How to Draw Tee with Radius Elbow in HVAC Ducts

Hello, Everyone,

Today I will show you how to draw Rectangle Ducts Tee, using LISP.

Download the required Lisp from here then add it to Autocad Lisps and run the Lisp by typing "tb" in the command bar then do as shown below:

1-After running the lisp it will ask you to:

   -pick the outer side of the main duct.

   -pick the inner side of the main duct.

   -Enter air flow quantity (CFM) for the main 

   -pick the inner side of the first branch duct.

   -pick the outer side of the first branch duct.

   -pick the outer side of the second branch duct.

   -pick the inner side of the second branch duct.

2-Pick lines as shown in the screenshot below:

3-After choosing lines as described above the lisp will draw the elbow for you!

Note: you can enter the proportion values for the CFM like(enter 6 for the main duct and if the flow is equally divided enter 3 for the first branch and accordingly the second will be calculated to be 3 or if not equally splits enter the proportion values for the division  for example "4:2")   

For more illustrations see the video below:

Download the Lisp from here

Note: you can use this lisp to draw other duct fittings like duct elbows, duct branches with 45°take-off and duct branches with two elbows in the same direction for more details see the below link

-To download more Lisps for HVAC Design drawings go to:

Autocad LISPS for HVAC Design Drawings

-If you get any error when extracting the compressed file download the latest winrar Version