PIR v Dawn Dusk

Someone recently described a 500w PIR flood light as "fixing a half bar electric fire outside".
Which has got me thinking. Especially given the unreliability of 500w halogen lamps/lights.
So, given the choice between a 500w PIR halogen & an 11w CFL dawn dusk light - which will be cheaper to run?
Obviously an 11w CFL dawn/dusk will be on for a much longer period, but is low energy, won't be triggered randomly & will have a longer service life PIR lights being a PITA IMO (sorry Rob)!
On the other hand a 500w halogen PIR in theory will be on for much shorter periods, but will consume much more power.
Again in theory an 11w CFL could be on for 45 times as long for the same energy.
So which one is the best deal for the customer?
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Dave - The Medway Handyman
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Depends what the customer wants. However, if an 11W CFL is good enough for the customer, a 500W halogen was never required in the first place. An 11w CFL is nearer to a 40W light bulb.
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Andrew Gabriel
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Andrew Gabriel wrote:

I find people have two thoughts on this. One is security lead, "a light switching on will deter burgulars", the other is convenience lead " if we/visitors arrive after dark there will be a light on".
I'm starting to think dawn/dusk meets both criteria. Just wondering about the energy costs.
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writes:

Get yourself off to B&Q, they sell a 500w style light which uses a fluorescent tube. You should be able to work out how much a light will cost to use. If someone fitted a small 11w light as a security light for me, I would ask if they were being serious. You look out of a window and see how much the small 11w lamp will light a garden compared to a 500w light. You can get a smaller 150w if you prefer.
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I fitted a 150w one about 4 years ago. It's still on its first tube. I estimate it's powered up about 30 minutes/day max during winter months. It would be worth trying to estimate how often it would be triggered and how long, once triggered, it would need to stay on for.

A 150w one?
[snip]

It's surprising how well a 150w one works ... unless you need it to cover a very large area.
Barry
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john wrote:

I'll have a look, thanks.

I have an 11w dawn/dusk light outside the front door, it does the job of illuminating the area.

150w seems to be the way forward - when I can track down a make that uses a relay.
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Homebase seem to have the best range of outdoor lighting I've seen so far. My local one had about 20 different models. I'm very pleased with the three "Dark Skies" ones I put on the back of my house a few weeks ago.
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You should really be using separate PIR and light, because they almost never want to go in the same place -- the light should be high up (particularly the type you are talking about), but the PIR should be low enough to have a sweeping view of the area covered. The separate PIRs are more professional devices which are more likely to contain relays. The combined lights/PIRs are cheaper products aimed more at the DIY market.
Two that I have used are these, and they both contain relays: http://cpc.farnell.com/jsp/search/productdetail.jsp?sku=SR00199 http://cpc.farnell.com/jsp/search/productdetail.jsp?sku=SR00915
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Can also fit a 300W lamp in a 500W fitting , they`re the same length.
Been told by local Crime Prevention Officer that PIRs are preferable in some circumstances because they change and alert anyone nearby that there is movement. Constantly on light just becomes part of the scenery.
11W CFL is fine for your porch it dosen`t cut it for lighting an area.
Have a few PIR floods lighting a lane/yard and quality does seem variable, B&Q Parkhurst are absolutely the worst had to change couple of them in last year. Homebase one seem to have lasted well.
Reccomend putting a little bit of copper grease on the front glass securing screw, helps when changing lamps, no more seized on glass.
Adam
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And 200W, but they're harder to find.
There are also energy saving versions -- 375W instead of 500W, and 225W instead of 300W. These have an IR reflective coating on the inside of the tube to reflect heat back on to the filament to enable it to reach the same temperature by using (and wasting) less power, whilst giving off same amount of light. These are also hard to find -- I have bought them in B&Q, but they don't often have them in stock. (I suspect the problem here is that people interested in energy efficiency wouldn't use halogens in the first place, so there's a rather small market interested in energy saving halogens.)
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writes:

If people believe a cheap PIR will deter burgulars then invite them to look at having proper window and door locks fitted and tell them to use them. Dave, you could make money fitting good locks not crappy PIRs (or both)
Adam
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A fire tends to be left on, a light doesn't unless there is lots of activity or it is faulty.

I have never known them to be unreliable, it's usually people don't know how to fit them or wire them.

Who cares, I would prefer a nice bright light rather than one that uses 11w and stays on.

No one will take any notice of a small 11w light.

Only while it is on.

So get a huge LED type which will use a lot less than 11w. You might need to make it yourself.

The cheapest one which is a 500w. It's more effective.

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On 6 Jan, 00:39, "The Medway Handyman"

PITA is hardly a technical term, Dave ! Apology accepted in good grace :>)
But every so often some one has to tug on the strings a little to remind the 'technical and professional' on their language !
Rob
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I would use dusk to dawn lighting myself. That would be on for near enough 5,000 hours per annum, which would use the same electricity as a 500W PIR controlled lamp running for 18 minutes each night. So.it all depends upon how often the PIR is likely to be triggered and how long it is set to be on for when it has been triggered.
....

Another consideration is that the PIR triggered light shows that there is movement in the area. On a patrolled factory estate, that can draw the attention of the guard from quite a long way off, so the application is important in deciding which is the best to use.
Personally, I prefer to have low power lamps on at all times. PIRs can be fooled, but an always on light leaves anyone trying to break in constantly illuminated, which is a useful deterrent in itself.
Colin Bignell
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Thats the info I was looking for. I reckon thats a good case for dawn/dusk.

True.
Good point.
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Dave - The Medway Handyman
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Just to spoil things, we have both, two 18W CFL dusk to dawn lights in the garden one at the back door and one on the side of the shed at the bottom of the garden, this provides sufficient lighting of the garden but nothing too bright to annoy the neighbours, it removes all the dark spots and as such there is nowhere to hide. Then we have a 150W halogen floodlight with PIR, so if someone was to enter the garden and approach the house this provides more lighting and acts as a detterrent, with nowhere to hide, perfect for keeping people out! Also when we are having a BBQ the garden is nicely lit without the harshness of a 500W spotlight.
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