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Thread: Do your t-5 bulbs get hot?

  1. #1
    pingman's Avatar
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    Do your t-5 bulbs get hot?

    I have a 4 tube 4 foot fixture and notice the t-5 fluorescent bulbs get quite hot. Almost too hot to touch. They are much hotter than my t-8 bulbs. Is this normal?

    I wonder if there is something wrong with the fixture?
    Does anyone else use t-5's and notice the bulbs being hot?

    Thanks!
    Peter.
    Please check my website for photos:
    http://www.flickr.com/photos/minicatt/sets

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    I went from T-12s to T-8s and noticed a huge difference. My T-12s I could pretty much unscrew after 12 hours of use. These T-8s are hot to the touch within a few hours. Not sure if it's just more lumens or whatever. But I guess with anything the better it gets the hotter it gets.

    House light fixtures can hold like 40-60 watts bulbs but put a 100 watter in there and it'll dry you off after a shower

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    Av8tor1's Avatar
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    Peter,

    T5's have to run hot, they are designed to run at a min of 39C, measured at the metal ring(if I remember correctly, I would have to dig through my refs to be 100% sure)

    Output drops proportionally as temp falls below this point. Cover tubes are recommended if T5's are to be used outside or in excessively windy environments (to maintain their temp)

    I measured mine with an infrared thermometer and about center of bulb I get around 160-170f with the ends a little over 100f... right where they should be, not too hot and not too cold

    well they could be a touch hotter, but they are in 59f ambient temps..

    HTH's
    Butch

    ref:
    This temperature of the lamp is measured at the cold spot of the lamp (the point where mercury condensates in the discharge tube at the stamped end of the lamp). This value is measured at the socket of the stamped side, approximately in distance 2mm of the glass.

    For optimum performance, this cold spot temperature should remain between 45oC and 55oC for the designed application.
    Last edited by Av8tor1; 01-28-2008 at 05:43 PM. Reason: add ref

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    Nepenthes's Avatar
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    Yea, my T5's get blazing hot. In fact during the summer I think I will revert back to using T8 fixtures to maintain cooler daytime temperatures. I grow my plants in terrariums so the heat gets trapped in there and the T5's are like an oven. I have 2 4ft (not actually 4 ft) 4 bulb fixtures and 4 single bulb-2 ft fixtures, and the plants are loving it right now, but last summer they gave me some issues. I used to have a fan blowing across the tops of the terrariums and it would also get the light fixture, and this seemed to help.
    - Daniel

  5. #5
    Admin- I'm growing CPs in the Desert of Tucson, Az. adnedarn's Avatar
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    I have 2x T5 HOs over my planted fish tank.. it was heating the glass up so much, i now leave it open, and have the lights directly over the water... I was worried the glass was going to break haha
    -Andrew
    Owner of TerraForums, FlyTrapShop.com, and cpforums.org.
    Support FlyTrapShop, support TerraForums! www.flytrapshop.com

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    lol that would be a watery mess

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    pingman's Avatar
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    Thanks all. Good to know that it is normal for these bulbs to run hot.
    Peter.
    Please check my website for photos:
    http://www.flickr.com/photos/minicatt/sets

  8. #8
    --Freedom Czar-- Fryster's Avatar
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    Yup. My T5's run HOT.

    Them boys does get toasty...........
    Only a moral and virtuous people are capable of freedom; the more corrupt and vicious a people becomes, the more it has need of masters. -- Benjamin Franklin

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