# LED- MH "equivalents"



## erics37 (May 7, 2009)

Yeah I haven't been impressed with the "standard" conversion ratio. I think next time I do an MH-LED conversion I'm going to take the suggested wattage ratio and just double it.


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## electricalwiz (Mar 12, 2011)

Honestly said:


> So I have a possible job replacing 22 175MH wall packs with LEDs. Looking at the RAB website, they said the 26w replaces a 175w MH. So I pulled up comparisons on their EZ Layout tool. My application is 30' height. MH was 2-4 fc up to 15' out. The brightest the 26w LED got was less than 1 fc. Does not seem very comparable in my book.
> 
> I asked one of their "specialists" and he advised to go up to 52w. Pulled it up and still less fc's on the 52w LED.  Any lighting gurus out there able to explain this to me?


LED is a direct light, you would be better putting up an induction wall pack


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## Honestly (Feb 3, 2011)

electricalwiz said:


> LED is a direct light, you would be better putting up an induction wall pack


They are using it more as a wall mount area light, so high mount full-cutoff. Why exactly would induction work better? I have not used induction yet.


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## electricalwiz (Mar 12, 2011)

Honestly said:


> They are using it more as a wall mount area light, so high mount full-cutoff. Why exactly would induction work better? I have not used induction yet.


A better light output with more lumens.
If you have a 175 watt MH a 100 watt induction is more than enough light, you may even be able to go down to a 70 watt induction.
Look at MHT lighting, or PM Dnkldorf he can sell them to you plus explain more of the benefits of induction


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## mbednarik (Oct 10, 2011)

I have used the RAB 52 watt fixture, They are comparable to a 175 watt MH. Buy one and replace it and see what it looks like. The 26 watt i great for the lower mounting heights but the 52 does great at that height.


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## Lighting Retro (Aug 1, 2009)

I've heard it explained that LED's don't register on foot-candle meters as well as other light sources. Not sure, but they always start to go into scotopic vs photopic when the numbers don't match up. I don't feel that inspires customers, but visually sometimes there is a noticeable improvement with lower foot-candles.


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## Electric_Light (Apr 6, 2010)

Lighting Retro said:


> I've heard it explained that LED's don't register on foot-candle meters as well as other light sources. Not sure, but they always start to go into scotopic vs photopic when the numbers don't match up. I don't feel that inspires customers, but visually sometimes there is a noticeable improvement with lower foot-candles.


It's called masking up objective shortcomings with anecdotal sales BS.


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## HARRY304E (Sep 15, 2010)

Electric_Light said:


> It's called masking up objective shortcomings with anecdotal sales BS.


:laughing::laughing::thumbup:


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## vinister (Apr 11, 2012)

leds emit a much narrower spectrum of light than other bulb types. Simple as that. MH bulbs emit a ton of light in frequencies that are not useful for visible light, but still register on your meter. 

What they are telling you is that the LED light puts out as much light as the MH in the frequencies that matter to human vision. Theoretically, they are correct. Subjectively.... well...


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## Electric_Light (Apr 6, 2010)

vinister said:


> leds emit a much narrower spectrum of light than other bulb types. Simple as that. MH bulbs emit a ton of light in frequencies that are not useful for visible light, but *still register on your meter. *
> 
> What they are telling you is that the LED light puts out as much light as the MH in the frequencies that matter to human vision. Theoretically, they are correct.


Then, your meter suck. Lumen is an arbitrary unit that is weighed to typical response of human eyes, therefore, a high quality light meter like Gossen Mavolux (which is about a grand) is standardized to the IES accepted spectral response of human eyes. 

Look into your TV remote's LED with your digital camera. You can see it come on even though you can't. This is because of difference of spectral response between the CCD and our eyes. Properly made light meter is designed to ignore and not register these value through optical and electronic filters. 



> *Subjectively*.... well...


Then, you create a story tailored to your economic interest in the same way used car salesmen do to close the sale.

All those scotopically enhanced has nothing to do with with LED or "induction" technology. It has to do with the difference in human eye response curve depending on light level. MH is available in 6500K+ as well. So, it needs not be LED or RF excited fluorescent to have a higher S/P ratio to compensate for lack of recognized photopic lumens. 

If you replace the 18W 2700K CFL with a 6500K one, by the reasoning of LED and induction marketeers, you've dramatically increased the "output" by claiming scotopic enhancement. These sales people incorrectly attributes this as a merit of LED/induction technology though.


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## Spark Master (Jul 3, 2012)

Check out a newish 7/11. They have impressive LED lighting. While the others I have seen do not really impress me at all.


