How do I solve failure to converge during warmup error?

convergence
energyplus
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I am simulating the same single zone at 4 cardinal orientations (N,E,S,W). The simulations run with no problems for every orientation except for the North. I get the following error message:

CheckWarmupConvergence: Loads Initialization, Zone="Zone_1" did not converge after 25 warmup days

I changed the warmup days to more than 25 but I still get the same error message. Any tip on how I can fix the problem?

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Alex Vlachokostas

asked 2015-02-04 11:19:32 -0500

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Jamie Bull

updated 2015-03-02 02:06:56 -0500

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I solved the warning error of "CheckWarmupConvergence: Loads Initialization, Zone="Zone_1" did not converge after 25 warmup days" by changing the "Loads Convergence Tolerance Value" from 0.04 to 0.07 under the object Building. The result values at the .csv file are very similar with before (when I had the warning error).

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Alex Vlachokostas

answered 2015-02-04 15:40:15 -0500

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I'm using Grasshopper/Honeybee and I don't know how I can change the tolerance value. As far as I know it's not included in the Honeybee components settings but it's possible to add "additional string" to idf file before running OpenStudio/EnergyPlus. Could you please let me know what do you exactly write to change the tolerance? Thank you

Aryan Shahabian (2018-06-05 06:19:48 -0500) edit

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Add this to your file: Output:Diagnostics, ReportDuringWarmup, ReportDetailedWarmupConvergence;
Then you'll have more information to dig into to diagnose what is going on. Look at timeseries data during warmup days. Compare the convergence summary data in the EIO files.

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Archmage

answered 2015-02-04 11:42:27 -0500

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'Archmage', thank you very much for your answer. I followed your hint and I understood that from the 4 convergence factors ("max temp comparison", "min temp comparison", "max heat load comparison", and "max cool comparison") the one that fails the convergence in my simulation is the "max heat load." Also, at the .eio file I can see the error in detail such as, "time step", "hour of the day", "warmup temp difference" and "warmup load difference" and read about it in the EP documentation (Output Details and Examples) but there is no troubleshooting of the problem. Any further hints? Thank you!