Outside lighting , wiring not in zones - advise please !!

[Steventhegreat]

Hi ,
I have a slight problem, I want an outside front light that is controlled by a switch, I am able to bring in a feed from the lighting at the bottom of the stairs (jb in ceiling void). The problem is as the actual outside light switch position will be situated underneath my porch which has a thick concrete lintel (12in approx) and the actual outside light position will be about 1/3 of the way up the stair wall. The only way around this is to chase a channel around this to the light and then to the switch, I know this will be outside wiring zones , Am I allowed to do this route and then use galvanised steel capping to protect the cabling from future nails in walls etc,
Any good advice is appreciated
Steve

 

[Adam_151]

How do you plan to attach the capping to the wall?

Now, once you have answered that, try and tell me that you think it'll protect the cable against a nail

[and before you say to earth it, bear in mind that an earthed metalic covering must be suitable for use as a CPC in order to meet the requirements to offer protection to the cable (or rather anyone unfortunate enough to meet it with a drill)]

No, capping isn't suitable, galv conduit is, SWA is, MICC is (but those don't lend themselves that well to what you want to do)

 

[Steventhegreat]

Cheers adam,
I was just going to revise my question and ask whether 1.5mm swa cable would be good to use in this situation,
I have never used it before, I will have to take it arould a 90 degree external corner, I guess ill have to make a nice deep chase then,
So with using swa am i good to go then !!!
Also can I just connect the SWA to my JB (Im currently using the small type jb for lighting , Can I use a larger 20amp type as to house the SWA cabling?
Steve

 

[stargazer]

Under the 17th edition of the wiring regs there is a requirement for cables concealed in a wall/partition at a depth of less than 50mm to be RCD protected, or enclosed in an earthed metallic covering / conduit or equivalent protection capable of resisting nails, screws etc. SWA will fulfil the second of these requirements, but you must terminate it correctly and earth the armour. Have a look here.

Whichever cable you use, you will be running it outside the safe zones. So why not take pictures of the cable installation before you make good? Note your picture with measurements showing the exact location of the cable from obvious starting points such as the floor, ceiling or wall. Laminate it and put it in an A4 binder next to your consumer unit with your other electrical certificates, consumer unit paperwork etc.

 

[ban-all-sheds]

I will have to take it arould a 90 degree external corner, I guess ill have to make a nice deep chase then,

There is no way that you'll be able to safely chase the wall deep enough to allow SWA to bend 90° within the chase....

 

[Steventhegreat]

Damn,
So to do this is to I could use SWA cable chased within 150mm of the ceiling in the safe zone then run it directly vertical to the switch which would be placed within 150mm of a extenal corner (which would be relocated to the stair wall) then across horizontally (by 4-5 inches) to the drilled hole is to outside light. then connect the SWA cable by glands to my outside light.


or could I use normal tw&e cable inside steel conduit buried into the wall and then go directly into the back of the light itself as it has a rubber grommet.
which method is best / safe ?


steve

 

[stargazer]

Is this all correct

No, because you are running cables outside the safe zone.
But running cables inside the safe zone in accordance with the latest regs will not stop somebody somewhere attacking it with a 10mm drill set for hammer action.

and safe?

TBH to make it as safe as possible I would forget SWA and instead run the installation in normal twin & earth, but RCD protect that circuit or that part of it. I would also make a careful record of the irregular cable run and keep it somewhere safe as I have suggested above.

 

[ban-all-sheds]

I can't really visualise the relative positions of things. Is the switch to be inside the house or outside?

Whatever you do, have you got the issue of the switch and the light being on walls at right angles to each other?

Am I right in thinking that the switch will be within 150mm of a corner?

 

[Steventhegreat]

Hi Guys ,
I will get a couple of pics tomorrow just so its easy for anyone helping me to visualise my explanantion...
Yes Ban the light and swich are at right angles to each other, (Imagine looking out of a front door , to the left side is the switch internally situated on a 200mm butt end of internal stair wall,
Then if you took a sidestep to the left you would be facing the stairs to which go up 3-4 steps then on your right side would be where the hole is for the light fitting .
so ill keep with the idea of using normal cable as stargazer has said, how would I RCD protect it,
Steve

 

[ban-all-sheds]

So could you not take a drop cable to the switch from a JB in the ceiling/floor void, then run a cable from the JB to the outside wall in the void, go through the wall and along the surface outside to the light?

To RCD protect it you just have to move the lighting MCB to the RCD side of your CU.

 

[Steventhegreat]

Hi Ban
I am not able to run the cable directly down the wall from JB to switch , as the switch is located inside the single storey porch and the Jb is located within the house inbetween this route is a 12in concrete lintel supporting the entrance to the porch , which is why the wiring route is somewhat out of the normal path.
When you say "then run a cable from the JB to the outside wall in the ""void"" , go through the wall and along the surface outside to the light"
How do you mean by Void ?
Thanks
Steve

 

[ban-all-sheds]

jb in ceiling void

 

[Steventhegreat]

Hi
I have taken 3 pictures to explain the situation, I have put them into my album, how do I put them onto this reply?

Ta
Steve[/img]

 

[stargazer]

The first picture is blank but the other two are below:-

It looks like the horizontal chases in the second picture are definitely outside the zones, and you’ve installed the wiring already? So my previous advice to RCD protect the circuit holds.

 

[Steventhegreat]

Thanks for reply stargazer

I can re-chase the wiring again as the whole wall is getting replastered soon , that is why I wanted to make sure it was ok before plastering was done,
I can chase out right up to the ceiling within safe zone but the route to to light it self which is just out of view will defininately be outside the safe zone,
Ban said on one of his posts the to protect it I need to move the circiut from MCB to RCD on right side of CU,
My CU only has MCB's which are all engaged,
Am I stuck lol !!

Steve