# wire sizes - what is standard

Discuss wire sizes - what is standard in the Electrical Forum area at ElectriciansForums.net

#### renault

DIY
Welcome to ElectriciansForums.net - The American Electrical Advice Forum

hi all. I am new here and am doing some work on my house. I have a question regarding wire sizes; As far as I was aware the sizes are 1.5, 2.5 then 6.0 etc (I am assuming this is the area of copper) however I have just come across 4mm. dia. in my house. Is this an old standard no longer used ?

#### Julie.

Esteemed
Arms
Standard, and current.

1mm^2, 1.5mm^2, 2.5mm^2, 4mm^2, 6mm^2, 10mm^2, 16mm^2....

There are rules though, you can't use 1mm^2 for anything other than lighting for example

OP
R

#### renault

DIY
Standard, and current.

1mm^2, 1.5mm^2, 2.5mm^2, 4mm^2, 6mm^2, 10mm^2, 16mm^2....

There are rules though, you can't use 1mm^2 for anything other than lighting for example
yes, thanks for that - but I have never seen anywhere that 4mm² is used for anything

#### pc1966

Esteemed
Arms
4mm is less common than 6mm as it is only rated for a typical 32A circuit in certain installation "methods" such as clipped directly to a wall where it can get rid of heat sufficiently easily. The other common 32A circuit in the UK is the Ring Final Circut used for 13A sockets, typically it is in 2.5mm as every socket in a RFC has two paths for the current to flow so typically the loads result in roughly half on each 'leg' back to the consumer unit (fuse box).

Of course, sometimes you also have to increase conductor size to keep voltage drop down on long runs (and related to that, keep fault impedance down so it clears quickly).

#### pc1966

Esteemed
Arms
Tables 7.1 (i) through to (iii) in the IET's On-Site Guide(pages 65-75) are your go-to reference for wire choice. That covers the length limits and installation methods for the majority of common circuits (combinations of cable size and over-current protection device).

#### littlespark

##### -
Esteemed
Arms
4mm single was used a lot as a bonding conductor between copper pipes in houses.
Less now with plastic pipes.

#### Dustydazzler

##### -
Esteemed
Arms
I haven't fitted any supp bonding since we have had to rcd the carp out of everything

I now only carry 1mm for lights , 2.5 for power and 6 for cookers

I do have some drums of 1.5 and 4mm in my garage but rarely use that size cable

#### littlespark

##### -
Esteemed
Arms
I must have a bigger van.

I carry 2 x 1mm, 1.5 and 2.5… a 4,6 and 10mm T&E . 1mm and 1.5 3c&e

There’s normally a drum of coax rolling about, plus cat5, bell wire and telephone wire at home.

Then the 1.5 and 2.5 singles…. (All colours of 1.5). And 4 and 10mm single earth wire.

Edit:
Plus numerous coils and cuttings of small size flex in 3183, 3093 and rubber. 3,4 and 5 core in some sizes…. 4mm flex for ovens, half drums of SWA and some 25/16mm tails kits.

Last edited:

#### telectrix

##### -
Mentor
Esteemed
Arms
hi all. I am new here and am doing some work on my house. I have a question regarding wire sizes; As far as I was aware the sizes are 1.5, 2.5 then 6.0 etc (I am assuming this is the area of copper) however I have just come across 4mm. dia. in my house. Is this an old standard no longer used ?
diameter of cable/s is irrelevant. except when choosing thre rightsizeof clip/cleat to fix it. all that matters, elecrically, is the csa. area of conductorr in millipedes or fraction thereof.

#### pc1966

Esteemed
Arms
I do have some drums of 1.5 and 4mm in my garage but rarely use that size cable
They are sort of "in-between" sizes. No need for 1.5mm for practically any lighting circuit as current small (and harder to wrangle it to light's terminals), but then not quite high enough for many fixed loads.

4mm is sort of the same in-between size. You often hear folk suggesting a radial in 4mm but in many install methods that is not 32A-safe.

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#### Markyd

##### -
Esteemed
What did the sparky that is obviously working with you to do the work say?

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