Lurch wrote in message . ..
On 16 Jul 2004 12:21:16 GMT, (Andrew
Gabriel) strung together this:

In article ,
(Mike Hall) writes:
"Andy Wade" wrote in message ...

Yes, provided that the circuits in question originate from the same consumer
unit or dis-board, and that the CPC for the ring remains in the form of a
ring.

Andy, but therin lies the crux of my question! - If I've joined all 3
cpc's, (2 halves of the ring and the lighting circuit) then the cpc
for the ring is now not a simple ring in itself.

I think that's fine. I can't quite remember exactly what the regs say,
but there are cases of ring circuits where the CPC clearly isn't a
ring, such as when it's provided by conduit or the outer of mineral
insulated cable. I think the important point is the CPC impedance at
any point must be no worse than if it was a ring, or you are going to
have to do calculations to ensure you are still withing allowable
earth fault loop impedance for whatever your protective devices are.
No amount of extra connections between CPC's can make it worse, actually
quite the opposite.

Although, I personally would seperate them as I have had occasions
where I have done something that is within the regs but extremely
uncommon and then spent more time and effort trying to convince people
that it's correct than it would've taken me to do it the common method
in the first place.


I agree.

Also linking them probably increases the chance of confusing whoever
next works on the installation - at least if they are doing it as DIY.
Presumably a professional would take the time to figure out what was
going on, not just make assumptions.

Depending on how obvious the layout is I can see some poor DIYer in a
few years adding a spur socket that uses the ring live and lighting
neutral.

Actually I am not keen on the whole idea of bringing two separate
circuits into one box - this means two circuits need to be isolated
before working in the box and what are the chances of every future
DIY-novice understanding this! (Yes I know it happens in ever hall
light switch...)