An Electrical Question

[dave the builder]

Virtually nothing wrong at all with that Lizzie, 2.5mm is fine assuming it fits the terminals ok, feeding an outside light of the lighting circuit is also OK as long as the circuit is not overloaded, isolation in this application only has to be available to the live connection.

what about nuisance tripping of the RCD  , circuit identification , local isolation for maintenance etc 
just because building regulation part p dropped mention of outside lights , does not give carte Blanche to ignore bs7671  . or revert to  15th edition practice               

I was making the point that whoever used 2.5 cable to a lighting circuit was showing a lack of knowledge, as no electrician would use that rated cable in such a manner.

As for a switch to the live, there was nothing in any form of switch and isolating fused spur. Therefore if the external light had become faulty it would trip the lighting circuit breaker and, without climbing up ladders to find the fault, would have resulted in the lighting being off for some time as anyone investigating the fault would not have known for a bit that the outside light was causing the problem.  There was no visible sign of any connection internally, and no way to isolate the external circuit.  To me that is at least bad and unsafe practice.

indeed , shoddy work
call the installer back and attach his/her genitals direct to the main incomer 
2.5 is an issue(not because of the size of conductor) BUT if it is flat twin and earth , it is not uv stable, so not ok to run unprotected outside to a light 

How many forum members does it take to answer an electrical question?

23 including one real cowboy builder to give the correct answer, ten other also correct answers, one to call the fire brigade and one smart ass to make a funny comment .

if building control and IET can't agree , what chance has joe public

PS STEMO. 10 w LED security lights? They are underpowered. Even pointing in the right direction they will be unable to illuminate your neighbours bedroom fully as they switch on and off each time a fox, cat or Amazon delivery van goes by. Two of these for example but they would need their own fused spur!   https://www.ebay.co.uk/itm/300W-LED-FLOOD-LIGHTS-INDUSTRIAL-HIGH-BAY-STADIUM-SECURITY-FLOODLIGHTS-UK/291414522263?hash=item43d9a8b997:m:mAsdOYnC3QPp3ttlhaUTTBg:rk:3:pf:0

or other appropriate means of double pole isolation and overcurrent & RCD protection 
these LED rarely pull anything like the stated rated current 
but will pull more ,IF a person is in contact with live parts 

[STEMO]

10W is enough to see us out and in. In fact, I had to point one downwards as a neighbour said they were too bright. So up yours, Roy Rogers 

[dave the builder]

10W is enough to see us out and in. In fact, I had to point one downwards as a neighbour said they were too bright.with the electrical fires burning the house down as well and the blue lights on the fire engines ,So up yours, Roy Rogers 

FTFY Mr STEMO 

[Marks DTM Calib]

It's an outside light ,so special location, requires double pole isolation from the lighting circuit which someone decided to connect it to,
fused spur is a double pole switch
if the outside light is powered by a plug (with correct sized fuse),which can be removed from a socket *with RCD protection (thus giving double pole isolation) it is effectively a portable appliance, not notifiable.
in this case, the lighting circuit is RCD protected ,(from what the OP said)
However, not all installations are up to date ,dual RCD consumer units or better.
some are ye olde wylex re-wirable  antiques with no RCD or even decent overcurrent protection 

I think you have fallen foul of the common sparky myth! (the regs can be complex in their wording in places)

Its not required as the regs are vague, yet practical. They state that all live conductors must have a means of isolation and reading deeper, this does not have to be specific to that circuit. Hence the main double pole isolator in the board satisfies that requirement.

In fact you don't need a switch at all based on the regs as isolation can be supported via the MCB or removable fuse and double isolation supported again by the main incomer.

[Doctor Gollum]

I have two outside security lights fed from a single pole switch in the kitchen, on the lighting circuit. The are 10W leds.

From the sounds of it, it's a miracle you haven't burned down half the street. Lizzie will be along imminently to chastise you vigorously!

You should probably film that

[ronnyd]

Idiot across the road located his security light right near the flue of his combi boiler. Every time the vapour is blown in the wind the light goes on and shines in our lounge . Also he has three cats that walk along the top of his wall and they keep triggering it as well. Think i will have to take out the PIR with my airgun.