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Re: [EnergyPlus_Support] Minimum "Fixed" Outside Air



My earlier reply may have already answered this question.  When I look at the 
eio output, the "Calculated heating design air flow rate" value equals the 
"outside air flow per zone" input from the ZONE SIZING object.  But the cooling 
design flow rates dominate, so the overall system flow rates are miuch higher 
than these reported values.  The other issues mentioned earlier (terminal unit 
type, VAV min fraction, and coil controls) most likely explain why the setpoint 
temperatures are not being met.  The systems in this input essentially have no 
heating controls.

Regarding the inconsistent flow rates.  The "Peak Vol Flow" row at the bottom 
of the Zsz.csv output file represents the raw output from the purchased air 
simulations for the design days.  The design heating flow rates reported here 
do not include an sizing factors and limit checks.  In this case, the min OA 
requirements for each zone are larger than the computed heating flow rates, so 
the min OA flow rate takes precendence.  The value reported in the eio output 
is after all adjustments.

Mike


On 11 Oct 2007 at 16:34, aboyemeplus wrote:

> I am having difficulties understanding why the System Sizing routine 
> limits the calculated system design air flow rate to a value lower 
> than the user-input "Fixed" mimimum outside air flow rate, when the 
> zone temperature is below the heating setpoint temperature. 
> Lowering the supply heating air temperature resulted in even lower 
> zone temperature without any changes to the calculated design flow 
> rate. In a sizing calculation, I would expect a higher flow rate to 
> be calculated to meet the setpoint temperature. Apparently i must be 
> missing something! Please provide insight when possible. If you need 
> a file to work with, use the IDF uploaded in the 
> PROBLEM_SUBMITTAL\MAB3 folder on 10/10. Thank you for your support.
> 
> Merid 
> 
> P.S.
> Calculated heating design air flow rates reported in the ".eio" file 
> (under the System Sizing Information section)  are different that 
> values listed in the ".CSV" file. Am I reading the reports wrong? 
> Please verify if you have some time.


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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