Cables in walls

[Chapster]

Hi,

I'm a bit unsure about cables in walls. I need to run some T&E and don't want surface-mount, so plan to put it in the brick and render walls. Now, do I just chase the wall and put the cable in, followed by render screed directly over the cable?

I know of capping, but can't recall if that's for surface-mounted cables as an alternative to trunking, or if it's for putting over cables in walls, to cover them before the render screed is put on top. The shape makes me think it's not ideal for covering cables in walls because the middle protrudes a lot, and that the shape is to accommodate cables on the surface of a wall with the edges laying flat on the wall ready for some capping nails to hold down in place.

Thanks!

 

[PrenticeBoyofDerry]

You can chase out for cables and cap over, that's what they are used for, to prevent damage to the cable when troweling over.
But it's a personal choice, but cables should run in permitted safe zones.
what are you doing?

 

[Chapster]

I'm going to be sorting out a 6mm T&E cable that the past occupants of this house installed for an electric shower upstairs. They've run it there by knocking a hole through an outer-wall internal brick next to the CU downstairs, putting the cable into the wall cavity which they must have then fished up to the attic, where it comes out the wall cavity, across the joists and then through the ceiling to the pull-switch. That cable shouldn't be in the cavity, so I'm going to chase the walls and do it properly.

I've never used capping so wasn't sure if it was for surface-mount cables or for protecting cables buried in walls. I'll have to get me some PVC capping.

Another thought: probably the same person who put the T&E in the wall cavity also decided to bond the gas pipe coming into the house by tapping from the earth in a socket nearby and running a bit of cable (on a connector block halfway too!) from it to the pipe. Since I'll need to run a single bonding conductor from the CU to the pipe, and I'll want that in the wall, I suppose I'll have to put it in conduit because it isn't sheathed?

 

[sparkwright]

far better to use capping rather than clipping cable to brickwork.

you may damage the cable rendering.

and in case of any future alterations, you may have half a chance with the cable in capping.

capping is fitted directly to brickwork before rendering, and its depth never causes any problems.

alternatively oval conduit could be used, but you would probably have to cut out some brickwork.

 

[RF Lighting]

Is the circuit RCD protected?

 

[Chapster]

Thanks for advice, will get some capping. The circuits are all RCD protected so I don't have to worry about earthed steel conduit or running on the surface. or running more than 50mm deep.

Regarding the bonding conductor I mentioned in post before this one, what do you think? Also, is it now the norm for 25mm tails, 16mm earthing conductor and 10mm bonding conductors? I've looked more closely and found that the bonding to gas isn't tapped off the socket, but does come from the CU. However, it's 6mm cable...

 

[RF Lighting]

What is your earthing supply type?

 

[Chapster]

TN-S

 

[RF Lighting]

In that case the main protective bond needs to be upgraded to 10.0mm². Is your water supply also bonded in 6.0mm²?

The size of your meter tails will depend on the size of the cutout fuse, as will the main earth as you are not on a PME supply.

 

[Chapster]

Thought it'd need upgrading. More chasing to do, but there we are. Water is also bonded with 6mm unfort, so double the work. Must be done though.

Can I put a single earth cable in the wall and bit of capping over it, or must it be in conduit as it wouldn't be sheathed, do you know?

 

[RF Lighting]

Providing it is run within the prescribed safe zones, it can be chased in to the plaster work

 

[GaryMo]

In that case the main protective bond needs to be upgraded to 10.0mm². Is your water supply also bonded in 6.0mm²?

They need only be at least half the size of the calculated size of the main earthing conductor (544.1.1).
If a 10.0mm² main earthing conductor is deemed satisfactory (even though a 16.0mm² conductor may have been installed) then a 6.00mm² protective bonding conductor will suffice.

You would need to work out the minimum size of earthing conductor with the adiabatic equation.
You'll need the size and type of main fuse and PEFC or Ze.

 

[Chapster]

Thanks everyone for all the very helpful advice. I'll be running all cabling inside the safe zones, although I suppose when dropping the bonding cable down the wall, that vertical line won't be a safe zone because it isn't going to an accessory...

Do you normally just have the bonding cable come straight out the wall through the plaster, or do you use some kind of outlet plate for the sake of safety or because you need something there to designate the vertical area above it as a safe zone?

 

[RF Lighting]

You could use something like a flush mounted architrave box, and then drill a hole in a blank plate to bring the cable neatly out of the wall, whilst nicely indicating the position of the safe zone.