Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page
Ask Your Question

Weather file, cannot find the first day

asked 2020-11-03 15:50:01 -0600

Aly ElHefny gravatar image

updated 2020-11-26 22:56:53 -0600

Hello everyone, I hope you are all doing well.

I'm facing the following error, when using a custom epw file I have put together using minute by minute weather data: * Fatal * Error occurred on EPW while searching for first day, stopped at 2019/2/16:26 IO Error=-1

I've changed the start day (from use from weather file) to Tuesday, I've tried starting at instance 0:01 and at 0:00 and also specified the starting year of the simulation. My design days are declared typical to the .ddy file for the region I'm simulating. I also tried declaring design days from weather file but had no luck. My header of the epw file as well as the (data periods) line seem ok when comparing with a TMY weather file: DATA PERIODS,1,60,Data,Sunday, 1/ 1,12/31 The data I'm using to generate the file is minute by minute and I'm using the file to simulate a 1 minutes resolution.

The custom weather file runs well on energyplus but this problem occurs when simulating multiple fmus through pyfmi. Also when I run a single fmu, I'm able to output different output variables and export them to external excel files through pyfmi.

Any hints on the reason behind that would be very helpful. Thanks and Stay Safe

Update: After extended testing, the setup works only if the start time is anywhere between January and somewhere in February. Any other start day beyond that will crash by this error. It looks like the code gives up relatively early on finding the start day. This problem does not happen when running hourly TMY file but rather with the larger minute resolution weather file. Can someone confirm that he experienced a similar behavior ?

edit retag flag offensive close merge delete

2 Answers

Sort by ยป oldest newest most voted

answered 2020-11-04 06:17:23 -0600

kwalkerman gravatar image

what weather file indicators do you have checked as "yes" under RunControl? Sounds like this issue:

Sometimes this error occurs when there is not enough information in the weather file to support all the weather indicators checked as "yes" under RunControl.

edit flag offensive delete link more


Hello @kwalkerman, thanks for your reply. The indicators are: Use weather file holidays and special days: yes, use weather file daylight saving period: yes, apply weekend holiday rule: no, use weather file rain indicators: yes, use weather file snow indicators: yes, I'm using EP 8.9.

Aly ElHefny gravatar image Aly ElHefny  ( 2020-11-04 06:39:08 -0600 )edit

try turning them to "off" & see if that fixes the problem, then you can drill down on which one is causing the issue.

kwalkerman gravatar image kwalkerman  ( 2020-11-04 07:00:48 -0600 )edit

I'm pretty sure the linked issue is not the exact problem, as the internals have changed quite a bit between 8.9 and 9.4, but I do agree that the problem is probably something similar. I also agree that switching up the yes/no values should shed some light on what's going on. That bug is assigned to me, so I'd be interested to know what is going on.

Jason DeGraw gravatar image Jason DeGraw  ( 2020-11-04 10:28:44 -0600 )edit

Hello Jason DeGraw and kwalkerman, I have turned all the weather indicators of RunControl to no and the problem is still there. I'm not sure if this is the reason since the weather file runs ok solely on energyplus v8.9 with same RunControl indicators.

@Jason DeGraw

Now I have multiple fmus simulated ok when wrapped with TMY (simulating minute resolution). Custom weather file ( minute raw data and minute simulation timestep ) running ok on ep v8.9.

Aly ElHefny gravatar image Aly ElHefny  ( 2020-11-04 10:49:05 -0600 )edit

The problem seems to happen when simulating multiple fmus wrapped including the custom minute weather file (simulating minute time step).

Aly ElHefny gravatar image Aly ElHefny  ( 2020-11-04 10:50:39 -0600 )edit

answered 2020-11-08 15:31:38 -0600

lklawrie gravatar image

You say "The custom weather file runs well on energyplus but this problem occurs when simulating multiple fmus through pyfmi."

Does this mean when you use the custom weather file with EnergyPlus standard, it runs. But when you are simulating fmus thru the other interface it does not?

It sound like the 2nd problem is that that interface is expecting only hourly weather files, not the multiple interval files of a minute. Would that make some sense why it fails?


edit flag offensive delete link more


Hello Lawrie, I'm happy to know that you are in good health. Yes, I believe that's exactly what is happening , and my question is, did anyone encounter this problem with simulating an energyplus fmu through pyfmi ? So the minute by minute file runs well through pyfmi only if it starts anywhere between January and somewhere in February. So this leaves me with the impression that, my pyfmi setup can run a minute resolution BUT there is a problem with that when finding the start day.

Aly ElHefny gravatar image Aly ElHefny  ( 2020-11-08 15:42:19 -0600 )edit

So I think the problem is that the code just stops early when searching for the start day. And that's why it runs ok when the start day is within its maximum search range.

Aly ElHefny gravatar image Aly ElHefny  ( 2020-11-08 15:49:25 -0600 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools

1 follower


Asked: 2020-11-03 15:50:01 -0600

Seen: 556 times

Last updated: Nov 26 '20