Ductwork Calculations

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To have Design Master HVAC perform ductwork calculations, go to

DM HVAC arrowDuctwork Calculations

The Duct Calculations dialog box will appear as shown below.


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.


Repeat the command, this time selecting an orange return duct. Your drawing should match the one shown below.


In order to turn off the non-plotting centerline layer to view what the drawing will look like when plotted, go to

DM HVAC arrowLayer Management arrowTurn Duct Centerlines Off

Design Master HVAC will remove the centerlines. If you zoom in on Conference 102 and Office 105, your drawing should match the one shown below. Note that the hidden lines are not properly drawn.


To have Design Master HVAC use the elevations of the ducts to draw hidden lines, type HIDE at the command line. Your drawing should now match the one shown below.


Note that when the hidden lines are drawn you cannot zoom or pan in the drawing. You must first type REGEN at the command line. Setting hidden lines for plotting purposes is done using a different set of commands, which is discussed further in the Plotting Hidden Lines page on our website.

Next, you will make a change to the ductwork and update your duct sizes and double-line.

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