2 black, green and white plug wiring for celing light

[grahamdoc]

I recently removed a light from our new house to find 2 black wires, a green wire and a white wire hanging from the celing in 2 seperate terminal blocks.
Before i attach the new light with the usual brown/blue/green & yellow combo Id like to check how this matches up.
There are also 2 earth wires in the new light.
On the old light, one of these earth wires was connected to the 2 black wires seperately on a single terminal block. The other 2 wires - green and white were connected to another seperate terminal block.
The new light has a 3 terminal block.
What will the configuration in the three terminal be as there are 4 wires from the celing, 3 in the light + 2 earth wires from the light also ?

Any help much appreciated

Also after fitting a dimmer all the lights outside the room with the dimmer have gone but there is no fuse replacement in the old mains system for this and the switch in the box will not got on (remains in middle or off)

 

[Chri5]

Graham- I take it the old light was working and so was the old switch.

You have wired the switch incorrectly and thus the MCB (switch style fuse that has an on / off setting) see's a fault and rightly won't allow you to turn the circuit back on.

If you isolate the switch wiring via tape covering each core I'd think that will bring back some of your lights.

As for the ceiling wire it seems odd that you have 2 x blacks and 1 x white !

Would you please post pictures of the ceiling area and the switch area wiring which will help us resolve the problems.

At old ceiling positions I'd expect to see black, red and a bare core sleeved with grn / yellow.

What type of property do you have, have you got access above the ceiling or do you live in a flat ?
Do the cables at the ceiling come via a metal tube ?

 

[grahamdoc]

Thanks Chri5

The house is a 1930s semi detached and the cables do come via a metal tube from the ceiling.
The old light had the 2 black cables from the ceiling running into a 1 point terminal then to a earth attached to the old light itself
What im unsure of is where the 3 cables on the new light go ? into a 3 point terminal that links to the white and green cables from the ceiling?
I will get a photo and post it as its not a configuration i have seen before

Thanks

 

[sparkwright]

Sounds like single core wiring.

Would assume two blacks are neutral
White live
Green earth

Would be best to check first though.
Is there a ceiling rose in another room that you could loosen the cover off and have a quick look?

 

[grahamdoc]

I have attached 2 pictures - one of the ceiling wires and the other the dimmer wires

Im not sure what wires to connect from the new light to the 2 terminal block on the ceiling as we have the usual blue/brown/green&yellow on the new light to be connected to the existing terminal with the green and white

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The seperate black terminal was connected to the earth attached to the old light. Im guessing this will be the same with the new one? If so what happens to the green and yellow earth wire from the new light? Does this become redundant as the earth from the light is connected to the terminal with the 2 black wires

Also I took the dimmer out and tried to bring the other lights back on but the mains switch still did not allow me to recover the other lights?
There are 2 red and a white here. The dimmer has a l1 and l2 and neutral connector. I attached the reds to l1 and l2 and the white to neutral and it worked but the other lights now do not.

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Thanks again

 

[sparkwright]

You can see at the switch that green is earth, because it goes to the metal switch box.

You can see you have two reds and one white at the switch.
So white is the switch live.
So at the light, white is LIVE.

And the blacks will be NEUTRAL.

In installations without RCDs, things can work with earth and neutral mixed up.
But you must not mix them up.

It was quite common in old conduit systems to use white (or more often yellow) as the switched live. This was because using red made it hard to tell the difference between a switched live and a permanent live.

Have you looked in other ceiling roses yet?

 

[Chri5]

It was quite common in old conduit systems to use white (or more often yellow) as the switched live. This was because using red made it hard to tell the difference between a switched live and a permanent live.

One to file under usefull info, ta.

 

[grahamdoc]

Thanks Sparkwirght

I will take a look at another ceiling rose tonight. Hopefully no nore surprises