Cooling tower VFD Min Speed
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  1. #1
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    Cooling tower VFD Min Speed

    What is the manufactors min speed/HZ on a cooling tower fan motor rated for inverter duty. I was taught 20hz was min speed to keep from over heating. Engineer wants to run with no minimum.
    "Dying aint much, its living thats hard." (Josey Whales)

  2. #2
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    I set fan applications at 10 Hz and pumps at 18 Hz on the drives I set up. I've had no reported problems after ten years of factory start ups.
    If this cooling tower is belt driven, I wouldn't go below 6 Hz or 10%.
    If it is gear driven, you can't go below what the gear drive manufacturer recommends what the min. speed should be for proper lubrication.

  3. #3
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    Was told by Marley that at 18hz your airflow pretty much stops thru the tower. I run the tower water up to 2F below setpoint before sending the drive a run command. Starts at 18hz and goes from their. If it drops 4F below setpoint the drive goes off. The towers and drives I just installed run within
    .15F of setpoint and usualy closer to .04F.
    Last edited by absrbrtek; 10-20-2008 at 06:00 PM.
    Your poor planning does not constitute an emergency on my part!!!!

  4. #4
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    Still did not teach you anything! 20HZ is safe but I would contact the tower box rep. Some of the boxes have a slinger for "splash" lubrication. Don't work so well at slow speeds. The motors require around 20HZ to get the fans on the rear to effectively cool the motor. TEAO might need more speed since they use ambient air over them.
    "I'm from Texas, what country are you from?"

  5. #5
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    LOL, that's what Marley recommended. Been online for a few 1000 hours with no issues.
    Quote Originally Posted by stickerhead View Post
    Still did not teach you anything! 20HZ is safe but I would contact the tower box rep. Some of the boxes have a slinger for "splash" lubrication. Don't work so well at slow speeds. The motors require around 20HZ to get the fans on the rear to effectively cool the motor. TEAO might need more speed since they use ambient air over them.
    Your poor planning does not constitute an emergency on my part!!!!

  6. #6
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    Quote Originally Posted by stickerhead View Post
    Still did not teach you anything! 20HZ is safe but I would contact the tower box rep. Some of the boxes have a slinger for "splash" lubrication. Don't work so well at slow speeds. The motors require around 20HZ to get the fans on the rear to effectively cool the motor. TEAO might need more speed since they use ambient air over them.
    Dident learn anything from you 20 years ago when you was my supervisor why should anything be different today? Hhhhmmmm is it me or you???????
    "Dying aint much, its living thats hard." (Josey Whales)

  7. #7
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    I would agree with the a 20HZ min. for that application , any new inverter start ups on pumps or ahu's I would set up for 15HZ to 20HZ and have had no problems at all.
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  8. #8
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    Quote Originally Posted by CaptJackSparrow View Post
    Dident learn anything from you 20 years ago when you was my supervisor why should anything be different today? Hhhhmmmm is it me or you???????
    That's why you live out in nowhereville where no one knows what you are doing is right or wrong. That's why C-alvin made so much $$$
    "I'm from Texas, what country are you from?"

  9. #9
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    Quote Originally Posted by stickerhead View Post
    That's why you live out in nowhereville where no one knows what you are doing is right or wrong. That's why C-alvin made so much $$$
    Well thats what I like about it! I get to decide what is right and what is wrong! No corprate policy or little Hitlers! Its right if I say its right and wrong if I say its wrong. Like the little trip to "trailer hill", That was WRONG!
    "Dying aint much, its living thats hard." (Josey Whales)

  10. #10
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    Thanks for the replies. I set min at 15hz as the know it all engineer agreed to. Its his motor!
    "Dying aint much, its living thats hard." (Josey Whales)

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    Quote Originally Posted by CaptJackSparrow View Post
    Well thats what I like about it! I get to decide what is right and what is wrong! No corprate policy or little Hitlers! Its right if I say its right and wrong if I say its wrong. Like the little trip to "trailer hill", That was WRONG!
    Whoo! You just slapped my brain! I thought you would have wanted to have forgotten that! Bad mental picture but it was funny! I will see if C-alvin remembers!
    "I'm from Texas, what country are you from?"

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    The question is not if you can remember but if can you forget!
    "Dying aint much, its living thats hard." (Josey Whales)

  13. #13
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    Quote Originally Posted by CaptJackSparrow View Post
    The question is not if you can remember but if can you forget!
    I was innocent but you and Tio wern't
    "I'm from Texas, what country are you from?"

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