A little wiring help before I burn down my house.

[JAMESWRIGHT2004]

First of all Hi, this is my first post and possibly not my last.

Now I'm not a complete idiot when it comes to DIY, but mostly building, tiling, plumbing etc. But I'm never sure with electrics. So I thought I'd run it past you guys before I do anything stupid.

Now, I have had a look at you superb lighting circuits sticky and think I have found the answer but would love confirmation.

I am replacing a light fitting, and stupidly I have taken the wires out of the old fitting and not marked down which one goes back where in the new fitting!!!!!

Details:

I have two switches opperating just the one light.

Out of the ceiling there are two 3 core wires coming out, each have a red, a black and a green. The two green wires were twisted together and ground, thats all I remeber.

One red and black wire produce the 240V the other don't seem to produce anything.

The connections on the new light fitting only have one terminal for Live, one for Neutral and one for ground.

Any ideas how to connect these up?

Looking at the diagrams (there isnt an exact replica of my circuit but tried to make an assumption on what I do from a similar), Would I:
Joind the two greens together and put them in the "Ground" terminal.
The 240v Black wire to the "Live" terminal
The other Black wire to the "Neutral" terminal"
And use an insulated connecting block to join the two reds independantly?


If you could get back to me about this that would be great, my garage/gym is a pretty dark place at the moment.

Many, Many thanks in advance

James

 

[Spark123]

Sounds like a start - providing the other cable is a switch wire

 

[PrenticeBoyofDerry]

How have you tested the cables and using what test equipment?
Was the fitting originally on a ceiling rose plate?
What you may have:
*Is a pair of CPC/earth cables terminated to the earth terminal and that's as it should stay.
* a permanent live, this will be a red (if existing done correctly) will read 230v-250V referenced to earth.
* a live to the switch, again red in colour, this will read 0v if not terminated and would be looped together with the permanent live to form the circuit.
* a switched live, this will be black and should have been marked up with red flag or sleeve. This cable becomes live when your switches are in the closed position. This would be connected to the live side of the lamp
* and the second black is a neutral. Terminated at the neutral side of the lamp
Ideally you need to confirm the function of these cable prior to energizing the circuit, so continuity readings would be advised.

 

[JAMESWRIGHT2004]

Sounds like a start - providing the other cable is a switch wire

Do you think its OK/safe for me to use a seperate connection block for the two reds as long as they are insulated well? I'm assuming that there are a lack of connections because it isnt comprehensive enough on the fitting to do this.

 

[Spark123]

As long as the separate connector block is in some sort of enclosure i.e. the base of the light etc.
Firstly though you need to double check the other cable is a switch wire.
As PBOD says - it ought to have a red sleeve on the black wire to signify it is being used as a live.

 

[PrenticeBoyofDerry]

Do you think its OK/safe for me to use a seperate connection block for the two reds as long as they are insulated well? I'm assuming that there are a lack of connections because it isnt comprehensive enough on the fitting to do this.

Standard procedure is to terminate these two cables together in terminal/connection block, if no spare at the fitting available. There is no need to offer any further insulation to the block, providing all bare conductors are within the terminal and this terminal is within the cover/enclosure of the fitting.

 

[JAMESWRIGHT2004]

How have you tested the cables and using what test equipment?
Was the fitting originally on a ceiling rose plate?
What you may have:
*Is a pair of CPC/earth cables terminated to the earth terminal and that's as it should stay.
* a permanent live, this will be a red (if existing done correctly) will read 230v-250V referenced to earth.
* a live to the switch, again red in colour, this will read 0v if not terminated.
* a switched live, this will be black and should have been marked up with red flag or sleeve. This cable becomes live when your switches are in the closed position.
* and the second black is a neutral.
Ideally you need to confirm the function of these cable prior to energizing the circuit, so continuity readings would be advised.

Hi, I have used a digital multimeter just to measure the voltage output of the pair of wires.

Yes it was originaly on a ceiling rose.

All you have written makes sense and looks like this is what I have. The black was sleeved and came from the perminant live red 3 core wire.

With the continuity testing, what would I need to check?

I have only just had the house rewired and got all of the checks and certs. done.

 

[Spark123]

As the black was sleeved it is almost certainly switched live.
This to L, both gn/yel to the earth terminal, black from the supply wire to the N terminal, both reds together.
(These are old colours hence I take it this part of the house wasn't rewired)

 

[JAMESWRIGHT2004]

As the black was sleeved it is almost certainly switched live.
This to L, both gn/yel to the earth terminal, black from the supply wire to the N terminal, both reds together.
(These are old colours hence I take it this part of the house wasn't rewired)

Excellent, thanks. Yes this wasn't rewired as it was just the garage light loop, it was tested and and all fine. That couldn't be said about a lot of the rest of the house.......

Is there a simple way to check if the sleeved wire is switched live? Just to be 100% sure? Or are we saying we are now sure?

Many thanks for everyone's help. It puts my mind to ease.

 

[EFLImpudence]

Is there a simple way to check if the sleeved wire is switched live? Just to be 100% sure? Or are we saying we are now sure?

Switch of the power and remove the wires again.

Connect the two wires of one of the cables (red and black) to a multimeter set to low ohms (beep).
If the meter beeps when you turn on the switch - this is the switch cable.