Cable protection in relation to regulations

[frediaz]

I have had this discussion with the inspectors. The regulations illustrate single walls and the position of cables in relation to outlets, to show the zones where it is allowed to fix cables without special protection. But what happens on adjacent walls? The cables have to go or come from somewhere.

On the image below I show a cable running horizontally level with a socket on one wall, so if there is no socket on the adjacent wall, but the cable is level with the socket on the other wall, does it need protection? If so, will those thin steel profiles that TLC direct and QVS sell do the job?

 

[ColJack]

yes it needs protection as there is no indication that it's there.. add a socket and you're good..

and no, those metal capping is not good enough to qualify as "earthed metalic covering".. a nail goes through them as easily as through the plaster..

is there a specific reason you can't run the cable vertical from the socket and go above the ceiling or abelow the floor?

 

[Lectrician]

The cable on the wall with no socket would require additional protection.

Thin flimsy metal capping is not acceptable.

Your best bet is to fit an additional socket, or a box with a blank plate on the blank wall. This would be cheaper and far easier.

 

[frediaz]

This is just an example of a cable running along the walls horizontally on a ring circuit, so it makes sense to keep it level with the sockets to avoid excessive cable length.

So what is a correct capping to use? can someone give me a link to a website that has them? and what does it mean "earthed", that it has to have equipotential bonding? Like an earth wire connected to an outlet's cpc?

I am starting to think that it is easier (and maybe cheaper) just to put a socket on every wall where the cable runs, to avoid the rigmarole of providing adequate earhed capping

 

[Lectrician]

Very rare to run horizontally around a room - sometime done in kitchens.

You need to run the cable in earthed steel conduit, earthed steel trunking, use a cable such as MI(PYRO) or SWA. The reg does extend to mention "covering to prevent damage", but there is nothing openly produced particularly for this use.

 

[ColJack]

while it may be economical in cable savings, it more than outstrips that in extra capping, acessories, time spent installing..etc..

the common way is to go up or down from the socket and then through the floor /ceiling joists to the next socket.. this adds as little as 800mm to the cable length ( 2x400 rise from floor ) buts adds only 400mm capping to the equation ( if you use it.. no need in safe zones.. )

the reason it's done in kitchens is that there are a large number of outlets on the same axis in a short distance, so the savings outweigh the costs..

if ring length is the reason for your thinking, then you just split the rings up into smaller rings..

 

[frediaz]

Yes, I am talking about voltage drop in radial and ring circuits when being concerned about cable lengths

 

[Lectrician]

I can see that concrete floors and high or vaulted ceilings may be an issue, but as said, rising up from below suspended floors, and down when concrete floors is the norm.

 

[ColJack]

if the average number of sockets on a ring is about 10-15 sockets.. ( fair enough assumption? ) then the total additional cabling involved would be 8-12 meters.. which is nothing in a ring

 

[frediaz]

I don't really fancy drilling all the floor joists on the way on the first floor and downstairs there is no space unless you put the cables on the edge of the flooring - not nice

 

[ColJack]

so instead of a few drill holes done with a sharp bit, you intend to chase out half the walls and nail capping / fix conduit to the walls.

why is there "no space" if you can get the cables under the floor at the edges, surely you can get it inder the floor in the middle?

 

[Lectrician]

It is also not recommended to chase to deeply or for extended lengths horizontally. Think of an axe and a tree....

 

[frediaz]

I have to leave a gap between the esxternal walls and the plasterboard to meet the U-value so I do not need to chase walls. The same applies to the water pipes.

so instead of a few drill holes done with a sharp bit, you intend to chase out half the walls and nail capping / fix conduit to the walls.

why is there "no space" if you can get the cables under the floor at the edges, surely you can get it inder the floor in the middle?

 

[ban-all-sheds]

I have to leave a gap between the esxternal walls and the plasterboard to meet the U-value

Then run the cables in the 150mm horizontal zone at the top of the walls, and drop down to the sockets...

 

[Lectrician]

best practice is still up and down