Re: [TRNSYS-users] convergence problem

[David BRADLEY <bradley@tess-inc.com>]

Caroline,
  You should first look at your time step. TRNSYS iterates at each time step to
find a solution to the system and if your equation is such that the air change
rate increases a lot for a small change in room temperature then over an hour
long time step, this translates to a large amount of energy transfer. I'd
consider using a time step no larger than about 5 minutes. If that does not
help, then you can turn to using a Type93 to base your control decision on the
room temperature from one timestep prior to the current one.
Kind regards,
 david


Quoting Caroline Hoffmann <HoffmannCaroline@gmx.de>:

> Dear TRNSYS users,
>
> Trying to do something simple, things are getting complicated?
> I would like to use the zone temperature of TYPE 56 as an input to define
> via an equation a dependent air change rate (simply spoken as the room is
> getting warmer, airchange rate is increasing).
> Doing this I get the message ?XXX WERE NOT CONVERGED WITHIN THE SPECIFIED
> TOLERANCE AT TIME?. I found in the archive the hint that in the case of
> using the room temperature as an input it is necessary to use a TYPE 2
> controller to achieve convergence. But with this solution as far as I know
> it is just possible to define a ?threshold value? (after which airchange is
> starting) and not a variable airchange rate as I would like to.
> Using trnflow would be a solution, but for this simulation I use a measured
> weather data set, which contains no data of wind speed.
>
> Could anybody give me please a hint how I could solve this problem within
> TRNSYS 15?
>
> Thank you in advance,
>
> Caroline
>
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David BRADLEY
Thermal Energy System Specialists, LLC
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