≥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

 

[JohnW2]

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.

You seem to have had much happier experiences than me. It's keeping things perfectly straight/flat which is the issue - the slightest tendency to bend, let alone 'twist', and everything often 'jams up' (in my hands)

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. .... 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.

This whole discussion has now actually become pretty moot (see below) but my very simple question about availability of a certain type of cable seems to have turned into a complex 'big deal'

There are certainly no secrets. The present switch, supplied by 3C+E is just inside the front door,and does 2-way switching of the hall lights, the other 2-way switch being on the first-floor landing. I'm about to install a light outside the front door, very close to that switch and simply want to change the existing switch to a 2-gang one so it can control the new light as well as the existing one (and I obviously need to get L&N for the new light down to that vicinity. It it extremely unlikely that there will be any 'future developments' that would need any more wiring in this location in the house.

However, I've been silly (I blame a combination of old age and the unacceptable heat ). I've just realised the the present 2-way switching of the hall lights has been done in the 'modern'('conversion') way, such that one of the strappers is a 'permanent live. That means that all I need (in addition to what's there already)is a neutral (which I'm pretty sure is available very nearby to the top of the conduit) in order to be able to install the new outside light and a switch (gang) for it. So it looks as if all I need to do is replace the exisiting3C+E with 5-core flex ('4C+E), of which I have plenty, and which hopefully will/would be a fairly straightforward 'change'! The situation would then look something like this (or am I missing anything?!) ...

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.

That's been one of my concerns, since I did a little playing with just one 1mm² insulated conductor (from some T+E) and struggled to get it in at all beside the existing cable

 

[securespark]

What I have done in the past is strip twin and earth and pull the stripped portion down the 5/8" conduit, such that the sheath is just inside the conduit. You'll need little rubber thingies on the ends though, if you haven't got them already.

I don't know if modern ones exist.

 

[JohnW2]

What I have done in the past is strip twin and earth and pull the stripped portion down the 5/8" conduit, such that the sheath is just inside the conduit.

It seems that that is what's been done- as you can see from my photo, the sheath is not visible at the bottom of the conduit, and nor can I get it to show itself by gentle pulling (I'm hesitant to do more than that until I'm ready to deal with any undesirable consequences!)

You'll need little rubber thingies on the ends though, if you haven't got them already. I don't know if modern ones exist.

What are/were these thingies -some sort of grommets?