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ASHRAE90.1 2016 and 2019 editions specify a cooling tower efficiency of 3.23 L/s·kW for baseline model.

According to an annotation in Table 6.8.1-7, this efficiency means the water flow divided by the fan motor nameplate power.

How can we input this efficiency to IDF file? There are two objects for coolingtower with variable speed fan: CoolingTower:VariableSpeed:Merkel and CoolingTower:VariableSpeed, but both don't have such an input field. Design Water Flow Rate per Unit of Nominal Capacity field is different from this efficiency since Nominal Capacity and Fan motor power are different.

I'm thinking about the following approach, but is it correct?

1. Run the simulation with Design Water Flow Rate and Design Fan Power set to autosize.
2. Get the autosized Water Flow Rate from the simulation result.
3. Calculate the Design Fan Power from the following equation: Design Fan Power[kW] = autosized Water Flow Rate[L/s] / 3.23[L/s·kW]
4. Input the calculated Design Fan Power to Design Fan Power field, and run the simulation again.