Need advice on a fan for my HPS light

Discussion in 'Grow Room Design/Setup' started by vashigopal, May 11, 2010.

  1. This is my first grow, and I just switched from CFLs to a semi-air cooled 150W HPS from HTG supply. I bought their $20 80CFM duct fan for the fixture, and it's doing a good job of removing the heat, but it started making too much noise today. I fiddled with it but can't get it to stop. It makes less noise when it's horizontal, but I need it to be vertical. I can hear the noise outside the cab, so it's not stealthy anymore.

    Lots of people recommend the S&P TD series, and I was going to get the TD100 or the TD100x, but I noticed in their specs that the max operating temperature is 104F. The heat coming off the lamp feels like it's at least 100, so maybe the TD is not the best choice?

    Right now I want to put the fan directly on the light, but for my next grow I'll probably re-do the exhaust so that I'm exhausting just the light, with a carbon filter on the outlet, for stealth. So, ideally the fan I get should be able to push (not pull) air through a carbon filter. But I could get a tide-me-over fan just to finish this grow. (I'm at about 40 days into flowering, and not sure how long it will go.)

    Attached are partial pics of my current set-up. On the ceiling there is a colander lined with carbon, and above that (outside the cabinet) 2 PC fans for exhaust. My cab is 14.5" x 14.5" x 60" high

    I'm also including a pic of the S&P spec chart, which comes from this site:

    I can't re-attach photos I used in another thread, so here are links:

    Thanks! I've got to post and run -- I'll be back later this afternoon, or this evening.

    Attached Files:

  2. 1) Max operating temperature is ambient temp for motor. Your plants will die before your fan at those temps.

    2) Go with the 100X over the 100.

    3) You have at least 2-3 weeks left. You flipped the lights 40 days ago? Then you have 4-6 Weeks left depending on strain. I would think about a carbon as they might start stinking real bad soon if they haven't already.

    4) Took a look at the pic you definitely want to utilize your vertical space a bit better. I will post a pic for you with my idea.
  3. [​IMG]


    For the Carbon Filter you could also run a 90 up top and put it horizontally if that works better.

    the reason I put the 90 on the hood is to protect the ducting and to gain some vertical space.

    Attached Files:

  4. Realized I should have made that a 90 coming off the fan to the ceiling not flex duct. Mentally correct that.
  5. #5 vashigopal, May 11, 2010
    Last edited by a moderator: May 11, 2010

    Thanks for your response and the diagram! The high heat that comes off the light is more than a foot above the plant, and it goes up and out, never coming near the plant. But this heat would be flowing through the motor. I'll put the temp sensor there and see how hot it really is.

    I was thinking the same thing. But take a look at the specs. AT 100/101CFM, the TD100 actually performs better under static pressure than the TD100X. I guess this is because the TD100X has slower RPM at this speed than the TD100?

    The plant does stink. The colander has a lot of carbon in it, and it's working so far, but it really reduces the airflow thru the PC fans. I think it's 40 days from when the first pistils started showing, but that was only 3 days after I flipped the lights. So if I'm wrong it's 37 days.

  6. The temperature of the air coming out of the hood fan is 107F! :eek:

    At canopy height the temp is about 78, so the plant is okay.
  7. Operating temp /= max air temp passed through just so you know.
  8. So the TD100 is not an option. I'd have to get the TD150 and a 6" to 4" duct reducer.

  9. The TD-150 will definitely cool that down plenty but its probably not needed. I have a TD-100X venting plenty hot air. /= means does not equal. what they mean is the motor itself can run at 104 degrees before shutoff. The 100X+ fans have an automatic thermal switch. The 100 is a slightly different design. The 100X will handle moving the air without melting or whatever. If it freaks you out though get the TD150 it will definitely do the job, just louder.

