Re: [EnergyPlus_Support] Unitary System Problem

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

The problem was inconsistent fan modes.  In the FURNACE:BLOWTHRU:HEATCOOL 
object, the Operating Mode was set to CycFanCycCoil, but in the 
COIL:DX:CoolingBypassFactorEmpirical object, the Supply Air Fan Operation Mode 
was set to ContFanCycComp.  Changing this to CycFanCycComp eliminates the air 
flow errors.  I'll post a change request (CR) to see if we can add a check for 
this or at least mention this as a possible cause in the airflow warning.

Mike


On 7 Apr 2005, at 12:48, Michael J. Witte wrote:

> 
> 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
> 
> 
> 
> 
> 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
> 
> 
> 
> 
> 
> 
> 
> 
> 






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

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/