T5HO does not degrade as much as we thought?

Discussion in 'Lighting' started by GreenNeedle, 14 Feb 2009.

  1. GreenNeedle

    GreenNeedle Member

    Messages:
    2,706
    Location:
    Lincoln UK
    This is quite an interesting page I found on the subject of lighting very high ceilings but the interesting point is way down on the page.

    It suggests that unlike all other fluorescents T5HO uses a 'programmed start' electronic ballast and will only degrade (lumenwise 5-6%) over its lifetime!!!

    The others are on 'instant start' electronic ballasts or magnetic 'flicker' ballasts which as we know do reduce lifetime.

    It also suggests that MH lights degrade a lot quicker too!!!

    Any thoughts? Please note we are talking T5HO here and not T5.

    White Paper - Fluorescent Vs. Metal Halide in Hi-Low Bay Applications

    AC
     
  2. TLH

    TLH Member

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    186
    Location:
    Northants
    I read something about this a while ago. I wasn't aware that T5HO had to be on a programmed start though. If that's true then good news.

    There are 3 types of electronic ballast though not just the 2 you listed. The types are Instant Start, Rapid Start and Programmed Start. I'm just gonna quote from Wikipedia here...

    Can you post a link to your white paper so I can have a read please.
     
  3. GreenNeedle

    GreenNeedle Member

    Messages:
    2,706
    Location:
    Lincoln UK
    http://www.aboutlightingcontrols.org/ed ... -bay.shtml

    Sorry I copied the title instead of the link in the first post. lol

    This came about because in a post on another forum someone suggested the following to me which I looked at and thought, that is wrong and went about doing some research

    T12 normal output puts out about 87.5 lumens per watt.
    While T5 High output puts out about 103 lumens per watt.

    So while being true that T5 is much more efficient, it certainly wouldn't be doubled. More specifically, after a few calculations I've determined that 1.8wpg of T5 equals 2.34wpg of T12, and about 2.2wpg of T8. Not a significant change by any means, but T5 is definitely stronger, thats for sure. I think the effieciency of T5 over other flourescents has been greatly exaggeratted over the years. Although it is partly true, not to the extent of what it has been told.


    So on lumens per watt after a little research by me.
    I can see from looking on most websites that T12 at best is about 85 and typically between 60 and 85. T8 are about
    90. T5 are about 100-110 and T5HO are about the same as T8.

    This is lumens per watt remember and not lumens per inch!!!!. T5 are the most efficient of the options but you don't get the lumens per inch there. however 2 T5s equal in W to a single T5HO will give more total lumens.

    The interesting point though is we all accept that tubes 'decline in output' through their life.

    This article is trying to explain why tall buildings should go fluoro instead of their old MH units. The MH beats the T5HO to a pulp in output terms when brand new but this article is explaining the 'mean' lumens which is the average through its life. It is fit for our purpose too as this statement taken from the page states:
    An MH will have lost 35% of its output at 40% of it's life whereas a T5HO will have lost 5-6%.

    At 40% of life the following figures are given as the lumens still being emitted as a percentage of the original output:
    MH (probe start) 65%
    MH (pulse start) 78-86%
    T5HO (Programmed start) 95%
    T8 (Instant Start) 95%

    This suggest we could feasibly use any fluorescent tubes on electronic programmed ballasts for much longer than the life we currently give them without a worry!!!

    For example 20000 hours x 40% = 8000 hours. That is 1000 days @ 8hours a day. so after 3 years we have only lost 5%!!!

    What would be interesting would be to see figures for tubes on magnetic ballasts to see their decline. Anothere thing that could be interesting would be to see at what point we actually need to change when we are using electronic ballasts. We can see at 40% we are fine but just how much longer can they go before they reac 90%, 85%, 80% etc?


    AC
     
  4. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

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    Location:
    Chicago, USA
    Andy,
    Lumens are irrelevant and thats just one reason why absolute comparison of T8 with T5 is a murky issue. Lumens is only a measure of the human response to light. Since we are much more sensitive to green wavelengths than to either red or blue this tells us nothing about the actual delivered energy of a bulb. A pink bulb such as a Grolux can output the same energy as a daylight bulb yet will look much dimmer to our eyes simply because the daylight bulb has more green content. The daylight bulb may not deliver any more useful energy to the chlorophyll than the Grolux, even though it will have more lumens per watt.