    Hope that helps.
  10. sorry, didn't realize what "/=" meant. Wouldn't the motor be at least 107 if the air surrounding it is 107? I'll bet the fan I have now is not meant to run at 107 -- that's probably why it's complaining. I was gonna wrap some foam around it to dampen the sound, but it's probably not a good idea to insulate it!
  11. I just can't imagine temps are going to be 104 with ventilation. don't worry about the air from the hps passing through harming it. OMG I just went back to get wattage... 150W you are FINE with the 100X more than fine. You could cool a 600W with a 100X EASILY. Don't get the 150 its WAY too overkill trust me on this one. It would be too much for a 150W
  12. There's something I don't understand -- the air that's coming out of the lamp is 107, and the fan that's pulling it is 80CFM. I would think 100CFM would pull the air faster, but the air going through the fan would be the same temp, because it would be in the same spot. Unless I mount the fan somwhere else, instead of right on the light? BTW, turns out my duct fan is rated for 140.
  13. I mounted on the ceiling with a short ducting run you are fine, I wouldn't found it right on the hood though, for vibration alone.
  14. Oh yeah, the ceiling -- it's half-inch foam core (rigid foam sandwiched between paper) and can't support anything. I broke the original ceiling. The colander is wired to hooks on the sides. (I think I mentioned on another thread that I have a bit of the McGuyver in me, but I didn't plan it this way, honest!) I have to re-vamp this set-up including getting a piece of plywood for the ceiling. But I was hoping to do that after this grow is finished.

    Do turns and bends reduce air flow? I could get the TD100X and mount it on the wall for now, and hope I don't trip that thermal switch. The space is so small that even though the light is only 150W, heat is an issue. If I get rid of the carbon colander and the PC fans, I'm worried the heat might become worse, especially because I'll have a carbon filter on the TD100X, and it'll be the only fan. So that's why I'm hesitant to make big changes right now, in the middle of flowering.

    There is vibration from the fan being directly on the fixture. I put silicone tape on the fan and that helps, but it's not a good arrangement, to say the least.
  15. You can wait till after this grow as long as you think it can wait.

    Do bends reduce airflow?

    Obviously you haven't read the ventilation FAQ. I have re-answered several questions there and spent a lot of time answering questions do me the favor of at least reading through it thoroughly please. I directly address this issue. It will reduce airflow but the run is so short it won't matter. You have a very tiny space / lamp to ventilate.

    Put the fan on the wall its fine. Wait till after this grow, or not, is fine. You need to determine these things as it is your grow.
  16. Sorry, I did read the FAQ but it was a while ago. I will go back and re-read. My question should have been "Don't turns and bends reduce air flow?" But still a stupid question. I appreciate your help.
  17. Uh...I couldn't have read the FAQ a while ago 'cause you just created it last week! Must've been thinking of some stickies I read. I've gotta run now, I will read it thoroughly when I get back. Thanks!

  18. Happy to help. After you give that a read let me know if I can assist further. Please post any feedback for me where I could expand etc on that thread.

    (I think I typed that early pre coffee pre smoke so forgive me) yeah 6:11 AM :smoking:
  19. I'm *almost* dialed in on this cab. Temps are about 79 with the a/c on. I've been doing a lot of research on fans, and I'm going to upgrade a couple of my existing fans, and add another little one inside, to blow under the light, and maybe she'll be able to finish flowering in comfort.

    Unfortunately the TD100 is just too big for my cab. I'm attaching pictures of it superimposed on the cab, scaled to the same size as the cab picture. If I were to mount it on the ceiling, there just wouldn't be enough room for elbows or turns of the ducting. I could mount it vertically on the wall, with the top of the fan flush with the ceiling, and run a "snake" shape curve of ducting to the lamp, but this run from the lamp to the bottom of the fan would be very short, maybe 5", and I'm not confident that the 107 air from the lamp would cool to 104 in this short run.

    But I've been learning a lot about fans. For instance, sleeve bearing fans are meant to be used perpendicular, with the air flowing sideways, not horizontal with the air flowing up or down. When they are used horizontally they start making more noise, and don't last as long as they should. Ball bearing fans can be used in any orientation.

    Another thing I learned -- there is a wide range of static pressure capabilites of PC/axial fans. Some of them are very good -- 7 - 15 mmH20 (that's about .27 to .5 inches of H20). The higher static pressure axial fans are all ball bearing. When I bought my PC fans I chose the highest CFM/dBA ratios. The fans I bought are all sleeve bearing and perform poorly under static pressure. I did know this ahead of time, but I thought all PC fans were roughly the same in this regard, and that higher CFMs would counter the low static pressure ratings. But that turned out not to be true.

    I found this thread about PC fans on another forum, and it was really helpful to me:

    Attached Files:

  20. Great info, nice research.

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