PIR sensor added to an existing lighting circuit with a isolation switch

justjust1 · Mar 9, 2011

Hi all,

as said in my previous post i am a trainee sparky @ collage doing some work on my extension @ home i have passed my level 2 city and guilds, and am starting 3 next wk.

I have a question! In my garage i have an existing lighting circuit i want to add a PIR sensor with an isolation switch for my outside lighting. When drawing my wiring diagram i got stuck!!!! I want to use Twin and earth because i can tack it directly to the wall but am now stuck with the neutral!!!

If i take the live feed down into the switch then into the PIR thats fine. But then i end up with one (on its own not in gray cable) neutral traveling from the feed into the PIR!!!!!! Hence not looking nice!!!! Am i going to have to wire it with single cable? or can i take the neutral down into the switch and join it with a connector block and send it back up to the PIR using a FCU?

I know this is a possibly a stupid question but am still learning!

yellowvanman · Mar 9, 2011

Not quite sure what you're trying to do exactly but what about 3c and earth cable?

telectrix · Mar 9, 2011

ah. i know what he means. you are thinking of looping in at the light or PIR. there is nothing wrong with feeding L/N to the switch, jointing the neutral in the switch enclosure, then feeding to the PIR , then from PIR to light, all in T/E. your switch should be a FCU, fused at 3A.

justjust1 · Mar 9, 2011

Top draw telectrix, thats exactly what i wanted to know!!!

Just to clear this up, if i use a FCU, i wont have to join the neutral though will i???? as it has a input and load?

If i did not want to do this, could i just use a 1 way switch with a connector block in the backbox joining the neutral or should i defo use a 3 amp FCU?

If that makes sense!!!

Deleted member 26818 · Mar 10, 2011

If you go to the switch first, then you would have to use 2 cables, and join the neutrals with a connector block, or you could use a DP switch.
Another option would be to go to the pir first, and then a switch wire to the switch, or perhaps to a JB or adaptable box and then spider off to wherever.