Just six inches

[BriantheNail]

Hello everyone,

Apart from always wanting to do a job right, I am nervous of doing something which does not comply with any building regulations so I would appreciate the benefit of your wide experience please.

I have a light switch in my hall which I need to move about six inches to one side from its present position.

Having lifted a floorboard in the room above, I find that there is enough slack in the twin core switch wiring to reach the new position without a join.

The cable runs down the wall inside an oval black enamelled metal conduit which is not earthed in any way into a flush metal box.

If I chase the wall horizontally between the bottom of the existing conduit and a new flush plastic? box can I just plaster over the extended cabling or will I have to run it in a short length of conduit?

I will welcome your advice.

Many thanks

 

[mikeyd]

Can you dig out and relocate the vertical conduit drop 6 inches? You are redecorating anyway.

 

[ricicle]

Doing it the way you suggested means that the cable would no longer be in a 'safe zone' (unless you left a blank plate over the old position)
You need to come directly vertical or horizontally to the new position.

 

[electronicsuk]

Unless, of course, you can earth and then create an elbow extension piece for the existing metal conduit, which would allow you not to worry about safe zones. However, it's not really a DIY job, there's no guarantee the existing conduit will be a metric size, and it'd probably be a complete PITA. Far better to completely reroute from top to bottom.

 

[BriantheNail]

Thank you all -
the reason I didnt want to move the existing conduit or install a new conduit is that the conduit in both cases runs up behind a 3 inch coving at the ceiling and I cant see how I could chase the new channel position up under the coving without damaging it.

Are you saying that provided I cover the cable extension with a metal cover it would be considered safe?

 

[electronicsuk]

Are you saying that provided I cover the cable extension with a metal cover it would be considered safe?

Not just any old metal cover. If you're thinking of galvanised capping, it's a no-no. You need cable that incorporates an earthed metallic sheath, or earthed metal conduit. The latter is not a DIY job due to the tools needed to make off the ends of the conduit, and as I mentioned before, it may not even be possible to couple a new length onto what you already have.

Cable incorporating an earthed metallic covering is also out, as you'd need to join it onto the existing wiring, and that can't really be done inside the wall.

That leaves you with the options of mechanical protection (which is not so well defined in the regs and best avoided IMO) or a new chase. It should be absolutely no problem to chase in behind existing coving - when I've done it in the past I've had good success with a flat metal bar bent to shape. If you damage the coving a little then it shouldn't be hard to make good and paint.

 

[BriantheNail]

Thank you Electronicsuk,

I think I understand what you are saying, its just that, as the existing conduit is not earthed (installed in the 60's), there seems no point in connecting any metal conduit extension to the existing unearthed conduit.

Thats why I was thinking that an undersurface metal conduit extension was just to prevent inadvertantly drilling into a live cable at a later date.

With regard to chasing up the wall, the wall is solid brick so angling a drill up under the coving seems quite hard and risky. [/b][/u]

 

[sparkwright]

The best way to do the job is to cut a new vertical chase directly above the new switch position.

Use oval conduit or capping because it is a better job, and will help you with possible future alterations.

One method of getting behind the coving is to make a small hole in the plaster BELOW the coving, then drill behind the coving with a long 10 mm masonry drill bit.

 

[skenk]

The safe zone at the top of the wall (top 150mm) will allow you to keep the cable coming through in the same place, then run horizontally 6 inches and straight down to your new location.

Although I agree with sparkwright, getting behind 3" cove is a piece of p***, try 18" with no access from above and it gets a bit harder!

 

[BriantheNail]

Skenk, are you saying that running the cable horizontally just below the coving; ie within a 150 mm "safe zone" is permissible, as this would certainly make my work easier!

 

[BriantheNail]

Skenk, are you saying that running the cable horizontally just below the coving; ie within a 150 mm "safe zone" is permissible, as this would certainly make my work easier!

 

[spark1]

Slenk is correct.

You will, however first have to gain access to the cable,which will mean removing the conduit which presumably pops up into the floorspace above.
you should be able to chase it out up to the position of the coveng then belt it down [after first puling up the cable] from above hopefully without damaging the coving.

 

[BriantheNail]

Thank you all - I should be able to manage now - I'm grateful for all your advice

 

[mikeyd]

Do you have modern twin+earth running down the conduit?

My house was full of that, conduit was doing nothing more than providing the guy who last rewired the house with a way of getting the cable down the wall.

Getting the cable down behind your coving might not be as hard as you think.

 

[skenk]

//www.diynot.com/wiki/electrics:installation_techniques:walls