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PIR Light Wiring

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#1 SimonH


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Posted 29 September 2013 - 10:32 AM

Yawn... yes I know - newbie... same old question... etc etc. But if someone could humour me I'd be grateful. I'll try to be brief.

I replaced an old outside light with new inc integral PIR sensor which seemed to work fine but now after a few months does not.

The switch inside has red in, red L1 out and black looped through from the cable/switch next to it. however the cable outside has 1 red and 2 black, no earth. The light obviously has a block with E N L and LS, the LS being only used I presume to connect the Pir to the bulb 'internally' as it were.

Problem is the light does not come on at all or (as a test) stays on permanently if i connect the red live to LS. Faulty sensor already maybe?

Sadly I can't trace the wiring easily as it seems to go via an inaccessible void in the porch roof space.

PS hope to be an active member as have a few houses to manage and maintain. ;)


Edited by joiner, 29 September 2013 - 11:25 AM.

#2 jsharris


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Posted 29 September 2013 - 10:54 AM


Sounds like a faulty sensor. I've had a few of these fail over the years (in fact the one outside my garage failed again last year and I've still not got around to replacing it). It should be earthed, and the normal feed to one would be a bit of 1mm² or 1.5mm² twin and earth, with the live switched from an internal wall switch if it's been converted from a switched outside light (although my personal preference would be to wire it from a double pole isolator switch).

It's unlikely to be a wiring fault if the light was working and now isn't, but the lack of an earth is worrying, unless the whole light and sensor has no exposed metal parts and is double insulated (shown by a box within a box symbol on it somewhere).

The wiring convention for these is that L is the live feed in, N is the common neutral, E is the earth and LS is the switched live output to the bulb. Connecting the incoming live to LS would bypass the PIR switch (which is usually just a relay inside the sensor part, operated by the PIR sensor) and put the light on all the time.

Edited by jsharris, 29 September 2013 - 10:54 AM.