extending cable

[JohnW2]

I know it is 2.5mm as i have bought it new. As for the 3mm cable it is slightly bigger than the 2.5mm and when measured the cross diameter is 3mm.

Mike, I imagine that most other people are getting as confused as me.

Cable sizes are specified by cross-sectional area of the main copper conductors, the ('Twin & Earth') type most commonly used for wiring domestic sockets having two main insulated conductors of 2.5mm² (area of copper conductor), plus a smaller bare 'earth' conductor. The diameter of a 2.5mm² copper conductor is about 1.78mm; a copper conductor of 3mm diameter would have a cross-sectional area of just over 7mm² - far larger than would be used for wiring normal sockets in a domestic situation.

What are you measuring? Does the 3mm diameter you measured perhaps refer to the diameter of one of the insulated conductors including the insulation?

I Will the 2.5mm be ok joined with the 3mm

One thing no-one seems to have asked you is how you plan to join the cables.

Kind Regards, John.

 

[17thman]

pi x radius squared
or pi x diameter/2 squared.

 

[JohnW2]

pi x radius squared
or pi x diameter/2 squared.

Indeed; that's how to work out area. What is your point?

Kind Regards, John.

 

[sparkwright]

I don't think I've read such a load of cobblers on this site.

As correctly stated by someone cable is measured by the cross sectional diameter of the conductor.

Cable sizes do not generally exist as 3 or 5 mm.

I can only assume you have measured the overall thickness of the cable.

The short answer to the question is that you should extend the cable using the same size as before.

Generally 2.5 mm2 cable is used for sockets, on occasion 4 mm2 is used.
Generally 2.5 mm2 is solid conductors, 4 mm2 is stranded.

Typical cable sizes are;
1 or 1.5 mm2 usually for lighting.
2.5 mm2 usually for sockets and immersions.
4 mm2 usually for 30 amp socket radial circuits, not as common.
6 or 10 mm2 usually for cooker and shower.

If your cable is about forty or more years old it may be the old imperial sizes, socket cables were stranded.

 

[holmslaw]

..

 

[skenk]

I hope the joint is going to be accessible or done in the appropriate way