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LED light development

Posted by ready2remodel (My Page) on
Sat, May 19, 07 at 12:55

Thanks to Davidr for your informative posting and for the link to Don's amazing web page http://members.misty.com/don/light.html

We are just about to start a remodel of our kitchen and want to "do the right thing" in lighting, so we looked at LED recessed can lights at a local "green building supply" retailer. In contrast to postings on this forum, we found a warm light fixture in the retailer's showroom that looked really bright! Could it be true that the technology has succeeded?! Of course, the sticker shock
factor on the price was definitely there. The lights
I am referring to are part of a lighting group called
"Enbryten LED Lighting" manufactured by a company by
the name of Permlight. Here's a link for your
benefit:
http://www.permlight.com/productlist.asp?catid=52
As Don pointed out in his site, the manufacturer describes brightness as a comparison to incandescent bulb equivalent output rather than using lumens. We are trying to grasp what this will mean in reality as we are by no means lighting experts. Anybody familiar with this light or any LED products that would sufficiently light a kitchen while saving energy? We are also thinking of using an "instant-on" type of CFL for pendants over the center island. Another thing we saw with our own eyes (my DW is about to kill me for putting a CFL over the computer desk. She says it takes forever to get bright enough).

Thanks, all.


Follow-Up Postings:

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RE: LED light development

The trick of LEDs is that they always look bright. That's their characteristic. As I've said here before, you need brightness when you need the light to be seen. You need illumination when you need to SEE THINGS BY the light.

The lumen output is what counts for home lighting. If the manufacturer doesn't specify lumen output, then it means he has something to hide.

If I'm reading the Permlight cutsheet right (and someone please correct me if I'm wrong), the zonal lumen summary indicates that the lumen output of this fixture is all downlight and amounts to about 308 lumens. That's equivalent to about a 30 watt incandescent light. Is that enough for you?

They claim an efficacy of 46 lumens per watt for the 3500K version. That doesn't agree with the figures above (I get half that, about 23 lumens/watt, pretty dismal). But even if we believe their figure, it's still significantly lower than compact fluorescents, which are in the 60 lumen per watt range.

I also note that the CRI (color rendering index) is given as a fairly mediocre 75. Most compact fluorescent are 82 to 86 CRI.

So, no, I don't think this is the breakthrough we're all waiting for. I think it's just fanciful ad copywriting.

Here is a link that might be useful: Permlight cutsheet


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RE: LED light development

Oh, man! That's discouraging. But what great information. I couldn't even find a cutsheet, so thanks for taking the time to dig it up. With our new kitchen remodel, we have been trying so hard to be environmentally conscious (Energystar appliances along with, we thought, LED lighting). You may have just saved us a bunch of frustration (not to mention money) as we are planning to put recessed lighting throughout the kitchen (with 2 or 3 pendants over a center island w/ drop-down table attached). Lighting is so important in a kitchen. I am leaning away from CFL's due to the mercury content. So, it looks like we'll go traditional incandescent (or halogen?) for now and hope that someone develops a "realistic" LED light that can be retrofit so we can do something to help reduce energy use/global warming. Again, MANY thanks. I'll be interested to see if anyone else benefits from your information or has additional thoughts on our lighting options.


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RE: LED light development

I am leaning away from CFL's due to the mercury content.

Mercury is nothing to take lightly, but in fact the mercury content of fluorescent lamps has been going down for years and is now quite minimal. Several types such as the Philips Alto range are so low in mercury that the EPA has approved of their disposal in landfills. (I don't agree; see below.)

In fact, in most areas of the nation, by using less electricity, CFs save far more mercury from powerplant emissions than the mercury they have in them. If you dispose of them responsibly at your area's household hazardous waste disposal facility, you've released almost no mercury into the environment.

Really, there's seldom much justification for using incandescents. We're talking about a technology that's over a century old here! Incandescents are much better heaters than light-makers - in fact the only time they might be useful is when you're heating your house with electric resistance heat, because in that situation you get the light for free. (Of course you should stop using them in the summertime.)


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RE: LED light development

While I'm not as vehemently anti-incandescent as David is, I've got to agree that the statements "trying so hard to be environmentally conscious" and "it looks like we'll go traditional incandescent" don't belong together.


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RE: LED light development

Just googled Alto. Dimmable, rapid start, non-hazardous waste. Wonder when they'll be available here (in Australia). Sigh.

