100% unmet hours in chilled water system
I have an HVAC system consisting of 2 electric chillers in a college. For some reason, my reported unmet hours are 100% although the system is operating (chillers producing 100 kW cooling load).
I've put Setpoint Manager: Warmest on the demand side for Supply Air Temperature, and also set schedules for cooling thermostat of 20°C on the Thermal Zone tab. Checking the outputs I see some zones temperatures are rising as high as 30°C.
What can I be missing here?
@Yael Could you post a link to your model?
You two chillers are perhaps just undersized. Try increasing the capacity ten folds, see if you still have the same problem.
@Avi How can I post a link of my model? I have two chillers that are big enough,however not all their capacity is used (on all operation modes). I suspect it may have something to do with my part-load ratio characteristics: I'm using 2 chillers, each of them contains 2 circuits with 4 scroll compressors (2 compressors aligned on each circuit). I have 4 steps of capacity: 25%, 50%, 75% and 100%. The way I defined the ratios: minimum PLR 0.1, max PLR 1, optimum PLR 0.25, minimum unloading ratio 0.25. Can it be that not all the compressors are operated because I defined something incorrectly?
@Yael you could upload it to some cloud service (Dropbox, google drive etc.) and share the link.
Maybe start by exposing the plant output variables and examine how the plant loop performs
Thank you. Link: https://drive.google.com/drive/folder... From what I saw the sensible cooling load arriving to all zones is about half of the cooling coil cooling load. That sounds to me too low. Also the CHW temperature difference between evaporator inlet and outlet is quite small, I tried to put a setpoint manager on the CH water inlet to the evaporator but it doesn't seem to work. Any ideas on what I'm doing wrong? Thank you very much!