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Topic Title: Routing behind skirting board - Does a 30mA RCD mitigate it?
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Created On: 02 February 2014 08:56 pm
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 02 February 2014 08:56 pm
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fuzzyfelt

Posts: 3
Joined: 02 February 2014

Hi,
I'm a non-registered DIYer who tries to comply with Part-P restrictions and keeps a copy of IET 17th Edition by my bed.

My current house looks to be about 16th Edition, so has 30mA RCD on the ground floor sockets.

I'm wanting to add a spur socket to the existing ground floor ring and I'm considering the routing. The floor is very old parquet laid on concrete so I don't really want to pull it up. Chasing horizontally from an existing socket is obviously possible but I'm a little lazy.

At the risk of being burnt at the stake, is it possible to route the T+E behind the skirting board? I understand it's outside of the safe-zones and won't be mechanically protected but it will be protected by a 30mA RCD. My interpretation the of reg, says that the RCD mitigates the mechanical risks meaning I could run T+E anywhere outside of the safe zones.

Can anyone clarify my interpretation?
 02 February 2014 09:07 pm
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leckie

Posts: 4705
Joined: 21 November 2008

Well the fitting of a 30mA rcd does not allow you to run cables outside the prescribed zones.

These are the wiring zones.

http://niceic.com/en/account/media/17thpg6.pdf


If the cables are installed greater than 50m from the surface you can install them where you want.

Edited to say prescribed instead of safe. To please phantom!

Edited: 04 February 2014 at 09:10 pm by leckie
 02 February 2014 09:12 pm
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505diff

Posts: 182
Joined: 20 March 2006

50M from the surface? I never going to help you with a few chases...
 02 February 2014 09:19 pm
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ebee

Posts: 6735
Joined: 02 December 2004

I`d give behind skirtings a big no.

Verticals pref but horizontals at a push.

I`m not over keen on the more than 50mm deep either (although it`s not usually achievable iun a domestic setting) and behind skirtings would even 100/150mmm be safe?
I think not.

I`d never go behind skirtings (apart from verticals obviously)/

Mechanical protection if out of zones RCD or Not

Besides which , without proper mechanical protection the cable to that socket must be RCDd if buried (even within zones) if less than 50mm deep (unless surface wired - i.e. trunking)

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 02 February 2014 10:06 pm
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fuzzyfelt

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Thanks guys. I've re-read again and it seems I need to apply 522.6.8 *AND* 522.6.6, which is kind of obvious really. I'd hoped I'd found the ultimate get-out of jail card.

I'll see if I can squeeze SWA round it instead.

Thanks again.
 02 February 2014 10:38 pm
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peteTLM

Posts: 3755
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You need a bit of cable to BS8436 which mitigates safe zones and is a lot easier to work with than swa in this application.

Chopping 50mm into a house is murdering its structural intergrity

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 02 February 2014 10:47 pm
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Jaymack

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Originally posted by: fuzzyfelt
I've re-read again and it seems I need to apply 522.6.8 *AND* 522.6.6

From which book?

Regards
 02 February 2014 11:54 pm
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rocknroll

Posts: 9677
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Originally posted by: peteTLM

You need a bit of cable to BS8436 which mitigates safe zones and is a lot easier to work with than swa in this application.

Chopping 50mm into a house is murdering its structural intergrity


It certainly is; Building Regulations guidance is, max 1 third of the wall thickness for vertical chases, 1 sixth for horizontal chase.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 03 February 2014 07:42 am
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aligarjon

Posts: 4053
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2.5mm 3core swa isn't very big. it might be a bit tight glanding it though. maybe if you use a 35mm back box and gland it the far end only you might get away with it.


Gary

-------------------------
Specialised Subject. The Bleedin Obvious. John Cleese
 03 February 2014 11:29 am
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WiredScience

Posts: 358
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Originally posted by: fuzzyfelt

Chasing horizontally from an existing socket is obviously possible but I'm a little lazy.



Maybe pay someone less lazy to do it then?

Or as PeteTLM says, use BS8436 cable. A certain screw and fix website sells LSX Earth Shield, described as "hybrid cable".

Don't forget your minor works certificate.
 03 February 2014 12:01 pm
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MrP

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Fuzzy
No problem running wiring it behind skirting board
Run your spur directly below an existing point into a one gang accessory box point of utilisation in the skirting board do not break the cable. From the point of utilisation run the cable diagonal to a new one gang box fitted in the skirting board directly below where your new socket will sit
Job done engineering solution to your problem
Fit an Rcd to the circuit if not already there job done and complies

MrP
 03 February 2014 05:11 pm
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AJJewsbury

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diagonal
??

- Andy.
 03 February 2014 09:08 pm
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weirdbeard

Posts: 3116
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Originally posted by: fuzzyfelt


I'm a non-registered DIYer who tries to comply with Part-P restrictions and keeps a copy of IET 17th Edition by my bed.



My current house looks to be about 16th Edition, so has 30mA RCD on the ground floor sockets.



I'm wanting to add a spur socket to the existing ground floor ring and I'm considering the routing. The floor is very old parquet laid on concrete so I don't really want to pull it up. Chasing horizontally from an existing socket is obviously possible but I'm a little lazy.



