Re: [EnergyPlus_Support] Unitary System Problem

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

It sounds like there is a bad flow rate somewhere in the input file.  Check the 
flow rate on the direct air unit, the primary air loop, and the furnace.  If 
you cannot find the problem, please upload the input file to the yahoo files 
area or send as a zipped attachment to energyplus-support@xxxxxxxx

Mike


On 6 Apr 2005, at 23:20, bartlettbmw wrote:

> 
> 
> I am trying to model a residential home for my Master's Degree Plan 
> B paper and am running into problems with the unitary system.  I am 
> modeling the home as a single zone and using the 
> FURNACE:BLOWTHRU:HEATCOOL as the plant.  I have specified the fan, 
> gas coil, and DX coil.  When I run the model, I get the following 
> error (60,000 times):
> 
> ** Warning ** COIL:DX:COOLINGBYPASSFACTOREMPIRICAL "DX COIL" - Air 
> volume flow rate per watt of rated total cooling capacity is out of 
> range.
>    **   ~~~   **  ...VolumeFlowperRatedTotCap=3.085E-006 Occurrence 
> info=CHICAGO IL USA TMY2-94846 WMO#=725300, 04/07 17:30 - 17:45
>    **   ~~~   ** Expected range for VolumeFlowperRatedTotalCapacity=
> [3.3560E-005--6.7130E-005]
>    ** Warning ** Enthalpy out of range (PsyTsatFnHPb)
> 
> Based on the text of the error, it appears that the airflow rate is 
> too low and the cooling coil is having problems.  I think I modeled 
> everything correctly, put the unitary system on the air loop and 
> connected it to the zone using a DIRECT AIR component as described 
> in the Input/Output reference.  I am modeling a 4 Ton cooling system 
> with 400 CFM/Ton.  This amounts to about 14,000 Watts and 0.75 m^3/s 
> airflow rate.  When I do a quick calcualtion, this should be about 
> 5.35e-5 m^3/sW (0.75/14000) and should be right in the middle of the 
> acceptable range (3.35e-5 to 6.7e-5).  For some reason, the model is 
> not seeing the airflow or is incorrectly calculating the cooling 
> load.  I was wondering if anyone has any suggestions, or has run 
> into this problem in the past with the Unitary system.  I am using 
> the FAN:SIMPLE:ONOFF component with 0.75 m^3/s flow rate.
> 
> I would really appreciate any suggestions/help..
> 
> Thanks
> 
> 
> 
> 
> 
> 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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