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Re: [EnergyPlus_Support] SimHVAC - max iterations exceeded -- error
You can add "Diagnostics, DisplayExtraWarnings;" to see more information about
how far out of balance things are when a max iteration error occurs. From the
symptoms you describe, I would expect to see that the simulation is not far off
from a solution and may simply be oscillating near the solution.
The max iteration errors are not related to the simulation warm-up period. For
each HVAC time step, the simulation iterates until the loop temperatures and
loads (at various checkpoints) do not change from one iteration to the next by
more that the tolerance criteria. The Maximum HVAC Iterations limit defaults
to 20. You could also try increasing this value to see if the simulation is
able to converge with more iterations using the "System Convergence Limits"
object. If you cannot come to a conclusion on this, you may upload the input
file to the yahoo files area, or send it as a zipped attachment to energyplus-
support@xxxxxxxx.
Mike
On 22 May 2006 at 6:47, Don Kins wrote:
>
>
> "Michael J. Witte" <mjwitte@xxxxxxxx> wrote: It could be air-side,
> water-side, controls, overloading, a wide variety of
> issues. You mention that the errors are occuring at certain hours of the day.
> What type of system are you modeling?
>
> Water cooled VAV system nothing special with respect to (WRT) heat recovery
> etc.
>
> Are the errors occuring during recovery
> from setback? Or at peak load conditions?
>
> The errors are mostly occuring just after a night setback time period but
> some errors are found during peak loading if the modeling day is set to peak.
>
> Are the zone temperatures being
> maintained during these hours?
>
> I have not found any obvious times when the set-points are not maintained
> within a small degree that would correlate to the hours the errors are
> occuring.
>
> If this is a system with hot water and chilled
> water loops, are the loop setpoints being maintained during these hours?
>
> The loop set-points are being maintained during the hours of error.
>
>
>
> Mike
>
>
>
> I am now in the process of reselecting equipment based on reasonable
> assumptions to make sure that something isn't under sized. We had originally
> had some challenges with a chilled water bypass loop that is not currently
> being used in the model. The flow in the bypass loop should have always been
> zero based on the schedule but sometimes showed some very small flows. I
> would like to be sure this is not the error but am not overly confident that I
> can delete the loop without causing more errors to occur.
>
> Is there any reasonable degree of certainty of how "wrong/inconsistent" the
> resulting airflows will be while the max simulation error is occuring? I am
> assuming given my level of experience that the max sim error is telling me
> that the trial and error solution of the load calc is not consistent after the
> warm up days have completed.
>
> Thanks for your help,
>
> Dan
>
>
>
>
>
>
>
> On 18 May 2006 at 18:19, Dan Karnes wrote:
>
> > Hey all,
> >
> > I am still learning daily about E+ and am in need of a little expert
> > advice. During certain days of simulation, I am getting a varying
> > number of errors regarding the max iterations. The error occurs for
> > particular hours of the simulation day.
> >
> > When trying to troubleshoot this error, can I limit my search to the
> > air side components only? I am not sure if there is something wrong
> > with the model or if it is a weather file problem.
> >
> > Any advice/experience anyone has to offer would be greatly appreciated.
> >
> > 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.
> >
> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.idf and press
> the
> > "search" button.
> >
> > 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
>
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>
> Attachments are not allowed -- please post any files to the appropriate folder
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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