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Re: [TRNSYS-users] Message 441

Dear Edward,
It is not always clear how to find an appropriate order in which to call the components. The kernel recognizes that some components should be called at different times during the simulation: for example, during each iteration or only when the simulation has converged. Integrators and printers (Type25) are some of the components that are only called when all of the other types have converged. The feature in the Studio tries to help, but as I said, this is not a trivial thing, and some rules may work sometimes and do not work in other simulations.
One of the most important capabilities in TRNSYS is to be able to simulate many different kinds of systems. One user's simulations may not look anything like another user simulation. Therefore, it is very difficult to point out the exact cause of the problem when there are many reasons why the simulations may go wrong. What I have seen is that the most useful error message is generally the first one, as when something goes wrong it usually triggers many other problems. 

Best regards,

Diego

Edward Halawa wrote:

Dear Constanze,

The similar problem you had occurred to my first program using TRNSYS
16.0 this week. I was a bit "annoyed" to find out that the cause was
that the components order is not "optimum". (Version 15 problem stil in
there in Version 16).

I used as my first program the Solar Water Heating project created when
you click on the "Solar Hot water System" icon which appeard when you
create "New" project.

In this project I added a number of new components (forcing functions
and printers Type 25b-user supplied units). After satisfied with the
connection I clicked on the "Component Order" to hit the "Optimise
Components Order". My program worked. However, when I edited again
(adding more forcing function, changing connection etc), I had your
experience and my program halt after time 440 hr - Error Message 441
displayed. It took me one day (!) to see that the problem was because:
the component order "did not make sense". Pressing "Optimise Components
Order" button did not optimise the order ! Printers are in the middle,
radiation processor is near the end of the order (which should be in
right after the Type 9 and before collector", etc. (Note: I changed Type
109 to Type 9 plus Type 16g because I have different format of weather
data).

After this my prgram worked ... :) :(

Note:
(1) My solution (checking the Component order or Optimimise it
"manually") may not work to solve your problem but it's worth trying.
It's a bit of trial and error ... This may be annoying for a program
containing large number of components).
(2) I do not rely much on the "Error Analysis" created by Version 16.0.
Information is too much but (for most of my first week) I could not
pinpoint the problem by reading it. For example, when it wrote something
like "The ouput file may be locked by Microsoft Excel ..." may be not
the real cause. (I closed Excel and the problem still there). But after
I deleted altogether Type 25b and replaced it with Type 25a, the problem
disppeared). (3) "Loading TRNSYS and processing the input files. Please wait ..." 
takes quite long time to disappear.

Regards,


ehalawa


Constanze.Bongs@csiro.au wrote:

Hi,

During simulation the following warning occurred:
Message 441: The inputs to the listed units have not converged at this
timestep. The values of the last iteration will be used to proceed. 
As I get this message more than thirty times Trnsys sends an error
message and stops the simulation. 
I already set the tolerance convergence to 0.5 (from 0.001) and
tolerance integration to 0.01 (from 0.001).
Can you explain to me what is happening and how I can fix it? Does

this

mean that the system is too complex to be solved and are the

simulation

results still useful? Which maximum values for tolerance convergence

and

tolerance integration still manage to give me reasonable results?

Cheers,

Constanze

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--

Diego A. Arias
TRNSYS Coordinator
Solar Energy Laboratory
University of Wisconsin - Madison
1500 Engineering Drive
Madison, WI 53706