2.5 twin and earth

[mike 109444]

Happened to be fiddling with a project and needed to checkup no some wire info namley when wire size is quoted as nn2 as in value is in mm square (even though wire was round) so checking on some 2.5 square twin and earth which was L and N = 1.6 dia which gives area as 2.01mm and Earth = 1.2 dia which gives 1.13mm area. My question is where do they get the 2.5 square figure from??

 

[rtbcomp]

The size quoted for wire is square mm, this written mm2 (2 being in superscript) and pronounced millimetre squared.

2.5mm square means a square with side 2.5mm long, clearly not applicable to round wire!

I agree with your calcs, if you multiply 0.8 by pi instead of 0.8^2 you get 2.514, so perhaps for all the years they've been multiplying the radius instead of radius squared by pi !!!

 

[TechnicAl]

Does it include the plastic insulation?

 

[piman]

Hello Rtbcomp,

as you say the cable conductor cross sectional area is what is quoted, in mm squared, but a 2.5mm square is 6.25mm squared. The area of a 1.6 diameter round cable is , as you say correctly, 2.51 mm squared so that is correct.

I'm old enough to remember before metrication when it was 7/0.029" rather than metric CSA.

Alec

 

[TechnicAl]

Hello Rtbcomp,

as you say the cable conductor cross sectional area is what is quoted, in mm squared, but a 2.5mm square is 6.25mm squared. The area of a 1.6 diameter round cable is , as you say correctly, 2.51 mm squared so that is correct.

I'm old enough to remember before metrication when it was 7/0.029" rather than metric CSA.

Alec

What?

 

[piman]

Hello Rtbcomp,

in other and perhaps clearer words, the cable size is it's cross sectional area, so for circular conductors it is radius squared times pi.

Alec

 

[rtbcomp]

I know, that's what I said!

 

[piman]

Hello Rtbcomp,

looking back I see what you meant by 2.5 square section. Actually the size given in the first post must be inaccurate as a 1.6 mm conductor is just over 2 mm squared.

Alec

 

[rtbcomp]

That's what he said 1.6mm dia = 2.01 mm^2.

He may have measured the diameter incorrectly, I'll check some of mine tomorrow if I remember.

 

[rtbcomp]

Mike, as a matter of interest, is the wire you measured the new harmonised stuff (blue & Brown) or the old red & black?

 

[madkayaker]

is the cable BASAC approved? there is quite a bit of dodgy stuff out there that does not meet the requirments but has been labled up as CE etc

 

[mike 109444]

New blue and brown + earth. One reason I was queering it is because some wire supplier talk in mm2 (yep I know super and sub script Blo**y ASKII) some in SWG and some even in AWG (and that's uk sites) If you happen to slip on to an American site gawd love us Thous as in "" and pounds as in lbs not to mention inches, feet..... When I was working in engineering workshop many moons ago was using both metric and imperial what fun. I would say I wuld not want to be on the reciving end of the "seawolf" missle but having heared how the first test firings went I would not have liked to be on the FIRING end!!! Duck

 

[brightspark]

Mike, as a matter of interest, is the wire you measured the new harmonised stuff (blue & Brown) or the old red & black?

it doesnt matter what colour they are the core size of cable are both the same 2.5 is 2.5

 

[rtbcomp]

it doesnt matter what colour they are the core size of cable are both the same 2.5 is 2.5

I was wondering if the newer wire was thinner but still called 2.5mm2 so as not to confuse electricians.

They've done similar with automobile cable, changed the composition of the insulation to withstand the extra heat produced by thinner wire carrying the same current as previously carried by the thicker wire.

 

[brightspark]

is the cable BASAC approved? there is quite a bit of dodgy stuff out there that does not meet the requirments but has been labled up as CE etc

the cable that got there basec approved licence suspended was atlas kablo made in turkey dated 8th of july 2010

 

[mike 109444]

Unless it says 2.5 on the spool and you measure the diameter (as 1.6) do the maths and come up with an area of 2.01mm. Measurement done with digital vernier, and yes it was zeroed and rechecked. Cable was from either b n q or screwfix don't recall.

 

[rtbcomp]

........Blo**y ASKII) ......

That had me thinking do you mean ASCII

You can use the Character Map to show fancy characters mm²

 

[madkayaker]

there was a lot supplyed through whicks 5 years back that was not upto standards and was recalled. it was new color but with a white outer.

 

[Robotstar5]

there was a lot supplyed through whicks 5 years back that was not upto standards and was recalled. it was new color but with a white outer.

Forced to use some from Wickes in the 90's, outer sheath was stuck to the insulation, a right pain to strip!

 

[madkayaker]

its good stuff these days and is well priced