Metal Halide UV Radiation

Discussion in 'Lighting' started by Jaco Schoeman, 27 May 2009.

  1. Jaco Schoeman

    Jaco Schoeman MASA Contributor

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    Hi Guys

    Just a question, I have read a few unexplanatory comments about MH's that needs a radiation filter or something as it gives off UV radiation or something.

    Can anyone please elaborate on this matter and bring me to light on the subject, as I have a very vague concept of this.;)
     
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  3. lIghty

    lIghty

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    Not sure how it works, but do know that any DE (double ended) bulb requires a shield, SE(single ended) don't, as the "bulb capsule" is enclosed in a large "tube" which asks as the shield.

    hope that helps a bit.
     
  4. Jaco Schoeman

    Jaco Schoeman Thread Starter MASA Contributor

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    A bit yes... But
    a) does this "shield" lower the light effectiveness?
    b) where does one get such a "shield" if you go DIY on MH?
     
  5. zee

    zee

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    To answer your question my DE MH ran too hot and glass broke.On the glass said UV Filter.I removed the rest of the glass completely and refitted the MH.And a week later my mushrooms and polyps start frying away,Rocks gone dark in colour!After replacing the MH they recovered.Couldnt find another UV filter glass.
     
  6. brettb2020

    brettb2020

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    MOST double ended bulbs dont have a uv filter, i have one that does:)

    But Tempered glass filters most harmful uv and wont break from the heat. Coral does need a little uv.
    Posted via Mobile Device
     
  7. lIghty

    lIghty

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    Not 100% sure here, but think you can use tempered glass?
     
  8. lIghty

    lIghty

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    What type do you have?
     
  9. Jaco Schoeman

    Jaco Schoeman Thread Starter MASA Contributor

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    So is it not then better to use SE Mh's rather than DE? What's the diffs then?
     
  10. zee

    zee

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    I think it would a safer option to use the SE MH as we`ve just learnt there is no need for a uv filter like the DE MH.
     
  11. zee

    zee

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    The older square type DE MH is the one I have and works like a bomb.
     
  12. Jaco Schoeman

    Jaco Schoeman Thread Starter MASA Contributor

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    But this again makes me questionmark MH in totallity!!! T5's does not have this problem... And with enough T5's and placing SPS at the right hight in the tank, I am again confident one does not need MH's... Except if you have a really deep tank of course, but then just have softies at the bottom and SPS at the top.
     
  13. zee

    zee

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    This is correct, so true.However Mh lighing also creates a neat shimmer in your tank,Like the sun.And I guess with T5`s you wont have heating problems.
     
  14. zee

    zee

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    And also the Mh switches on like the sun raises...so beautiful.
     
  15. brettb2020

    brettb2020

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    lighty iv got no idea what make my bulb is. but is says uv filter on the bulb.

    you loose the equivalent light output of about about 15watts through 6mm glass.

    but remember a light is measured watts, all that means is how much electricity it uses. not how much light it gives of. light is measured in lumens.

    a T5 gives of about 60 - 90 lumens per watt. where a MH gives of about 120 lumens per watt. meaning its more effecient and they take a hell of alot less space!

    if it wasnt for MH i wouldnt be able to grow alot of corals in my tank because i dont have the space for more than 4 T5's. i dont have corals yet but i can anything i want now. hence the reason we use T5's
     
  16. Jaco Schoeman

    Jaco Schoeman Thread Starter MASA Contributor

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    True Brett. And zee, yes the shimmer is stunning. But just on heat: T5's and MH's give out the same amount of heat, the only diffs is that T5's do it over a greater surface area...

    Okey guys, so help me, in a cube, lets say 650 x 650 x 500, what would jou suggest? 150 W 10000K MH and two actinic 24W T5's or 6-8 24W T5's? The reef will be mixed, with some sps but mostly softies.
     
  17. brettb2020

    brettb2020

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    i would say go with the MH and T5 way. i just upgraded to exactly that setup and WOW! doesnt only look awsome! i know my corals are going to be happy and im not limited as far as light is concerned.
     
  18. zee

    zee

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    Yes I agree.
     
  19. RiaanP

    RiaanP Moderator

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    Well a MH of 150 plus 2 T5 of 24 W = 198Watt
    8 T5 of 24W = 192Watt

    No real different in running cost.

    Heat, same issue, both ways.

    Height above water. Here is the difference. The MH unit is higher and without a glass shield should be 150mm or more above the water. (for splashes and globes exploding...) Where a multiple T5 unit will be lower / closer to the water.

    Also will this be in a canopy or not. Single MH suspended on cables above the tank should look good (depending - I cant, got a high slopped knottipine ceiling).

    Hanging the MH and T5 open above the tank, might look ugly and unfinished or busy (especially DIY units :whistling:).
    So have to place it in a canopy. Then that canopy have to be at least 400mm high! I'm designing my own 800mm cube, and this is my current design issue. So Jaco, if you want, I can show you what I got so far.
     
  20. brettb2020

    brettb2020

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    riaan you are correct that the 2 different setups have about the same wattage and therefor use the same electricity, but, light is not measured in watts, its measured in lumens. and MH is 120 lumens per watt and T5's are 60-90 lumens per watt. so by using the MH you are a getting a minimum of 450 lumens more light!

    just another reason MH is the way to go :)
     
  21. RiaanP

    RiaanP Moderator

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    Yes, i forgot about the lumens, Brett you are right there.
    That is why I'm going MH 250w 14000K and 4 T5. Then I got option to play more with different T5 globes like actinic + 10000K combo's for colour correctness / enhancements

    So end of day it comes down to only two issues, Height of light unit and Lumens...
     
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