Thin singles for steel conduit

[endecotp]

Dear Experts,

My lighting wiring is all singles in steel conduit. I would like to replace a single switch with a double or possibly triple switch, giving more control of individual lights. A challenge will be pulling more wires through the existing conduit. (There are of course other options for routing the wires if necessary.)

My question is: what do the regs say about the wires that can be used in steel conduit? With modern lamps the current is tiny, and there is plenty of choice of >230V-rated flexible thin wire available - but is it permitted? (With suitable protection of course.) And is anything thinner than 1mm^2 ever actually used?

Thanks.

 

[EFLImpudence]

Who knows?

 

[endecotp]

Thanks! From what you've posed, being in steel conduit doesn't make any difference, and flexible (i.e. stranded) 0.75 is allowed. But no smaller, unless it's for "signalling and control".

 

[JohnW2]

Who knows?

I presume that you know that what you posted comes from the pre-Amd2 version of BS7671:2018? As I'm sure you know, with the advent of Amd2, the distinction between "Lighting circuits" and "Power circuits" disappeared (thankfully ).

..... not that any of this makes any difference to the OP's question relating to a lighting circuit.

 

[EFLImpudence]

Thanks! From what you've posed, being in steel conduit doesn't make any difference,

No.

and flexible (i.e. stranded) 0.75 is allowed. But no smaller, unless it's for "signalling and control".

I think so.

 

[EFLImpudence]

I presume that you know that what you posted comes from the pre-Amd2 version of BS7671:2018? As I'm sure you know, with the advent of Amd2, the distinction between "Lighting circuits" and "Power circuits" disappeared (thankfully ).

..... not that any of this makes any difference to the OP's question relating to a lighting circuit.

Yes.

Is there a new table?

 

[plugwash]

flexible (i.e. stranded)

When talking about conductors, "flexible" is usually taken to mean the same as "fine stranded".

Something like https://cpc.farnell.com/pro-power/t...5113&s_kwcid=AL!5616!3!426684131036!!!network}!890422401526!&gad_source=1&gclid=EAIaIQobChMI2KnklZ6ojAMVqoBQBh3h3TUdEAQYASABEgK3__D_BwE would seem appropriate.

 

[JohnW2]

Yes. Is there a new table?

Yes ... well, a slighly revised version of Table 52.3 (apologies for poor photo - I don't have an electronic version of Amd2) As has been said, it allows down to 0.75mm² for flex, or 0.5mm² for "signalling and control" curcuits ....

 

[securespark]

Just how many conductors are you trying to get down the conduit?

And how big is the conduit?

How many of the switches are two way?

If all of them were two way you could get away with 8 singles for a three gang 2 way switch if you were able to re-jig the wiring.

Is it important to not disturb the decoration?

Edited.

 

[SUNRAY]

I was trying to imagine the difference between 0.75mm² flex and 1.0mm² solid conduit singles, according to Harry Hill there is only one way to find out... F I G H T. Actually there is a better way:

What size conduit do you have?

I haven't checked conduit capacities but I do know I've pulled 12 x 1.5mm² + 1 x 6mm² stranded into 2 full lengths (6m or 7.5m??) of 20mm tube, I suspect that was beyond the capacity chart (but tube installed by others knowing what we planned to install and they were certifying plus the MCB rating was only 6A per curcuit). From that I'd imagine 20 x 1.0mm² in a switch drop would be achievable.

 

[endecotp]

Just how many conductors are you trying to get down the conduit?

And how big is the conduit?

How many of the switches are two way?

None are two way; it will be 3 or 4 wires where there are currently 2.

It’s relatively thin conduit but I can’t measure it right now. Whatever the smaller “normal domestic” size is. Another unknown is bends.

 

[Murdochcat]

Out of interest how would you plan to draw additional cores through the existing conduit?

Smart bulbs may be a better solution

 

[securespark]

It depends. There are many different kinds, types, sizes and shapes, both imperial and metric.

Do you have either a picture of the conduit or access to it to take one?

4 single insulated conductors should be doable providing there are no kinks. I have on occasion found an obstruction where the conduit has not been continuous and has been extended, but pulling through a new cable was not possible without removing the plaster covering the join.

 

[securespark]

Out of interest how would you plan to draw additional cores through the existing conduit?

I would pull all the existing ones out, first attaching a draw wire.

Then pull all the required cables back down in one go.

 

[Murdochcat]

I would pull all the existing ones out, first attaching a draw wire.

Then pull all the required cables back down in one go.

My question was aimed at the op

Did an EICR a few years ago where somebody chopped sections out of the conduct to add lights - meaning the once great CPC was rendered useless