At the risk of being burnt at the stake, is it possible to route the T+E behind the skirting board? I understand it's outside of the safe-zones and won't be mechanically protected but it will be protected by a 30mA RCD. My interpretation the of reg, says that the RCD mitigates the mechanical risks meaning I could run T+E anywhere outside of the safe zones.



Can anyone clarify my interpretation?


If you are lazy, you might as well just plug in an extension lead?

Owning a copy of the regs means diddly squat, but if you are intending to comply with the regulations, then when you've run the 30mA RCD protected cable behind the skirting, make a note of it in the departures section, with photos ideally - as it surely can't be said to be any more dangerous than cables run in the normal safe zones, which only electricans seem to be aware of?

-------------------------
:beer)
 04 February 2014 08:10 am
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phantom9

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Safe zones? Prescribed zones please. Please, not safe zones. I wish people would be more purist. A zone where a cable is located is hardly safe is it? This industry is absolutely bonkers. I think you will find no reference whatsoever to a safe zone in the regs.
 04 February 2014 09:13 pm
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leckie

Posts: 4705
Joined: 21 November 2008

Well if the cable is in a prescribed zone I assumed it must be safe, otherwise we wouldn't install it there.

Edited to remove a derogatory comment!

Edited: 04 February 2014 at 09:29 pm by leckie
 07 February 2014 08:07 pm
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fuzzyfelt

Posts: 3
Joined: 02 February 2014

Many thanks for your expert advice.

peteTLM, WiredScience: I wasn't aware of BS8436 cable so it looks an ideal solution. Thank you.
 08 February 2014 04:10 pm
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WiredScience

Posts: 358
Joined: 25 January 2012

There's more info to consider.

From The Afumex LSX Earthshield datasheet...

When BS8436 cable is used to comply with BS7671:2008 clause 522.6.5 (ii), or 522.6.6 (i), or 522.6.8 (i), not only are the requirements of BS7671 on current rating, voltage drop, grouping etc. to be met but the recommendation of BS8436 for current rating and protective devices should also be followed.

Only Type B circuit breakers conforming to BS EN 60898 or Type B RCBOs conforming to BS EN 61009-12 should be used. They shall also have a maximum let-through energy (I²t) not greater than 42000 A²s for 1.0mm² and 1.5mm² cable and 60000 A²s for 2.5mm² cables.
 08 February 2014 04:42 pm
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weirdbeard

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Assuming the cables aren't plastered over behind the skirting before it is fixed then strictly speaking they aren't subject to the regs regarding cables concealed in a wall, afterall the skirting could be skirting trunking.....

-------------------------
:beer)
 09 February 2014 09:54 am
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phantom9

Posts: 1757
Joined: 16 December 2002

Couple of points raised in this thread worth clarifying. And, so as not to ruffle feathers, as you have to keep the regulars happy, these are my opinions..

If cable trunking is specifically designed to be used as skirting board the cables will be in it, not behind it, which complies fully with the regs. Can we still run cables behind a skirting board?.

The rules for routing cables are contained in 522.6.100 through to 522.6.103.

522.6.100 deals with cables under a floor or above a ceiling. This is not applicable to skirting boards.
522.6.101 deals with cables concealed in walls or partitions at a depth of less than 50mm from the surface and by inference (see 522.6.102) under the supervision of a skilled or instructed person. This could apply to skirting boards.

522.6.102 in essence requires a 30mA RCD on the circuit if using prescribed zones and less than 50mm deep. A skirting board is not in a prescribed zone so this Reg. does not apply.

522.6.103 deals specifically with cables at any depth including partitions containing metal parts (such as studs and noggins). This could apply to skirting boards.

With regards to 522.6.103, there is an all important paragraph at the end of the reg. For a cable installed at a depth of 50mm or less from the surface of the wall or partition the requirements of Regulation 522.6.101 shall also apply.

So, we have just two Regulations to consider for cabling behind skirting boards, 522.6.103 and 522.6.101 if cable would be less than 50mm deep.

522.6.101 and 522.6.103 have identical wording except for (v) and (vi) in each reg.

It is my opinion that a cable can be run behind skirting if either of the above Regs. are complied with. A 30mA RCD on its own without considering all the other requirements, would not be sufficient.

Edited: 09 February 2014 at 10:07 am by phantom9
 09 February 2014 10:02 am
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phantom9

Posts: 1757
Joined: 16 December 2002

I have to add, in all honesty, this is one more example of how convoluted the Regs are. All those words to arrive at an answer to a simple question, can you run cables behind a skirting board. Isn't it really time they were simplified. Its beyond a joke.

I have been told in the past in no uncertain terms that you cannot run cables behind skirting boards under any circumstances. Humph.

Its fair to say that under normal circumstances, ie if using T&E (6242Y), that you cannot do it. This could easily be worded in to the Regs to make it simple. It is highly unlikely that any of the other required measures would be adopted just to make it possible. Under normal circumstances wiring behind skirting boards is best avoided.

Edited: 09 February 2014 at 10:17 am by phantom9
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