1450 First Ave.
Page 9 of 10
Chippewa Falls, WI 54729
(800) 283-1141 or (715) 723-1141
Fax: (715) 723-7890
DA40T User Manual
Pacer Instruments, Inc
Rev 1.0
www.pacer-instruments.com
11-Aug-2007
Phone: 1-800-283-1141
APPENDIX E – AIRFLOW VOLUME CALCULATIONS
Theory:
To calculate cubic feet per minute (CFM) from a measured air velocity (FPM), you need the
calculated cross-sectional area of the airflow stream:
Volume Flow (CFM) = Velocity (FPM) X Area (sq ft).
In rectangular ductwork this cross sectional area equals the Width times the Height.
W x H=A (cross-sectional area)
In circular ductwork this cross section area equals the radius squared times
π
(3.14).
R x R x 3.14=A (cross-sectional area)
To convert an area calculated in square inches to an area calculated in square feet (which is
required for the Volume Flow equation above) divide by 144: (area in sq in.)/144 = (area in sq
ft.).
Example:
The air duct is rectangular, the width is 24 in. and the height is 12 in. The air velocity reading
through the duct is 450 FPM. Calculate the Volume Flow.
Step 1:
Cross-sectional area = 24 in. x 12 in. = 288 sq in.
Step 2:
288 sq in /144 = 2 sq ft.
Step 3:
Volume flow = Air Velocity x Area, therefore, Volume flow rate = 450 FPM x 2 sq ft. = 900
CFM.
APPENDIX F – ERROR CODES
E-08
Temperature lower than -95.0ºC or -139ºF
E-09
Temperature higher than 205.0ºC or 401.0ºF
