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  1. #1
    Join Date
    Jul 2010
    Location
    Chicago Suburbs, IL
    Posts
    3

    Calculating Cooling Capacity of AC Units

    This company im working for hasn't done an audit of their HVAC system in 20+ years. They have a bunch of Modine CSC-1515 units in their warehouse that were manufactured in the mid 60's.

    I have little experience in the HVAC field, and few resources at my disposal (Manual N for Load Calcs). I have the Design Specs of the units from a previous audit, but would like to calculate the Cooling Capacity of each unit and am having difficulty calculating the BTUH / Tons refrigeration output.

    Any help with equations or references to such is appreciated.

    Thanks.

  2. #2
    Join Date
    Apr 2006
    Location
    mechanical room
    Posts
    1,302
    CFM X Delta HT X 4.5 = total cooling btu

    Return WB of 61.7= 27.62 btu's per lb of dry air (plotted on pycrometric chart)

    Supply WB of 54.2= 22.74 btu's per lb of dry air (plotted on pycrometric chart)

    Subtact the two and you get 4.88 that is you Delta HT

    So lets say 1000 cfm X 4.88 X 4.5= 21,960 BTU


    1000CFM X 4.88 = 4880 X 4.5 = 21,960 Total BTUs removed.

    1000CFM X (16°Delta X 1.08) = 17,280 Sensible BTUs removed.

    21,960 - 17280 = 4,680 BTUs Latent removed.



    measuring indoor cfm for gas-oil heat

    cfm= btuh output divided ( 1.08 x delta temp. )

    measuring indoor cfm for electric heat

    cfm= volts x amps x 3.414 divided ( 1.08 x delta temp. )

  3. #3
    Join Date
    Apr 2006
    Location
    mechanical room
    Posts
    1,302
    best cfm measurement is a tesp measurement and match it to the blower performance chart

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