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  1. #1
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    High CFM per ton

    Curious running a system with 680CFM per ton (3400CFM on 5 Ton) with a constant full load (60,000BTUs) running a 80F with 60% humidity where everything runs great. The question I have is whether I run the system at 3400CFM or 2000CFM our latent and sensible loads "seem" to remain the same while maintaining the exact same conditions which should not be the case as per the math. Technically by dropping the CFM we should see a major bump in latent but our moisture removal stays consistent at roughly 18 pints per hour whether we drop the CFM or not. What am I missing?

  2. #2
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    Aug 2002
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    and who set this up?

  3. #3
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    Is the system cycling? Keeping it at 80 it may not matter much. Is this a larger system with one compressor down or something? Give us an idea of the scenario here.


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  4. #4
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    Feb 2004
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    Not enough information. Major infiltration, faulty instruments, incorrect measuring methods, system unable to stabilize due to inconsistent loading.
    Problem I have is your saying they are the exact same conditions when we know that's doubtful. Not doubting you. It's just something might be overlooked.
    I might start with the 3400 cfm. How was that determined.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

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  5. #5
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    Jun 2003
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    How are you determining the outputs and changes?
    Lowering air flow will decrease sensible cooling and increase latetent cooling plus decrease the total capacity of the system.
    Keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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  7. #6
    Join Date
    Mar 2016
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    What happens when you go from 2000 CFM to 1500 CFM?

    Did you check the inside of the cabinet for condensate blown off of the coil?
    It's an upside down world we live in.

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  9. #7
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    Mar 2015
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    Medford, N.Y.
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    What is the advantage to the HIGHER CFM???

  10. #8
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    Dec 2012
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    Quote Originally Posted by TechmanTerry View Post
    What is the advantage to the HIGHER CFM???
    Given the information in another current thread its possible the oversized blower acts as a load and extends the run times. We will have to hear from the op though. MrCfm


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  11. #9
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    You got some good responses. The main question I have has already been ask but how are you measuring airflow?
    No man can be both ignorant and free.
    Thomas Jefferson

  12. #10
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    Quote Originally Posted by WAYNE3298 View Post
    You got some good responses. The main question I have has already been ask but how are you measuring airflow?
    Its not a ecm blower with dip switches and lights that pushes 3400 cfm. I know that much.


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  13. #11
    Join Date
    Jun 2003
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    Madison, WI/Cape Coral, FL
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    Higher cfm = warmer coil=more total cooling capacity=more sensible capacity= less latent capacity=t-stat statisfied quicker
    This is the most important part of setting up an a/c.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  14. #12
    Join Date
    Mar 2015
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    Medford, N.Y.
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    Hay,OP,where in the world are you? There is no "change" to the system/structure when going from 3400 CFM down to 2000CFM??

  15. #13
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    Beatrice, NE
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    I am interested in the equipment. I have never seen 5T equipment that will move 8.5 ton of air. If the charge was set with 3400 CFM then it can't be right at 2000.

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