Assessment Worries.

[wcampbell]

Hi all.

I have my assessment coming up for my two installations and am not sure about one of them.

I've run 16mm T&E from meter in my house to CU in extension carrying 100A Main Isolator, 63A RCCB, 32A mcb socket circuit, 50A mcb shower circuit, 6A mcb light circuit.

The main DB in the house has the usual 16mm E in MET and 10mm bond to services ( TN-C-S ).

The PFC at the extension CU is 0.70 KA or 700amps and my calc is as follows:

Sq Rt 700 x 0.1 / 115 = 2mm Earth.

But the OSG says I need 16mm E conductor.

The extraneous metal work in the extension are a continuation from main house so no bonding needed at extension CU.

Do I need to run 16mm from extension CU to MET in house as well as the 6mm E from 16mm T & E?

Thanks for any replies.

 

[Snapester]

If the second DB is over 2m away from the origin of installation it is required to have an isolating switch at the origin of the supply. So you should run some tails into a KMF switch and then run you 16mm T&E and run a then you will need to run an earth 4mm+ i would say 10mm would be sufficient enough, it needs to be above 4mm as anything below will require mechanical protection. You should also make notes of your calculation for load etc as the assessor will like that.

 

[Snapester]

Also what it the main fuse at the cutout? 60A or 80A as if its 100A then you should be using 25mm into the switch.