On Mon, 10 Feb 2014 19:27:09 +0000, "dennis@home"
wrote:

On 10/02/2014 17:14, Tim Watts wrote:
On Monday 10 February 2014 16:17 Harry Bloomfield wrote in uk.d-i-y:

Phil L explained :
paulfoel wrote:
Currently got wiring in the attic that runs a light. Originally just
a pull switch and bulb/holder but I've replaced with strip light.

However, what I want to do now is have plug socket up there. Is it
acceptable to run this wire into a double plug socket. (Then I can
put plug on end of wiring for light also and just plug this is
leaving me with one space socket).

Or leave well alone because its a light circuit?

It'll be on the lighting circuit.
Meaning that if you turn all the sockets off at the CU, this socket
will still be live.
It also means that if whatever you have plugged into it trips, the
whole lighting circuit will trip.

Whether this is 'acceptable' is up to you and no one can stop you,
but it's not really advisable....if it's only going to be used for
occasional use, it's probably easier just to run an extension reel up
there when required.

I agree, you have to consider that someone may come along and assume
it is safe to plug a 3Kw heater in there. Much safer would be to run a
spur off the upstairs ring, to a twin 13 amp socket, then use one
outlet for the light, via a suitably small fuse in the plug, leaving
you one outlet for your angle grinder, wander light, or what ever.

There is almost always an easy cable route from the 1st floor
floor-level, upto the loft space - airing cupboard etc..

If you then somehow manage to trip that, you will still have some
working light on the floor below.


well, in the worst case, it will take out the protective device (fuse) -
which will be annoying, but not actually dangerous...

A 5A fuse in a spur probably won't blow before the 6A breaker in the CU
anyway so its not actually going to improve protection.
It may make the circuit easier to understand.


Electrically speaking, you can wire a 13A socket straight off the
lighting wiring without compromising safety, provided the lighting
circuit remains fused at its 6 amp maximum limit.

If you're fitting a 13A socket in the loft or attic, it's usually for
the purposes of providing power to something like a masthead amp or TV
aerial distribution amp both of which would be more than amply served
by a half amp fuse[1] which minimises the risk of a house fire should
a fault develop on the (now fused) 13A socket spur.

Of course, there still remains the risk of a fire from a fault in the
amplifier kit itself but, provided it has been designed to the
mandatory safety requirements for such 'domestic appliances' this
aught to eliminate such risk. The only problem is that, unlike a radio
or hairdrier, it is operating 'out of sight' of any human supervision.

I'd be inclined to mount such devices on a metal shelf with heat
resistant deflectors (steel sheeting) to stop any flamage from
reaching any flamable construction materials and, for good measure,
install a loud smoke detector above, but to one side of said kit,
ideally with a repeater just outside of the loft hatchway or attic
doorway.

In my case, that last bit of paranoia has remained merely an idle
inclination to this day (although I might try the smoke alarm idea).

[1] If you needed to provide power for powertools, you'd just plug in
a suitable mains lead extension into one of your regular 13A sockets
unless you were planning on turning your attic into a workshop (in
which case we wouldn't be discussing the use of a lighting circuit
feed for a 13A socket now, would we?).

Fitting a 13A fused box in the spur feed to the 13A socket allows you
to fit a half or 1 amp fuse which will be more than ample for the
socket's intended purpose yet reduce the risk of a fault on the spur
from blacking out that lighting circuit. It's just a matter of "Good
Practice" and common sense to splash out on such a 'luxury item'.

The same applies to fusing up 30A ring main circuits with lower rated
fuses when appropriate. My top floor ring main currently has a 15A
fuse link fitted because the only loads are my son's "HiFi" and
widescreen TV and computer stuff with no 2kW electric fan heaters in
sight.

The 15A fuse link has never blown in the past 7 or 8 years since I
downgraded the circuit to a "15A Ring Main". The risk of a fire in the
ring main circuit, though slight enough to be deemed acceptable
according to the regulations is now somewhat safer again.

I like the principle that you can replace a large fuse link in an
existing fuse carrier with smaller rated fuse links (Wylex CU) since
it makes it very simple to downgrade the ciruit capacity on an as
needed basis without compromising safety (in this case, boosting
safety), since it's a trivial exercise to refit the original larger
fuse should the smaller one blow due to unanticipated overload.
--
Regards, J B Good