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Re: [EnergyPlus_Support] Exceeding max iterations
If the system has been described with consistent flow rates and no node
connection errors, then max iteration errors can often be eliminated by using
smaller values for the "convergence tolerance" in controllers and other HVAC
components. Using values of 0.0001 or smaller will often eliminate most, if
not all, of these errors. There is also a bug in version 1.2.0.029 where the
combination of a VAV system with return fan and zone exhaust fan will cause
such errors. The only connection between this and the length of the RUN PERIOD
is that these problems can pop up more often at part-load conditions than peak
load. EnergyPlus is certainly intended to run a full year simulation.
The ** Warning ** No valid range found for Loop Demand=-4245251.64 in
Load Range Based Operation Scheme=CHILLER OPERATION means that the chilled
water loop demand has exceeded the largest load range value in the "Chiller
Opearation" scheme. Increase the last "load range upper limit" value to be
something very large.
Mike
On 1 Sep 2004, at 8:09, beyangj wrote:
> Dear,
>
> Now I have some problems about maximum iteration. When I define the
> Runperiod in my EnergyPlus's input file as follow:
> RunPeriod,
> 1, !- Begin Month
> 1, !- Begin Day Of Month
> 12, !- End Month
> 31, !- End Day Of Month
> Tuesday, !- Day Of Week For Start Day
> Yes, !- Use WeatherFile Holidays/Special Days
> Yes, !- Use WeatherFile DaylightSavingPeriod
> Yes, !- Apply Weekend Holiday Rule
> Yes, !- Use WeatherFile Rain Indicators
> Yes; !- Use WeatherFile Snow Indicators
> After the simulation, it gives many warnings about exceeding max
> iterations. I don't know why this happened.
> I run the example file of lgoffvav.idf in the Energyplus's
> Examplefiles folder, there are two warnings about exceeding max
> iterations. But when I define the Runperiod in the lgoffvav.idf the
> same as before for one year, there are also many warnings about
> exceeding max iterations, and the elapsed time is 57min 04sec. I
> wonder whether the Energyplus's runpeiod is only for a few days, not
> for one year or more?
> When I define the Runperiod in my input file only for two days,
> there are 4 warnings about exceeding max iterations, but the results
> are not correct. There is a warning as follow:
> ** Warning ** No valid range found for Loop Demand=-4245251.64 in
> Load Range Based Operation Scheme=CHILLER OPERATION.
> ** ~~~ ** All equipment will be turned off. Other cases of this
> condition will not be reported.
> I don't know how to deal with the problems, could you help me?
> Thanks in advance!
>
> Best,
>
> Stewart
>
>
>
>
>
> 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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