Outside light wiring

26 Oct 2012
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United Kingdom
After some advice on wiring in an outside light.

I intend to utilise an existing 2 gang plug socket. from this i will run some 2.5mm 3 core to a switched FCU and then on to the exterior light.

is this ok to do?
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The basics are okay.
You only require two core and earth (AKA twin and earth) for the spur from the socket to S/FCU
You need to be aware that any new cable buried within walls less than 50mm will require 30mA RCD protecting, if this is not already offered to the socket circuit. or the cable will require mechanical protection (this is not metallic capping)
If the circuit is a ring final circuit, you can only spur from a socket that is not already a spur, unless this socket is a fused spur.
The external cable must be suitably protected against the environment and any external influences.
The socket can be knocked out from the CU, does that mean the spur off will automatically fall under the same protection?
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The socket can be knocked out from the CU, does that mean the spur off will automatically fall under the same protection?
If that means 'will the spur be isolated by the same opd which isolates the socket?' then - of course.
I have taken the donor socket apart and found a single cable of earth neutral and live. Now I know obviously that this is a final socket but how do I know if it's a spur or not?
If the socket circuit is a ring then there is no such thing as a "final socket", and that one is a spur.
It's the first plug as you enter the kitchen but exists on its own. All the other plugs in there follow each other anti clock wise around the room. If it is a spur can I still run off it to a fcu then to a outside light?
Either because it isn't needed, as there's only one socket on the spur, or it is needed because there's more than one socket on the spur and they were installed by someone who didn't know what they were doing.

If the latter the FCU needs to be before the first socket.
The socket can be knocked out from the CU, does that mean the spur off will automatically fall under the same protection?
If the new circuit is for sole use for the external lighting, it will not require a FCU providing the circuit is cable and fused rated correctly. But you will still require RCD or mechanical for buried cables(as my previous post), this can be done be either the use of earth protected cable, a RCBO or a RCCB with MCB, if the latter I would still install a double pole isolation switch for the external light, to prevent power loss on other circuits if outside light becomes faulty.

If the socket is a spur from the ring, then you cannot spur again, unless a FCU in a position immediately after the original ring feed socket and before the first spurred socket, therefore all additional outlets from the original feed socket are protected by a FCU, again I would introduce a double pole isolation/functional switch for the outside light, this could also be a switched FCU down fusing the circuit.
This spur is just for 1 wall mounted PIR external light with a switch on the internal wall.

no buried cables needed.

I'm pretty sure the existing socket is alone on its spur - its only 2m from the CU and no other plugs are in that gap.

Considering the above and comments from before, i should be ok to run to a FCU switch then on to the external light - correct?

apologies for my novice level.
Right I'm clear now thanks for the help.

Do I go buy an FCU cut into the cable supplying the socket and wire in the FCU. Then replace the socket and carry on to a switch for an exterior light?

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