PIR Security Floodlight.

[sg31]

I've had a 20W LED floodlight at the back of the house for a while but it decided to commit suicide recently. It is no more, dead.

There has been a spate of burglaries in the area so I decided to fit a floodlight with a PIR as a deterrent. Job done but unfortunately being an idiot I gave no consideration to the combi boiler flue close to the PIR. Once it went dark, the floodlight was of and on all the time because it was sensing the flue exhaust gases. My own fault I should have thought it through a bit more, I've no idea why I didn't.

Anyway, I can do away with the PIR and just fit a floodlight but I do think a security light would be a good idea. The light is in the centre of the wall about 4 ft above the vent.

How far away from the vent would I need to go to avoid the problem occurring?
What are my options other than a PIR to get the light to come on if some toe rag approaches the rear of the house?
Has anyone any other advice that might help?

[Dorn1]

I'd stick with the PIR floodlight, but move it to avoid the plume from the boiler. How far? - as in "piece of string"! Its the warm moisture cloud that sets of the PIR and that depends on wind direction, strength and ambient temperature. A few meters should be enough, but point/block the PIR so it sees less of the plume, but more of the area of the "threat axis". Hopefully your heating will be off when you need the light to operate automatically. You can also get separate PIR detectors (only) and connect that into the light.
HTH
C

[supremetwo]

What are my options other than a PIR to get the light to come on if some toe rag approaches the rear of the house?
Has anyone any other advice that might help?

LED floodlights with microwave sensors are available from such as CPC/Farnell.

[bungeejumper]

Can't you get floodlights with a remote PIR that can be mounted somewhere else? Not too far away, for obvious reasons.

BJ

[sg31]

Thanks for the replies.

I've been in the garden today watching the steam plume from the boiler as it comes out of the vent in the middle of the rear wall and blows across the rear of the property. At times it was fully dissipated at the corner of the building. I used ladders to get near the vent and the heat seems to dissipate a metre to 2 metres from the vent. OK this was only done by hand so there may be some heat I can't detect.

I understand that the PIR will detect heat, it must be sensitive to detect a human body at 6m or so. Does the movement of the steam also set the PIR of or is it the heat within the steam?

As it stands I don't think a PIR will work because of the boiler vent. Mine can't be the only situation where a boiler vent causes problems with a PIR so I would expect there should be a handy solution.

I've not come across a microwave sensor before and have no idea how they work. If it is just movement sensitive it wouldn't be suitable because there are bushes nearby.

I'll have a look at microwave sensors as a possibility, thanks for the suggestion supremetwo.

[saechunu]

Can't you get floodlights with a remote PIR that can be mounted somewhere else? Not too far away, for obvious reasons.

This is what I have and gives much more flexibility.

You can situate the PIR in a different place to the lamp, and lets you wire more complex setups such as multiple PIRs (positioned in different places) triggering a bunch of connected lamps.

Also gives you flexibility to replace a broken lamp separately from a broken PIR. Plus integral PIRs can sometimes be pretty ropey quality-wise.

I've got a bunch of Friedland Spectra L220N PIRs connected to a bunch of LED floodlights and it works well. There's a lot of adjustment in the PIR direction (L-R and U-D), plus you can block out parts of the coverage. One of the PIRs is pretty close to (faces) a condensing boiler's flue outlet but doesn't get triggered by the plume. Obviously that doesn't guarantee the same for you but at least you can reposition the PIR to wherever you want it to minimise the chance of this. FWIW I never get any false alarms with these PIRs so would use them or similar again.

[csearle]

You can also get separate PIR detectors (only) and connect that into the light.

Just a point, all the LED floodlights I've so far seen with integrated PIRs have a built-in three-core lead (including Earth) and have no way of overiding the PIR with a separate switched feed from a separate PIR.

Chris

[csearle]

Does the movement of the steam also set the PIR off or is it the heat within the steam?

The sensor inside the PIR detector just senses infra-red, i.e. heat. The little white or black screen visible on your floodlight is a lens that concentrates heat impinging upon the screen so that the amount of sensitivity varies depending upon the angle it is arriving from.

So as a cloud of hot steam wafts across the field of sensitivity its heat is effectively modulated because of the lens and causes the amount arriving at the sensor to fluctuate - which in turn sets the thing off.

If it is possible to mount the PIR floodlight a bit below the flue this will probably solve your issue. You might need to run surface trunking (or rewire it) in order to achieve this.

Regards,
Chris

[sg31]

It's not a problem to re-site it below the boiler exhaust. How much below would you suggest?

If that doesn't work I can reuse this light in another area and buy another light and separate PIR to solve the problem.

[csearle]

It's not a problem to re-site it below the boiler exhaust. How much below would you suggest

Well at least 30cm but really as much as you can without compromising the light/sensor coverage too much. By putting it below it remains below the rising steam most of the time. You could observe it and and judge for yourself how low you need to go.

Cheers,
Chris

[sg31]

csearle, thanks I'll see what I can do.

[csearle]

csearle, thanks I'll see what I can do.

Keep us informed, knowledge is power. . C.

[sg31]

Just to say I've not forgotten about this. Life has interfered, as it often does. I will up date when I can.

[csearle]

Just to say I've not forgotten about this. Life has interfered, as it often does. I will up date when I can.

Look forward to it. C.

[beeswax]

I'm thinking of fitting one soon at the rear of my house and wondered if they are all pretty much the same or are there any that stand out as better and they seem to vary a lot in cost too. Does the filament last as long as they say...10,000 hours or summat as that could be a lifetime?

[quelquod]

The 10000 hours is a bit misleading IMHO as it really refers to the LED lifetime in continuous operation. I've seen many of the newer LED floodlights which died a flickering, flashing death after only a few weeks of operation which isn't many hours considering that they're probably only on for a minute or two in every hour at most so reliability still seems to be a bit suspect. I have a couple whose duty cycle is unlikely to be even 1% so 10000 hours is likely to mean literally a lifetime. Generally well before that though either the internal relay will have failed or the lens will have become opaque or some other bit of the electronics will have died so that the thing no longer works.

[sg31]

I've finally had time to play around with this problem.

The light and sensor unit had to go. because of the windows, vents etc it wasn't possible get a suitable position that didn't look odd.

I went for the separate light and sensor ( Friedland Spectra, as suggested by saechunu). The boiler vent is roughly 2.1m above the outside ground level, I tried fitting the sensor 300 mm below the vent but that did allow the vent plume to cause false triggers (for want of a better word) when the wind was light to moderate. The air at the rear is turbulent because of the attached garage and various tall shrubs.

I dropped the sensor to 500mm below the boiler vent and so far everything seems to be working well, no false triggers so far. I was concerned that the sensor was now only 1.6m above ground level, it looks low to the eye but the detection range is perfectly adequate.

The light itself is set at 3m and lights the area well.

Early days obviously, it will be interesting to see what happens on a very windy day, but I'm reasonably happy that the problem is solved.

Thanks to everyone who chipped in with advice, particularly Chris and saechunu.

[csearle]

Thanks to everyone...

Thanks, good feedback, hope it all continues to go well. Chris