2 Blacks For Live

[Bobbya82]

Just about to replace a modern light with a standard rose, however there seems to be 2 black cables connected to the live on the fitting, it was my understanding that there should one switch live black cable for live and 2 black cable for the neutral. See photo.

Please could some explain why and how I should wire up the rose fittin

Many thanks.

Pete.

Untitled

• Bobbya82
• 5 Oct 2014
• 2

Untitled

• Bobbya82
• 5 Oct 2014
• 2

 

[JohnW2]

Just about to replace a modern light with a standard rose, however there seems to be 2 black cables connected to the live on the fitting, it was my understanding that there should one switch live black cable for live and 2 black cable for the neutral. See photo.

You're understanding of the common/'normal' situation is correct. Although there are other possible explanations, it's quite possible that the blue and brown going to the light fitting have been connected to the wrong blocks (the light would still work). You really need to do some testing to find out - do you have a multimeter and are you confident to use it for testing a live circuit?

The almost completely bare earth wire going to the fitting is definitely not acceptable - it should all be sleeved in G/Y sleeving.

Kind Regards, John

 

[Bobbya82]

Hi John,

Yes I noticed the earth as well, installed by previous owners. Unfortunately I dont have a multimeter and dont think I would be completly happy testing on a live circuit. So from what your saying the light fitting should still work if the live is connected to the neutral and neutral is connected to the live?

If I wired in the live to the single black cable and the 2 blacks to the neutral would that cause a problem?

I could try getting in the loft and trace the cable, under the assumnption the black cable going back to the switch should be live?

Thanks again,

Pete.

 

[Lectrician]

Yep, I would say the fixed wiring as standard, and the brown/blue have been connected back to front.

 

[Bobbya82]

Thanks for the reply lectrician and John, just confirm then you recommend wireing up the normal way? 2 blacks to neutral and 1 black to live?

Cheers

Pete.

 

[Taylortwocities]

Yes, thats what he means.

 

[Taylortwocities]

Yes, thats what he means.

The one black to live should have a bit of red sleeving round it to mark that its a switched live.

 

[JohnW2]

Hi John, Yes I noticed the earth as well, installed by previous owners. Unfortunately I dont have a multimeter and dont think I would be completly happy testing on a live circuit.

Fair enough.

So from what your saying the light fitting should still work if the live is connected to the neutral and neutral is connected to the live?

Yes, it would certainly work but depending on the type of lampholder you were going to use, there might be a theoretical safety issue (see below).

If I wired in the live to the single black cable and the 2 blacks to the neutral would that cause a problem?

As above. It would work. If you are going to use a 'bayonet' lampholder (B22) then there would be no problem (there is no difference between the two terminals of such a lampholder). If it were a screw-in one, it is safer if the threaded part (much easier to touch) is connected to neutral.

I could try getting in the loft and trace the cable, under the assumnption the black cable going back to the switch should be live?

That is a possibility. If our assumptions are correct, the single black wire (currently connected to the blue of the light fitting) certainly should go back to the switch - the other two blacks probably don't.

Kind Regards, John

 

[Bobbya82]

Traced the cable back to the switch and it was the single black connected to the blue neutral in the fitting. Have rewired correctly.

Thanks for your help.

 

[JohnW2]

Traced the cable back to the switch and it was the single black connected to the blue neutral in the fitting. Have rewired correctly. Thanks for your help.

You're welcome. As we suspected, then - I'm glad it's sorted out.

As has been said, there really ought to be a bit of red sleeving over tha black switched live, at both ends, to indicate that it is a switched live (not a neutral).

Kind Regards, John

 

[ban-all-sheds]

Unfortunately I dont have a multimeter

Assuming that you believe that you should have screwdrivers rather than trying to make do with the point of a vegetable knife, wire cutters rather trying to make do with scissors, and so on, then you should regard owning a multimeter as just as essential, if you want to do work on your electrical installation.