In article , John
Rumm writes
Hzatph wrote:

The 16 circuits have:

4 ring mains
2 power spurs (cooker, immersion heater)

^^^^^^^^^^^^^^^^
Prone to high leakage!

Try turning off / pulling the fuse for this and see if it helps.

If that does not find it then you are going to need to start testing the
wiring for each circuit with a megger.


Also look for Nutral/Earth shorts or leakage, these are often overlooked
and don't usually show up until some current is flowing through the
system.....
--
Tony Sayer