4 core equivalent to 3 core?

[slowdog]

I've moved to a new build property and the builders have handily put in a switch and run some electric cable out externally above the patio doors so that I can install my own external light.

I've got an external PIR light to connect and the instructions that came with it tell you the obvious connections for 3 core (i.e. neutral = blue, live = brown, earth = green/yellow). However, the cable that's been installed is 4 core (black, grey, red and bare).

What colour in the 4 core is equivalent to the other colours in 3 core?

TIA.

 

[Adam_151]

Black Grey and Red? Sure its not Black Grey and Brown?

Anyhow, the installer should have sleeved it to indentify the condcutors, in which case you'd have two browns (one being permant phase and one being switched) and a blue (neutral)

Now, if it was me doing it, I'd have made the Brown permanent phase, sleeved the black as brown and made that the switched phase, and sleeved the grey as blue and made that the neutral... but there is no saying that your installers have done as I would... so can you access the other end?

 

[slowdog]

Hi Adam,

Unfortunately I am unable to get to the other end of the cable as it's a a new build house and everything's just pre-wired in.

You could well be right about Black, Grey and Brown. There were definitely three different colours and just the one bare wire (which I assume is Earth), though. No sleeve colours to help, unfortunately.

If the bare wire = Earth, and the grey wire = Neutral, then the other two wires = Live? So the black could be the switched phase with the grey being the permanant phase, or vice versa?

Why would this make a difference if the light was only expecting the normal brown, blue and earth? There's an extra terminal for extending the wiring to other lights but I thought the switch stuff had already been handled by the builders.

 

[DESL]

Ask the builder.

If you haven't got the means of testing don't assume the cores are wired correctly

I've seen the black conductor used as neutral.

But as stated they should be sleeved with appropriate colour to comply with regs.

 

[ColJack]

but if the end is simply stuck through the hole and coiled up then it wouldn't be stripped back..

the ends will be in a light switch somewhere.. possibly in the room nearest the light, or near the back door etc..

take some light switches off and have a look.. they should not be connected unless the other end is made off in a water proof box..

 

[slowdog]

Thanks, ColJack. The switch is indeed by the back door. The other end (on the outside) is covered with tape and put in waterproof box. Hence, the site manager giving me the impression it would be an easy enough job to connect up my own light.

 

[ban-all-sheds]

Have you taken the switch off to look at what's there?

It is an easy job to identify the conductors, provided you've got the right tools. If you don't own a screwdriver though then even getting the switch off will be hard.

 

[ColJack]

take the cover off, take a photo and post it here, we can tell you what wires do what..

 

[Observer]

The reason for the additional core could be for a second switch live to a PIR to allow manual over-ride - i.e. permanent live to PIR terminal, switch live to over-ride terminal, neutral, earth (or two switch lives from separate switches).