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EnergyPlus severe error - CalcIndirectResearchSpecialEvapCooler

What is the significance of the error,I have used 2ZoneHVACDatacenter idf file. How do i solve this problem ?

ERROR :

 ** Severe  ** CalcIndirectResearchSpecialEvapCooler: calculate secondary air mass flow failed for Indirect Evaporative Cooler Research Special = EAST DATA CENTER IEC
   **   ~~~   **  Environment=WHOLEYEARDAY, at Simulation time=03/26 18:15 - 18:30
   **   ~~~   **   Iteration limit [500] exceeded in calculating secondary air mass flow rate
   **   ~~~   **   Simulation continues
   ** Severe  ** CalcIndirectResearchSpecialEvapCooler: calculate secondary air mass flow failed for Indirect Evaporative Cooler Research Special = WEST DATA CENTER IEC
   **   ~~~   **  Environment=WHOLEYEARDAY, at Simulation time=03/27 06:03 - 06:05
   **   ~~~   **   Iteration limit [500] exceeded in calculating secondary air mass flow rate
   **   ~~~   **   Simulation continues

EnergyPlus is trying to calculate the proper air mass flow in the secondary stream of the evaporative cooler, but can't converge on a correct air mass flow value after trying to calculate it for a max of 500 iterations. EnergyPlus tries to converge by calculating secondary air mass flows that are within a tolerance of 0.01 (not sure of units, but maybe this is kg/s) between concurrent iterations. Both the 500 maximum iterations and 0.01 convergence tolerance are hard-coded into EnergyPlus source code, so there's not much you can do as a user other than adjusting these in the source code and building your own version of EnergyPlus -- not recommended for the faint of heart :)

Without looking at your model (it would be helpful to include a link for others to provide better solutions to you), my guess is that you are autosizing the secondary air design flow rate, but then the secondary air flow scaling factor you set is not realistic.

These are "severe errors", but EnergyPlus is still progressing to finish the simulation. To ensure that these error messages are OK to overlook, try looking at output variables for System Node Temperature and System Node Mass Flow Rate for inlet and outlet air nodes associated with the secondary stream of the evaporative cooler around the timesteps mentioned in the error messages ("03/26 18:15 - 18:30" for EAST DATA CENTER IEC and "03/27 06:03 - 06:05" for WEST DATA CENTER IEC).