routing behind skirting board

[slippyr4]

Point of clarification, gentlemen: i've read and re-read plugwash's text, and it seems to mean that a drop to a light switch, or a run to a socket, needs to be in this protected earthed metal cover. Mine are under the plaster with plastic capping, which is quite common - is that not allowed any more in new builds or alterations?

(iv) be installed in a zone within 150 mm from the top of the
wall or partition or within 150 mm of an angle formed by two
adjoining walls or partitions. Where the cable is connected to
a point, accessory or switchgear on any surface of the wall or
partition, the cable may be installed in a zone either
horizontally or vertically, to the point, accessory or switchgear.
Where the location of the accessory, point or switchgear can
be determined from the reverse side, a zone formed on one
side of a wall of 100 mm thickness or less or partition of
100 mm thickness or less extends to the reverse side.

 

[dingbat]

... i've read and re-read plugwash's text, and it seems to mean that a drop to a light switch, or a run to a socket, needs to be in this protected earthed metal cover.

The subject under discussion is concealed cables that are outside of the 'permitted zones'. If your switch drop/socket run is vertical or horizontal from the visible accessory then they do not need extra protection because that's where you'd expect them to be, so you're not going to go drilling holes... are you? If they are elsewhere - in unexpected places, such as behind the skirting - they need the supplementary protection.

 

[ban-all-sheds]

See these:


http://www.niceic.org.uk/downloads/C5-43.pdf


http://www.niceic.org.uk/downloads/concealedcables.pdf


http://www.iee.org/Publish/WireRegs...les_concealed_in_thin_walls_or_partitions.pdf
.
.
.

 

[JohnD]

Ta.

 

[ronald3]

Thanks all. Will cut channel into wall and run horizontally with PVC channel.

 

[HDRW]

... It is possible to buy plastic skirting / dado with provision to run cables in it, see http://www.tlc-direct.co.uk/Main_Index/Trunking_Pvc_Index/index.html

Hang on, though - that doesn't fit any of the allowed routings, does it?

And if it's because plastic skirting counts as trunking, why doesn't wooden skirting with a groove routed in the back of it?

Cheers,

Howard

 

[plugwash]

i think it all comes down to expectations, if something is obviously trunking then you would hope that people woultn't drill it, if its not obviously trunking then its concealing the cables and so i would presume you would have to follow the concealed cables rules.

 

[mattylad]

Sorry for bringing up a really old thread, but I'd like to find out what he current position is on this?

I have a length of 2.5mm t/e that is currently run behind approx 10' of skirting.

I can see no other path for this (having stone floors & 2' thick walls).

I do however have easy access to metal covered fire alarm cables.
While replacing the cabling for this cct should I replace this length behind the skirting with the fire alarm cable?
(and is this a req of the 17th?)

Cheers,
Matty

 

[RF Lighting]

Neither of those methods comply with either the old or current regulations.

 

[ban-all-sheds]

It could be replaced with BS 8436 cable....

 

[NotHimAgain]

Check this http://www.voltimum.co.uk/news/4173...opics.bs8436/Caution-over-BS-8436-cables.html
before using BS 8436 cable.

Basically it has limited fault current capability and should only be used as a means of complying with section 522 if the mcb is <= B32 and the prospective fault current is < 160A (you need to check that figure).

 

[mattylad]

OK, thank you for your comments.

So what is the required fix for having a cable behind a skirting then?

 

[NotHimAgain]

We are concerned with section 522 of the 17th Edition of BS 7671. In particular with 522.6 as this deals with impact. Assuming that you install the cables such that they not are subject to any tension or compression during the installation process - we are really left with the risk that the cable could be damaged at some future date, most likely by penetration by 'nails, screws and the like'.

522.6.6 offers various methods of compliance these could be summarised as:

1) Use a wiring system that incorporates an earthed metal screen that is sufficiently robust. This must ensure that if the cable is penetrated the circuit protective device would operate. To do this the wiring system must be able to handle the prospective fault current.

2) Use a means of mechanical protection sufficient to prevent penetration by nails, screws and the like.

3) Install the cables in a defined 'safe zone'. Note: In most cases this now also requires additional protection by RCD.

Taking each of these (3) is not applicable because the area involved is not a 'safe zone'. (2) is difficult because the wording of the regulation does not specify any limits - so if you propose to use 15 mm steel plate I will propose to drive my nail with a cartridge gun! This leaves (1) which includes such things as steel conduit, trunking and various cables.

BAS has already mentioned BS 8436 cables and these are OK within the limits specified above. Other cable solutions include various types of Steel Wire Armoured (SWA) or mineral Insulated (MI). Now you mention 'metal covered fire alarm cables' - if these are in fact MI cables to BS 60702-1 you could use them.

I do not know you level of skill so forgive me if I am stating the obvious - but MI cables require special tools, glands and training to install.

On a broader point, this is not a good location for cables, but I do note that you have limited options.

 

[mattylad]

I cant find any indication as to what BS8436 cable might be, would 2.5mm Pryo cable fall under this?
(given that I work for a fire alarm manufacturer, this is easy peasy to get )

I have had a look at the roll of cable I have & its a pirelli FP200 Gold type which has a metal sleeve under the outside PVC casing bit although IMO its not good enough to provide any protection from screws entering it, however it would provide an instant ground short if that is what is required.

 

[NotHimAgain]

FP200 will not do - the fault handling ability of the metal foil is not up to the job - its not as good as BS 8436 cable.

Pyro is a mineral insulated cable and this would be OK but, as I indicated above, this is not an easy job.

Just to be clear - the reason FP200, and in some cases, BS 8436 cable will not do is because - in the event of a nail penetrating the cable and just contacting the line conductor and the foil - the foil could vaporize before the protective device has had time to open. This would leave the nail live.