Earth Bondiing For Sub Main

[Carol]

New to the game and it all looks different in the real world! I am about to upgrade one of the installation CU's which is CU1, CU2 is already new, but I have a quick question, I have a PME system, supply split at a Henley block to serve CU1 direct and secondly to a switch fuse isolator which then feeds CU2 via SWA to service an extension. The earth bonding to the switch fuse isolator comes from the MET in CU1. Should I firstly put an isolator switch in between Henley and CU1 and then install an external MET and connect to main earth supply and then feed CU1 and switch fuse isolator direct?

 

[Richard Burns]

I would say that from what you describe the situation is OK (assuming there is continuity everywhere!).
The earth bar in CU1 is acting as the MET for both installations, if someone were to remove CU1 then you might lose the MET but as it is the main supply this seems unlikely.
You can isolate CU1 from its main switch if required, though having an isolator can be useful when changing a CU.

It does depend on who is prepared to pay for what! It can be left, but if someone wants it neatening up and made more convenient then you can do as you have said.