10 mm limit ?

[carlbridge]

hi
ive seen something that does not appear correct , in an new build extention , there is a 10 mm cable supplying the extention consumer unit , in c/u , there are 3 ring circuits and 6 x 1 mm cables , i was told this 10 mm cable will be fed from the original consumer unit in the house , is this acceptable , or should the extention cable be 25 mm ? thanks .

[siggy]

OK Not current with UK regs......... What with me residing in Canada

Somethings to consider

What is the maximum demand for a ring main? 36A breaker IIRC

1mm² would be what 5A lighting circuits

Also not sure of method of running cable from old con unit to new and the power factor corrections required (through walls/ under insulation etc)/ if required

BUT

3x36A=108A

6x5A=30

Total 138A

From table 4D2A multicore pvc-insulated cables non armoured (reference 16th edition) green cover


a 70mm² can carry 139A

Also not touched domestic side of UK stuff since "Green cover book" came out so may be totalling barking up to wrong tree

[Edward Current]

Hello Carlbridge.

As Siggy has said firstly you need to determine the maximun demand of the 'extension'.

We would also need to know the type (armoured, etc ?), distance, and installation method of the existing cable, then we could advise what kind and 'rating' your protective devices need to be.

Are you saying that the new 'extension' consumer unit has 3 rings etc, or are you reffering to the existing c/u ?



Regards
Ed.