In the previous step, we defined the supply-side condition. In this step, we'll define the return. This is actually quite simple as we will use a gage pressure condition to represent exhaust air to the return ducts.
1. Left click on the return surface.
2. Click Edit from the Boundary Conditions context panel:
3. On the Type row, select Pressure.
4. Leave the Unit as Psi and the Pressure value = 0.
5. Click Apply.
What it should look like...
6. To verify that the boundary condition is correctly applied to the return, check the Design Study Bar and the colored stripe on the return surface: