Cables buried in wall less than 50mm UK

[Steve89]

Could somebody please clarify a certain aspect of this for me? I have posted in the IET forum and got no reply.

So say you install cables in a wall/partition less than 50mm below the surface. You run the cables in the specified zones and you protect it with a 30ma RCD.

Do you still need to use earth armouring, earthed metal sheath or earthed steel conduit? Or is the RCD sufficient?

Reg 522.6.204 of BS 7671:2018 seems to state it is not.

I'm studying to do the latest regs and was under the impression cables were permissible at a depth of less than 50mm as long as they we're protected by RCD 30ma. Is this now not the case with the new regs (18th edition). Do they need this mechanical protection too?
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No need to answer this I have found the answer. Guidance notes 3 clearly states that a RCD 30ma is sufficient protection.
It is clearly worded, unlike the regs, the on-site guide
and the explained illustrated 18th Edition Wiring Reg books, which are very unclear and seem to be missing an OR from their wording which would clearly indicate this to be the case. Well that was 2 hours of study time wasted!

 

[Steve89]

Poor Dave!
Though I do agree with teletric, turning the page on the regs is hardwork! Especailly if your reading it cover to cover like I am. It's heavy going!

So just to put you at ease, the cables will be going in the zones and protected by an rcd. I'm going to run the cables over 50mm deep except on one wall which has the runs going down to the switch. I'll offer them the choice of some extra protection there.
It's a bathroom for my sister.
Though lockdown has to end first and I need to do my 18th edition exam. Kinda in limbo at the mo. What a time to go self employed! xD

 

[Baddegg]

How or why are you going to get the cables more than 50mm in a wall?....in a stud wall you could just about do it if you stripped the wall back but on a brick/block wall I wouldn’t be going that deep mate......it’ll be rcd anyways so there’s no need either, and any work in a bathroom will need rcd protection as well it’s not a choice for ya sister to make....

 

[Andy78]

So the confusion came from here;

Reg 522.6.201 says (i.) Less than 50mm deep use the 150mm from ceiling and horizontal/ vertical runs.
(ii) Complies with reg 522.6.204
I took this as both requirements for indents needed to be met

and when you go to reg 522.6.204 it says the cable shall; then goes to list the mechanical protection and selv/pelv.

I took this as it it need to comply with both, but reading again i see that the note beneath 522.6.201 says "Where (i.) applies but not (ii) cables shall be provided with RCD".

Not very clear at all!

You are missing the word OR from the end of indent (i) of 522.6.202. That provides clarity.