2.5 singles

[cotasoc]

Hello.
A non electrician here..
Just asking out if interest.
2.5mm twin?
You know the stuff.
So what does the 2.5mm refer to ?
Area of the conductors, I would have thought - but - I was looking at 2.5mm single conductors that go inside conduit. They look fatter than the 2.5 T&E conductors - and they're stranded.
So - for the singles, is it an equivalent cross section area of copper ?
Or equivalent current carrying capacity ?
Neither? Both ?
And what is the current carrying capacity for 2.5mm ,anyway ?
I thought it was 20A - but on the 2.5 T&E shelf at B&Q it says 27A max current.
Or do they mean "peak current for a short while, but don't leave it on or it will burst into flames" ?
Would be interested to know ?
Cheers,
All the best.

 

[ColJack]

something that is solid is going to be smaller than something of the same area with gaps in it..

the strands are round and so leave little sort of triangular gaps between them even when touching ( take 7 coins of the same size and arrange as in a stranded cable and you'll see.. )

so yes it's the CSA of the conductor/s

the ampacity ( CCC ) of a cable depends on a number of things, such as ambient temperature, insulation over it, grouped together etc.

2.5mm T+E can take 27A in ideal installation circumstances, but if you start running it with other cables or in a hot space ( near rad pipes under the floorboards etc ), or under loft insulations or in an insulated stud wall etc, then you have to reduce that.

 

[flameport]

2.5mm refers to the cross sectional area of the copper wire(s).

Stranded will always look bigger than a solid core, since there are small gaps between each strand.

Current carrying capacity depends on how and where the cable is installed. What packs at B&Q claim is the maximum is probably the maximum under ideal conditions (free air or clipped directly). In real life, the capacity can be much less, particularly when run through insulation.

 

[cotasoc]

ok.
Thank you both.