Ductulator calculats duct dimensions using equal friction method or velocity method. Select the duct size from the table that can carry that volume of air 3. The Flow Velocity is then determined with the following equation: √0.75 = 0.866 • 4005 x 0.866 = 3,468 • Flow Velocity = 3,468 Ft/Min. Copyright 2020 GarageSanctum | All Rights Reserved | www.garagesanctum.com. Y = Duct width in feet. An 18” diameter round duct has a Duct Cross Sectional Area of 1.77 Ft², A = π x r² or A = 3.14158 x .5625 r = radius of duct in feet, Example: Identify the volume of air that will be passing through the duct 2. These duct sizings should be more than sufficient residential air conditioning and furnace heating applications. Air Flow in CFM (Q) = Flow Velocity in Feet Per Minute (V) x Duct Cross Sectional Area (A). what is the procedures and what steps I should follow. The difference between the total pressure reading and the static pressure reading is the Velocity Pressure. Printable pdf Version of this Application Note. π= 3.14159 Higher static pressures and larger air volumes should be dealt with on a job to job basis.eval(ez_write_tag([[300,250],'garagesanctum_com-medrectangle-3','ezslot_2',104,'0','0'])); GarageSanctum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Use volume dampers for every branch to ensure proper distribution of air. If you connect the Total Pressure Probe to the HIGH port on a differential pressure sensor and the Static Pressure Probe to the LOW port on the differential pressure sensor, then the sensor’s output will be the Velocity Pressure, as shown in the figures below. 18” diameter is 1.5 feet, therefore the radius is .75 feet • r² = 0.75² = 0.5265 • π = 3.14159 © 2017 Building Automation Products, Inc. All Rights Reserved. To calculate Air Flow in Cubic Feet per Minute (CFM), determine the Flow Velocity in feet per minute, then multiply this figure by the Duct Cross Sectional Area. Equivalent Rectangular Duct: Enter Round Duct Diameter. V = 4005 x √0.75 If you have any questions about this procedure, please call your BAPI representative. dealt with on an individual job basis. Read Duct Diameter (inches) and Duct Velocity (FPM). Duct Sizing Chart CFM. This chart should not be used if you are designing a full duct system. These duct chart are based on equal friction method with a friction loss value = 0.1 inch/100ft.