Ask The Trades - Wiring Question

Ray Baker

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Wiring Question
Dec 15^th, 2014, 5:00pm

Hi,

I am installing an outside security light, which is wired for just standard live, neutral and earth, but the cable issuing from the inside of the house is (I think!) a 3-phase cable, with black, brown and grey sheathed cables and a bare cable, which I assume to be the earth.

Question is, which of the black, brown or grey cables do I connect to the live and neutral terminals on the light?

Thanks.... Ray

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Lectrician

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Re: Wiring Question
Reply #1 - Dec 15^th, 2014, 6:36pm

Three core plus earth is often used on PIR lighting to provide an override facility.

You will likely find one core is permanent live, one switched live, and one neutral.

Unfortunately, with this cable, different electricians use different colours.

Brown is likely the permanent live, but the switched live and neutral could be either the black or the grey (where any over-sleeved?).

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Ray Baker

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Re: Wiring Question
Reply #2 - Dec 16^th, 2014, 7:07am

Lectrician wrote on Dec 15^th, 2014, 6:36pm:

Three core plus earth is often used on PIR lighting to provide an override facility.

You will likely find one core is permanent live, one switched live, and one neutral.

Unfortunately, with this cable, different electricians use different colours.

Brown is likely the permanent live, but the switched live and neutral could be either the black or the grey (where any over-sleeved?).

Thanks for the reply.

No, none of the cables have any sleeving or other markings on them, so no real indication....

So no real way of knowing whether I should wire grey or black up to neutral?

What would happen if I were to pick the wrong one? Would the light just not work, or could it cause damage to the rest of the installation or elsewhere?

Thanks.... Ray

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thescruff Global Moderator Trade Member Author Offline Who said plumbing was easy. Posts: 6037 Total Thanks: 147 For This Post: 0 Gender: Trade: Plumber	Re: Wiring Question Reply #3 - Dec 16^th, 2014, 8:48am Is there a switch you can trace it back to source I would think it very unlikely a sparky would just stick a live cable through the wall, is the inside connected.
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Ray Baker GDPR opt-out Total Thanks: 147 For This Post: 0	Re: Wiring Question Reply #4 - Dec 16^th, 2014, 10:14am thescruff wrote on Dec 16^th, 2014, 8:48am: Is there a switch you can trace it back to source Good idea! Yes, there is a switch, and I can see that the blue (neutral) is connected to the grey of the 3-phase, so that's that mystery solved! Thanks everyone for your help... All the best.... Ray
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thescruff Global Moderator Trade Member Author Offline Who said plumbing was easy. Posts: 6037 Total Thanks: 147 For This Post: 0 Gender: Trade: Plumber	Re: Wiring Question Reply #5 - Dec 16^th, 2014, 12:00pm Hold it. in the switch it's likely to be a switch live not a neutral. Can you post a pic showing the connections.
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Ray Baker

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Re: Wiring Question
Reply #6 - Dec 16^th, 2014, 1:32pm

thescruff wrote on Dec 16^th, 2014, 12:00pm:

Hold it.

in the switch it's likely to be a switch live not a neutral.

Can you post a pic showing the connections.

Hi,

I hadn't noticed before, but (inside the switch) the grey that's heading outside has got a blue sleeve, and the black has got a brown sleeve, which I guess would mean that grey is neutral?

Here's pic anyway...

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thescruff Global Moderator Trade Member Author Offline Who said plumbing was easy. Posts: 6037 Total Thanks: 147 For This Post: 0 Gender: Trade: Plumber	Re: Wiring Question Reply #7 - Dec 16^th, 2014, 1:55pm Best wait for Lectrician, but looks to me as though the brown is the switch live and the black the live
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Ray Baker

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Re: Wiring Question
Reply #8 - Dec 16^th, 2014, 2:15pm

I've teased the wiring out a bit, so that it's easier to see what's going on....

There's a 3-core cable coming from the rest of the house, which then is connected to a 3-phase, 4-core cable inside the switch base-unit before heading outside....

The brown goes into the power-switch and the brown that goes outside comes out of that switch.

The blue from inside is connected to the (blue-sleeved) grey via a connecting block.

The black from outside (brown sleeved) is just floating around in the air, and not connected to anything!

This suggests 2 things to me...

1. The grey must be the neutral, and the brown the live.
2. Why on earth bother with the 3-phase cable, when the 3rd (black) wire isn't connected to anything!!

Weird!

Rgds... Ray

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Lectrician Administrator Trade Member Author Offline Ask The Trades Posts: 8814 Total Thanks: 108 For This Post: 0 Braunton, North Devon United Kingdom Gender: Trade: Electrician	Re: Wiring Question Reply #9 - Dec 16^th, 2014, 4:43pm Black is unused, grey is neutral, brown is switched live. It's not wired to allow any means of override, if you're happy with that, it's fine. Most PIR lights these days allow an override by flicking the switch on and off quickly anyway.
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Ray Baker GDPR opt-out Total Thanks: 108 For This Post: 0	Re: Wiring Question Reply #10 - Dec 16^th, 2014, 6:38pm Yes, I think that's exactly the situation, and it does allow for an override by flicking the switch off and on.... It's all working! Thank you everyone for your help - a learning experience for me, and a very useful and friendly web-site All the best.... Ray
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