Need some help please. I've got an overhead supply with no earth. When I moved in about 20 years ago there was an old cast iron fusebox with wired ceramic fuses. All the earth conductors for the (radial) circuits were twisted together and clamped to the fusebox casing, but there was no connection to earth. Also the meter tails were old VIR cable about 6mm² and were heating up.
The first thing I did was to put in a new CU and an earth rod, connected by
16mm² sheathed earth cable, and new 16mm² double sheathed tails. The CU has MCB's and a 30mA RCD main switch which controls all the circuits. Since then I've rewired all the circuits one by one and put in equipotential bonding, now altered to comply with 16th Edition, which I'm pretty sure would pass inspection. The problem is the OSG says I should have a 100mA RCD for non-ground floor sockets - I don't understand the reason for this. Do I need to change the CU again? I would have thought my 30mA RCD was even safer.Also, I've never tested the impedance/resistance of the earth rod and I don't understand what I need to do here. The rod is driven into the earth oversite under the floorboards in the understairs cupboard. I drove it in about 1m but it would not go any further - either I hit the chalk or a big flint - so I cut off the top 200mm or so.
What do I need to do to bring the installation up to modern standards please? I've got the latest OSG but it doesn't explain in words I understand.
TIA Peter