3 core and earth cable to outside PIR security light

[mobwell]

I have a problem. I have a faulty outside PIR security light and removed it to replace it with a new one. The cable through the wall to the light is a 3 core and earth cable, but the new security light has instructions for wiring to a 2 core and earth cable. I should have paid attention to how the old light was wired but I didn't. The problem is the instructions show where to attach the brown, blue and earth cable to the light's junction box but not what to do with the fourth yellow cable. The three core and earth cable goes through the wall into a fused switch in the bedroom which also has a 3 core and earth and a 2 core and earth able going into it. At the moment the yellow cable from the 3 core and earth is directly attached to the yellow of the cable going to the outside light.

Basically I just need to know what to do with the yellow cable supply to the securit light.
Hope you can help

 

[fireman22]

hang on how many cables? 1 3core into outside light, 2 3core in switch and 1 2core in switch, yes?

 

[Steve]

you've confused me. first the 3c+e is AT the light.

3c+e doesnt have a brown and blue core. So how you've managed this is beyond me. It will be either <brown black grey> OR <blue red yellow>.

What does the yellow core attach to in the FCU? You say its "attached to the yellow of the cable going to the outside light" - which we already knew, but where does it terminate?

 

[Taylortwocities]

Probably it is wired to do an override from the switch, or maybe to power a second lamp.

No guarantees but I would expect the yellow to go to the output of the PIR that goes to the lamp in the PIR unit. Sometimes (but not always) marked as L'.

So that make
Red = live
Blue = neutral
Yellow = switched live

But, as I say, no guarantees

TTC

 

[mobwell]

sorry for the confusion. The 3c+e cable to the light is red,blue,yellow +earth, it was simply that the instructions with the light were blue,brown+earth for a 2c+e conncetion.
The fused switch has 3 cable : two 3c+e (one of which goes through wall to light) and one 2c+e. The yellow cable that goes through the wall is connected directly to the other 3c+e yellow and does not go via the switch. All the other cables go via the switch.

 

[Steve]

so where does the second 3c+e go? we need to know really.

Is there another PIR outside light by chance?

 

[mobwell]

the instructions for wiring the light are for a 2c+e (red,brown,earth) cable. It says connect blue to 'N', earth to earth and brown to 'L'. If I connect the 3c+e cable I have I assume its earth to earth, blue to 'N', red to 'L' , but I don't know where to connect the yellow

 

[Steve]

the instructions for wiring the light are for a 2c+e (red,brown,earth) cable. It says connect blue to 'N', earth to earth and brown to 'L'. If I connect the 3c+e cable I have I assume its earth to earth, blue to 'N', red to 'L' , but I don't know where to connect the yellow

nononono

in the FCU, look where the FCU connects to the wires to this light. there is a neutral out and a live out. then replicate these 2 in the light. 3C+E can be used in any way, never assume the colours where a neutral is concerned.

the yellow may well be a switched live from another PIR light - or a switch, so that you can override the PIR in this light, or so both PIRs operate both lights together. Dont connect it if you're not sure.

 

[mobwell]

there are 3 other lights connected to one pir on the other side of the house but these have a cable which enters the wall on the ground floor near the circuit box. I'm pretty sure these have nothing to do with the pir light I'm having problems with which enters upstairs. It appears to be stand alone, but I have no idea where the other 3c+e cable in the FCU goes. Any idea how I can find out?
I can look in the FCU to confirm the identity of the blue and red, live and neutral (and earth) wires for the 3c+e supply to the light, but as the yellow does not enter the FCU and I don't know its source, could I just connect the red, blue and earth cables to the security light and blank off the yellow cable end? I do have a multimeter if this helps.

 

[mobwell]

this is a new house to me. I've found a fused switch in the kitchen but not what it does. This could be connected to the FCU upstairs for the security light. Who knows. Unfortunately it is grouted into the tiles and cannot be removed to check its wiring. Using a multimeter on the upstairs FCU and someone downstairs switching the switch, is it possible to see if the downsatirs FCU controls the yellow cable to the security light

 

[Steve]

Turn all the power off while using your multimeter on resistance!

It will say on the back of the FCU which wire is live.

That fused switch in the kitchen might be for the lights, but it shouldn't be - if it were for the lights it would be a switch, since there is a fuse in the other one.

Try opening the PIR on the other side of the house, see what cables you find.

are both 3C+E connected to the output of the FCU? (just not the yellow)?

 

[securespark]

As I see it, the feed to your light is live loop, switched live, neutral & earth.

If your replacement fitting does not have the option to fit a switched live to the unit, you need one that does.

I guess you have an override switch somewhere?

I am working on the assumption that you have a feed to a PIR somewhere - the 3 core & earth the others are trying to ID.


I am also assuming that you have a circuit where fittings and PIR's are connected with the same "bus" cable of switch (yellow), loop (red) & neutral (blue), and override switches connecting the red to the yellow.

This is a BIG assumption, I know, so take care!

 

[mobwell]

Looking at the FCU the 3c+e blue is N and the red is L. I don't think the kitchen fused switch has anything to do with it as I can turn off the power to the security light FCU by flicking the upstairs ring mains off (kitchen switch still has light on). The FCU to the security light has the 2c+e to 'IN' and the two 3c+e to the 'LOAD' I still don't know where this second 3c+e goes.

As the original security light has been removed and I'm just left with the 3c+e cable sticking out of the wall I don't really know what to do. If I cannot find the source of the yellow cable can I just put a block on the end or wrap in insulating tape or is this dangerous?

 

[mobwell]

secure park.
The PIR for the security light in question is built into the security light itself, so the yellow cable is not a switch from a PIR. I assume then that I don't need a securitylight with switched live. Is this right?

 

[mobwell]

As the 2c+e is supply to the FCU and the two 3c+e are load could it be that the 3c+e that goes into the PIR security light should be connected red, blue, earth to feed the security light's PIR which in turn has a switched live output to feed the light itself (along with blue and earth).

Then there are two possibilities which a few of you have mentioned and I have taken a while to understand
1)There may be a PIR overide switch somewhere such that the light can be switched permanently on by a switch on the other 3c+e
2)The switched live output from the PIR could be used to switch on another security light somewhere else

Either way I guess I should connect the PIR's switched live output/light's switched live input to the 3c+e's yellow cable.

Any thoughts please.