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# EnergyPlus: enforcing user defined fan speed through actuator

Looking through the EMS documentation, there is an actuator that I would like to use for the fan: “Fan Air Mass Flow Rate". However, I am afraid it is not making any difference when I set this in my EMS program. This actuator is for a Fan:ConstantVolume fan. I also tried an actuators for System Node Setpoints for the inlet and outlet nodes (Mass Flow Rate Setpoint). Is this not possible? Have anyone tried this?

Here is my actuator and program:

  EnergyManagementSystem:Actuator,
PSZ2_Supply_Mass_node,    ! Name
PSZ-AC:2 Supply Equipment Outlet Node, ! Actuated Component Unique Name
System Node Setpoint,     ! Actuated Component Type
Mass Flow Rate Setpoint;  ! Actuated Component Control Type

EnergyManagementSystem:Program,
PSZ2_SetCoolingPower,
SET PSZ2_Supply_Mass_node = 4.06;


I saw the following link using a schedule for the object AirTerminal:SingleDuct:Uncontrolled. Is this my only option? link text

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The fans do have an actuator Fan for Fan Air Mass Flow Rate. The value must be between the maximum and minimum fan flow rate and the fan must be available to operate. Unfortunately I don't see an example in the EMSApplicationGuide.pdf.

However, setting the fan air mass flow rate is not the only consideration. The type of terminal unit used at the zone level may also have an impact on the air flow rate. As described in the link above, the EMS actuator for the terminal unit can also control air flow rate, thereby eliminating the need to control the fan since air flow at the zone level returns to the fan inlet.

An example for a fan actuator:

EnergyManagementSystem:Actuator,
PSZ2_Fan_Mass_Flow_Rate,    ! Name
PSZ-AC:2 My Supply Air Fan, ! Actuated Component Unique Name
Fan,                        ! Actuated Component Type
Fan Air Mass Flow Rate;     ! Actuated Component Control Type

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