Thanks for the info on LED's. DS said that's where it's heading so I'm always interested to find out what's happening with them.


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RE: LED light development

David:

I have been considering these downlights for my kitchen, too, and am interested in your responses in this thread. Below is a link to a DOE publication that I believe reviews the LED fixture we are talking about.

It seems that the LED lamp is rated at over 40 lpw, but the luminaire, itself, is rated at about 20 lpw. That would explain the discrepancy in Permlight's cutsheet. However, I'm confused. If the Lamp is rated at 40 lpw, how does it lose efficacy when it's used in the luminaire?

TIA.

Here is a link that might be useful: Dept of Energy Publication on LED Downlights


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RE: LED light development

Part of the problem is that the LED manufacturer has provided incomplete information.

Notice that in the column for "Rated lamp lumens," under the LED light, the DOE document has "unknown." The manufacturer doesn't specify this figure. They do, however, give a specification for efficacy in lumens per watt. It looks as if that's what the DOE is quoting two rows below that.

In most cases a luminaire (what most of us call a "fixture") absorbs some of the light in its housing and/or lens. That's what the efficiency percentages are about, and that's why the figures for the luminaire efficacy are lower than the figures for the lamps themselves.

There's no spec for the LED luminaire efficiency.

What we do have is a lumen output spec for the entire unit (300 lumens, about the output of a 30 watt light bulb), and a power requirement spec for the entire unit (15 watts). Hence the real-world efficacy of 20 lumens per watt, a pretty mediocre showing for such an expensive fixture.

What causes the discrepancy? I hate to say it, but my guess is that the manufacturer is fudging a bit. Not exactly lying, just stating "best case" numbers.

They may be calculating the higher l/W figure from the output for one LED element by itself, in perfect temperature and electrical conditions, when it's brand new (it will dim over time), and in free air or even with air circulation for cooling, and not installed in the fixture.

Once it's fitted to the fixture, conditions are never optimal. Temperature regulation is a problem and may require a reduction in forward current. The power supply may not be stable enough to operate the elements at their most efficient point. The elements may not be well matched in their electrical characteristics, so at best only one can be set up to operate at peak efficiency.

There's also bound to be some absorption of light output by the fixture itself, because of the way the LEDs are mounted, and the way their light is diffused by the lens.

The LED light does have some advantage in lamp life. It's rated 40,000 hours; a typical CF will last between 10,000 and 20,000 hours. If relamping is a serious problem (say if the fixture is 20' up and located over a stairway) this might be a good fixture to use. The length of the payback would depend on your costs to relamp. Most home users would probably never see any payback at all.

Don't misunderstand me. I sound like I'm dismissing LEDs, and I'm not really. There are things LEDs do well. Their brightness makes them outstanding as indicators (traffic lights, auto tailights, appliance pilot lights). They often beat out tiny, low output incandescents (flashlights, Christmas tree lights, maybe night lights) in efficiency. They're good where colored light (red, green, yellow, blue) is what you want. For these applications, LEDs are often the ideal choice.

But in their present form, using LEDs for general home or office lighting is like trying to drive from Boston to LA in a golf cart. With extraordinary effort, you can do it, but it's not really the right tool for the job.


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RE: LED light development

I have to say I've learned more from Davidr than from some classes I've taken! I really like your Boston-LA analogy. You have me convinced that the CF is a great compromise of my conscience with functionality. And I am definitely the type to dispose of flourescent bulbs properly. Do the CF bulbs require a special fixture?
Many thanks!


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RE: LED light development

Do the CF bulbs require a special fixture?

Only if you live in California. ;-)

Everywhere else, you can buy almost any incandescent fixture you like and retrofit with screw-base CFs. The retrofit CFs have gotten so small that they fit almost any fixture. If in doubt, take a couple CFs along to the lighting store and try them in various fixtures.


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RE: LED light development

David,

Did you notice the other active threads about CF's? They seem to agree with your comment about fixtures, but note that there aren't switches that are UL listed to dim CF's. You probably already know this, but thought I'd give you a heads-up just in case you didn't see them.


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RE: LED light development

I thought I'd seen most of the recent threads. Did I miss something?

From what I've seen, dimming is coming along fairly well with CFs. You can now get pretty good dimmable retrofit CFs, ones which work nicely with ordinary triac dimmers.

