Wiring Colours

MikeGP · Dec 22, 2020

Hello,
I am replacing a dimmer switch in my house. In the switch there are the following wires: red (connected), yellow (connected), and blue (not connected). Could someone please advise what each is as, in the switch, I can not see any lettering saying which pole is which. I am attaching a photo.

westward10 · Dec 22, 2020

Was the blue definitely not connected and didn't break off when you removed switch. Is it two way switching whereby there are two switches controlling one light.

littlespark · Dec 22, 2020

I’d say red is permanent live, yellow is the switched live. Without testing properly, the blue could be a neutral, or just may not be connected at either end. Or as westy suggests, it’s part of a 2 way circuit.

just be certain you’ve got the power off.

MikeGP · Dec 22, 2020

Hi Guys, Thanks for replying. The blue was definitely disconnected as it was laid across the back of the box. The switch is a single switch to a single ceiling light fittting.

westward10 · Dec 22, 2020

Doesn't really matter which way you connect the red and yellow at the new switch. The blue should be made safe by putting it into a connector.

7029 dave · Dec 22, 2020

littlespark said:
I’d say red is permanent live, yellow is the switched live. Without testing properly, the blue could be a neutral, or just may not be connected at either end. Or as westy suggests, it’s part of a 2 way circuit.

just be certain you’ve got the power off.

That would be my configuration. On rewires I used red perm, yellow and blue as S/L if needed.

MikeGP · Dec 22, 2020

Thank you so much guys. ?

loz2754 · Dec 22, 2020

Just be aware that if the dimmer you are fitting is metal, it will need to be connected to earth. Is there a green and yellow wire in the switch box?

Zerax · Dec 22, 2020

And when you remake the terminations... you don't want any copper exposed... so in your pic, they should look like the red conductor not the yellow one.

7029 dave · Dec 22, 2020

Zerax said:
And when you remake the terminations... you don't want any copper exposed... so in your pic, they should look like the red conductor not the yellow one.

Yeah no shiners.

MikeGP · Dec 22, 2020

No problem guys - all understood and, no, the box is plastic. The yellow wire was actually fully home - it just came a bit adrift when I turned the box to take the photo. I will make sure it is tight home. Thanks again.