Zone HVAC power components

asked 2020-05-11 13:30:05 -0600

Divya's avatar


I am using EnergyPlus to schedule the HVAC thermostats for a building with 45 conditioned zones. My HVAC is using 4 PSZ systems with one conditioned zone for each and one PIU system with 41 conditioned zones. I would like to control each zone thermostat according to occupancy. I am trying to find the power required by HVAC for each zone to maintain the given thermostat settings, but there is no such output variable given by EnergyPlus. After looking at the variables listed in the EnergyPlus '.rdd', '.mdd' and '*.mtd' files, I found that the following might be useful, but could not find the exact relation between them:

  1. Facility Total HVAC Electric Demand Power = Sum of Fan Electric Energy (Supply fans+PIU fans)+ Reheat coils for each zone + Cooling Coils (for Systems) + Humidifiers
  2. Output:Variable,*, Fan Electric Power,hourly; !- HVAC Average [W]

I want the cooling power for each zone. I only could see the power required by system cooling coil. I tried to see:

  1. Output:Variable,*,Zone Air System Sensible Heating Rate,hourly; !- HVAC Average [W]
  2. Output:Variable,*,Zone Air System Sensible Cooling Rate,hourly; !- HVAC Average [W]

The sum of sensible heating/cooling rates is higher than that of heating coil/ cooling coil powers. Will the outdoor air cooling or heating affect this relation? I could not clearly relate this with the Zone Mechanical Ventilation Heating/Cooling Load Increase/Decrease. Can someone point out me if I am missing any other variables?

I also tried to see the district cooling or heating supplied by the Ideal load Air System for the same building and found out that the sum of district cooling + district heating is higher than the Facility HVAC power provided by the actual systems.

Any help for getting the relations between these components to get the individual zone HVAC powers is appreciated.

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