How to identify size of cable

[timb106106]

Please can someone clearly state how to identify 6mm2 twin and earth cable?
I know I need 6mm2 but don't know if my kitchen is wired with it. If it isn't of course it is Part P to install a dedicated cooker radial circuit as most of the threads on this forum state, if it is 6mm2 then the job is done.
Does the 6mm2 relate to the area of ONE of the copper cables viewed end-on and excluding the insulation? That seems awfully thick. What would the diameter of one of the copper cables be?
I think it would be useful for people if the diameters of the commonly used cables were posted onto the site along with the mm2 for identification purposes.

Thanks very very much

Tim

 

[Bahco]

Try here.

Might be of some help.

 

[breezer]

I think it would be useful for people if the diameters of the commonly used cables were posted onto the site along with the mm2 for identification purposes.

it has been for years, its in the wiki or the sticky

 

[Bahco]

Amended link for you to try.

 

[RF Lighting]

See item 26 in the sticky. (although this is only a guide, and measurements will vary depending on manufacturer, and age of the cable)

6.0mm² relates to the cross sectional area of one of the conductors.

If you have a micrometer, you can measure the diameter of one of the strands, and then with some mathematics you can calculate the actual CSA of the conductor.

 

[JohnD]

a very easy way is to buy some 6mm T&E cable clips (these days they are embossed "6mm") preferably just a few in a handy pack (or find an electrical person who will give you one)

pull the pin out or it will stick in you

Try it for size against a sample piece of cable on the Electrical shelf (it is a tight, clip-on fit) so you know how it feels.

Then go home and see if it fits your cable in the same way.

It is very handy to keep a few sample cable clips so you can tell the difference between sizes that you can't differentiate by eye. 4mm is rarely used but sometimes found on older cooker circuits. 10mm is bigger. 2.5mm is easy to recognise by eye IMO. 1.5mm and 1mm are fairly similar.

this is much much easier and cheaper than using a micrometer or vernier gauge

 

[timb106106]

wow!
thanks very much for your quick replies. Item 26 in the wiki was a useful substitute in the absence of information about the diameters of the actual conductors. It's clear that I don't have 6mm2 as per Item 26 the outside nominal diameter of the cable sheath fits best with 10.3 mm x 6mm = 2.5mm2.
A rough workout of the area confirms this:
Conductor diameter measured with a ruler is a bit less than 2mm diameter (lets say 1.8 )
area = pii(3.14) x 1.8^2 / 4 = 2.54mm2

To work out diameter of conducter for a given area you;
square root (4 x area /pii) (3.14)
and for 6mm2 cable you get a conductor diameter of 2.76 ~ 2.8mm.

So diameter of 6mm2 cable will be about 2.8 mmin diameter - less than I expected and only 1mm wider than I have at the moment.
What a difference a mm makes! Probably about £200 for a new circuit.


Thanks all,
Tim

 

[securespark]

How many strands does your "2.5mm²" conductor have?

What colour are they?

 

[timb106106]

one copper strand. the sheath is grey (marked BASEC), the live is sleeved in red, the neutral is sleeved in black and the earth is of course bare except when within boxes.
Why do you ask?
What will I expect to pay for fitting of a (6mm2 or 10mm2 as the electrician sees fit) circuit stretching about 8m and provision of a 40amp MCB into a spare on my CU with a two pole switch (without 3-pin additional plug socket) at the cooker end? There is access to the underfloor joists as the basement ceilings are all down leaving the cable-runs exposed so routing should be pretty easy.
Tim

 

[Click-Sure]

I'd be opting for 10mm2 cable for a new cooker circuit, cable that was too small got you into this mess in the first place!

As for price, its very hard to say, but use a spark you've dealt with before, or comes reccomended and they'll give you an idea where you stand and how much you'll be looking at cost wise. I don't charge for simple quotes like the job you require.

There may be other issues with your electical installation in general (main bonding for example) that requires attention before another circuit can be installed/modified.

 

[ColJack]

How many strands does your conductor have?

A question that we ought to start asking first in future...

 

[timb106106]

got a sparky that I've used before lined up to do the job in 6 - 10 mm2 his decision.
I'm sure he'll check the mains bonding though visually it looks ok.
Quite happy with the price it's not too much for peace of mind.
The whole question arose because I asked someone how you determined cable thickness and they misadvised me that the mm2 quoted in cable thicknesses was measured across the width of the sheath so it gave me false hope that I was adequately cabled.

Thank you for all your help - I'm sure I'll be back

 

[ebee]

The only sure way is to accurately measure the dia of the conductor core or cores and apply Pi D squared over 4 (or Pi R squared) because the sizes quoted are cross sectional area of the conductor not diameter.

I have a list of sizes I`ll see if I can find it.

Measurement via a micrometer would be most accurate, followed by vernier caliper then steel rule.
Once you get used to the sizes then "Rack of the eye" should suffice

Found it

Cable Diameters

CSA Dia mm Dia inches No of Strands
1.0 1.128 0.0444 1
1.5 1.382 0.0544 1
2.5 1.784 0.0702 1
4.0 0.853 0.0336 7
6.0 1.045 0.0411 7
10.0 1.349 0.0531 7
16.0 1.706 0.0672 7
25.0 2.132 0.0839 7

Sorry pasting does nowt for the spacing here

 

[bondy]

what about 2.5 multi strand. i am compiling a list together. do any of you have the csa sizes for multi strand cables below 4mm

 

[jason1958]

Stranded can mean new (metric) or old (imperial).

Taking old imperial, eg, 14th regs, 1966+.
Current ratings Clipped-Direct

Rarely used
- 1 strand, 0.044-inch dia, 0.0015in^2 / 0.98mm^2 CSA = 12A

Thin lighting off 2-way switching to each hall wall bulb
- 3 strand, 0.029-inch dia, 0.0020in^2 / 1.28mm^2 CSA = 15A

More common old lighting
- 3 strand, 0.036-inch dia, 0.0030in^2 / 1.97mm^2 CSA = 19A

Into power circuits
- 7 strand, 0.029-inch dia, 0.0045in^2 / 2.98mm^2 CSA = 23A
- 7 strand, 0.036-inch dia, 0.0070in^2 / 4.60mm^2 CSA = 31A
- 7 strand, 0.044-inch dia, 0.0100in^2 / 6.87mm^2 CSA = 37A
- 7 strand, 0.052-inch dia, 0.0145in^2 / 9.59mm^2 CSA = 46A
- 7 strand, 0.064-inch dia, 0.0225in^2 / 14.53mm^2 CSA = 61A

The largest conductor size in PVC-sheath/PE-insulation to
BS1557 was 0.06in^2 CSA. Higher ratings for Butyl/Silicone.

Earliest PVC/PE Twin-&-Earth was 1948, rare.
- Grey, Black or ???? PVC sheath
- CPC may be bare - more typical with grey sheath if CPC present
- CPC may be green sleeved - more typical with black sheath if CPC present (like French twin & earth)

NOTE even if you do have CPC in an old lighting install, it may
not be connected to anything - it may be floating or even live.


If you ever use LSOH cable, particularly Prysmian which seems
stiffer than others, stranded in 2.5mm is easier to work with.

Current ratings increased with time from 13th-14th-etc regs.
13th regs clipped-direct were 5/10/15/20/28/36/43/53A for above.