Replacing outside PIR light with standard light (no pir)

[Monkeysoon]

Hi everyone
Can someone pleeeeaaase help! I am trying to replace an outside wall light, which was broken yesterday buy a swing door. Don't ask! Clearly this would normally be relatively simple. However, the original light was in a fact a PIR LIGHT that was being used a normal light ie it didn't sense light, you just flicked the switch on and off inside to use it.
Having taken the old light off the wall I can see that there is 3 core and earth (grey, black, brown and earth) coming out of the wall BUT the sparky doesn't seem to be using the live (brown)! There is a connecting block with the black (in the hole marked L?), grey (in the hole marked N) and earth wires connecting. Having said that I didn't see all the original connections and the old light seemed to have more wires in it. Anyway lets keep this simple. I have bought a standard 150 watt halogen light which has a simple connecting block with room for earth, live and neutral. I'm really not sure about connecting the live to what the sparky had used as the live (black wire) etc. What do I do? And surely I'm going to have a spare wire in any case. What do I do with that?

 

[TicklyT]

I would copy the wiring the sparks has used in the old unit, and fit a piece of connector block (salvaged from the old lamp?) on the spare wire to keep it out of harm's way.

Just to confuse things, all three colours, brown black and grey in a 3C+E cable are colours used to identify live wires In this colour coding scheme a neutral wire is identified by blue. It was the same with older cables - Red, yellow and blue were all phase colours too, and there was no black to identify a neutral.

For completeness, there should be a blue sleeve fitted over the wire used for the neutral, and maybe a brown sleeve over the switched live wire (the jury is still out on that one as the colour already identifies it as live).

I would think twice about the position of the fitting if the same accident could happen again. To mis-quote Oscar Wilde, 'To lose one light fitting is unfortunate, but to lose two begins to look like carelessness'

 

[Albert]

I think that it could be very helpful if you can identify the wires. Normally if it was wired in a traditional way, think about a ceiling rose; live from CU or previous light fitting is connected to the rose, the second live connects to the supply live and goes to the light switch, from the light switch you might have a return to the rose which is the switch live. The live of the light fitting connects to this switch live , the neutral of the light to the neutral of the supply, and earth always together.

Imagine that the connections behind your light fitting are like a rose but with connection blocks. It is possible that before this light fitting there was an other light that was with a sensor and the third core was for permanent live via the switch.

To be sure you must identify the wires and IMHO the easy way is to turn off the CB and with a continuity tester trace the wires between the switch and the light.

 

[Monkeysoon]

Thanks for the quick reply Tickly. Just to clarify, you would advise I section off the brown wire - this is the one apparently not being used. I'm not a sparky, but would a sparky really use the black wire for live and leave the brown unused altogether? Why would a sparky do such confusing thing?!

 

[Monkeysoon]

Thanks Albert. Yes there was a sensor light as I said in the original post! But the fact is there is only room for 3 connections on the new light - earth, neutral & live. In terms of the connector block I would have assumed the brown wire from the 3 core & earth was live, black netral and yellow/ green earth. But the old sparkys wiring has thrown me a bit thats all.

 

[Albert]

Thanks for the quick reply Tickly. Just to clarify, you would advise I section off the brown wire - this is the one apparently not being used. I'm not a sparky, but would a sparky really use the black wire for live and leave the brown unused altogether? Why would a sparky do such confusing thing?!

As I mentioned in my previous reply, it might be that the black is a switch live from the switch, and the brown was for the permanent live. In any case if the black was used as live it should have a red or brown sleeve/tape. And yes you might find different colour wires that are used as live although they are not red or brown, so therefore it is so important to identify the wires. A very good example is a 2 ways light switch.

When you identified the wires it is possible that you do not need one of them, as advised before just put it in a connection block and isolate it, and theoretically you have left with 3 wires: earth, live (switch live) and neutral. Do not forget to put a sleeve on the live if it is not red or brown.

 

[Monkeysoon]

All sorted! Thanks for the advice chaps - wouldn't have wanted to go ahead without it. I guess the original electrician should have taped the switch live - would have made things much clearer. Anyway many thanks its much appreciated. Alex.

 

[TicklyT]

The spark might have considered the brown wire as a permanent live, which is not required for either the fitting you used to have or the fitting you now have. He would have then been left with two other phase colours to use for switched live and neutral. Whichever colour he choses for neutral is wrong unless it is identified with sleeving.

The two colour codes for cables commonly found are each complete systems in their own right. Modern cables use Brown, Black and Grey as lives, with Blue as neutral. Older cables used Red, Yellow and Blue as lives , and Black as neutral.

Each system should be considered seperately, as some of the same colours appear in both, but have entirely different meanings.

You should not assume black is a neutral just because that was the colour of neutral wires in a different colour scheme, nor is it safe to assume a blue wire in an older cable is a neutral because that is neutral identification used in modern wiring.

A friend of mine learnt - very painfully- that Americans use Green to identify live wires.

Many years ago there was concern over electrical appliances 'liberated' from Germany. The German system used Red to identify earth connections .

 

[Taylortwocities]

There, probably, was an earlier light on the wall (broken too, by the door?)
That one probably needed a permanent live, neutral and also used a switched live as an over-ride.

Sounds like you are sorted now !

 

[Monkeysoon]

Thanks again. Just out of interest what kind of light WOULD use the permanent live then. Presumably a proper PIR light I guess.

 

[Taylortwocities]

Correct! with the switched live giving the facility to have the light on permanently

 

[Albert]

In this case you might have, 2 switches; one to isolate the supply to the light fitting and when the switch is on the light will come on depends on the PIR settings, the other would be the permanent live supply that will go via the second switch and by-pass the PIR, so when it is on the light will come on and when off the light will be controled by the PIR.