PIR Light Wiring Confusion

[eyedee]

I'd really appreciate some help with an issue I'm having with a PIR light wiring. I currently have a rather ancient PIR light over the backdoor of my kitchen. It has a single switch inside the kitchen to make it constantly illuminate, but it is always on in the PIR detecting sense, even when the switch in the kitchen is set to off.

I'm looking to replace it with a simple non-PIR light (just on and off) but can't get my head around the current wiring setup. I'm sure it'd be more obvious if I could trace the wires back to their source, but the wiring goes underneath the bathroom floor which is completely tiled, and I don't want to go smashing it out if I can at all help it!

I assumed the PIR light would be fed by a single 2 core/3core and earth cable, but it's actually fed by twin 2 core and earth cables. I've attached a photo (bad lighting means it's a bit poor, sorry) which is labelled and shows 4 terminals.

Two pre-2005 live wires (red one from each cable) are input into Terminal 1b, the 2 earths into Terminal 2b, a single neutral into 3b, and a neutral (sheathed as live) into Terminal 4b.

I'm guessing the sheathed neutral in Terminal 4b is a switched live? Does this mean one of the cables comes directly from the switch, or is it something else entirely? I've been trying to figure it out, but I'm definitely no expert and the design of the wiring run is where it all goes to pot for me.

Untitled

• eyedee
• 24 Nov 2013
• 1

 

[EFLImpudence]

If you delete 'neutral' from terminal 4 in the picture it will be self-evident.
You have -
1 Live loop - keep separate.
2 CPCs (earths)
3 Neutral
4 Switched live

Have a look here. It is the same as a ceiling rose.
//www.diynot.com/wiki/electrics:lighting:lighting_circuit_layouts



Neutral is the term for the return path of the current after a load.
It is not a name for blue or black wires.

Wires can be anything we want; they do not know what colour they are.

 

[eyedee]

That's very helpful, thanks.

So I assume that means my current PIR light is as the 'Dining Room' back plate in the diagram because with only two twin core and earth cables there isn't a third cable to feed to a further light?

 

[Taylortwocities]

Correct.
In the diagram, the black wire from the switch should have a red sleeve on it to indicate that this wire can be live and is not an neutral conductor.


For new "harmonised" wiring we would now mark a blue conductor with with a brown sleeve.

 

[eyedee]

Yes, the current switch wire does indeed have a red sleeve fitted. I'll be sure to mark the wiring correctly.

Thanks again. I'm looking forward to fitting the new light later this week.