[TRNSYS-users] Internal error in solar radiation distribution when shortening simulation's time step.

[Javier Vega via TRNSYS-users]

Hi,

I'm a Chilean mechanical engineering student currently working in my
thesis. I'm doing simulation of combined Solar and Heat Pump Systems and
recently I'm stuck with this problem, with no clue of how to solve this
situation.

I wanted to describe a 5 stage building with 78 appartments. As a result, I
made 89 thermal zones on the Type 56 module. I worked before on little 1 to
5 thermal zone buildings.  The thing is, I have a 1 hour interval
meteorological data file and the system runs well if I simulate with 1 hour
timestep. But, if I try to do simulations with shorter timesteps (which is
a necessity for what I'm doing)  I get the following warnings and fatal
error:

Examples:

*** Warning at time       :       355.333333
    Generated by Unit     :     4
    Generated by Type     :    16
    Message               : The calculated horizontal diffuse radiation
exceeded the horizontal extraterrestrial radiation and was set to the
extraterrestrial for 2 timesteps during the simulation.

*** Fatal Error at time   :       355.333333
    Generated by Unit     :     2
    Generated by Type     :    56
    Message               : Internal error in solar radiation distribution
(sumsitot) of    76.095 % at time   355.33wave length band no.3 1:total
solar, 2:visual solar, 3:non visual solar

I've lowered the timestep simulation with the control cards in the
simulation studio to 45min-30min-15-min-5min, and I've also done my own
weather file with a 5min timestep. The problem appears with all previous
scenarios, but the fatal error always comes in a different timestep if I
change the interval.

It's important to say I've noticed the solar radiation data must be
interpolated by Type 16, and that's what I'm doing (if I haven't done
anything wrong with that).

My biggest problem with this issue is that I don't understand it, so I
don't know how to track it. If the problem comes from solar radiation, why
would type 16 make a bad interpolation? And especially, why is it Type 56
the one who gives the fatal error?. I've tried to look for "sumsitot" in
the trnsys documentation and the internet but I haven't found anything that
helped me understand it.

Hoping for help,sincerely thanks
Javier Vega Benavente
Mechanical Engineering Student, Universidad de Concepción, Chile
Contact: (+569) 93529373
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