# T5 Light output over time...



## sanj (10 Jun 2010)

Hi,

I was wondering if anyone has a link to information on T5 light output over time.

I am just testing new T5 lights with a PAR meter and I was thinking, doesnt this light out put drop after the first few weeks and then stabilise? I was wondering roughly how much it was. I have the figure of 10% in my head for some reason.

I will be testing anyway, but I just wanted to know if anyone could confirm. PAR is rather high at the moment in areas.


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## dw1305 (10 Jun 2010)

Hi all,
Electronically ballasted T5's have little attenuation over time, they produce much the same intensity and wavelength of light until they fail. The technical term is the  "Lamp lumen depreciation factor (LLDF)" and it will be in the order of 0.95 for T5's (meaning that they lose about 5% of their brightness during their life). 

Metal Halides and most other discharge lamps have much quicker depreciation, but then have a long period (thousands of hours) after the end of their rated life where the value plateaus and only subsides very slowly. Low pressure sodium lamps (the yellow street lights) for example don't show any LLDF, and some of our high pressure sodium grow lights have lasted for c. 50,000 hours.

This graph doesn't have T5's on it, but they would be better than T8's by about the amount that T8's are better than T12s (the improved efficiency is from a combination of the thinner tube diameter, less mercury and the electronic ballast).







cheers Darrel


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## sanj (10 Jun 2010)

Thanks Darrel, 

i thought there was a faster initial decline, i,e in the first hundreds of hours, but instead it seems a more steady decline in the first year befrore leveling off.


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## dw1305 (11 Jun 2010)

Hi all,
I think that most of the reduction in light levels is caused by the mercury (from the excited vapour) sticking  to the phosphor coating of the tube, it is the dark staining you see at the ends of old T12 tubes. Via Wikipedia.
http://en.wikipedia.org/wiki/T5_fluorescent_lamp#Energy_efficiency


> The lamp has a coating on the inside of the glass wall that stops the glass and phosphors from absorbing mercury. This barrier coating reduces the amount of mercury needed from approximately 15 mg to 3 mg per lamp. Since mercury absorption causes the lampâ€™s light output to depreciate over its life, the coating helps to keep light levels much closer to initial output......"


cheers Darrel


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## chris1004 (13 Feb 2011)

Hi,

Just been looking for some info on fluorescent tube life span and came across this informative post.

Most common advice (manufacturers and the MATRIX spring straight to mind) is that you should change tubes every year but looking at the above graph I'm wondering if this is this really necessary? A 5% loss of output on a T5 (10% for a T8) doesn't sound like much at all. 

I've read somewhere that certain parts of the spectrum fail more than others and I've also read some of Clive's posts that detail how the spectrum isn't anywhere near as important as most manufacturers claim.

So I'm guessing that changing the tubes isn't at all necessary until they are about 15000 hours old which at 10 hours a day 365 days a year is about 4 years. That would save me a stack of cash if its right.

Is this then just another example of the matrix selling us stuff that we simply don't need?

Regards, Chris.


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## dw1305 (13 Feb 2011)

Hi all,


> I've read somewhere that certain parts of the spectrum fail more than others


Yes, this is just another part of the matrix, it just isn't true of modern lights. Electronically ballasted fluorescents are good until they stop working. In my opinion a lot of the advertising material from Aquarium light manufacturers is border-line fraudulent and definitely both untrue and deliberately misleading. 

cheers Darrel


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## sanj (14 Feb 2011)

I think Aquatic products are very much in the grip of the Matrix. Its all about knowledge and I dont have enough yet.

In the light of the above, it would seem that the case for LEDs is weakened slightly on the replacement level.

I know you cant expect everyone to buy a PAR meter, it is certainly not necessary, but I am using mine to keep check on that parameter at least. More sensible approach would be to stay in tune with your tank and notice the changes.


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## GreenNeedle (14 Feb 2011)

On the replacement times it is 5% dropff for flouros on electroic ballasts over the first 40% of life.  Then you have to weigh up how optimistic the manufacturers 'tube life' is.

A couple of years ago I went through all this so I'll dig up the info but the statement I made was something like:

Most macnufacturers suggest something like a 36000 hours life.  Lets say that a conservative reality is 20000.

That means if using an electronic ballast the tube will drop off 5% over the first 8000 hours which is 1000 days.

That means a flouoro tube should last circa 3 years.  Compare that to 7ish years on LEDs.  Then consider you only need circa half the wattage of LEDs to match the flouros.  Thats where the saving is.

A DIY LED unit will cost about twice the price of a DIY flouro unit but you will save half the electricity cost over 7 years plus the LEDs will last twice as long.

No idea on energy costs but I would suggest with LEDs you save money over that 6-7 year period plsu the price of the replacement tubes as well.

I'll find some links and post them up soon.

AC


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## GreenNeedle (14 Feb 2011)

Some of these links may appear to be rants rather than debates but they do have some really interesting detail and not just from me either 

If you like reading this is a good thread.  You'll end up thinking what a moaning old G** I am though. lol
http://www.barrreport.com/showthread.ph ... salers-Rig

And another on TFF:
http://www.fishforums.net/index.php?/to ... -t5-vs-t8/

This is more to do with the subject of this thread:
http://www.barrreport.com/showthread.ph ... geing-T8-s


This took some finding. lol  Half way down the page is the lumens at 40% lifetime graph.  However I would add that lumens drop off being low doesn't mean the actual PAR hasn't dropped further.  I wouldn't think it would however the spectrum may move over time and be outside of the PAR range whilst still being visible?  I don't know on that one.

http://lightingcontrolsassociation.org/ ... lications/


AC


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## dw1305 (15 Feb 2011)

Hi all,
Good post "SuperColey", all the answers are hiding in there, it won't be that long before all lighting is LED's. 

