I probably should know the answer to this, but here goes.
I've come across a 13A double socket installed in a loft that looks as
though it has been jury-rigged from the upstairs lighting circuit. The
socket is feeding several appliances from loft light to TV ariel
amplifier - nothing too sinister in terms of the power being drawn.
I need a convincing argument to convince the householder that it isn't
safe, if indeed it isn't.
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Hmmm - I know what you mean - it sounds "wrong" but I am having
difficulty thinking of exactly why!
While not exactly a "recommended" solution, I suppose you could argue
that so long as the circuit is suitably protected at the CU, then it is
not dangerous in itself. Any overload via the socket would simply trip
the protection device at the CU. The 1.00mm sq cable has more than
enough capacity to cope with anything you will be able to draw from a 6A
An overload on the socket that caused a trip, would however take out the
loft light - this may not be that good an idea, especially if that
leaves you hoping from rafter to rafter in the dark!
Why should it be invalid? When we sold our old place, the previous people
had installed a socket for their fish tank electrics which had been wired
off the lighting circuit by orange flex. Our purchasers requested an
electrical installation inspection (not because of this) and when the guy
came to inspect it he noticed this but explained that as it was protected by
a suitable fuse at the CU, there was technically no problem with it. Of
course, ideally it shouldn't be like that - however ideals and requirements
are very different.
I cannot see why an insurer would be able to successfully invalidate
insurance when an NICEIC (?) certificate says the installation is okay and
If its earthed is reasonably safe. Nonetheless it isn't good practice,
as some unsuspecting eejut might try and run an electric fire off it and
start a real one :)
If it were me, I would replace the SOCKET with - say - a 5A one and mark
it 'light duty only' (har har) to enbsure that no one tries to pull 13A
Irts probably against regs too, but regs are there for eejuts, and wise
men can use common sense.
Depends on the fuse. Old rewireable types can take an age to go for
slight overloads - the tables in the back of the regs imply that a
current draw of 13A will take 5 seconds to blow one of these (perfectly
safe), and 10A (2 bar fire) will take 100 seconds - over a minute and a
half (fig 3.2A, appendix 3).
Having said that, 1mm cable is good for 11.5A continuous even when
in conduit and partly enclosed in insulation (table 4D5A) so starting
fires may not be easy.
The biggest problems are likely to be, as stated, possible lack of
earthing on an older lighting circuit (and thus no earth at the plug),
having a fuse blow and taking out the lights at the same time, and the
fact that an installation with this kind of modification suggests that
other "non-ideal" work may also have been done.
Martin Angove: http://www.tridwr.demon.co.uk /
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Whilst it may be electrically safe if the protection is correct on
that circuit it is potentially unsafe in its consequential effects.
If someone was in the loft and plugged in a higher current device then
the lighting circuit would be lost, leaving them in darkness in what
is typically a hazardous area.
Swapping the sockets for round pin 5A ones would probably regularise
the lighting aspect. Not sure if fitting the other applicances also
via 5A outlets or FCUs with 1A fuse (or upto 5A...) would be OK. It
would certainly be safer though.
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