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Re: [EnergyPlus_Support] Re: 100% OA and DX Coils



The problem is not the dual DX coils.  Even with just one DX coil, the errors 
happen.  For some reason some early iterations at certain time steps are 
throwing a flow rate >8 m3/s at the ventilation system mixed air outlet.  The 
reported flow rate for this node is always 3.781 as it's supposed to be.  But 
when the DX coils see the higher flow rate, the warnings are tripped.  I'm 
passing this along to someone else for further investigation.

Mike


On 9 May 2007 at 1:03, asheaffe wrote:

> I uploaded the file that I am having trouble with.  There are two 
> BypassFactorEmpirical coils (please disregard fact that they are 
> currently named MultiMode) in series in a constant volume system.  I 
> have hand sized them to be within the cfm/ton limits (as near as I 
> can tell) and I am still getting warnings about being over those 
> limits (high air flow).  
> 
> Andrew
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> <mjwitte@...> wrote:
> >
> > Assuming this is a constant volume system, two dx coils in series 
> will work.  
> > The coils need to fall within the allowable flow/capacity range 
> (0.00004027 to 
> > 0.00006041 m3/s per watt of rated total cooling capacity, 300 to 
> 450 cfm/ton).  
> > For example, for a flow rate of 4500 cfm, each coil could have a 
> capacity of 10 
> > to 15 tons.  I have actually done simulations like this.  If you 
> cannot get 
> > this to work, please provide an input file.
> > 
> > If this is not a constant volume system, then you will need to use 
> > Coil:DX:MultiSpeed:CoolingEmpirical with the same contsraints at 
> full flow.
> > 
> > Mike
> > 
> > 
> > On 3 May 2007 at 20:30, asheaffe wrote:
> > 
> > > To All,
> > > 
> > > I am having a hard time getting EPlus dx coils to handle a 100% 
> > > outdoor air flow.  I am using a 100% outside air stream as a 
> DOAS air 
> > > stream, so I want the temp to be neutral - 18C, and I have a 
> > > predifined volume airflow.  I have tried putting two multimode 
> coils 
> > > in series and two standard bypassfactor coils in series.  In 
> both 
> > > situations, I get a ton of warnings when I run the simulations - 
> > > namely that the cfm/ton is out of range during the simulations.  
> I 
> > > must be setting something up wrong.  Is there a way to set up DX 
> coils 
> > > to that I can meet that 18C exit temp without the warnings?
> > > 
> > > Thanks,
> > > 
> > > Andrew
> > > 
> > > 
> > > 
> > > 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.
> > > 
> > > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf 
> under the
> > > Documentation link and press the "search" button.
> > > 
> > > Yahoo! Groups Links
> > > 
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support      
> > EnergyPlus-Support@...
> >
> 
> 
> 
> 
> 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.
> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the
> Documentation link and press the "search" button.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 


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





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