Personally, I've found that if you make the parts for Tubing or Piping (only round ducting) they are more versitile and easier to work with. I also have found that it's easier to do a save-as of existing route parts (from SW library) and modify as desired.
Unfortunately, there is a myriad of problems with SW routing, and at times you have to find a work-around in order to avoid errors and crashes.
Note, HVAC falls under "User-Defined Routes"
See https://www.youtube.com/watch?v=VPwwbUz7p34
Once you've made your custom part / development, add in C-Points as described in SolidWorks Help, (http://help.solidworks.com/2018/English/SolidWorks/sldworks/HelpViewerDS.aspx?version=2018&prod=SolidWorks&lang=English&path=sldworks%2fc_introduction_toplevel_topic.htm&verRedirect=1)
Do NOT use revolves to make routing parts.
Personally, I've found that if you make the parts for Tubing or Piping (only round ducting) they are more versitile and easier to work with. I also have found that it's easier to do a save-as of existing route parts (from SW library) and modify as desired.
Unfortunately, there is a myriad of problems with SW routing, and at times you have to find a work-around in order to avoid errors and crashes.
Let us know how it turns out!
Good luck!