Oval Conduit Sizes

[GarfieldTheFirst]

Hi,
I am embedding existing surface mounted conduit circuit into wall due to decorating. Can the existing 2 cables of a circuit 2.5mm be put into oval conduit? does it need to be 1 cable per piece of conduit? If so what size is appropriate? Also do you need to put in backboxes with oval cutouts (if there is a such a thing) so conduit goes into the backbox, or use standard ones and squash the oval to round at entry point? and does it then still need a rubber grommet?
Advise again please....

Thanks

 

[sparkwright]

Hi,
I am embedding existing surface mounted conduit circuit into wall due to decorating. Can the existing 2 cables of a circuit 2.5mm be put into oval conduit? does it need to be 1 cable per piece of conduit? If so what size is appropriate? Also do you need to put in backboxes with oval cutouts (if there is a such a thing) so conduit goes into the backbox, or use standard ones and squash the oval to round at entry point? and does it then still need a rubber grommet?
Advise again please....

Thanks

You again.

No need for conduit, but I really recommend it, as so very useful if you need to alter the wiring in the future. It's cheap enough anyway.

Plastic oval conduit is fine. It's also fine to run more than one cable in the same conduit.

It's fine to use a box with circular cable entries with oval conduit, assuming you are using regular 'twin and earth' cable.

Use grommets.

You don't have to have the conduit entering the box, but you should line up the conduit nicely with the box.

 

[phatboy]

With nice new, straight cable, its possible to get 2x 2.5mm T+E in 20mm oval conduit.

I would then hold the conduit into the wall securely using a few 16mm t+e cable clips.

 

[winston1]

With nice new, straight cable, its possible to get 2x 2.5mm T+E in 20mm oval conduit.

I would then hold the conduit into the wall securely using a few 16mm t+e cable clips.

Use the next size up oval conduit. It makes it so much easier, especially if you need to make changes next year.

I usually file out the knock outs in back boxes to fit oval conduit with a round file. Again makes everything easier and you won't need a grommet.

 

[GarfieldTheFirst]

Don't the clips rust when rendered or plastered over?

With nice new, straight cable, its possible to get 2x 2.5mm T+E in 20mm oval conduit.

I would then hold the conduit into the wall securely using a few 16mm t+e cable clips.

 

[seasickstevie]

Don't the clips rust when rendered or plastered over?

Rust? Plastic T&E clips?

 

[sparkwright]

The nails don't usually rust when plastered over.

I use galvanised clout nails either side of the conduit.

 

[ekmdgrf]

http://www.screwfix.com/p/tower-female-adaptors-20mm-white-pack-of-2/70059

That should stop even the most determined plasterer from inserting plaster between the backbox and the conduit, welding the cable in place.

 

[SimonH2]

http://www.screwfix.com/p/tower-female-adaptors-20mm-white-pack-of-2/70059

But that's for 20mm round conduit.

 

[ekmdgrf]

http://www.screwfix.com/p/tower-female-adaptors-20mm-white-pack-of-2/70059

But that's for 20mm round conduit.

Turns out that they sell that too:

http://www.screwfix.com/p/tower-conduit-heavy-gauge-20mm-x-2m-length-white/57073

I'd get some other stuff though. The Tower stuff is a pita to cut. Rather brittle and tends to shatter.