

If the steel conduit is to be used, a earthing tail will be ran between boxes and any accessories. If a seperate earthing conductor is to be run, is it best to terminate it in the box, and run a seperate conductor to the accessory, or terminate the conductor in the box and run a conductor to the accessory?

Also, what advantages does galvanised conduit offer to the other option? And finally, if there are any tips you know of when working with conduit, please share them with me.

Thanks!

 

[mapj1]

Unless you can guarantee perfect threaded joints in the conduit, and no flexible sections, and the removal of paint at all boxes, thread an earth core through the tubing. It avoids trouble later on if the earth impedance rises as the system ages. Ideally, at any box where the live is interrupted to go to a machine there should really be a proper earth block or terminal in the box. That way, if a machine is to be moved, all its 'tails' are the same length.
All sounds sensible, good luck
M.

 

[breezer]

galvanised conduit is used outside, black enamel conduit is used inside, take your time when bending / threading it