Wiring to outside lights.

[scooby1]

On one wall of my house I have 3 lantern-type outside lamps. The current goes to the first one which has a PIR which then operates the other two lamps when the first one is activated. Looking at the attached image it can be seen that there are two power cables coming out of the wall to the first lamp. I presume that one is the feed to the first lamp and the other supplies the feed to the other two lamps.

Could someone please answer what must be a very basic (and maybe stupid) question please ? Why have both cables got 3 sheathed wires and 1 bare earth (presumably) wire ? Why did the electrician, who wired all the house when it was built 10 years ago, not just use twin with earth ?

I would be very grateful for any advice/help/information please. Thank you.

 

[terryplumb]

Depends on what the conductors are connected to( possibly one isn't ). I would hazard a guess that one is a permanent live,and another a switched live ,one neutral and one earth.

 

[EFLImpudence]

Why have both cables got 3 sheathed wires and 1 bare earth (presumably) wire ?

Because it is three-core and earth.

Why did the electrician, who wired all the house when it was built 10 years ago, not just use twin with earth ?

Presumably because it needed or might need three-core an earth.

 

[john4703]

I've used four core to wire up my outside lights as I have a pir at each end of the run of lights. Maybe the electrician was wiring with this in mind or maybe at one time there was another pir in use.

 

[scooby1]

All sorted now. Thanks for the help that some of you gave me.