Old School PIR vs LED Loads

securespark · 24 Aug 2021

Getting my lad to replace some lamps at his Granny's, which are several old school PIRs feeding Aluminium and glass ES bulkheads.

The bulkheads had 100W ES Thorn GLS lamps in, but they have all popped off one by one.

I have an old school PIR (built to control TH loads when LED wasn't a thing) at home controlling a coach lantern with one LED GLS.

Seems to work great every time.

I guess there shouldn't be any issues? I can't find any spec for them to check the loads.

The PIRs are visually like these, but not sure if they are BG brand.

JohnW2 · 24 Aug 2021

securespark said:
.... I have an old school PIR (built to control TH loads when LED wasn't a thing) at home controlling a coach lantern with one LED GLS. ... Seems to work great every time. ... I guess there shouldn't be any issues? I can't find any spec for them to check the loads.

"Old school" PIRs will presumably have a relay output, in which case there would be no problem with very small loads - no different to having your LEDs controlled by a mechanical switch.

Kind Regards, John

plugwash · 24 Aug 2021

If the PIR has a separate neutral supply it will probablly be fine, where you get problems is stuff that tries to power itself by leaking current through the load.

JohnW2 · 24 Aug 2021

plugwash said:
If the PIR has a separate neutral supply it will probablly be fine, where you get problems is stuff that tries to power itself by leaking current through the load.

True, but I don't think any "old school" PIRs did that, did they? Apart from anything else, as I said, they did their switching with a relay, and I doubt that they would have been able to get enough current 'by leakage through the load" to power a relay.

In fact, even 'later', whilst "no neutral" dimmers etc. became quite common, I'm not sure that I've seen a PIR that tried that approach. Ones such as secure illustrated certainly don't.

Kind Regards, John

securespark · 25 Aug 2021

There are, of course, 2 wire passives designed to replace switches. But they're a different kettle of fish, aren't they?

JohnW2 · 25 Aug 2021

securespark said:
There are, of course, 2 wire passives designed to replace switches. But they're a different kettle of fish, aren't they?

Sure -although, as I said, I'm not sure that I've ever seen (certainly never used) one of them. However, as I said, in the case of standalone PIRs like the ones secure illustrated, I certainly don't think you'll find 'no neutral ' ones (and I am not sure that one would very often want one).

Kind Regards, John

SimonH2 · 4 Sep 2021

I have heard of, but not actually used, "no neutral" PIR sensors. As suggested, I suspect they would either not work, or make the light glow all the time, or make the light flash, if used with a low power lamp such as an LED.

JohnW2 · 4 Sep 2021

SimonH2 said:
I have heard of, but not actually used, "no neutral" PIR sensors. As suggested, I suspect they would either not work, or make the light glow all the time, or make the light flash, if used with a low power lamp such as an LED.

Agreed, just as with 'no neutral' dimmers etc. However, I suspect that they only exist as the type designed to replace light switches and, as I said, not in the sort of stand-alone PIRs that secure illustrated. I've used a good few of them, and certainly have never come across a 'no neutral' one. In fact, in the way they are usually/commonly used/connected, the controlled light is usually fed from the PIR unit, so that unit obviously has to have a neutral.

Kind Regards, John

sparkymarka · 4 Sep 2021

JohnW2 · 4 Sep 2021

sparkymarka said:
<a bit of the Clipsal 750 range PIRs>

Fair enough - but what the bit of the manual you posted doesn't tell us is (in context) the important bit about the minimum load for the (no-neutral') 750WP, which it appears is 40W (far to high to work with most LEDs).

Kind Regards, John

sparkymarka · 4 Sep 2021

JohnW2 · 4 Sep 2021

sparkymarka said:
<more bits of the Clipsal 750 range PIRs manual>

I wonder how long ago that was written? - it seems a little surprising that a whole page of text about 'low lighting loads' does not even mention LEDs!

I also wonder how the 'minimum load current' of 20mA in the bit you've just posted sits with the 'minimum load' of 40W (about 174mA at 230V) in the bit I posted!

Kind Regards, John

sparkymarka · 4 Sep 2021

I used to fit loads of the 3 wire versions about 10-15 years ago , fantastic pirs 18m range didn’t false alarm but it’s hard to get them in the uk now

JohnW2 · 4 Sep 2021

sparkymarka said:
I used to fit loads of the 3 wire versions about 10-15 years ago , fantastic pirs 18m range didn’t false alarm but it’s hard to get them in the uk now

As I said, I've also fitted many similar 3-wire ones, but not that make.

Kind Regards, John

securespark · 7 Sep 2021

Well, me and son number 2 went round fitting 13W ES LED GLS lamps and they all work.

There are two not working: I only bought 6 and there were 7. The other is a BC.

One PIR needs replacing as the Fresnel lens is broken, but the unit is still working.

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Old School PIR vs LED Loads

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