PIR Sensor

[scottpetrie]

I have just bought 5 downlighters and a PIR sensor for my soffits. The PIR has an input and an output. Do I have to wire the mains straight to the PIR, then daisy chain along to the downlighters from there or can I put it in anywhere? Only reason Im asking is because the location for the PIR is at one end of house, & mains input is at other, so was going to wire the downlighters along towards it. Or do I have to run a long length of cable to PIR first then work my way back?
Thanks

 

[Taylortwocities]

The PIR can go anywhere in the chain, or at either end. It doesn’t matter, all the lights are connected in parallel

 

[bernardgreen]

Use three core and Earth

Core 1 Live from source direct to PIR Live
Core 2 Neutral from source to all lamps Neutral and PIR Neutral
Core 3 Switched Live from PIR to all lamps Live

Earth core to lamps and PIR

 

[sparkwright]

Typically you would run T+E from the source all the way to the INPUT on the PIR, then T+E from the OUTPUT of the PIR to the lights.

or

Bernard's way, but you would have to join the browns in a separate connector block at each light, and most modern fittings don't have the room for this.

or

Use a junction box.
The junction box will have a T+E from the source.
One or more T+E going from the jb to the lights, they don't have to be in a 'daisy chain', whatever is easiest for the cable-running point of view.
And a 3 core+E cable from the jb to the PIR.

If you use a junction box, make sure it's somewhere accessible. No point making it difficult for the next man.

 

[scottpetrie]

PIR does not have an earth but the downlighters do?

 

[sparkwright]

The PIR can go anywhere in the chain, or at either end. It doesn’t matter, all the lights are connected in parallel

To clarify for the op - assuming you have the correct number of wires in the cables - see Bernard's post.

The PIR will need a permanent live in, a switched live out, neutral, earth.

Even though the PIR doesn't require an earth connection, an earth wire should run to it, and if there is more than one earth wire running through it, these must connected together with a separate connector block or wago.

 

[bernardgreen]

but you would have to join the browns in a separate connector block at each light

Assuming brown is the Core 1 Live to PIR then it can sometimes be achieved at the lamps by removing the cable sheath to expose the cores. Cut and strip the Neutral and Switched Live cores and connect these into the terminals of the lamp. The core that is Live to the PIR remains un-cut and the excess packed out of the way in the lamp. This takes up far less space than cutting the core and then re-joining the ends with a terminal block.

It does require a bit of skill and care than just cutting all three cores and the Earth.

 

[scottpetrie]

The PIR has a live and neutral. No earth. If I go straight from source to PIR, what should I do with the earth? Also, does that mean each lamp then wont have an earth? The spec sheet says no earth is required as they are sealed units.
The source wire is bang in the middle of my house above front door. Can I wire in a lamp to this then tee off to the left for 2 lights and the PIR, and tee off to the right for the other 2 lamps?
Or, should I feed source to PIR then each lamp in turn from there (but what about earth)?

 

[scottpetrie]

To clarify, the wire hanging from my soffit is T&E. The PIR has only a live and neutral in, & live and neutral out. Do I just run the cable to the PIR (not connecting earth), then daisy chain live and neutral from PIR output, to the 5 downlighters?
If I did this, would I have to leave my switch on for the PIR to be active?
Would the override feature still work (switch on,off,on to be permanently on)?
Does someone have a wiring diagram I could follow?

 

[flameport]

If the PIR has no earth connection, you will have to provide one. It must be connected through to all of the lights.

If you want it to work, the switch will have to be left on.
If it has that override feature it will work. Most PIRs do not have it.

 

[JohnW2]

The PIR can go anywhere in the chain, or at either end. It doesn’t matter, all the lights are connected in parallel

There is nevertheless obviously a need for a 'permanent live' feed to the PIR and the OP was trying to avoid having a cable connecting 'the mains' to the PIR' (since the PIR will be physically near the end of the run of lights). As bernard has said, that could be done with 4-core (3-core + earth) cable, with the 'third core' (the permanent L) going 'through' all the lights as the cable passes through them to eventually get to the PIR at the end.

Kind Regards, John

 

[scottpetrie]

All the units are double insulated and do not require an earth according to the instructions. Also, the PIR only has 2 inputs and 2 outputs, physically nowhere to put an earth. If I use my existing wiring, am I correct in saying I do not need a permanent live to PIR as the switch will be left on?
Is there a way to wire it so I can have the lights come on and stay on with the switch like normal, but when I switch the switch off the PIR takes over?
Thanks

 

[Taylortwocities]

Is there a way to wire it so I can have the lights come on and stay on with the switch like normal, but when I switch the switch off the PIR takes over?

Yes! You’ll need 3 core & earth from the switch to the PIR. 2 core and earth to the lights. Join the earths in the PIR enclosure in a spare bit of terminal block(choc block). The cables must be earthed even if the PIR and lights themselves don’t need an earth.
Typical connections like this:

This has a 2 gang switch so u can have lights always on, always off or PIR controlled.

 

[JohnW2]

.... If I use my existing wiring, am I correct in saying I do not need a permanent live to PIR as the switch will be left on?

I'm not sure what you mean by "the existing wiring", given that you said that you had just bought the lights and PIR, and asked about how you could wire them.

You DO need a 'permanent live' to the PIR (to connect to the 'input' of the PIR). In this context, "permanent live" means that, when the PIR is being used, that remains live all the time, even when the PIR has not switched the lights on (the lights are fed from the 'switched live', aka 'output', of the PIR).

There are two ways you could do that. Firstly, if you did not want the 'manual over-ride' option just described by TTC, then you could could run a 2-core cable ('permanent live' and neutral) from the house/switches to the PIR, and then 2 core cable (PIR-switched live {from PIR 'output') and neutral) from the PIR to the chain of lights. However, that would involve a separate cable all the way from the house to the 'distant' PIR - which I thought was what you wanted to avoid.

Secondly, as bernard, TTC and myself have said, if you used 3-core cable ('permanent live'. 'PIR-switched live' and neutral) for 'everything' (from the house [the switch(es)], from PIR to one light, and between the lights), then you could take such a cable from house to first light, then between each of the lights and hence to the PIR at the end of the run (hence just the one cable, without the need for a separate cable from house for PIR) - and that would also enable you to have the 'manual over-ride' facility as shown by TTC. The 'permanent live' would just 'pass through' each of the lights (not connected to anything at lights - and therefore would need some sort of 'connector block' if you cut the cable at each light) and would only be connected to the ('input' of the) PIR at the end of the run.

Kind Regards, John

 

[scottpetrie]

Thanks for that. For the existing wire, what I mean is there was a single light on the old soffits, which has been removed whilst new soffits were put up. There is now the old existing single length of T & E wire in the soffits, coming from the hallway switch. My query is if I use that for the new PIR, I would have to cut the earth at the PIR as there is only 2 inputs and 2 outputs. Then daisy chain from there, to the row of downlighters. Therefore because the PIR only has 2 inputs and 2 outputs, I cant use 3 core and earth, is that correct? Do I need a different PIR, then I could run a length of 3 core & earth from switch to PIR?
If I wire it the way I mentioned with the T&E, am I correct in saying that the lights will come on when sensor is activated, & I will need my switch on all the time?
Or…am I best just wiring straight to the lights, forget about the PIR for now, & install a smart switch with timer?