EPW Warnings in BEOpt 3.1.1

asked 2026-06-18 12:58:19 -0500

muhl

217 ●6

updated 2026-06-19 12:35:51 -0500

Aaron Boranian

14480 ●93 ●25 http://bigladdersoftware.com/

Why am I receiving these errors? I used the standard weather data provided.

3.xml:  Warning: No EPW design conditions found; calculating design conditions from EPW weather data.
1.xml:  Warning: No EPW design conditions found; calculating design conditions from EPW weather data.
2.xml:  Warning: No EPW design conditions found; calculating design conditions from EPW weather data.
4.xml:  Warning: BackupHeatingActiveDuringDefrost does not apply when system has separate backup heating.
4.xml:  Warning: No EPW design conditions found; calculating design conditions from EPW weather data.

Thanks

Comments

That's strange, you should not be seeing them for any TMY3 EPW weather file (which is what BEopt ships). Can you provide your BEopt project file?

shorowit ( 2026-06-18 13:50:59 -0500 )edit

Absolutely (here)! Sorry it wasn't with the original post.

muhl ( 2026-06-22 10:18:07 -0500 )edit

Hi @muhl, I can't seem to download the file from that link, it only lets me view it. Can you fix it? Or you can email it to me.

shorowit ( 2026-06-23 09:49:14 -0500 )edit

I updated access to Editor. https://drive.google.com/file/d/1CYpk...

muhl ( 2026-06-25 11:43:56 -0500 )edit

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answered 2026-06-25 13:15:10 -0500

shorowit

13112 ●235 ●9 https://www.nlr.gov/bu...

Apparently there are a number of TMY3 weather files that don't have any ASHRAE design conditions in them. If I knew that at one point, I had forgotten it. When this happens, BEopt (or, really, OpenStudio-HPXML) will calculate the 1% and 99% design conditions from the 8760 hourly weather data to use for HVAC design load and autosizing calculations, in which case it throws a warning because those calculations differ from the approach ASHRAE uses to develop design conditions. But there isn't any other option.

Since the BEopt user cannot do much about this warning (other than modifying the weather file), we should really suppress the warning. We'll do that for the next BEopt release. Thanks for bringing this to my attention.

For what it's worth, I looked through all the U.S. TMY3s and found 151 of the 1011 have no design conditions. For Connecticut, 3 of the 7 have no design conditions.

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Does this warning have implications for both BEOpt and OS-HPXML in calculating results that match BPI-2400? Do we need to adjust the 3 of 7 files in CT to match ASHRAE to align more closely to Manual J sizing? (Thank you for the specific call-out for CT!)

muhl ( 2026-06-26 10:55:57 -0500 )edit

I don't think you need to address it. Even if you introduced the ASHRAE design conditions for those 3 locations and it changed autosized HVAC capacities by 5 or even 10%, that's not going to move the needle very much on the simulation results.

shorowit ( 2026-06-26 12:46:56 -0500 )edit

@shorowit Or even just change the category from Warning to something less sever like Notice, since the information might still be useful for some people?

jpierce ( 2026-06-30 07:25:09 -0500 )edit

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EPW Warnings in BEOpt 3.1.1

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