CPC size from switch fuse

gooner85 · Sep 22, 2011

Hi guys, just a quick one.

If you have a TNCS system, then the main earth is 16mm

Instead of going to a CU it goes to a 60A switch fuse. from the switch fuse to the consumer you would use 16mm cable.
My question is would you still need to have a 16mm earth going through the switch fuse to the CU.
It would seem to me that you could go from the MET in 16mm and then it could be reduced to the CPC with the 16mm cable.

Thanks in advance

Guest123 · Sep 23, 2011

Coming out of the load side of your switchfuse you have your distribution circuit which you cansize accordingly using appropriate calcs CCC, VD, thermal constraints, shock protection etc etc.

The TN-C-S 'rules' will only apply to the supply tails & main earthing conductor supplying your switchfuse.

The only additional consideration in this instance is your protective bonding conductors and where they will be connected.