Light controlled by both switch and PIR

[letshaveit]

I have an outside light that is switched from inside the house but I now wa= nt it to be switched also by an external PIR that runs on 240 volts. I don'= t want to use two-way switches but want to know if its is safe/feasible to = do this ie have the light fitting supplied with two potentially live wires = and two neutrals.

What I want to achieve is the ability to have the light switched on by the = internal switch and left on for say a couple of hours - irrespective of wha= t the PIR does. The internal switch is not intended to over-ride or control= what the PIR does.

[Mike Barnes]

[e-mail]:

Should be OK but just make sure that the switch and PIR are on the same circuit from the CU. Every PIR I've used has a relay (I can hear it click on/off) and that would certainly be OK as you've effectively just got two switches in parallel.

With you so far...

Surely when the switch is on it *does* override the PIR.

[Mike Clarke]

It's quite likely you can achieve this by just adding the PIR in series with the switch. Many PIR's have the ability to stay on continuously by just flicking the switch "off - on" quickly, with some of them you might need "off - on - off - on". It will then stay on until you turn the switch off and then revert to automatic when you switch it on again.

[Yvonne]

What I meant was that if the switch was on, then the PIR could not switch the light off when it was triggered ie it would not act like a two way switch.

[Mike Barnes]

Yvonne :

Fair enough, you should be OK then. I have a similar setup here and it works fine.

[John Rumm]

Yup, easy enough:

[fred]

In article , John Rumm writes

Don't think the article says it explicitly but I think the PIR will need to be a relay based one (ie one with a neutral). The non relay ones self power by dropping a little power from the series connection with the lamp either on or off so bypassing a non-relay PIR with a switch may cause problems.

[John Rumm]

>>> h_PIRs

Yup you are right. Aside from the ones designed to replace a light switch, most of them require L&N and hence are suitable. Even the internal ones built into some lamps can usually be rigged to run like this, although you need to watch the switched load since their relays are usually fairly small.