Mixing cable types

pff · 29 Aug 2009

Is it wrong to mix flex and solid wiring in a junction box?
I have several outdoor lights that i wouldnt want to connect with T&E as it would become exposed to the elements, and i think just not be as good, but reading around it seems cable types are not to be mixed in a junction box for some reason. Have i misunderstood?
I dont particularily want to fit sockets to all of my lights...
where can i make the change?

Goldberg · 29 Aug 2009

I don't know of any reason for not joining flat sheathed T&E and flexible cables in a junction box, but you need to ensure that (a) the cores have matching CSAs, and (b) that the flex is 3-core, i.e. has an earth core.

Where did you read of it being wrong?

pff · 29 Aug 2009

There were some older posts on here where people had indicated that it shouldn't be done.
All of its in 2.5mm, overkill for lighting i suppose.
Is it wrong to mix CSA's then? Is that just incase of confusion or overloading cables later on or because it makes a less secure connection?
Is it ever ok to mix cable sizes as long as the circuit is protected properly?

wingcoax · 30 Aug 2009

Where flex and solid are joined in JB most sparks like to put flex under solid so screw does not cut strands.

Goldberg · 30 Aug 2009

333rocky333 · 30 Aug 2009

There is a new reg in the 17th regarding termination of some types of flexible cable, mainly fine stuff which requires the ends to be ferrulled or similar.
A lot of stuff with flex supplys, like transformers, etc now come pre crimped

pff · 30 Aug 2009

I'll go and check what way round they are tomorrow then.
Might as well have a look at getting some bootlaces too.
Thanks for the tips guys!

333rocky333 · 30 Aug 2009

pff said:
Might as well have a look at getting some bootlaces too.

They require a special crimper to put on really.

To be honest you often see bare end flex terminated in j/b s especially above downlighters.

sparkwright · 30 Aug 2009

mk junction boxes have two screw-down fixings on each terminal so you don't have to put flexible and solid in same hole. would recommend doubling the ends of the wires over where possible before connecting.

JohnD · 30 Aug 2009

333rocky333 said:
They require a special crimper to put on really.

I have a special crimper for uninsulated bootlaces. It would be a bit expensive for occasional DIY. Can you do an adequate job with an ordinary crimper, or would you have to use insulated bootlaces?

333rocky333 · 30 Aug 2009

Never tried really,
A ferrule crimper squashes it on in about 3 places and wont pull off the cable,I have seen people just push ferruls on and then just use the screw to clamp it on, not as good, but stops the strands splaying out or the screw shearing the strands.

insulated and bare ferrules use the same crimper anyway, you can fit pin crimps with a normal lug thru crimp tool.

Goldberg · 31 Aug 2009

As 333rocky333 has said, pin crimps are a good alternative if you already have a ratchet crimper, but it can get a bit tight in a full box (ooh-er missus).

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Mixing cable types

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