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So, in the OpenStudio 1.2.1 Application (with OpenStudio 3.2.1), for an OS:Fan:VariableVolume, I just entered 0.65 for "Fan Total Efficiency", 5.37 for "Pressure Rise" and 0.93 for "Motor Efficiency". Then I did a model_run_sizing_run() and looked at various outputs, which look plausible.

However, I was also curious to see what the fan outputs would be, so I used the following:

  fan_volume_flow_rate = supply_fan.autosizedMaximumFlowRate().get
  fan_eta = supply_fan.fanEfficiency()
  motor_eta = supply_fan.motorEfficiency()
  total_eta = supply_fan.fanTotalEfficiency()
  runner.registerInfo("#{supply_fan_name} has SA = #{fan_volume_flow_rate/0.3048**3*60.0} [cfm], FE = #{fan_eta}, ME = #{motor_eta} ,TE = #{total_eta}.")

Much to my surprise, both fan_eta and total_eta report as 0.65, when I would have expected fan_eta to report as 0.65/0.93 = 0.698925, so that 0.930.698925 = 0.65. Am I missing something? Shouldn't total_eta = motor_etafan_eta?

So, in the OpenStudio 1.2.1 Application (with OpenStudio 3.2.1), for an OS:Fan:VariableVolume, I just entered 0.65 for "Fan Total Efficiency", 5.37 for "Pressure Rise" and 0.93 for "Motor Efficiency". Then I did a model_run_sizing_run() and looked at various outputs, which look plausible.

However, I was also curious to see what the fan outputs would be, so I used the following:

  fan_volume_flow_rate = supply_fan.autosizedMaximumFlowRate().get
  fan_eta = supply_fan.fanEfficiency()
  motor_eta = supply_fan.motorEfficiency()
  total_eta = supply_fan.fanTotalEfficiency()
  runner.registerInfo("#{supply_fan_name} has SA = #{fan_volume_flow_rate/0.3048**3*60.0} [cfm], FE = #{fan_eta}, ME = #{motor_eta} ,TE = #{total_eta}.")

Much to my surprise, both fan_eta and total_eta report as 0.65, when I would have expected fan_eta to report as 0.65/0.93 = 0.698925, so that 0.930.698925 0.93*0.698925 = 0.65. Am I missing something? Shouldn't total_eta = motor_etamotor_eta * fan_eta?

So, in the OpenStudio 1.2.1 Application (with OpenStudio 3.2.1), for an OS:Fan:VariableVolume, I just entered 0.65 for "Fan Total Efficiency", 5.37 for "Pressure Rise" and 0.93 for "Motor Efficiency". Then I did a model_run_sizing_run() and looked at various outputs, which look plausible.

However, I was also curious to see what the fan outputs would be, so I used the following:

  fan_volume_flow_rate = supply_fan.autosizedMaximumFlowRate().get
  fan_eta = supply_fan.fanEfficiency()
  motor_eta = supply_fan.motorEfficiency()
  total_eta = supply_fan.fanTotalEfficiency()
  runner.registerInfo("#{supply_fan_name} has SA = #{fan_volume_flow_rate/0.3048**3*60.0} [cfm], FE = #{fan_eta}, ME = #{motor_eta} ,TE = #{total_eta}.")

Much to my surprise, both fan_eta and total_eta report as 0.65, when I would have expected fan_eta to report as 0.65/0.93 = 0.698925, so that 0.93*0.698925 = 0.65. Am I missing something? Shouldn't total_eta = motor_eta * fan_eta?

So, in the OpenStudio 1.2.1 Application (with OpenStudio 3.2.1), for an OS:Fan:VariableVolume, I just entered 0.65 for "Fan Total Efficiency", 5.37 for "Pressure Rise" and 0.93 for "Motor Efficiency". Then I did a model_run_sizing_run() and looked at various outputs, which look plausible.

However, I was also curious to see what the fan outputs would be, so I used the following:

  fan_volume_flow_rate = supply_fan.autosizedMaximumFlowRate().get
  fan_eta = supply_fan.fanEfficiency()
  motor_eta = supply_fan.motorEfficiency()
  total_eta = supply_fan.fanTotalEfficiency()
  runner.registerInfo("#{supply_fan_name} has SA = #{fan_volume_flow_rate/0.3048**3*60.0} [cfm], FE = #{fan_eta}, ME = #{motor_eta} ,TE = #{total_eta}.")

Much to my surprise, both fan_eta and total_eta report as 0.65, when I would have expected fan_eta to report as 0.65/0.93 = 0.698925, so that 0.93*0.698925 = 0.65. Am I missing something? Shouldn't total_eta = motor_eta * fan_eta?