Electricity Cables

[alicia]

Hi

Just about to put a new light in the bathroom. It will be attached to the mirror. The old light, had a black and white cable. The new lamp has a blue and brown cable. Should I connect blue with blue and brown with white. There is no earth (yellow and green). Would be grateful for any input as dont want a curly perm or even worse maybe.

Many thanks.

[dxf]

Hola

If there are only two wires to connect to two wires on the light then it doesn't really make a difference as the light will work no matter which way you connect. The correct way is to test with a neon screwdriver that lights up when the live wire is touched - connect to the blue wire, the brown being a common return

Davexf

[TorreDelAguila]

Wrong, wrong, wrong.
Brown = live (230v)
Blue = neutral (0v)

Yes, the light will work either way round.
If the bulb is screw-in, it is preferable for live to end up on the small contact at the bottom of the socket, and not on the threaded side contact, which might more easily be touched.

[Enrique]

Hi Alicia,

Please ensure the circuit is OFF before connecting up

As this job sounds above your pay grade get a qualified Electrician in............and stay alive.

[alicia]

Hi,

Many thanks for your kind replies and help.

Enrique is probably right. This job could well be above my pay grade. But I did manage to disconnect the old lamp. Thanks for reminder about turning off the electricity as well. Always valid. Will have a go today.

Once again thank you.

[biribiri]

If it's an older property do not assume that blue = neutral, brown = live etc. In my experience it all depends on what bits of wire the person doing the original job had to hand and there is no guarantee that the colour of wire used at one end of the circuit matches the colour at the other.
Before we had our house rewired the main light in the living room had black and red wires at the switch that changed to blue and yellow from a junction box then ended up as brown and green at the light fitting. Each joint had been made by twisting the wires together and then wrapping with a bit of sticking plaster.

[wollie]

The brown will be the live and the blue nuetral, you will need to establish for sure which is the live on the original wiring, though it is likely the black we need to know for sure.
There are two reasons for this, first it is better to have the live switched for the light as the power does not enter the light when off.the other reason as mentioned earlier is the live should be at the back of the light and if it is wired incorrectly be at the side where the bulb is screwed in.
I do not know if there is a small screwdriver called phase tester available in Espana but anyone of your handy neighbors will have a tester...

[spanish_lad]

Its best to chck which way the cables are, as above.

If the new light is led it may only work one way round.

[TorreDelAguila]

Virtually all commercially available LED lights (mains and 12v) are designed to run on AC, and polarity doesn't matter. This is especially true where the LED bulb is designed to fit into a traditional lamp socket, whether bi-pin, bayonet or screw.

Only 'component' LEDs and some specialist items such as LED strips and 'ropes' are intended to operate from DC, where polarity does matter.

[gerryh]

LED lights (... and 12v) are designed to run on AC,

Being pedantic that is a bit of a dodgy thing to say. I know what you mean as I believe you are also into electronics.
LED lights that are designed to run off 12v AC, via a transformer are OK but it is possible, and easy to buy 12V LED lights that will only run off DC where the polarity matters.
Cheers
Gerry

[TorreDelAguila]

Yes, that right. Not easy to summarise.
Only safe tack is to read the label, to check whether intended for AC or DC, and what voltage.

It's no wonder the sales assistants in the Lighting section of Leroy Merlin are permanently busy!

[spanish_lad]

Indeed. I was meaning more that if the new light is a complete led fitting it may well not work the other way around. The op didnt say they were changing a bulb holder. They said 'a new light'. If it has a two pin plug already on it then chances are that it will. Its a bathroom so its gonna be 240ac, ive used a few 12v strips in aquariums and cars and i know tjey have to be right, but ive also bought 240ac 10a lightbulb to replace a 120w florescent bulb in a floodlight and it didnt work the 'wrong' way around...

Didnt mean to cause an argument..

[Gasman]

Alicia said on 2 October <Will have a go today. >
We dont seem to have heard from her since !!! Did she get the curly perm, or is she OK ... ?
ALICIA - how are you and how is the light fixture?

[knowal]

@spanish_lad - I bet you don't mean a 10a lightbulb, that would be 2.5kW. A tad bright!

[spanish_lad]

Doh! 10w.. Not 10a