On Wednesday 12 February 2014 03:44 Johny B Good wrote in uk.d-i-y:

On Tue, 11 Feb 2014 23:53:15 +0000, John Rumm
wrote:

On 11/02/2014 20:43, Johny B Good wrote:
On Tue, 11 Feb 2014 10:42:42 +0000, John Rumm
wrote:

On 11/02/2014 04:47, Bill Wright wrote:
John Rumm wrote:

No need for the 5A FCU. The 6A MCB or 5A fuse will take care of
any overload.

My reason for including it was not for protection of the wiring,
but for adding discrimination if possible.

Use a 1A or 3A fuse then.

Indeed... although it does depend on what the main circuit is
protected with. There are some 10A lighting circuits about which
will offer more scope.

I suspect such circuits would only qualify for the higher 10A
rating
when completely wired up with Pyro cabling and appropriate fittings.
a

10A is well within the capability of even 1.0mm T&E in some cases, and
1.5mm T&E in most.

There used to be a restriction on not using SBC and SES lamp fittings
on such circuits, but that was deleted with the issue of the 17th
edition.

more likely scenarion in commercial premises rather than in premises
of the domestic persuasion (i.e. a house) where the limit has always
been 6A fusing at the CU panel afair.

10A is used domestically as well... I have certainly met it a few
times.

Well, not being an electrician by trade, I've been unable to find any
references to the regulations, only anecdotes regarding 10A lighting
circuits (including the use of a ring lighting circuit) so I can't
quote 'chapter and verse' as to whether this is an acceptable
departure from the regulations or not (I know some leaway exists
within the regulations but this seems to be quite a large departure to
my mind).

10A lighting circuits are "standard" (by the wiring regs) as are 16A
(though the latter are almost unheard of domestically).

I have designed by house with 2 x 10A lighting circuits, type C breakers
on 1.5mm2 cable to make the system a) able to cope with upto quite a lot
of lighting; b) more trip resistant when lamps fail.

I saw no real disadvantages to doing it that way - I prefer 1.5mm2 cable
over 1mm2 as I find the latter a little flimsy.

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