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!

 

[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.

 

[davesparks]

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

That has got to be the most ridiculous criticism of the regulations I have seen yet.

How self entitled do you have to be to want everything put on one page for you? What do you expect them to do print them all on one damn page or maybe supply a slave to turn the pages for you?

 

[telectrix]

dave, my post was meany as being funny. i should have added a smiley.

 

[DPG]

That has got to be the most ridiculous criticism of the regulations I have seen yet.

How self entitled do you have to be to want everything put on one page for you? What do you expect them to do print them all on one damn page or maybe supply a slave to turn the pages for you?

You in a bad mood Dave?

 

[Steve89]

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!

So i went to the onsite guide and it has a list;
A cable installed in a wall or partition must. Then it goes onto list the requirements a, b c, d.. Each of these option has an or after it except after the RCD.
Which makes it sound like it's an additional requirement to one of the rest.

So luckily GS3 states in plain and simple! But thanks for all your replies, I've had nothing from the IET forum still!

(Just tried to upload pics from each book, but they've fail to upload!)

 

[7029 dave]

dave, my post was meany as being funny. i should have added a smiley.

No sense of humour eh

 

[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.