Hello everyone,
I have some fundamental questions regarding what approach should I take when I'm trying to model certain HVAC systems. I would really appreciate any help!
These are the systems I would be interested in:

1- MAU with 100% OA. Heating only

2- MAU with 100% OA, Heating only but capable of adding a heat exchanger from exhaust.

3- AHU in general

What I am trying to understand is what system type should I chose to represent these. I have no problems working around the heating and cooling types.
I'm really new to the industry and even though I know these questions might sound basic I hope I can get some help.

Thanks in advance!

Alejo