Size of this cable. Main cutout

Luke105 · Nov 29, 2018

Is there a certain cable size which enters into the house into the main cut out?

Or what are the most common?

Can you tell me the size of the cable in photo.

Thanks

Richard Burns · Nov 29, 2018

A standard domestic house service supply will generally be 25mm² or 35mm² concentric cable the centre single core being the line conductor and the outer helical wound concentric conductor being the combined neutral and earth.
The cable in the picture looks fairly standard and fairly old, it is not possible to specify exactly what cable size is there but it is probably 25 or 35 mm².

Luke105 · Nov 29, 2018

Thanks for the response. I thought 25mm would be a standard but I’m glad you explained the cable in depth. Thanks

mjf · Dec 1, 2018

As above, but most old service cables will be 16mm copper concentric. If it's over head fed it will be copper. If it's underground fed it could be Hybrid concentric. So a solid aluminium phase with copper neutrals. A 25mm hyb will have a 25mm aluminium phase with 16mm copper neutral. And a 35mm hyb will be a 35mm aluminium phase with 22mm copper neutrals. 35mm copper concentric is rare but occasionally used. Most mains Lv underground cables from the sub are now aluminium phases with copper neutrals called wave con or wave form cable. Most new lv over head is stranded aluminium insulated known as ABC

DefyG · Dec 1, 2018

Sometimes and looking very similar a 'split concentric' cable is used whereby the outer helically wound conductors (N(ins'd) & E) are separate.
Still seen this recorded as TN-C-S (PME) though.

TJ Anderson · Dec 1, 2018

DefyG said:
Sometimes and looking very similar a 'split concentric' cable is used whereby the outer helically wound conductors (N(ins'd) & E) are separate.
Still seen this recorded as TN-C-S (PME) though.

That's interesting. Are the N&E conductors joined at the cutout though? It would just be TN-S otherwise surely?

davesparks · Dec 1, 2018

TJ Anderson said:
That's interesting. Are the N&E conductors joined at the cutout though? It would just be TN-S otherwise surely?

It is used for TNS services but a lot of people wronglt assume black cable = TNCS

mjf · Dec 1, 2018

Yes split concentric is TNS, the outer concentric neutrals strands will be individually insulated and the earth strands will be un insulated. However back at the mains joint it will often be connected to a 3 core CNE (combined neutral earth cable) so neutral and earths connected togerher in the joint. Unless connected to an older 4 core paper lead cable in which case they will be kept separate.