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## Electric_Light (Apr 6, 2010)

Spark Master said:


> Check out a newish 7/11. They have impressive LED lighting. While the others I have seen do not really impress me at all.


That doesn't show if they're really impressive from cost and energy consumption level. 

The LEDs they use at 7-11 is such a hard light that it casts a very strong shadow.


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## bullmike (Jun 13, 2011)

A utility rep that was at my facility told me that the LED cost vs. MH is still way off . That LED is still too high to change to for the tax incentives.


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## Electric_Light (Apr 6, 2010)

Have a look at this. Not a huge power reduction, but 30W per fixture.
http://www.usa.lighting.philips.com/pwc_li/us_en/connect/tools_literature/downloads/411074.pdf

The idea behind these lamps is that they can get away with lower wattage because the ceramic arc capsule don't decay as rapidly as quartz capsule. The 145W one starts at 93 lm/W and drops to about 65lm/W at end of 20,000 hour rated life. 

http://www.usa.lighting.philips.com...ture/downloads/Gas_Station_Brochure_FINAL.pdf

http://www.usa.lighting.philips.com/pwc_li/us_en/connect/tools_literature/downloads/p-6000.pdf


You don't necessarily have to go with these, but when you're looking at LEDs, a fair comparison is the latest technology in HID with fresh lens and reflectors. 

Brand new LED fixtures against near end of life yellowed out lens with decayed quartz MH don't cut it.

"26w replaces a 175w MH" 
Totally dishonest without explicitly telling how they came up with that and the reasoning behind it must be reasonable. 
Let's assign some pathetically low value for MH, say 25 lm/W. A possible figure for luminaire efficacy when taking into consideration the lamp that is near end of life, yellowed to hell lens and dirty reflector. 210W input x 25 lm/W = 5250lm

5250lm/26W =202 lm/W. Ain't happening.


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## Honestly (Feb 3, 2011)

I am thinking about getting the 52 watt and doing some real life comparing. The real savings for them will come in maintenance. They are paying like 5k/yr right now just for bulb and ballast replacement. Those RAB LEDS advertise 100,000 hr @ 70%.


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## Electric_Light (Apr 6, 2010)

I don't like the way they present specs. It's unconventional and ambiguous as heck. They don't provide any information on fixture efficiency. 

For lighting design, electrical efficiency of ballast is usually not discussed. I've no clue why they include it. What's relevant is ballast factor and input watt. 

Lamp output x fixture efficiency / input watt = luminaire efficacy and that's what matters in the end. 

What they are providing appears to be lamp-ballast system efficacy, which does not factor for fixture efficiency. 

http://www.rabweb.com/specSheet.php?product=AJH150FXPSQW
Their own 150W MH wall pack. 
185W in 14,000 lumen out at lamp. 
Let's just use 60% utilization and you're still at 8,400 lm. 

http://www.rabweb.com/product.php?product=WPLED26
Anyways, they claim:
" Equivalent to 175W MH wallpack " 
30W in 1816 lm out at (fixture, or the lamp source? ) 
Let's be generous and give 'em 1816 lm out the fixture. 

They fail to explain industry accepted equivalency between these two. If you were to use cherry picked mounting height and beam hot spot and apply the "scotopic" multiplication factor, you might possibly perhaps come up with similar "fc values".

Use honest fc based on photopic lumens. Does it really surprise you that you can't equal a fixture with a 14,000 lumen source with a fixture containing a 1816 lm source?


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## Electric_Light (Apr 6, 2010)

Honestly said:


> I am thinking about getting the 52 watt and doing some real life comparing. The real savings for them will come in maintenance. They are paying like 5k/yr right now just for bulb and *ballast replacement*. Those RAB LEDS advertise 100,000 hr @ 70%.


switching topic from objective performance...

What's the age of the existing system? What makes you think that LED drivers are not going to experience failure as the fixtures approach similar age, or that they're more reliable than MH except for MH relamping?

What does their "warranty" cover? On-site, parts and labor? Are they going to replace all affected fixtures if for some reason the output permanently falls below70% during 5 year period?


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## Honestly (Feb 3, 2011)

Electric_Light said:


> switching topic from objective performance...
> 
> What's the age of the existing system? What makes you think that LED drivers are not going to experience failure as the fixtures approach similar age, or that they're more reliable than MH except for MH relamping?
> 
> What does their "warranty" cover? On-site, parts and labor? Are they going to replace all affected fixtures if for some reason the output permanently falls below70% during 5 year period?


