CFM Question
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Thread: CFM Question

  1. #1

    CFM Question

    Hi' friends I need some help with this'''' If I has three phase AHU with this? only one cooling coil'' (268 v 270 v and 270 volt) ( 7 amp 7 amp and 8 amp)and ( 25deg DT) I need to know the cfm. any help please'''
    juan clavell santiago

  2. #2
    Join Date
    May 2004
    Location
    Los Angeles, CA
    Posts
    1,560

    Please be a bit more clear on future posts........

    Dear Oly77,

    At best your posted question is vague. You seem to have an air handler system, your measured volts at A, B, and C are 268, 270, and 270 respectfully, your measured amps at A, B, and C are 7, 7, and 8 amps respectfully, and your delta T is 25 degrees F (educated guess). You now what to know what your CFM is.

    “IF” you have a resistance heater, and “IF” the amps on the heater ONLY are the measured 7, 7, and 8, and the heater has a heat rise of 25 degrees F, then:

    CFM = BTU/Hr / 1.08 x TD

    CFM = (7 + 7 + 8) x (268 + 270 + 270) x 1.73 x 3.41 / 1.08 x 25
    3 3

    CFM = 7.333 x 269.3 x 1.73 x 3.41 / 1.08 x 25

    CFM = 11,649 BTU/Hr. / 27

    CFM = 431.4

    “IF” on the other hand, ANY of the above prerequisites are not correct, then the above CFM calculation is not correct.

    Hope this helps…..and next time please be a bit more clear as to what the readings are.

    Respectfully Submitted,
    John J. Dalton CM

  3. #3
    what you need to help me ?Dalton
    juan clavell santiago

  4. #4

    cfm

    measure your rpm on the blower pulley, take static preasure readings on supply and return duct near ahu. plot readings on manufactures data sheets.
    This is not as accurate as a duct traverse but it will get you in the ballpark.

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