For backwards compatibility, I modeled a HW heating system with a boiler in the Main Building Loop in OS Ver 2.5.0. The annual building heating unmet hours were 66.5 hours, a reasonable number. I then placed the boiler in a primary loop with an ideal Heat Changer representing a low loss primary/secondary header. The unmet hours jumped to 2705.5 hours.
I then imported the file into OS Ver 3.1.0 and the unmet hours were essentially similar at 2681,5 hours. Looking at the key parameters in DView, the boiler energy production was what you would expect up until mid-August when it ceased. At the same point, the heat exchanger on status dropped from 1 to 0. The primary boiler loop temperature was holding set point until about mid-June when it started to climb and peaked at 100C in about mid-August, which correlates with the shutdown of the HX.
Out of curiosity, I imported the file into OS Ver 3-6-1 and the unmet heating hours dropped to 70.2 hours similar to the single main loop system. It seems that in the previous OS versions, the scheduled setpoint manager is not controlling the loop temperature and when the loop reaches its maximum allowable limit the heating system shuts down. I have attached a clip of Dview. Burgunday is the Primary Loop Boiler Output Temperature, Beige is the Heating Load energy, Blue is the heat exchanger transfer energy and Slate-Grey is the heat exchanger operational status.
Is this a version problem or is there parameters i missed in the older versions of OS?
