Installing an outside light - cable route?

[Schinklegroover]

Not so much an electrics question but more "how do I install an outside light with the minimum destruction to my walls?"

I'm installing a lamp outside my front door, under a porch. Taking power from a switch just inside the door (converting to a 2gang to control inside and outside lights). I can't install the light on the other side from the switch as it'll be too low down the wall. Am I going to have to accept that I'll need to cut a hole in the wall in order to feed the cable through?

Wall construction is (out-in) facing brick - cavity - kingspan - thermo block - dot and dab plasterboard.

The cable to the light switch runs down a conduit between the thermo block and the plaster board, but I can't tap into it without starting to chop holes in the plaster. Or can I?

 

[LearningSpark]

Before you get too carried away, with the power turned off unscrew the switch from the wall and see what cables there are at the switch. If there is no nuetral you will need to take a feed from the nearest ceiling rose.

 

[Taylortwocities]

Do take some time to discover how lighting circuits work.
Its all in the WIKI
//www.diynot.com/wiki/electrics:lighting

 

[ban-all-sheds]

Am I going to have to accept that I'll need to cut a hole in the wall in order to feed the cable through?

No - you could fit an oil lamp, or a battery powered one.

The cable to the light switch runs down a conduit between the thermo block and the plaster board, but I can't tap into it without starting to chop holes in the plaster. Or can I?

Difficult to tell from here....

 

[PrenticeBoyofDerry]

Not so much an electrics question but more "how do I install an outside light with the minimum destruction to my walls?"

First thing you need, is to be sure that all the relevant conductors are available to create an electrical circuit.

I can't install the light on the other side from the switch as it'll be too low down the wall. Am I going to have to accept that I'll need to cut a hole in the wall in order to feed the cable through?

Can you not drill straight out from switch and run cable up the outside wall, until required height is reached?

The cable to the light switch runs down a conduit between the thermo block and the plaster board, but I can't tap into it without starting to chop holes in the plaster. Or can I?

Is there room in the conduit to run another cable?

 

[Schinklegroover]

I've already had the switch off and wired in the new double-switch to check that it all works - I've got three lots of twin and earth and another with black-brown-grey-earth as the existing light is dual-controlled with a switch at the other end of the hall. I've marked up all the incoming cables and wired it back into its previous state so I'm confident that all that's in order.

There's space to run another cable down the conduit but not a huge amount - one could push a cable through it but it's not so big that it would be possible to drop a drawstring through it with ease (I can access the top of the conduit just below ceiling height because the door chime sits there, but too high for the light as the porch canopy is on the other side of the wall!)

Was hoping to avoid a cable on the outside wall but I guess it may be the lesser of two evils.

 

[ban-all-sheds]

I've got three lots of twin and earth and another with black-brown-grey-earth as the existing light is dual-controlled with a switch at the other end of the hall.

But do any of them carry a neutral?

There's space to run another cable down the conduit but not a huge amount - one could push a cable through it

Don't bank on it.

 

[PrenticeBoyofDerry]

I've already had the switch off and wired in the new double-switch to check that it all works - I've got three lots of twin and earth and another with black-brown-grey-earth as the existing light is dual-controlled with a switch at the other end of the hall. I've marked up all the incoming cables and wired it back into its previous state so I'm confident that all that's in order.

Did you find any blue core conductors that were terminated in a connection block or were they all fitted across the switch terminals in either com/L. L1 or L2?
There is the extreme likelihood, that you don't have a neutral at the switch plate and your neutrals are looped in at the light fittings!

 

[ban-all-sheds]

I beginning to wonder if he really grasps all this....

 

[Schinklegroover]

Appreciate your help, gents, but like I say, I already wired up and tested the cabling, it's the routing that I'm more concerned about. I'm not an electrician by any stretch of the imagination but I noted the existing wiring, consulted the wiring diagrams and got it all rigged up without issue - I just now need to replicate it on the other side of the wall! Don't have my diagram to hand as I'm at work but, yes, there's a connector block within the switch which has, from memory, 3 neutrals connected to it.

 

[Schinklegroover]

Just closing this one out in case anyone else has the same problem - I ended up putting the lamp back-to- back with a picture on the internal face of the wall. Cut a 3" x 3" access hole and fed one end of cable to existing switch, then drilled through to the outside to the lamp position. Wee batten across the hole the plaster board, re-fixed the square I cut out and voila - quick skim and some paint and it's good as new (well, almost, but it's behind a picture, so who'd know?)

 

[bernardgreen]

What is to prevent someone drilling into that cable ?

New cables must be run vertically or horizontally from an obvious fitting.

As there is no fitting behind the picture there is nothing to warn people that there is a cable in the wall.

 

[ban-all-sheds]

Cut a 3" x 3" access hole and fed one end of cable to existing switch, then drilled through to the outside to the lamp position.

Please read this: //www.diynot.com/wiki/electrics:walls

Unless the cable you've run from the switch to the hole in the wall runs horizontally or vertically from it you MUST remove it and reroute it so that it complies with the rules for concealed cables. Note that horizontally as far as the picture and then turning to run vertically upwards won't do.

There simply is no alternative - if you do not (and this is not an exaggeration, it has happened) somebody could die because of what you have done.

Also, if the circuit is not RCD protected it should be, so if necessary look into adding that.

 

[Schinklegroover]

It's vertically run from the switch, but outside the conduit because getting into that would have required a lot more destructive work. From the hole to the switch I just dropped a weighted cord, collected the end from behind the switch and pulled the cable down through the cavity.

 

[Schinklegroover]

Oh, and it's a brand new house so elecs all to current standard - 2 RCDs for different circuits in the house, and I'm testing them quarterly!