Wiring lights on exposed beam in flex

[Steve T]

Hi all,

I'd like to replace some MR16 halogen fittings on an exposed wooden beam to new GU10 fittings which I will be fitting led lamps into. The current fittings are wired in 2 core flex as they're only 12v, can't see a problem with that.

For the new lights I'm planning on using black 3 core 1.0mm flex, so effectively the flex will be fixed wiring, even though its exposed and clipped direct to the beam. As I understand it, it is permitted for use in fixed wiring. I will also be using ferrules on the screw connections in the lights. Reason I don't want to use T&E is because the beams are dark brown and I think black flex would look nicer and be easier to hide, it will be seen unfortunately as there is a mezzanine above the beam the lights are on. As I understand it, 1.0mm is the minimum size cable required for lighting circuits hence my choice of 1.0mm flex, however I have seen it mentioned that if you're using flexible cable you could use as low as 0.75mm which is rated at 6A so in theory would be ok on a 6A mcb when clipped direct in free air, which would be preferable as its easier to hide.

Can anyone please confirm which is the correct size to use, 0.75mm or 1.0mm, and that flex is ok to use in this situation?

Thanks for any replies!

 

[SparkyChick]

I would probably be inclined to install a fused connection unit where the transformers lived (you're going to be installing a junction box of somekind I'm guessing), drop in a 3A fuse and use 0.75mm flex.

Table 4F3A does give a CCC for 0.75mm of 6A.

 

[Steve T]

I would probably be inclined to install a fused connection unit where the transformers lived (you're going to be installing a junction box of somekind I'm guessing), drop in a 3A fuse and use 0.75mm flex.

Table 4F3A does give a CCC for 0.75mm of 6A.

Thanks, that's a good shout, I might be able to hide an FCU at the end of the beam where the transformer was, just not sure whether the edges of the box would go over the edges of the beam, will have to check tomorrow. I was going to use one of the old style 6A brown JBs, which are of course very small. Failing that I could probably just use 1.0mm flex and live with the fact that it will be bigger than 0.75mm, probably better than having an unsightly FCU. I also wasn't particularly happy that the 0.75 flex is rated the same as the MCB, not that the lights should draw anywhere near 6A but still.