lighting 2 black and a grey - WTF

[cressers]

I am putting in new ceiling light and there are 2x black and 1 grey wire.

Am i right in thinking to use 1 black and 1 grey as L&N and leave one floating?

[cressers]

sorted.

Use 1 grey, 1 black - leave the other one unconnected.

[Jukka Aho]

I am putting in new ceiling light and there are 2x black and 1 grey wire.

Am i right in thinking to use 1 black and 1 grey as L&N and leave one floating?

Modern buildings use brown for live, blue for neutral and green/yellow for protective earth, as per the current regulations.

Old buildings may feature varying “interesting” color schemes based on the age of the installation. In those old installations, live is usually black or brown and neutral is grey, white, or light blue.

From your description, it sounds you’re looking at wiring that has been meant to be “compatible” with a chandelier. Chandeliers often come with two separate sets of lamps which can be switched on independently of each other. The corresponding wall switch is probably a split-in-two “dual” affair as well, isn’t it? So you get two independently switched live wires in the connection box, with a single (shared) neutral wire.

Note that sometimes you may encounter a dangerous, illegal, careless installation where the switch is on the neutral wire – i.e. the live wire is always live, regardless of the position of the switch. Always check the wires at least with a test pen before commencing any work, and if in doubt, take the fuse out of the fusebox or just flip the main switch off. Better be safe than sorry.