Re: Twin and Earth Cable Sizes

["Paul Robinson" <ukcueman@xxxxxxx>]

From: "Neil Fuller" <neil@xxxxxxx>
> >>First the disclaimer: I am not an electrician.
>
> I am an Electrician!!!!!
>
<snip>
> >>My lighting will be fed from a single circuit on the
> consumer unit via a 6mm cable and protected by a 32A MCB
>
> That's fine but you could also feed the second board straight from the
head using a 'junction box' specifically made for the purpose - A Service
Block (TLC order code MK1100) This would save a valuable way in the main
consumer unit.

Where the SWA comes in from the meter, I'm using 2 x 10 way consumer units,
and when everything is finished, I will have several spare ways left. The
lighting unit is additional to this. So the loss of one way for lighting
doesn't matter. It will be more transparent afterwards anyway, and provide
a
means of turning off all my CBus stuff should I ever need to.

<snip>

> The 'Won't happen in practice' is allowed for in the 'Regs' - It's
known
as diversity. For instance, using your 'equation' you could only have 2
single 13 amp sockets on a 32amp sub-circuit if diversity wasn't allowed.
In
practice, you can have as many 13 amp sockets as you wish as it is
recognised that many loads only take mA at 230v.
>
> My copy of the 'regs' is at work so I can't quote actual figures. If
you
really want to know, I'll look it up...

No, that's okay. I was already aware of diversity and that a 32A breaker in
my case was overkill and should never trip. The secondary lighting unit's
breakers should trip under overload conditions.

<snip>

> Finally, finally - Don't forget the earthing on the new consumer unit.
Many do!
A sparky friend will be checking things out before it gets commissioned.
But
I'll remember that anyway!

>
> Neil
Thanks,
Paul