Wiring a PIR (2023 Update)

[Bega]

Your reply on this thread is concise and too the point, unfortunately (for me) that was 4 years and your schematic drawing link is no longer available. Any chance of reposting please pal?

[John Rumm]

Since you have not included any context[1], we don't know who you are replying to, or which diagram you are missing.

Is this what you wanted?

[1]

[alan_m]

[Peter Johnson]

The diagram shows two PIRs on one circuit. Is it possible to connect PIRs on different circuits? (I could find out the hard way, but I thought I'd ask first.)

[John Rumm]

Do you mean PIRs on different circuits, but controling the same lamp(s)?

In which case, no you can't do it directly since at best you would be using a borrowed neutral half the time (and so would trip a RCD / pose a shock risk for someone working on a circuit they think is isolated). At worst then you would be shorting the line conductors of two circuits together. Doubling the threshold at which the MCBs would operate (probably leaving the circuit unprotected from overload and/or unable to clear a fault condition, risking electrocution or fire).

However you could do it indirectly, using relays.

So that the lamp is connected to circuit 1 by the relay switched output of *two* separate SPST relays with their switched outputs wired in parallel. The first relay coil then being powered by the PIR on circuit

1, and the second by a PIR on circuit 2. That way the PIRs never connect the circuits together, and the lamp is always only connected to the L & N of just the one circuit.

The only downside being that the lamp will only operate when its circuit is powered.

(let me know if you want a wiring diagram of that, and I can draw it)

[Brian Gaff]

If you want answers from the wider Usenet, not just the terribly designed home owners club, you have to paste in some of the message you are replying to, or better still find a news server and client software and ignore home owners club as its broken software causes these issues all the time out here. Many now block messages from them. Brian