Re: [EnergyPlus_Support] Unable to autosize VAV dx coil

["Michael J. Witte" <mjwitte@xxxxxxxx>]

My apologies for the very delayed response.

1.  Changing the nominal SHR from 0.76 to 0.75 solves the problem in this case. 
 I have submitted this as a CR (#6403) to see if the error message could 
perhaps give a suggested SHR or do something to help get past the situation.  

2.  During unoccupied hours, SYSTEM AVAILABILITY MANAGER:NIGHT CYCLE will 
activate the system, but there is no way to force the system to stay at the 
minimum flow rate.  

Mike

On 27 Jul 2004, at 3:27, Michelle Smith wrote:

> I have uploaded files for a 2 story building with a DX rooftop VAV 
> unit. We are applying for LEED certification of this building and 
> need to show energy savings over the minimum ASHRAE 90.1 
> requirements.
> 
> I am not sure why E+ will not autosize the DX coil for this system. 
> I have a sunlit area too small error which I have been unable to 
> correct, perhaps this is also the problem with the autosize. 
> Solutions to both issues would be greatly appreciated.
> 
> It had been running, until I updated the ground temperatures and 
> changed the design day schedule to be always on. When the design day 
> schedule was set to be off during unoccupied hours, the warm-up 
> loads were causing the VAV box and reheat coil to be EXTREMELY over 
> sized (4-5 times bigger than required.) The VAV dampers were not 
> opening past minimum except for the morning hours.
> 
> That brings up another question, is there any way to model a single 
> duct VAV system that comes on at minimum flow during unoccupied 
> hours to meet a night setback temperature?
> 
> Michelle Smith
> Belle Engineering, LLC
> 
> 
> 
> 
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
> 
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
> 
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 



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




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