On 03/09/16 22:19, charles wrote:
In article ,
DICEGEORGE wrote:
I'm thinking of installing a Wylex 2 pole RCD 100 Amp 100mA
in a box like on the TLC page linked below.

Just after the main incoming electricity company fuses,
meter and isolator switch,
but before all the henley blocks, consumer units,
solar panel connections, old fuse boxes etc

The supply is TT, I have 2 earth spikes outside the door.

Any advice for or against?

when I put a new CU in this house shortly after we moved in 40 years ago,
the advice was use one RCD for the whole supply. It has serious
disdvantages* and nowadays separate RCDs or MCBOs are recommended for each
circuit.
*Major disadvantage is that if something trips the RCD everything in the
house goes out - including lights.


You use a single time delayed Type S RCD for fault protection on a TT
supply.

Then regular RCDs or RCBOs on the final circuits. These are guaranteed
to trip first, leaving the main RCD to handle any upstream faults or
faults on non RCD circuits.

The main RCD is there to ensure a L-E fault trips with a relatively high
impedance earth (the current would not be enough to trip an MCB).