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Re: [EnergyPlus_Support] FCU fan sizing



Thank you very much Germán.

Cheers,



2013/12/23 Germán Campos <ecoeficiente@xxxxxxxxx>
 

Fan power is calculated as airflow x pressure rise / fan efficiency. So you have to adjust those parameters so the fan power is the one you really have. You normally adjust pressure rise and fan efficiency since they don't affect the rest of the model. Airflow is usually conditioned by outdoor air requirements and cooling/heating capacities.

Regards,


_______________________________

Germán Campos

Aurea Consulting  


2013/12/23 Felipe Duran B-GREEN <felipe@xxxxxxxxxx>
 

Germán,

Thank you very much for your reply. I had only changed the maximum airflow rate in the ZoneHVAC:FourPipeFanCoil object. Now I have changed it in both of them, and now I got the correct fan power, 1764 W with 0,36 W/CFM. So as far as I understood, the critical unit is the fan power more than the fan power per CFM. Am I right?

Kind Regards,



2013/12/23 Germán Campos <ecoeficiente@xxxxxxxxx>
 

When you say you have tried to modify the maximum air flow rate? Have you tried changing it in the ZoneHVAC:FourPipeFanCoil and also in the fan without success?

Regards,


_______________________________

Germán Campos

Aurea Consulting  


2013/12/23 <felipe@xxxxxxxxxx>

 

Dear Group,

I am trying to model a existing group of FCUs (7) with the following characteristis:
Max. Air Flow 1400 CFM x 7 = 9800 CFM
Fan power 252 W x 7 = 1764 W
So I ve got a a fan power per CFM of 0.18 W/CFM

When energy plus calculates the max. airflow it gives me 4788 CFM (half of the "real" installed equipment). I have tried to modify the maximum air flow rate but I have no been able to do it. So have tried to "force" the pressure rise so it gives me the total fan power with the half of the instaled maximum airflow rate I got 0.36 W/CFM.

Since I can not modify the maximum air flow rate, is it  fair to size the FCU fan considering its fan power per CFM (0.18 W/CFM)? even though the sizing results will be half of the FCU actual power (882W instead of 1764 W)?







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