Customer wants his commercial parking lot lights replaced, he has 150watt metal halide 15' high, attached to the building (the bulbs & or the ballast are reaching the end of there life span). I suggested LED flood fixtures, he didn't really care but would want a cost and life span analysis (no problem). The problem is a comparable fixture. Seems like a 41 watt led fixture is comparable with 150 watt Metal halide, but the lumens are substantially different. These fixtures are expensive $300-$500 (would love to do the job one time). Is this wattage comparable? any brands liked more than others? Have LEDs been around long enough to depend on them? Thanks for any thoughts
LED floods vs. metal halide
- Thread starter Bam
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- Placerville, CA, USA
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- Retired PV System Designer
The lumen output does not translate to brightness on the ground if the two fixtures have different light distributions. The LED manufacturer may also just be fudging the " comparable" cross references.
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kwired
Electron manager
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- NE Nebraska
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- EC
If he balks at the $300 - 500 initial cost you need to show how much energy differences will be after 5 years, they likely pay for themselves, and in 5 years the MH probably are near need of relamping, the LED is likely going to go for maybe another 5 years yet. But then again, these haven't really been around long enough to know for certain, and either technology will have some that don't last as long and some that last longer than expected.
junkhound
Senior Member
- Location
- Renton, WA
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- EE, power electronics specialty
In addition to the previous valid comments you have gotten:
A concern with LED lifetimes is radiation degradation. Placerville has about twice the cosmic radiation as sea level (at 50,000 feet it is 500X higher!). Needed to research this as put rope LEDs as emergency lights in space station to define the hatch outlines in case of meteor impact and long term radiation a concern there.
Good news though, particle level at 2000 ft altitude is only about 5-6 per cm^2 second, less if the LED are under a rain hood or indoors (e.g. radiation shielding).
It takes about 2 BILLION particles to degrade light output by about 50%. So, say 1 cm^2 LED area, 3 particle per seconds gets thru the fixture, 2 billion seconds = 21 years till light output is cut in half.
On top of that there is the reliability of the power supply, which most LED fixture mfg rate at 25 year MTBF. So, 1/2 your LED will fail due to power supply failure in 25 years, those left will be about 50% output.
You will be lucky to get 10,000 hrs out of a metal halide, say 2-1/2 years of operation. Just on replacement, one could pick a 6X or 7X factor cost of halide lights for the cost of bulbs + replacement labor.
http://nepp.nasa.gov/docuploads/63DDE3EC-93E2-454A-A05BF2DD9F3E0803/Led-99.pdf
A concern with LED lifetimes is radiation degradation. Placerville has about twice the cosmic radiation as sea level (at 50,000 feet it is 500X higher!). Needed to research this as put rope LEDs as emergency lights in space station to define the hatch outlines in case of meteor impact and long term radiation a concern there.
Good news though, particle level at 2000 ft altitude is only about 5-6 per cm^2 second, less if the LED are under a rain hood or indoors (e.g. radiation shielding).
It takes about 2 BILLION particles to degrade light output by about 50%. So, say 1 cm^2 LED area, 3 particle per seconds gets thru the fixture, 2 billion seconds = 21 years till light output is cut in half.
On top of that there is the reliability of the power supply, which most LED fixture mfg rate at 25 year MTBF. So, 1/2 your LED will fail due to power supply failure in 25 years, those left will be about 50% output.
You will be lucky to get 10,000 hrs out of a metal halide, say 2-1/2 years of operation. Just on replacement, one could pick a 6X or 7X factor cost of halide lights for the cost of bulbs + replacement labor.
http://nepp.nasa.gov/docuploads/63DDE3EC-93E2-454A-A05BF2DD9F3E0803/Led-99.pdf
mgookin
Senior Member
- Location
- Fort Myers, FL
- Occupation
- Retired inspector, plans examiner & building official
Hi Bam:
Welcome back to the forum.
It looks like you have 3 questions regarding comparable wattage, better brands and reliability. There are lots of qualified lighting guys on here and you'd likely reach them better by putting this question in the Lighting category.
Anyway, I know a lot about Philips and haven't heard anything bad. Any major brand will have a qualified sales person for your region who can provide more technical information than you want in addition to energy savings predictions. Ask him the questions you asked here and if it makes you more comfortable, come back here and ask others if they concur or if the guy is trying to take your (your client's) money.
Good luck with your project.
We have done a lot of LED conversations for commercial retail stores a few years ago and now we are seeing a ton of these lamps failing. We did not supply the lamps it was from the customer, but these lamps where from the top couple lighting companies. They replace them under warranty, but still after how many I have seen fail I'm on the fence about if I was to supply the lighting.
James L
Senior Member
- Location
- Kansas Cty, Mo, USA
- Occupation
- Electrician
That's good stuff. I have spoken with several manufacturer reps about conflicting specs, longevity claims, etc. I was pretty frustrated with trying to find some high wattage LEDs to replace MH, and was troubled by claims that an LED of 1/3 the wattage could replace MH. I can see 1/3 the wattage replacing HPS because of such factors as S/P ratio and maintained lumens, but an LED replacing Metal Halide is going to have to be watt-for-watt to get the same light output.
That means the customer isn't going to save any money on his electric bill, he's just going to have a gimmick product
But I was also finding too many of them saying they were discontinuing production of some higher wattage LEDs (60+ watts) because of reliability issues. Lower wattage LEDs seem to be doing just fine, though, especially as incandescent replacement
I would be curious what kind of warranty would be offered by the OP if he's the one supplying the fixtures. Every type of light can have premature failure, manufacturing defects, etc. Where are the fixtures coming from - local supply of some sort, or online ordering?
If I were on the hook for warranty work, I would want something that I can get off the shelf instead of having to reorder, ship bad parts, etc.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Once again, there can be enough difference in the light output distribution from the two luminaires to account for some of the difference.
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James L
Senior Member
- Location
- Kansas Cty, Mo, USA
- Occupation
- Electrician
Probably some, but not enough. If the fixtures are barn lights mounted on the wall, then a good 1/3 of the light is shining back onto the building and is rendered ineffective. But if he's got wall packs that's a different story.
Considering that a 150w MH bulb has about 12,000 initial lumens, and a 41 watt LED has about 3,000 initial lumens, I don't see any conceivable way that light distribution is going to make up a 4-to-1 lumens deficiency of the LED
I think I found what the OP is comparing:
http://www.businesslights.com/howard-lighting-lc12-41-watt-led-medium-canopy-light.html
here is a quote from the web page:
LED companies like to "compare" against HIDs with no specifics as to which ones. The claim made on their web page is probably an accurate comparison to High Pressure Sodium because of maintained lumens and S/P ratio of the Kelvin color temp. But that 41w LED fixture is probably gonna look like a punk up against a 150w Metal Halide
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arion
Member
- Location
- sapporo Hokkaido Japan
ive done a lot with led lighting in fact one of my hobbies is building insanely bright flashlights and other optical monsters out of off the shelf leds from mouser .my first and still most powerfull one was made out of 200 10 watt 5000k led emitters. it runs on 3.3 volts dc at 6.7 amps. and without a focusing system on this thing i can light up an area of open space roughly 2 acres deep the entire thing fits in a case the size of a shoebox and can run for days on a 200 ah li ion battery
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