Whether you want to communicate with someone, plan your approach for modeling or label your nodes for an EnergyPlus simulation, it's often useful to draw out a schematic of an air loop or a plant loop, so you can see all the equipment and connections you need.
I usually do that by hand, but it's not easy to share it or to modify it. Using AutoCad for that is overkill.
I was wondering if people have found an easy to use and quick sketching tool, preferably free (and open source even better).
Ideally I'd like something with a library of common things where you can drag and drop your objects, and snap some connecting lines forced at a 90° angle. If you move an equipment, all connections would still be snapped to it. It would ideally also handle nicely lines crossing each other (creating bridges)
