[TRNSYS-users] Convergence problems with type 56 possibly involving cooling load

[Ethan Lust]

Hello,

I am trying to simulate the operation of a climate control unit (vapor
compression air conditioner and electric resistance heater) in a small
closed space.  The climate control unit (CCU) (Type 202 and the accompanying
DLL7) is an original component created from manufacturer's data.  Prior to
the heater and air conditioning code within the Type202.f code, there is a
switch that keeps the air conditioner and heater from operating
simultaneously.  The climate control unit is operated via a PID controller
(Type 23).  In addition, the space also has an internal heat load due to
some electronics, hence the three type 9a components and the Type 41c.     

If the heat from the CCU is input into Type 56 through the heating function
in TRNBuild and the cooling output from the CCU is attached likewise, there
are a number of points over the course of the TMY2 year at which the program
"bogs down" and stops with the calculations though no error message is
produced.  Occasionally an error message will pop up stating that there are
6 errors (no matter how many I have set to allow within the control cards),
which all relate to temperature divergence at a wall, according to the list
file.  I have tried increasing the convergence tolerance with no luck.    

If the cooling portion is removed, the program proceeds fine, with or
without the internal loads attached.  

I have sought help for a similar problem, to which I was suggested to
decrease the cooling output and/or decrease the time interval to aid in
convergence.  I've tried reducing the cooling input to very low values (the
DLL I'm sending has it cut in half) with no luck.  The current time interval
is a dreadfully slow 5 seconds.  

I have also tried connecting the cooling output of the CCU to the Type 56
using the gain function (using a negative value as input) with the same
result.  

Attached are the project, bui, component (fortran and proforma) files and
the DLL.    

Please help!

Thanks,
Ethan Lust
University of Maryland
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