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?
[automerge]1588514851[/automerge]
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!

 

[westward10]

In fact if earthed containment or cable sheathing is used then additional rcd protection would not be required.

 

[davesparks]

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.

The regs used to be very clear on this point, can you post an image of the regulation which you feel is unclear? I don't have a regs book to hand at the moment.

 

[Andy78]

Read 522.6.202.

Either use zones and rcd OR comply with a method from 522.6.204

 

[telectrix]

regs. are unclear in my view. have a look at 522.6.202
this implies that cables can be run anywhere , diagonal or out of zones as long as said cable/s comply with 522.6.204.

 

[Andy78]

regs. are unclear in my view. have a look at 522.6.202
this implies that cables can be run anywhere , diagonal or out of zones as long as said cable/s comply with 522.6.204.

That's correct. Zones are only for cables buried less than 50mm and not complying with 522.6.204.

 

[telectrix]

That's correct. Zones are only for cables buried less than 50mm and not complying with 522.6.204.

agree, but even so, few of us would consider running cables out of zones unless absolutey necessary.

 

[Andy78]

agree, but even so, few of us would consider running cables out of zones unless absolutey necessary.

Absolutely. It's a convention worth sticking to, and it would have to be a quite awkward situation to consider using a cable out of zones yet less than 50mm deep.

 

[davesparks]

regs. are unclear in my view. have a look at 522.6.202
this implies that cables can be run anywhere , diagonal or out of zones as long as said cable/s comply with 522.6.204.

Which they can, so it is perfectly clear

 

[telectrix]

Which they can, so it is perfectly clear

doesn't help when you have to turn the page between the relevant regs.