Revert fan flow back to normal after ems input

asked 2021-04-10 14:43:55 -0500

Via EMS, I want to adjust the fan air flow at some moments. I know how to adjust it. However, I can't figure out how to get it back to the orginal speed after the moments of fan increase via the ems. For simplification, I now have this.

EnergyManagementSystem:Actuator,
    FANN,          
    5 ZONE PVAV FAN,  
    fan,            
    Fan Air Mass Flow Rate


    EnergyManagementSystem:Program,
       Fanprogram   
        IF (DayOfWeek ==2),    
        SET FANN=15,      
    ENDIF;

For this example, I want to increase the fan flow rate to 15 kg/s every 2nd day of the week. After the 2nd, day I want to revert it back to the speed what it would normally do. However, now it stays on 15 kg/s forever. I want it to go back to the default value after the 2nd day is finished. And this default value varies over time (depending on heating/cooling load), so it is not a constant value.

I hope someone can help.

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answered 2021-04-10 17:37:59 -0500

shorowit

10881 ●179 ●9 https://www.nrel.gov/b...

Please refer to the EnergyPlus EMS documentation on actuators where it says:

Actuators override things inside EnergyPlus whenever the actuator’s Erl variable is set to a value other than “Null.” Null is a special built-in variable used to deactivate an actuator. Once an actuator starts overriding, it will continue to do so until the actuator’s Erl variable is set to Null. You should set the actuators to Null whenever you want the EMS to revert to normal operation.

Thus, you should be able to do this:

    EnergyManagementSystem:Program,
      Fanprogram   
      IF (DayOfWeek ==2),    
        SET FANN=15,      
      ELSE,    
        SET FANN=NULL,      
      ENDIF;