Query on PIRs ....

[BeeLZeebub]

Could someone please explain the wiring for a PIR to give it an override function? (I'm assuming the lamp is separate and I know most modern units have this function in-built - but this is simply a hypothetical question. I'm a novice but recently replaced a 'modern' PIR lamp and reading around the subject aroused my interest ...)

I've read that one way of wiring the PIR to give it an override function (to allow a flick of the switch to keep the lamp on constantly) is through the use of a permanent live using three core and earth. But where would do you attach the PLive in the PIR?

As I see it, if you attach the PLive to (what I believe is termed) the 'switched live' terminal in the PIR (i.e the 'lamp side' of the PIR, call it L1) then are you not bypassing the switch, resulting in a lamp on constantly regardless of switch position? Alternatively, if you attach the PLive to the live (L) terminal (switch side of the PIR), then surely this is just replicating the switched live, yielding no override?

I've concluded that you must attach PLive to L1, but I cant get my heaad around how this would work. I understand how a PLive works for an extractor fan that stays on after the switch is opened, but this is baffling me .....

Can someone help a layman out and put him out of his misery ....?
Thanks.

 

[EFLImpudence]

You will, in effect, need another switch to connect the PL supply to the SL output of the PIR (or directly to the light}

Whether you use a separate second switch or a switch which can do both operations is up to you.

Most PIRs allow you to have the light on permanently by manipulating the switch in a certain way thus making your query unnecessary.

Untitled

• EFLImpudence
• 16 Sep 2011
• 2

Edit - added diagram - couldn't see one in wiki

 

[BeeLZeebub]

... many, many thanks for that EFL, really appreciated. As I said, I knew the question was academic, but I needed to know !!