"Doctor Drivel" wrote in message
...

"Tim W" wrote in message
...
Sidney Endon-Lee
wibbled on Wednesday 11 November 2009 10:10

I'm looking at replacing a somewhat old consumer unit. I'll freely
admit that my electrical skills are not up to it, and I probably don't
have all the necessary test kit, both of which are a shame.

Anyway, a local firm has scented an opportunity (all the places on the
same development have the same, old, consumer unit) and have sent
round a fuzzy before and after picture of what replacing with a new
RCBO based unit would look like, and estimated a standard price, with
an addition if you need more 'ways'.

Anyway, it looks, from the picture, as though they'd remove isolating
switches and seem to have a design that has:

a) an RCBO per way; and

Which provides the same level of isolation as the MCB that might be there
in
a different, but complaint, installation.

b) an RCBO acting as a 'main fuse', sized to be 'equivalent to' the
current main fuse.

Your "main fuse" is the one in the elect co's cutout, typically near and
definately before the meter.

A time delayed (type S) RCD may be used in place of the main CU isolator,
or
before it in a separate box, if you have a TT (earth rod) installation
earth. This is not and RCBO - it doesn't deal with current overloads and
it
doesn't need to, any more than the main 100A switch in a CU would. The
supplier's fuse does that.

You could also have a non delatey 100A RCD - but this would be
essentially
stupid along with RCBOs.

Hence the question in my title. Is an RCBO a suitable isolator?

As much as any equivalent device that might be used is. It will typically
only isolate L and not N (although I have two double pole RCBOs that do
isolate L+N for outside circuits, because it seemed like a good idea,
though beyond basic requirements).

This means that you should not use the RCBO to act as eg as a shower
isolator - you still need the local DP switch. But in every other
respect,
the RCBO is a complete replacement for and MCB or fuse.



An RCBO can eliminate equipotential bonding in bathrooms. I believe the
lights and power all have to be off the same RCBO.

As long as all electrical circuits that enter a bathroom are RCD protected
then the supplementary bonding in the bathroom may be ommited. There is no
need for all the circuits to be supplied by the same RCD or RCBO though.

Adam