Running of SWA, sub main

[Engineer54]

Whats the earth rod for?? is it a TT installation? and if you ran a new sub main in the new DB would be TNS......

No it wouldn't!!

Well if the original supply is PME/TNC-S, it's always prudent to provide a local earth electrode to reinforce the multiple N-E connections. But don't waste your time, if your thinking along the lines of your typical 200 ohms!!... lol!!

if it was me the new sub main would be 100mA protected, then drop to 30mA for sockets etc...

It would need to be 100mA S type RCD to ensure full discrimination with downstream 30mA RCDs. Most active faults will be in excess of 100mA, so unlikely that a straight 100mA RCD will discriminate, both units would likely trip...