"Sidney Endon-Lee" wrote in message
...
Than-you for all of the very quick replies. I hope I can clear a
couple of things up

My place is one of a large development of purpose-built flats, built
by the GLC in the 1970s. They all have Wylex rewireable fuses in the
consumer unit, which has a 60A incomer. When I moved in, there was
still an original GLC card of fuse-wire in the cupboard with the
consumer unit. I've not had to use any of it myself, other than for an
electrician to add another 'way' to correct a d-i-y bodge I found in
the kitchen (unfused spur off a socket with three sockets off the
single ring, said spur providing power for the dishwasher, washer/
drier, and sink waste-disposal unit, with a Fridge/freezer plugged
into the ring socket.)

As far as I know, the supply is not TT. Whether it is TN-S, TN-C, or
TN-C-S, I have no idea.

As for why replace it, I like the idea of incorporating RCD
protection, so I'd been thinking off and on about doing it for quite
some time - the flier just crystallised some of my thoughts.

The flier has a fuzzy picture, so I may have mistaken a simple 'main
switch' for an RCBO - the only reason I know they are RCBOs is because
that's what they say in the text, rather than MCBs. My preference
would be to have individual RCBOs if I am replacing what's there, as
I run a fair amount of IT equipment/switch mode power supplies, and
I'd like to have enough headroom for leakage currents.

I've learned something about MCBs (thanks John) and overcurrent. Some
people I've spoken to have preferred fuses because (summarising their
words) "they tolerate a fair degree of overcurrent, and don't weld the
contacts together in fault currents"

Thank-you again all.

Sid

I would tend to go for double-pole RCBOs on all circuits. And, I'm this is
right, have the bathroom's light and power off just one and I know it is
easier said than done, that is why some have an RCBO on a surface patress
over the bathroom door in the hall. I think double-pole RCBOs is standard
in new installations in Germany - they use radial rather than ring circuits.
More expensive but worth it.