[TRNSYS-users] solar hort water system trnsys 16.01

[David Bradley]

Javier,
   There is a discussion of some of the difficulties associated with 
modeling controllers with discrete time steps in section 5.1 of the 
05-Mathematical Reference manual.

   Another problem that you may be having is insufficient thermal 
capacitance in your system, particularly if you have a collector loop that 
consists of a pump, collector, and heat exchanger. You need to make sure to 
include enough piping in the loop to store at least 1 time step of fluid. 
Without the piping, there is no capacitance in the loop (assuming that you 
are using the Type1 solar collector or some other model that does not 
include capacitance effects) and the controller will have an impossible 
time converging on a decision without coming up against its oscillation 
limiting parameter. The "high limit cut out" parameter may also be a 
problem. If your collector temperature gets above the high limit cut out 
temperature then the controller automatically shuts off the pump for that 
time step. The following time step, the controller tries again and may turn 
the pump on, leading again to oscillations.
Kind regards,
  David


At 05:10 4/27/2006, javier mota wrote:
>Dear all:
>i am javier mota from 3i-ingenieria, madrid
>we are looking the file "solar hot water system" in trnsys
>16.01(FILe>new>solar hot water system)
>we have looked the behavieour of pumps, signal control, of controller.
>we  have seen that some times controller must be on because T
>upper-tlower>death band but in this circumstances controller signal is off.
>We look too that even when the off condition is not reached beacuse
>Tupper-tlower<death band lower is not correct the controller is of. For
>example death band=0;
>Tupper>tlower and pumps stopped.
>I suspect that this may have relation with parameter 1: oscilation, but
>really i don´nt know.
>May anybody tell me something about this.
>where can i founf more information about controller.
>may i think that even of this things program works properly?
>thanks in advance
>
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