Which cable?

[xAlex]

I'm putting up a security light and am running the power from a spur upstairs, into the loft. The cable outside will be a suitable 1.5mm flex. The question is: would you run T+cpc from the spur to a JB in the loft and then connect the flex, or would you just run flex from the spur? Distance up the bedroom wall to the exit to the outside would be about 7m.
Thanks.

 

[Space cat]

Unless the light is very close to the exit hole I would take the twin and earth to the light in heavy duty 20mm PVC conduit. At the exit hole I would use a single entry junction box with watertight lid, screwed and siliconed to the wall with a hole in the back. At the other end I would use a two entry box with a downward pointing gland in the second hole for the flex.

If the light is close enough to the exit hole I would dispense with the conduit and put a gland in the first box but I would still join flex to twin and earth in that box. Suppose you have to take the whole light down. How easy will it be, standing on a ladder, to get the wires out of it? And what will you do with the bare ends? And how would you replace a damaged flex that goes all the way back to fused spur on the other side of the wall? It's so much easier to get a short piece of flex out of a junction box.

 

[xAlex]

Thanks SpaceCat. A comprhensive reply.

 

[Space cat]

You're welcome.

PS: Here's a tip I forgot to add. PVC conduit expands a lot when it warms up so you need to allow a little movement. On vertical runs I solvent weld the bottom end only and I don't push the top end hard up against the stop. On a horizontal run I leave both ends free.

 

[Steve3948]

There is no regulation that says you cannot clip 1.0mm2 T&E direct to the wall, and not bother with conduit which would look OTT.

Why take flex into the light when you can take the T&E straight in.
Less connections the better.