    Another issue that makes things ambiguous is efficiency, which is really just ratio of output power versus input power. In the case of a bulb, this means the ratio of output radiant power versus electrical input power. The problem here is that commercial rating for bulbs are based on "lumens per watt" which is not really efficiency but instead called "efficacy". Again, this is meaningless for plants.

    The nearest to "absolute comparison" that can be made between bulbs from a plants perspective is to compare the Photosynthetically Active Radiation (PAR) being emitted by bulbs of similar shape. A PAR meter will measure the absolute number of photons crossing a unit area per second at a unit distance from some reference point, most likely from the surface of the bulb or from the centerline of the bulb.

    The same argument applies to "HO" bulbs. Does anyone know, without actual PAR data how a High Output bulb compares to a standard T5? What does "output" refer to in this case? Does this mean high lumen output or high PAR output? As noted above one can achieve high lumen output simply by changing the wavelength output by playing with the phosphor mixture.

    So I've discovered that we need to stay away from lumens. They confuse the issue because lumen is an illusion, therefore anything based on this parameter can be manipulated and is therefore also an illusion.

    Now, I'm not arguing the relative loss of output over time. I don't know the answer to that question. I'm simply saying we don't have the proper data to make this assessment and that we cannot use office building parameters for our purposes.

    Cheers,
     
  5. GreenNeedle

    GreenNeedle Member

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    2,706
    Location:
    Lincoln UK
    Ceg. You already know I pay no attention to Lumens etc and know all about PAR/PUR being the defining measurement. Yu also know that I know about CRI/K being virtually pointless. ;) I am not arguing any of that. I've said the very same thing for long enough. lol

    What I am trying to point out with this article is that where I have been suggesting changing bulbs every year isn't necessary on electronic ballasts this article is suggesting that far from it degrading far enough after 2 years of use it is fine for 3+ years!!!

    Not sure on how the PAR readings would apply to this. If you had a tube in your tank and measured the PAR when you bought it and then came back and measured again the same tube in the same tank 3 years later would the PAR have gone down by more than 5-6% ??? The lumens would have. Would it have lost PAR at the same ratio or more or less??

    AC
     
  6. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,952
    Location:
    Chicago, USA
    Andy, thats my whole point. :idea: The PAR degradation may or may not be related to the Lumen degradation. In order to test this, as you say you must measure PAR at given distances and then measure periodically at the same locations during the course of the year. The phosphor degrades, not just the contacts, so the degradation rates may not track together and may certainly not be proportional.

    In any case I agree with you in that I see no reason to arbitrarily change out bulbs just because a calendar year has elapsed. You can get just as much algae with 1 year old bulbs as with brand new bulbs so that means there's still plenty of energy left in the old bulb. I recall reading that most of the degradation occurs within the first few months anyway, but again, without careful PAR measurements it's impossible to tell.

    Cheers,
     
  7. GreenNeedle

    GreenNeedle Member

    Messages:
    2,706
    Location:
    Lincoln UK
    Yeah I think Tom's said that they lose a bit at the beginning and then level out after that degrading slowly. A bit like Depreciation on a car but not as extreme I suppose ;)

    AC
     
  8. a1Matt

    a1Matt Member

    Messages:
    2,498
    Location:
    Bromley
    Over the years I have not made any observations with regards ot different ballasts but i have noticed that it can vary with different makes\models of tubes.

    I found that Triton\Triplus tubes don't degrade as much as other T8 lamps I used to use.

    This is very unscientific, just my personal observations. I always assumed it was down to them using a different phosphor.

    I also used to work in a shop that sold fluorescent lighting and noticed the same variance there between different brands\models (I couldn't tell you which ones, it was quite a long time ago).

    Overall I think they do all follow the same basic curve of losing a good chunk of output when new, then very very slowly tailing off, then near the end of life losing another big chunk. (like a reverse bathtub curve).
     

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