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# Central Heat Pump System Plant temperatures are getting far too cold

Hi all,

I am modeling an HVAC system based on a Central Heat Pump System. The system is used to fulfill both cooling as well as heating requirement of the building.

In this scenario, I have modeled two buildings in two separate energy models and run the simulation using District cooling and heating components. These buildings are basically served by a single HVAC plant so I take out the cooling and heating load profiles of these buildings and use it in a separate model by the help of LoadProfile:Plant object. In this model, I modeled the actual HVAC plant along with Central Heat Pump System to fulfill the cooling as well as heating requirement.

While running the simulation I am getting an error

** Severe  ** Plant temperatures are getting far too cold, check controls and relative loads and capacities
**   ~~~   **  During Warmup, Environment=RUN PERIOD 1, at Simulation time=01/01 17:00 - 18:00
**   ~~~   ** PlantLoop Name (DemandSide)= HW PLANT LOOP
**   ~~~   ** PlantLoop Setpoint Temperature=48.9 {C}
**   ~~~   ** PlantLoop Inlet Node (SupplySide) does not have a Setpoint.
**   ~~~   ** PlantLoop Inlet Node (DemandSide) does not have a Setpoint.
**   ~~~   ** PlantLoop Outlet Node (SupplySide) has a Setpoint.
**   ~~~   ** PlantLoop Outlet Node (DemandSide) does not have a Setpoint.
**   ~~~   ** PlantLoop Outlet Node (DemandSide) "NODE 40" has temperature=-103.0 {C}
**   ~~~   ** PlantLoop  Inlet Node (DemandSide) "NODE 39" has temperature=-102.7 {C}
**   ~~~   ** PlantLoop Minimum Temperature=5.7E-014 {C}
**   ~~~   ** PlantLoop Maximum Temperature=100.0 {C}
**   ~~~   ** PlantLoop Flow Request (SupplySide)=12.0 {kg/s}
**   ~~~   ** PlantLoop Flow Request (DemandSide)=1.8 {kg/s}
**   ~~~   ** PlantLoop Node (DemandSide) "NODE 40" has mass flow rate =12.0 {kg/s}
**   ~~~   ** PlantLoop PumpHeat (SupplySide)=4138.6 {W}
**   ~~~   ** PlantLoop PumpHeat (DemandSide)=0.0 {W}
**   ~~~   ** PlantLoop Cooling Demand=0.0 {W}
**   ~~~   ** PlantLoop Heating Demand=7676447.2 {W}
**   ~~~   ** PlantLoop Demand not Dispatched=5086447.2 {W}
**   ~~~   ** PlantLoop Unmet Demand=7675426.1 {W}
**   ~~~   ** PlantLoop Capacity=2590000.0 {W}
**   ~~~   ** PlantLoop Capacity (SupplySide)=2590000.0 {W}
**   ~~~   ** PlantLoop Capacity (DemandSide)=0.0 {W}
**   ~~~   ** PlantLoop Operation Scheme=HW PLANT LOOP OPERATION SCHEMES
**   ~~~   ** PlantLoop Operation Dispatched Load = 2590000.0 {W}
**   ~~~   ** PlantLoop Operation Dispatched Load (SupplySide)= 2590000.0 {W}
**   ~~~   ** PlantLoop Operation Dispatched Load (DemandSide)= 0.0 {W}


I am trying to solve it but unable to figure out. I appreciate your help.

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Hi, I've had the same problem but shifted to the overheating (and not fortunately during the warm up, so i've been able to catch the temperature trend). I'm not sure the "SmartMixing" always works well. Anyway, for my purpose, I solved (not in a brillant way) by temporarly forcing Off the HW loop through an High Temp Turn Off availability manager.

I hope to manage a better solution, maybe with some other user tips. Regards, Alessandro

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Thank you for the advice!

( 2020-06-22 01:36:15 -0600 )edit