Problem: When you draw the double lines for your ductwork, certain ducts extend far beyond where they should stop.
Cause: If two pieces of ductwork are almost, but not completely, aligned, sometimes the previous duct will overshoot the next duct when double lines are drawn, as shown in this image:
Solution: Straighten the duct using the Straighten Next Ducts command.
1. Find the duct that is being overextended.
2. Run the Straighten Next Ducts command and select the previous duct to the one that is overextended.
Ribbon: DM HVAC->Ducts-> Straighten Next Ducts
Pulldown Menu: DM HVAC->Duct Centerlines->Straighten Next Ducts
The duct will be straightened and the double lines redrawn.