2 Light fiitting wires

[DIYdorris]

Just fitting a new light to bedroom. Took old light fitting off and foung 2 neutrals, 2 lives and 2 earths (the earths are fused/twisted together). Should I insulate one set of liv and neutral? Any thoughts?

 

[Niloc]

Have you managed to get the new light to work? Be careful, you may not have 2 lives and 2 nuetrals, one of the black wires could be a live switch wire.

 

[DIYdorris]

haven't tried it yet as was unsure on what to do with rogue wires. There are 2 red, 2 black and 2 earth. How would I tell if one was a live switch?

 

[Softus]

Are you working on electrics without any means of testing wires to tell you which are live? Or without knowing how to?

 

[dingbat]

Or without making a note of what went where before you disconnected?

 

[Pensdown]

haven't tried it yet as was unsure on what to do with rogue wires. There are 2 red, 2 black and 2 earth. How would I tell if one was a live switch?

Before we can help, was the existing light switched on it's own or does it come on with other lights?

 

[Niloc]

In your old light, can you remember if the 2 black wires were connected together in the same terminal? or were they connected in separate terminals?
If they were in separate terminals, then one of the blacks is a live switch wire that returns from the lightswitch.
You have 2 cables poking through your ceiling, you need to find which one of these goes to the switch before you can proceed.

 

[Welstead]

I always mark down the colours of wires down on paper before I disconnect anything. It makes life so much better!

 

[davelx]

And I usually take a photo with my digital camera too.

 

[securespark]

I'm sure this all makes the OP feel much better...

 

[davelx]

OK.

Unless there are other fittings controlled by the same switch, it sounds as if this is the last fitting on a loop wired lighting circuit (you might take a look inside another rose on the same circuit to see if there are three cables coming in to confirm this).

If so, then most probably all you need to do is connect the two reds together in a choc bloc and connect the light fitting between the two blacks. The black that is coming back from the switch (switched live) should really have a brown( or red) sleeve or tape on it.

Do you have a multimeter of some other means of measuring continuity?

If so, you can identify which is the switch cable: isolate the circuit (ideally turn off all power), separate the wires, switch off all other light switches on the circuit, turn the switch for this light on and check for continuity between red and black in each of the two cables.

One of the two should give a near zero resistance reading. Turn the switch off and check the same pair again and you should get no continuity. This is the switch cable.