Welcome to the TRNSYS Users Forum.
The forum is a place where people can interact and have discussions about different topics involving the use of the TRNSYS software package. Here you can post topics for discussion or questions on using TRNSYS and get advice from other users or TRNSYS experts. This forum is not intended for detailed technical support. Users should contact their distributor’s hotline for such assistance.
Some tips for success on using the forum:
- Follow the Forum Rules posted in Forum Administration.
- There are categories for different types of topics and questions. Post your topic or question into the proper category.
- Before posting a topic or question search the existing topics (and the TRNSYS Users listserv archive or Post archive) to see if a similar topic or question has already been answered.
- Use a descriptive topic name. Don’t use attention getting subjects, they don’t get attention and only annoy people.
- State the version of TRNSYS and which add-ons your are using.
- Include enough specific details for your topic of question to be answered. Just posting “Why am I getting an error?” without describing the specific error and what you are trying to do when you get the error will not receive a response that fixes your issue.
- Remember when people help you, they are doing you a favor. Be patient, help people out by posting good descriptions of what you need help with, and be polite even if a response does not solve your issue.
- Moderators may edit your post for clarity or move your topic to a more appropriate category.
Setting a simulation to run for a full month results in an I_LENGTH value of 28.
For example Jan 1 - Feb 1, May 1 - June 1. The Simulation start/stop time hours update correctly in the Settings dialog, but the DCK always has 28 as the I_LENGTH value. I can't seem to figure out any rhyme or reason to the value.
- May 1 - April 1 => I_DAY = 28
- Jan 1 - Jan 1 12 h => 8016
- Jan 1 - Jan 14 => 7
- Jan 1 - Jan 21 => 14
- Jan 1 - Mar 1 => 56
- Jan 1 - Apr 1 (May 1, Jun 1, Jul 1 ...) => 56
- . . .
****************************************************************************
Control cards
*******************************************************************************
* START, STOP and STEP
*|[SIMPAR|Simulation Parameters
EQUATIONS 5
I_MONTH=2880
*|<Month of the simulation |C:\TRNSYS18\Exe\Month1.dat|1|2|2
I_DAY=1
*|Day of Month for Simulation Start |||0|1|1|31|3
I_LENGTH=28
*|<Length of Simulation |C:\TRNSYS18\Exe\Length.dat|2|1|4
START=I_MONTH+24*(I_DAY-1)
STOP=START+I_LENGTH*24
EQUATIONS 1
STEP=5/60
*|Timestep |hours|hours|0|1|0.0000277777778|10000.00000|1000
*|]
SIMULATION START STOP STEP ! Start time End time Time step
I'm not sure why these equations are being used.
When I create a simple project: START, STOP, and STEP, are simply written directly to the deck file without the above equations.
I have resorted to simply running 28-day long simulations for now 🙁
wsdols Topic starter
07/01/2025 3:47 pm
Hey Tim,
The snippet is from the .dck file which is being generated each time I run the simulation from Simulation Studio via the .tpf file.
There is no .trd file in my project folder.
Manually changing the I_LENGTH in the .dck file does not work as it just gets overwritten again.
I suppose I could edit/re-import the .dck file, but this I_LENGTH behavior seems like an “unplanned feature” to me.
I do find length.dat file in TRNSYS\Exe\, and it reflects the whacky I_LENGTH behavior.
6
1, One Day Simulation
7, One Week Simulation
14, Two Week Simulation
28, Four Week Simulation
56, Eight Week Simulation
365,One Year Simulation
I don't find any details on the content of this file in the documentation.
Can I edit it to set the desired length of my simulation?
- Stuart
TimMcDowell 08/01/2025 5:00 pm
@wsdols Please send us the tpf file so we can see why it is creating such a dck file.
The snippet you included is from a TRNSED file (*.trd) and not a deck file (*.dck). The extra comments in the file are there to define the user interface for selecting parameters. In this case, the simulation length is supposed to be user-selected from a file called length.dat. If you are not using TRNSED to select the parameters, you should be able to change the value of I_LENGTH to the number of days you want to simulate.
I think that the "write TRNEdit commands" option might be unintentionally set to "true." What that option does is to start writing some additional lines into the *.dck in preparation for starting to make a TRNSED distributable. You can switch it off using one of the radio button fields in the project settings (where you set the simulation start/stop times but on the "advanced" tab.)
As a side note, the I_LENGTH equation isn't used unless you open the *.dck in TREdit and reset the length of the simulation using a TRNSED pulldown menu.
best,
david
