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Thread: LED groom heat?

  1. #11

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    Quote Originally Posted by Max - LEDTonic View Post
    What Shreder said above^
    One watt will produce 3.41 Btu/h, and 100w LED, HPS, MH, or CFL, will all produce just as much heat, 341 Btu/h.

    The difference between them is how much light they can produce with 100w, and that differs a lot.
    Even if a light source is 100% efficient and all of the 100 watts are turned into light, the light will eventually turn into heat. While mylar is highly reflective, every photon will at some point be absorbed on a surface, and become heat. Energy cannot be created or destroyed, it can only change form (the first law of thermodynamics), and the lowest form of energy is heat.

    The more efficient lamps we use, the fewer watts we need to reach a certain light intensity. Aside from air exchange and ventilation to transport and manage heat, lamp efficacy is key when it comes to creating as little heat as possible.
    Some of the light energy is converted to carbohydrates and stored in our plants but that's only between 3-6% of all the light that lands on our plants according to Wikipedia - Photosynthetic efficiency, which is a rather small part of all light created in our grow spaces.

    Removing the LED's driver from a grow space will have an impact as it accounts for between 5-15% of a lamp's total heat output, as LED drivers often are between 85-95% efficient. Large MeanWell and Inventronics drivers are top-tier and often around 94% efficient. 6% of 630w results in around 38 watts of heat produced by the driver.

    The 650r is a great lamp and produce as much light as a 1000w DE HPS (1770 µmol/s), while only drawing 630 watts.
    Single-ended 1000w HPS lamps are even less efficient and seem to produce between 1000-1300 µmol/s, depending on the brand (source: Jacob A. Nelson & Bruce Bugbee).
    Good information, thanks Max.

    On a related note, does it matter to the plants if the light is changed during veg and/or during flower? E.g an HPS 600 to a considerably more powerful LED?

    I've decided against upgrading to LEDs for the time being for several reasons, but one of those reasons was that I'm 4 weeks into flower didn't know how the plants would react?

    Any advice please?

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  3. #12

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    I haven't personally done a switch in the middle of a grow so I can't speak from own experience.
    It doesn't necessarily have to result in chaos but I believe it could.

    Light intensity is one part that might affect your plants but spectral composition can have a large impact as well. While two lamps drawing the same amount of power produce the same amount of heat in total, LED lamps mostly emit the heat upwards through heatsinks and doesn't emit it in the form of light downwards. HPS lamps emit a lot of the heat produced in the form of far-red and infrared light, downwards. This part of the spectrum will raise the leaf temperature and increase transpiration. When plants suddenly drink in a new way driven by a new spectrum, they'll also use nutrients differently and in different ratios.
    With that said, it's probably possible to dial it all in and do a successful switch in mid-flowering, but I wouldn't do it.
    Changing the room temperature, light intensity and spectral quality at the same time could result in undesired results, as adaptation is hard work and can be stressful.

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  5. #13

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    Quote Originally Posted by Max - LEDTonic View Post
    What Shreder said above^
    One watt will produce 3.41 Btu/h, and 100w LED, HPS, MH, or CFL, will all produce just as much heat, 341 Btu/h.

    The difference between them is how much light they can produce with 100w, and that differs a lot.
    Even if a light source is 100% efficient and all of the 100 watts are turned into light, the light will eventually turn into heat. While mylar is highly reflective, every photon will at some point be absorbed on a surface, and become heat. Energy cannot be created or destroyed, it can only change form (the first law of thermodynamics), and the lowest form of energy is heat.

    The more efficient lamps we use, the fewer watts we need to reach a certain light intensity. Aside from air exchange and ventilation to transport and manage heat, lamp efficacy is key when it comes to creating as little heat as possible.
    Some of the light energy is converted to carbohydrates and stored in our plants but that's only between 3-6% of all the light that lands on our plants according to Wikipedia - Photosynthetic efficiency, which is a rather small part of all light created in our grow spaces.

    Removing the LED's driver from a grow space will have an impact as it accounts for between 5-15% of a lamp's total heat output, as LED drivers often are between 85-95% efficient. Large MeanWell and Inventronics drivers are top-tier and often around 94% efficient. 6% of 630w results in around 38 watts of heat produced by the driver.

    The 650r is a great lamp and produce as much light as a 1000w DE HPS (1770 µmol/s), while only drawing 630 watts.
    Single-ended 1000w HPS lamps are even less efficient and seem to produce between 1000-1300 µmol/s, depending on the brand (source: Jacob A. Nelson & Bruce Bugbee).
    Want to see if I have this correct. If someone is running a 1000w hps and decides to use a LED the equivalent of a 1000 hps the LED
    would draw roughly 660w. If this is correct then the heat from the LED would be based on 660w and not 1000w and there fore less heat
    then the 1000w hps for the same amount of light?

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    Correct! Worth mentioning, while fairly obvious, is that different HPS lamps and different LED lamps have different efficacy (µmol/j) and 660w LED will not always equal 1000w HPS.
    We must look at and compare the true wattage and efficacy, or even better, if it is listed, the total light output as PPF, measured in µmol/s.

    As example, if an LED lamp's efficacy is 2.0 µmol/j, we'll instead need 885 watts to get the same light output of 1770 µmol/s.

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  9. #15

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    Quote Originally Posted by Max - LEDTonic View Post
    Correct! Worth mentioning, while fairly obvious, is that different HPS lamps and different LED lamps have different efficacy (µmol/j) and 660w LED will not always equal 1000w HPS.
    We must look at and compare the true wattage and efficacy, or even better, if it is listed, the total light output as PPF, measured in µmol/s.

    As example, if an LED lamp's efficacy is 2.0 µmol/j, we'll instead need 885 watts to get the same light output of 1770 µmol/s.
    I used 660w as just an example. Understand different makers are going to have different numbers. Just hoping it will help
    someone who thinks a LED equivilant to a 1000w hps puts out just as much heat.

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