Editing and Recalculating Ducts

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To edit a duct system's sizing criteria, go to

DM HVAC arrowDuct Centerlines arrowQuery Duct

When asked to select a duct to query, select the first duct in the system in which you wish to change the sizing criteria. For the tutorial, select the first supply duct, which should have a circle P at its beginning. When the Duct Information dialog box opens, set the Shapes to Round to Flat Oval as shown and highlighted in yellow in the screen shot below.


To edit other features of ducts in a system, go to

DM HVAC arrowDuct Centerlines arrowEdit Multiple Ducts

When the Duct Settings dialog box opens, type "12" for the Maximum Depth as shown and highlighted in yellow in the screen shot below. Then press Edit a Duct Branch.


Design Master HVAC will take you to the drawing and ask you to select a duct to edit. Select the same duct you edited using the Query Duct command. With the new setting, when the ducts in the supply system are sized, they will first be sized to be round. When they reach the new maximum depth of 12 inches, they will then be sized to be flat oval ducts with a depth of 12. The width will be determined by the airflow in the duct. Because of this, the ducts in that system need to be resized and the double line redrawn. To recalculate, go to

DM HVAC arrowDuctwork Calculations

The Duct Calculations dialog box will appear. Make certain the Ducts in a System option is selected, then press Calculate CFM, Size Ducts, and Calculate Pressure. Design Master HVAC will prompt you to select a duct in the system you wish to calculate. Select a blue supply duct. Design Master HVAC will take a few moments to calculate the CFM and pressure, size the ducts, and draw the double line all in one step. Your drawing should now match the one shown below.


Congratulations! You now know how to perform the basic ductwork calculation and double line functions using Design Master HVAC.

See Sections and 3D for the next tutorial.

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