Wiring in new outdoor light

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raydenl

97 posts

Master Geek

# 201635 27-Aug-2016 17:05

I'm attempting to change an outdoor light. I have done a few DIY jobs like this in the past, but this one is a bit trickier than those (for me) due to the number of other wires coming into the light fitting.

There's the 3 twisted pairs (red, black and blue), the blue is earth (as it was bolted to the metal casing). I assume the two red untwisted wires are from the switch?

They were in a terminal block, but I was stupid and removed the wires before writing down how they were wired :-/

The new light has a two wire terminal block (N & L), and is plastic so nothing to connect the earth wires too.

Can anyone provide any assistance?

Cheers

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# 1618390 27-Aug-2016 17:13

is there another light/s off the same switch?

could always pull the switch off the wall and see what colour wires are there

raydenl

97 posts

Master Geek

# 1618392 27-Aug-2016 17:17

No, the switch only controls this single outdoor light. However, if I disconnect the twisted pairs, then other lights in the house no longer work. But those lights are not controlled by this switch.

mentalinc

1752 posts

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# 1618394 27-Aug-2016 17:18

One person supports this post

raydenl:

No, the switch only controls this single outdoor light. However, if I disconnect the twisted pairs, then other lights in the house no longer work. But those lights are not controlled by this switch.

Sounds dodgy as.

Suggest you get someone to figure it out.

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JeremyNzl

273 posts

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# 1618395 27-Aug-2016 17:27

One person supports this post

Unless you have a meter/voltstick at least you would be best to get a professional in.

If the fuse is in the twisted pairs are live

I believe what you have is the black and red twisted pairs are phase/positive and neutral

with the red pair running off to a switch.

If that is the scenario, one single red goes with the red twisted pair in an insulated terminal and the other single red end into the positive terminal of the light.

The black twisted pair goes into the neutral terminal on the light.

If the light fitting is plastic the two earth terminals that are twisted need to be clamped together to pass the earth on to other fittings down the chain.

Looking at the state of the red pair , the light that has been previously fitted has had a loose terminal or not suitable for the load.

those ends need bared and retwisted, but only if you can verify zero voltage.

If none of this makes sense or if you cannot be sure the red pair is connected to a switch, turn off the mains insulate all the bare wire and refit the cover and get a sparky.

tieke

314 posts

Ultimate Geek

# 1618398 27-Aug-2016 17:36

raydenl:

... if I disconnect the twisted pairs, then other lights in the house no longer work. But those lights are not controlled by this switch.

That's pretty normal - you've got a circuit used for various lights and this one is obviously early in the run. The run to the next light comes off this one, and so on:disconnecting the twisted pairs means the lights on the rest of the drop no longer have power.

raydenl

97 posts

Master Geek

# 1618401 27-Aug-2016 17:39

Yea, sounds like this:

Some electrical installations may have lighting circuits wired where the cables running from the switchboard are connected at the light fitting and then looped between light fittings (known in the trade as 3-plate wiring), this means that live wires are always present at the light fitting rather than at the switches.

Thanks for the help guys!

gregmcc

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# 1618402 27-Aug-2016 17:44

2 people support this post

raydenl:

Hi

I'm attempting to change an outdoor light. I have done a few DIY jobs like this in the past, but this one is a bit trickier than those (for me) due to the number of other wires coming into the light fitting.

There's the 3 twisted pairs (red, black and blue), the blue is earth (as it was bolted to the metal casing). I assume the two red untwisted wires are from the switch?

They were in a terminal block, but I was stupid and removed the wires before writing down how they were wired :-/

The new light has a two wire terminal block (N & L), and is plastic so nothing to connect the earth wires too.

Can anyone provide any assistance?

Cheers

red, black and blue........um it looks green to me, this is the point where you step back and get an electrician

Sideface

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# 1618430 27-Aug-2016 18:53

gregmcc:

<snip> red, black and blue........um it looks green to me, this is the point where you step back and get an electrician

To the OP - are you colour-blind? There are no blue wires in the image.

This is a very serious question - your life may depend upon the correct answer.

Red-green colour blindness and electrical wiring can be a lethal combination.

Get an electrician.

Sideface

Jase2985

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# 1618431 27-Aug-2016 18:55

definitely blue

andrewNZ

2130 posts

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# 1618434 27-Aug-2016 19:31

The green has done what it often does and faded to blue. This may be one of the reasons new earth wires are green/yellow.

Yes the light is 3 plated, so be careful. It means that the fitting always has live wires unless you turn off the circuit / mains.

Location: Dunedin

gregmcc

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# 1618441 27-Aug-2016 19:40

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Jase2985:

definitely blue

.....another person with colour blindness......look closer to where the wire emerges from the white TPS it's green there, and looking at this picture and using common sense (yes some people do lack common sense) it tells me that the wire is in fact green.

shk292

1732 posts

Uber Geek

# 1618448 27-Aug-2016 19:50

Jase2985:

definitely blue

I'm worried if you're an ET

raydenl

97 posts

Master Geek

# 1618490 27-Aug-2016 21:09

LOL it's blue people! trust me, not the badly taken photo with bad flash. I agree at some point it was probably green. Sheesh. Regardless it is the earth wire(s) - blue, green or pink with purple spots. As I've previously stated they were bolted to the metal chassis. Red is unmistakably red, black is unmistakably black.

(and yes I am aware sometimes blue is used as neutral and brown as live - but this is clearly not the case here)

Thank you to the people who have provided helpful comments. And yes, I may just get an electrician to do the work... maybe...

Jase2985

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# 1618494 27-Aug-2016 21:16

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shk292:

Jase2985:

definitely blue

I'm worried if you're an ET

be worried all you like, but the OP has confirmed its blue, might have been green at some point in the past

My last medical showed no issues with colours

i would use a meter anyways

Rikkitic

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# 1618618 28-Aug-2016 10:03

If you really know what you are doing, just do it. If you are uncertain, you should really get a professional. Deadly voltages are not something you should learn on.

Assuming you do know what you are doing but just don't have the right tools available, you can work out the right wiring with a test light. Get a light fitting, put a bulb in that you have just tested and know works, add wires for the connection. Cut the power to the house, double-checking that everything is off, then hook the test light to the red and black wires, leaving the two loose red wires unconnected. If the light comes on when you switch on the power, something is wrong and the two red wires do not do what you think. If it doesn't, connect the light to the two red wires and repeat the test. Again, it should not come on. The test is just to make sure there is no voltage difference between those wires. Finally, connect the light where you think it should go, connect the two red wires together, and test again. If the light comes on, those wires do indeed go to the switch. Make sure to cut the power between each test.

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