Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
I believe that you are witnessing the impact of EnergyPlus's methods of accounting for loop fluid capacitance and pump heat.
In short, EnergyPlus puts an imaginary storage tank at the inlet of each plant side -- supply and demand. The volume of each tank is the volume of fluid in that respective side of the plant. The tank temperature is then solved for using an energy balance. This is why you find that supply outlet temperature does not always equal demand inlet temperature, and demand outlet temperature does not always equal supply inlet temperature.
Pump heat is also lumped into the plant loop fluid's capacitance calculations through these imaginary storage tanks.