In the mean time any linear electronically ballasted fluorescents look good, if you don't mind trading length of lamp life for brightness then an "ordinary"  T5 or T8 running on the correctly rated soft start ballast (rather than being an over-driven HOT5) will run efficiently over a long time period. The main reason for these lamps increased life is greatly reduced cathode wear from the "multi-pulse" nature of the starting strike. This leads to the other point, the less often you turn the lamps on, the longer they will last. In fact if you don't turn them on at all, they are good eternally, but more seriously a single 8 hour growing period every day will give a longer lamp life than 2 x 4 hour periods.

cheers Darrel


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## chris1004 (15 Feb 2011)

Hi all ,

Thanks for saving me a stack of cash.

I was just about to replace a pair of Dennerle T5 tubes that are just over a year old and would cost in the region of £50 to replace. I can hear Clive laughing already   .But I do like the colour that they give off. Maybe they'll be good for another couple of years yet then.

I'll stick with florescence's for the time being as I already have the starters but if I were to buy some new lighting in the future I'll definitely look into LED's as a very viable alternative.

Its scandalous how trading standards lets these manufacturers claim just what the hell they want to. Surely there are laws against this sort of misleading advertising? 

Regards, Chris.


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## GreenNeedle (16 Feb 2011)

Lol.  If you are using Dennerle tubes and then follow Dennerle's advice then they may last half as long........

..Why?  they warble on about having 2 seperate photoperiods (like the siesta) to emulate tropical thunderstorms. lol.  Therefore that means you turn the light on/off twice a day instead of once (see Darrel's post above.)

Check out their site for lots of other goodies to chuckle at.

Trading standards aren't going to get involved in a subject where even those who are in the hobby aren't overly sure.  Light is one of those blank areas where no-one really knows for sure.  We in the hobby can't agree with each other and it's one of those strange subjects where we the hobbyists are actually the experts.  there is no real professional scientific data applied to aquatic environments within aquariums.  All that we know comes from us and those that came before us.

Similar to that they aren't going to take issue with a fert that says 'Free from Algae causing N&P' because their own government research scientists tell them this is why the rivers, lakes, ditches etc are algae fests 

AC


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## SteveyG (18 Feb 2011)

SuperColey1 said:
			
		

> On the replacement times it is 5% dropff for flouros on electroic ballasts over the first 40% of life.  Then you have to weigh up how optimistic the manufacturers 'tube life' is.
> 
> A couple of years ago I went through all this so I'll dig up the info but the statement I made was something like:
> 
> ...



Don't forget that a WHITE high flux LED will typically drop to 80% over 20000 hours. Coloured LEDs (non phosphor coating) have a better lumen maintenance. 

I have a couple of white Lumileds 1W LEDs in my house that turn on for 10 hours a day have been installed for about five years now, and they are noticeably dim now. Just as a test, I replaced one of them with an LED from the same batch and to my eyes the light output looked to have dropped more than 20%


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## GreenNeedle (18 Feb 2011)

Indeed.  that ties in with the article linked to below where it shows the luxeon 3W light intensity when new and then a projected intensity after 11 years.  Suggests a 30% drop off but of course no-one knows the reality.  I would suggest even the manufacturers/inventors don't know the reality.  they must be testing them for 23:59 hours a day and emulate the on/off over 12 hours periods then after a month or 2 measure and then project from there.

Of course we know that with fluoros it drops slowly and then falls substantially from a certain point. lol

http://www.advancedaquarist.com/2006/8/review2

AC


p.s. Stevey.  Just noticed your sig and read through it.  Great job there.  Making me jealous now


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## SteveyG (18 Feb 2011)

I suspect the lumen maintenance varies substantially between LEDs and manufacturers too. Different phosphors, temperature conditions and intensity of light probably all have significant effects.

In one of the projects at work we are currently using some leading edge high power white LEDs in a medical diagnostics device, and we notice a 25% drop in the number of emitted photons within the first ten hours from completely virgin LEDs. After this initial drop, we see a fairly linear decline, but the numbers seem quite alarming. With closed loop control (a PIN diode servoing the LED current), we have to set a target of 65% of the LED's maximum output just to maintain a constant output over the life of the instrument!



			
				SuperColey1 said:
			
		

> p.s. Stevey.  Just noticed your sig and read through it.  Great job there.  Making me jealous now



Thanks  8)


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## dw1305 (18 Feb 2011)

Hi all,


> I suspect the lumen maintenance varies substantially between LEDs and manufacturers too. Different phosphors, temperature conditions and intensity of light probably all have significant effects. In one of the projects at work we are currently using some leading edge high power white LEDs in a medical diagnostics device, and we notice a 25% drop in the number of emitted photons within the first ten hours from completely virgin LEDs. After this initial drop, we see a fairly linear decline, but the numbers seem quite alarming.


 Thanks "SteveyG", I'm trying to buy some LED growlights and a PAR meter for work at the moment, so this is a very interesting observation. 

cheers Darrel


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