Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
It's not clear whether you're using HVAC templates which will generate most of what you need automatically.
If you need more than that then using a GUI like OpenStudio is a good option - probably the first thing to try unless you know that it can't model the system you're interested in.
Finally, if you really need to get into the nuts and bolts, the HVAC documentation (Plant Application Guide) is reasonably clear on the workflow to follow for a range of different system types.
