Black and white wires?

Craig01nire · Post by **Craig01nire** » Fri Sep 17, 2021 9:58 pm

Hi all,

I wanted to replace an external wall light - pretty straight forward I thought until I opened the existing one up. Instead of the usual brown and blue wires for live and neutral I have black and white along with the earth as shown. The bulb holder gives no clear indication but there is a 't2' beside the terminal where the black wire is.

How can I tell which wire is which? Any help appreciated. Thanks

arco_iris · Post by **arco_iris** » Fri Sep 17, 2021 10:03 pm

For a conventional lamp or light bulb, which way round does not matter at all.

It may affect LED lamps, if they don't work, swap the wires over or turn the bulb round.

That's the short answer & all you need at this stage.

Craig01nire · Post by **Craig01nire** » Fri Sep 17, 2021 10:38 pm

Thanks very much for that. It is being replaced by a LED lamp and I had thought it may not have mattered which way round the wires went - just didn't want to risk damaging anything.

Thanks again!

kellys_eye · Post by **kellys_eye** » Sat Sep 18, 2021 8:47 am

Black and white are (used to be?) the American/continental way with black being 'live' but, as said, the polarity in this case is unimportant ALTHOUGH there have been some cases where the (LED) bulb had a metal surround that was an exposed 'live' connection if you put it in the wrong way round. I haven't seen this on any of the later style bulbs though so you should be perfectly safe.

etaf · Post by **etaf** » Fri Sep 24, 2021 7:25 am

Are you replacing the entire light fitting or just the bulb for an LED version
If bulb , then answered above
If the entire unit, you ,may find a junction box behind the light fitting which connects to a Red&Black or Blue&Brown cable depending on age of wiring, I can not see from the image how that fitting is connected to the house wiring.

Neelix · Post by **Neelix** » Fri Sep 24, 2021 2:36 pm

kellys_eye wrote: ↑Sat Sep 18, 2021 8:47 am Black and white are (used to be?) the American/continental way with black being 'live' but, as said, the polarity in this case is unimportant ALTHOUGH there have been some cases where the (LED) bulb had a metal surround that was an exposed 'live' connection if you put it in the wrong way round. I haven't seen this on any of the later style bulbs though so you should be perfectly safe.

Not sure I agree with this

If the bulb is an ES, then correct polarity should be observed

kellys_eye · Post by **kellys_eye** » Fri Sep 24, 2021 3:05 pm

Neelix wrote: ↑Fri Sep 24, 2021 2:36 pm If the bulb is an ES, then correct polarity should be observed

Yup, I was referring to other types of bulb and here's a link to a video that shows how they (GU10) can sometimes end up with exposed live connections

https://www.youtube.com/watch?v=keaE7QTKTYE

ericmark · Post by **ericmark** » Tue Oct 12, 2021 9:31 am

From the replies to video at least 8 years old, and in the early days of LED lights there were also some corn cob lights with exposed live parts. It does not really matter as to which way around as the lamps are reversible, only with Edison screw lamps does it matter.

I have noted many Smart Bulbs only available as E27, and with BA22d lamp holders you have to use an adaptor, which means you have no idea which way around the bulb is, but since one would normally switch off the lamp before changing bulb although technically wrong, it is unlikely to cause a problem.