Conduit - cables in walls

19 Jul 2008
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United Kingdom
Where do things stand with conduit and cables behind walls nowadays with new regs etc. I'm not an electrician but I am curious as to whether the cables need to be 'withdrawable' from the conduit ducting within the plaster?? Does the conduit need to be metal or is plastic acceptable?
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As well as the 16th rules, they've added the requirement for RCD protection.

There's an article in Wiring Matters I could link you to, if the IET site hadn't gone AWOL...

522.8.2 implies that you ought to be able to withdraw cables in conduit.

Plastic is OK, as long as you aren't intending it to provide mechanical protection
From my understanding if the conduit is to give mechanical protection it is required to be metal and earthed.

If it is pvc conduit the circuits must have supplementary protection i.e. RCD

unless >50mm inside the wall

Anyone else?
if I have a cable on the surface of a brick wall, with a stud wall built in front of it that is 100mm ( it's to hide gas, water and waste pipe ) then I shouldn't need RCD right? it's 100mm from the lounge side of the brick wall, and 100mm from the surface of the stud wall..
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Generally though I think that people would balk at their rooms being made smaller even more than at the cost of RCBOs... ;)
Thanks guys

When you refer to 'mechanical protection' what do you mean?
strong enough so that you can't mash the cable with a hammer, or drive a nail through it without noticing it's there first..

as for my room being smaller.. it's my kitchen and the wall in question is having the cooker on it and already has rad pipes.. it will also have a prep' sink so needs a drain..

concrete floors and another flat below me so I lose 4 inches of my room to hide it all.. :rolleyes:
Shouldn't all conduits be metal as all of them tend to be prone to getting a nail rammed through it at some point.

In other words, where would you install a plastic conduit and not a metal one? :confused:
surface where you can see them and where they are more for minor impact protection.. ( ie where you might kick them but not where you can drive a car into them.. )

or for use in roof spaces or down partition walls.
In other words, where would you install a plastic conduit ..?
Anywhere where you might want to replace, modify or add to the wiring, without having to redecorate.
I have never seen electricians use the metal conduit as a standard. I have always seen these plastic white conduits running down the wall to switches and sockets. I suppose when the plaster has been who is going to find out???!!!!

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