Hi, here is how I would draw your plant loop in terms of EnergyPlus, I haven't included the heat exchangers because I am not sure how that would work right now, but I thought this would be a start. In EnergyPlus it is always good to look at things in loops. I find once the basics are done the more complicated parts of the system can be modelled.

(updated due to @mjwitte comment below)

The bypass pipe should be connected too. I just forgot to draw the line. You can add more pumps and put them where they need to be, I just wanted to start with the basic loop.