"Christian McArdle" wrote in message
. net...
| I am contemplating fitting an RCD (Residual Current Device /
| Earth Leakage Relay ) in the power supply to my house between
| the meter and the fuse box.

Often, the easiest way to add RCD protection to an existing installation
(using DIN rail CU) is to replace socket circuit MCBs with single width
RCBOs, if they are available. It isn't necessarily the cheapest way,
although if there are only 1 or 2 circuits to be protected, it can still
be
cost effective. It is certainly the best way to do it, however many ways
there are.

cheapest way is to replace the CU switch
with an RCD switch
but then we don't want the light going out

see separate thread for thaat