≥6-core flex?

[JohnW2]

If your scaling is anywhere near correct (it looks to be in the pic) I wonder why you are not looking at staying with 3C&E

The scaling is pretty accurate, but it is, of course, based on the dimesnions of flat cabled, which varying quite a bit.

As for your question, maybe your experiences are very different from mine - but it would seem 'obvious' to me that it would be very much more difficult(if not impossible!) for me to try to to run two flat cables, side by side, with 'all four corners' touching, or nearly touching, the walls of the conduit, than to have just a single, round cable not much bigger than half the ID of the conduit, almost 'floating around' within the conduit (probably not touching the conduit in more than one place).

In fact, I could make life even easier for you since, at least in terms of my present requirements, I wouldn't need 2 x 3C+E - one 3C+E and one T+E would suffice at present.

 

[mikehammer69]

No need for that - 1.0 mm² YY (which is 'allowed') is only fractionally larger but, electrically speaking, totally unnecessary for supplies to two LED lights

The concern always with undersized fixed wiring is what happens after

I appreciate the 1mm complies

 

[SUNRAY]

The scaling is pretty accurate, but it is, of course, based on the dimesnions of flat cabled, which varying quite a bit.

As for your question, maybe your experiences are very different from mine - but it would seem 'obvious' to me that it would be very much more difficult(if not impossible!) for me to try to to run two flat cables, side by side, with 'all four corners' touching, or nearly touching, the walls of the conduit,

The reality in my experience is keeping the cable flat/straight/smooth during the pull-in allows them to slide in fairly easily just as you describe.and of course much easier if Mrs JohnW2 is as handy as Mrs Sunray in assisting with these matters.

than to have just a single, round cable not much bigger than half the ID of the conduit, almost 'floating around' within the conduit (probably not touching the conduit in more than one place).

Yes of course and I have indeed done something very similar on a number of occasions, without full details of the job (which I wouldn't dream of asking or expecting from you) I'll assume this will entail requiring adding some form of junction box which may not otherwise be required.

In fact, I could make life even easier for you since, at least in terms of my present requirements, I wouldn't need 2 x 3C+E - one 3C+E and one T+E would suffice at present.

That would of course simplify the matter. Are you implying there may be future developments here, if that is the case I'd be looking for more at this point, a 12*1 is still only 11.1mm, I know I have some 18*1.5mm² which would happily be able to wend its way but from that chart is 15mmØ so I imagine a non starter.


My first action would be to slide a cable rod into the space beside the existing cable and see how easily is goes in, you may be surprised.

 

[JohnW2]

The concern always with undersized fixed wiring is what happens after

Someone always says that, but in this case it seems just plain silly! What on earth could happen in the future to require the cable feeding two light switches to be 'massive'?

In any event, what we're talking about is worse (sillier!) than that since 0.75 mm² flex in NOT, electrically speaking.'undersized', since wth a CCC of 6A, it's adequately protected by the 6A OPD of a lighting circuit. The only thing it is (may be!) 'under' is some ('inexplicable') seemingly arbitrary 'minimum cable size'.

Until very recently, we had the same nonsense with 'power' (as opposed to 'lighting') circuits which had an arbitrary minimum cable size of1.5 mm², even thiose the CCC og 1.0² mm cable would be adequate in some situations. However, they have 'seen the light'over that one, and there is no longer a distinction bewteen 'power' and 'lighting' circuits, the minimum therefore now being 1.0 mm² for both.

I'm not convinced that the people who write these regs ever both to read what they have written before 'publishing'it