Help with PIR please

[benunited]

Hi folks

Moved into my house a while back and the PIR/outside security lights were working OK.

There are two lights and one PIR in between them.

Then the PIR went so I've tried to replace it. Stupidly(!) I didn't check the wiring of the PIR I was removing, as I thought it would be a simple replacement.

So I connected the neutral, live and earth - all the while wondering why there wasn't two cables, one the feed and the second going to the first light (which I assumed would then go to light number two).

Anyhow, I wired it up - and the lights are on permanently, unless I switch them off. As a guess I changed the live to L1 - same thing.

So I had a look in the garage loft and found four cables all meshed together in electrical tape, presumably around electrical connectors!

So it seems one cable is the live feed, one is light number one, one is light number two and the other goes to the PIR.

Is that not a strange way of doing things? Doesn't it also mean that the lights will always be on permanently if the live feed is switched on?

Not sure what to do so any advice much appreciated!

Thanks

Ben

 

[ekmdgrf]

There are many, many ways to wire lights. When it comes to switches and PIRs, there are many more still. One may choose to wire both lights to the PIR or the PIR to one light and then that light to the other. The switch might be wired as an override either to force the light off or force it on. I don't see how a PIR can work with only two wires, you generally need a line and neutral to power it and then it provided a switched line output. Have you missing a cable hiding in there or something? Perhaps you can do a David Bailey impression and post some pictures?

 

[benunited]

Thanks for the reply

I've tried to upload an image - David Bailey I ain't. I've in fact uploaded a diagram of what seems to be happening:

Live feed > connector covered in electrical tape > three cables coming out of this mess > one to light one, one to light two, one to the PIR.

Don't think I'm missing any cables. Lights are on permanently when switched on

 

[benunited]

//www.diynot.com/network/benunited/albums/

 

[ekmdgrf]

I can't see how that PIR works without three wires + CPC (earth). Uh no, please tell me the previous installer didn't use the CPC as a live conductor?!

You may be best (with the power off and confirmed as being off) take the tape off the choc block and see how it's wired up.

 

[benunited]

Feck, thought you might say that!

Wiring has been a bit ropey in this house.

Traced a cable in my house loft soon after getting here thinking I wonder where that goes. Answer, nowhere, live cable just lying around. Taped at the end right enough but still just a live cable with nowhere to go.

Thing is, a builder lived here before me. Not sure if I should or shouldn't be surprised

Thanks for the advice. I'll try what you suggest

 

[JohnW2]

I can't see how that PIR works without three wires + CPC (earth). Uh no, please tell me the previous installer didn't use the CPC as a live conductor?!

Why (for basic operation) three wires? Surely all that is needed is a permanent L and N feed to the PIR and then switched L (switched by the PIR) and N from PIR to each of the lights - or have I missed something?

Kind Regards, John

 

[sparkwright]

I can't see how that PIR works without three wires + CPC (earth). Uh no, please tell me the previous installer didn't use the CPC as a live conductor?!

Why (for basic operation) three wires? Surely all that is needed is a permanent L and N feed to the PIR and then switched L (switched by the PIR) and N from PIR to each of the lights - or have I missed something?

Kind Regards, John

I think I may be missing something...

If there's one cable at the PIR, you would need three wires at the PIR, plus an earth wire.

A permanent live, a switched live, and a neutral. With one cable at the PIR, this cable would go back to a junction box, or a joint within the light or light switch.

That said, I believe there are PIRs that don't require neutral, but I've never seen one yet.

 

[JohnW2]

I think I may be missing something... If there's one cable at the PIR, you would need three wires at the PIR, plus an earth wire.

You would. Maybe the mistake is mine, in believing the diagram we were shown, which seemingly shows three cables at the PIR (a feed, plus one 'output' to each light):

Untitled

• JohnW2
• 1 Dec 2014
• 1

Edit: ... or, on second thoughts, maybe that 'blob' is the JB (rather than the PIR, as I had assumed) - in which case you would be right!

Kind Regards, John

 

[benunited]

Hi folks,

The black 'blob' in the diagram is a junction box - kind of.

At least that's where the four cables converge and are wrapped in electrical tape. I think it may actually just be connectors rather than a junction box.

From the 'blob' there's three cables. One to a light, another to a light and the other to the PIR.

Thanks

Ben

 

[sparkwright]

If, with the power off, you look at the joint you describe, and determine where the PIR wires connect exactly to the other wires, then we will know how the PIR was originally connected.

 

[JohnW2]

The black 'blob' in the diagram is a junction box - kind of. .... At least that's where the four cables converge and are wrapped in electrical tape. I think it may actually just be connectors rather than a junction box. ... From the 'blob' there's three cables. One to a light, another to a light and the other to the PIR.

Thanks for clarifying - my mistake!

In that case, ekmdgrf and sparkwright are right. For it to work, there would normally have be three wires (plus earth) from PIR to that sort-of junction box. As ekmdgrf said, it is possible that the earth of 2-core+earth cable has been used as a live conductor (very naughty/dangerous) and just about possible (although I think very unlikely) that, as sparkwright suggested, the PIR does not need a neutral.

What sort of cables are we talking about - normal house wiring cable ('twin+earth' - two wires plus a bare earth wire) or flexible cable (with three insulated wires)? If the latter then, if the earth (green/yellow) one has been used as a live conductor, that would be slightly less naughty than if it had been T+E cable!

Kind Regards, John