I'll admit, it seems as if the retrofits are always a couple of years ahead of the dedicated fixtures in dimmers - as in almost everything. This may be because they sell in larger quantities so as to justify the development investment.

However, the necessary dimming bits are out there. Dimming CF ballasts are available. It's just that (AFAIK) they all presently require special dimmers; they don't use $5 Home Depot triac dimmers.. And they're not exactly mass market items.

Give 'em a few more years, and I expect that Title 24 will stimulate the competition and production volume. If a couple more states pass legislation emulating California's, things will really take off.

Europe seems to be ahead of us in these kinds of development, probably again because of their expanding energy conservation legislation. There are times that I really wish that the US standard household voltage were 240 volts, as in Europe. I could be wrong, but I think it would be a relatively simple matter to double-list fixtures for the EU and the US if the voltage were the same.


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RE: LED light development

> I really wish that the US standard household voltage were 240 volts, as in Europe

x2. Yes, we wouldn't need separate circuits for 1800w hair dryers. 240V dishwashers could feed off of *cold* water lines and quickly heat their own water, still allowing the machine to finish its work sooner. 240v clothes washers fill with cold water (preventing stains from setting) and then use their built-in 2500w heater to quickly heat the water anywhere from lukewarm to near-boiling temperatures if needed for powering out dirt, obliterating any need for caustic bleach in the process. The more common 120V washers either don't heat the water at all (bad for cleaning) or have wimpy 1000w heating elements that lead to 2-hour cycles. A 240V combination washer/dryer would combine faster washing (since it heats the water faster) and faster drying times (since it has twice the wattage for the heating element). Faster charging for future electric cars. We really should start converting over. It'll save us time in the end.

Also, think of how much cheaper and easier working with the thin 240V/7.5A for basic outlet and lamp wiring would be. Power strips for electronics, extension cords for small window a/c units, etc. wouldn't be so thick.

240V rocks.


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RE: LED light development

"240V rocks."

And if you ever get across it you will understand it REALLY hurts.

It is actually pretty hard to kill yourself with 120 V, but 240 V (and not the 240 V Edison circuits we use in the US) is markedly more dangerous.

That is why many countries with 240 V wiring have fuses built into every plug.

It was chosen in countries that did not have copper easily available from mining allowing the use of smaller conductors (but thicker insulation).


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RE: LED light development

I don't see how 240V/7.5A would hurt any more than 120V/15A. "High Voltage" sounds scary, but it's high amperage that's really dangerous if unleashed.

I like the UK setup best, with every outlet fused. Bulky connector plugs are a downside, but it's as safe as electricity can get IMO.


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RE: LED light development

"I don't see how 240V/7.5A would hurt any more than 120V/15A. "High Voltage" sounds scary, but it's high amperage that's really dangerous if unleashed. "

The 240 V doubles the current you have flowing through you compared to 120 V, and it hurts a LOT more.

While current is what kills you still need voltage to drive it though you.

That is why a 1.5 V D-cell that can deliver 5-7 amps is NOT a hazard.

The UK setup is not really any safer, just uses less copper.


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RE: LED light development

Most European receptacles are recessed, and part of the plugs' pins are shrouded in insulation. Both of these greatly reduce the risk of contact with live plug pins. IMO, with those safeguards, their 240v system may well be safer than our 120v one.

That's because virtually all of the common US NEMA plugs, regardless of voltage, don't have any comparable feature. IMO, if those connectors had just been invented today, the company's lawyers would never let them put them on the market. It's way too easy for the user to contact live parts.

It gets even worse when cheap receptacles get old and don't retain the plugs well. Plugs that sag and expose parts of the live pins are a genuine hazard for little kids and pets, and it's also possible (though less likely) for conductive debris to fall on them and cause a short circuit.

But the US plugs are pretty well established, so I don't see them being replaced by anything safer any time soon.


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RE: LED light development

The 120 V system does not need as extensive a set of safety feature.

You have to try pretty hard to touch the blades of a plug while they are in the receptacle deep enough to be energized.

The contacts in receptacles are not that close to the face of the receptacle.

Better is often the enemy of 'good enough.'


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RE: LED light development

Back to the OP - we just put in Cree LR6s in our kitchen and they are fine. Plenty of general light and almost enough that we don't need the under cabinet LEDs that I already bought. We went with the cooler color (3500K?)and its not too blue. The only down side is that they aren't very dim-able but if we are looking for mood lighting we'll use the U/C lights.


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