I am by no means an expert in lighting design...
The current system is probably 20+ years old.
I would LOVE to hear some real world examples concerning driver life from people who have done LED new or retrofits.. Of the two fixture models that I am considering, by RAB and Lithonia, neither gives any specifics that I have found as to expected driver life. They both offer a 5 yr warranty on the drivers, which seems to match the longest warranty of MH ballasts. I am contacting both companies to try to get more info.

Both warranties are standard fixture replacement warranties, no labor.

I am glad you asked these questions, as I realize I need to do a little more research on driver life to give the customer an accurate cost analysis.


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## Honestly (Feb 3, 2011)

Lithonia responded with expected driver life of 50,000hr.


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## Electric_Light (Apr 6, 2010)

Honestly said:


> Lithonia responded with expected driver life of 50,000hr.


About the same quoted for fluorescent ballasts. Obviously, this greatly depends on the case temperature. 

Electronics in LED system probably live an easier life as they're usually fitted with massive heat sink fins. 

The power supply on computers live a fairly easily life as well as they're fan cooled.


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## Steven Rothschild (Nov 7, 2012)

*LED Conversions*



Honestly said:


> So I have a possible job replacing 22 175MH wall packs with LEDs. Looking at the RAB website, they said the 26w replaces a 175w MH. So I pulled up comparisons on their EZ Layout tool. My application is 30' height. MH was 2-4 fc up to 15' out. The brightest the 26w LED got was less than 1 fc. Does not seem very comparable in my book.
> 
> I asked one of their "specialists" and he advised to go up to 52w. Pulled it up and still less fc's on the 52w LED.  Any lighting gurus out there able to explain this to me?


Rules of thumb being tossed around are divide the MH by four. That is possible because the led is directional while the MH throws light everywhere and consequently is not as efficient. Also the CRI is much higher and the Kelvin too if the job can handle a higher Kelvin. Of course this is a very general rule a lumens per watt and efficacy of the luminaire will vary depending on the LEDs and the luminaire design. 

A light meter will not measure LED light effectively so don't bother going there. Also, a human can't see a 10% or less lumen variance, and an old MH is not putting out anything near what a new lamp would due to significant lumen depreciation with the technology. 

My preference is to keep the wattage difference to 2 or a little more and definitely less than 3 and . If you are converting from HPS to LED you can divide by 4 and it will be better just due to the CRI. 

Again, the quality of the luminaire matters. Many LEDs have 50 LPW. Many luminaires have efficacy of 75%. A 100w luminaire with 75% efficacy and 50LPW LEDs will put out less light than a 100w luminaire with 88% efficacy and 95 LPW.


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## Electric_Light (Apr 6, 2010)

Steven Rothschild said:


> Rules of thumb being tossed around are divide the MH by four.


Maybe according to LED salespeople training sessions.



> That is possible because the led is directional while the MH throws light everywhere and consequently is not as efficient.


Fixture optics in a luminaire is just as important as the lens on a camera. Poor optics used in some fixtures is not a reason to favor LED technology over HID technology.



> Also the CRI is much higher and the Kelvin too if the job can handle a higher Kelvin.


Until recently LEDs were pretty much 6500K range. There are some 2700Ks and anything in between these days though. Both LEDs and MHs come in a range of CRI in 60s to low 90s. 



> A light meter will not measure LED light effectively so don't bother going there. Also, a human can't see a 10% or less lumen variance, and an old MH is not putting out anything near what a new lamp would due to significant lumen depreciation with the technology.


Cover up made up by sales people to mask the fact that their claim is exaggerated. "can't notice 10% or less"... must be used as an excuse to sell something not quite up to par but "yo won't notice it". 



> My preference is to keep the wattage difference to 2 or a little more and definitely less than 3 and . If you are converting from HPS to LED you can divide by 4 and it will be better just due to the CRI.


Total BS. CRI and lumen are unrelated quantities. 



> Again, the quality of the luminaire matters. Many LEDs have 50 LPW. Many luminaires have efficacy of 75%. A 100w luminaire with 75% efficacy and 50LPW LEDs will put out less light than a 100w luminaire with 88% efficacy and 95 LPW.


You're confusing efficiency vs. efficacy. 
LPW is efficacy. Fixture light utilization is efficiency.


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## 10492 (Jan 4, 2010)

Steven Rothschild said:


> Rules of thumb being tossed around are divide the MH by four.



:laughing:

That's pretty funny......


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## Lighting Retro (Aug 1, 2009)

Dnkldorf said:


> :laughing:
> 
> That's pretty funny......


It's probably used more commonly than you think.


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