Square elbow and wye fittings in Design Master HVAC can have turning vanes inserted on them.
When you manually insert one of these fittings, you will be prompted for whether or not they should be inserted. If you want to change this setting for a fitting that already exists, insert the fitting again.
There is an option that controls whether turning vanes are included on these fittings when they are inserted automatically. To set this option, use the “DM HVAC->Customization->Edit Project List” command. In the “Fittings” section, change the “Turning Vanes on Square Elbow and Wyes” setting.
If you change this option in the middle of a project, you will need to redraw the ductwork to have the turning vanes updated.