[TRNSYS-users] Problems with results in heating system

[Jeff Thornton]

Ale,

Don’t use Type 661 to prevent convergence issues - it only masks the problem and creates new ones.  It sounds like you are having issues with the mass flow rate.  I would plot every mass flow rate and make sure the system is behaving as expected.  You should also try the TRACE command and watch what’s happening each iteration to try and pinpoint the problem.

Jeff

Sent from my iPhone

> On Jun 29, 2018, at 5:19 PM, Ale Vargas via TRNSYS-users <trnsys-users at lists.onebuilding.org> wrote:
> 
> Hi everyone! I have read previous mails about problems with convergence in closed loops but I can't solve my problem...I have tried with diferents options: rearranging components in control cards (in logic order), decreasing time step, putting types with higher thermal mass at the end of the order of calculation. Just one option I haven't tried: putting type 31 instead of just links between types.
> 
> But one option worked and helped with convergence: putting type 661 (delayed output device). The problem about this is that results are not correct. 
> 
> About my simulation: I'm working on a hybrid heating system for a house. It consists in a heat pump that gives heat to the house through radiant floor, and extracts heat through horizontal ground heat exchanger and flat plate solar collectors. This system has two tempering valves: 
> 
> 1. First valve controls that mass flow does not pass through horizontal ground heat exchanger if soil is very cold (mass flow goes through a bypass) 
> 
> 2. Second valve controls that mass flow does not pass through tank if tank outlet towards the load is colder than mass flow. 
> 
> The diagram is attached to this mail. 
> 
> I ran the simulation and I obtained results so weird: sometimes the thermostat gives the signal of 1 (on, when the house need heating) and the flow out (to source) of heat pump is 0. And sometimes thermostast gives the signal 0 (off, house doesn't need heating) and the flow out (to source) of heat pump is 1532 kg/hr or 3065,83 kg/hr. Mass flow of heat pump to load is ok, but to source is strange. Then I realized that all mass flows of the side of the source were weird in the system: diverters, pumps, ICG, tank...The side of load is ok. 
> 
> I think that some type is giving outputs in a different time compared to other types, but I don't know what type is giving the problem: when I see the list file, it says:
> 
> 
> *** Warning at time       :      2935.000000
>     Generated by Unit     : Not applicable or not available
>     Generated by Type     : Not applicable or not available
>     TRNSYS Message    441 : The inputs to the listed units have not converged at this timestep. The values at the last iteration will be used and the simulation will proceed.
>     Reported information  : UNITS: 21  23  42  46  45  38  40  22
>  
>  
> *** Warning at time       :      3000.000000
>     Generated by Unit     :    27
>     Generated by Type     :     2
>     Message               : The controller was stuck during 12 percent of the simulation timesteps.
> 
> 
> 
> *** Warning at time       :      3000.000000
>     Generated by Unit     : Not applicable or not available
>     Generated by Type     : Not applicable or not available
>     Message               : The simulation failed to converge during 2 timesteps (2% of the time).
> 
> 
> *** Warning at time       :      3000.000000
>     Generated by Unit     :    23
>     Generated by Type     :   114
>     Message               : Pump mass balance failed during 7 timesteps. Please check the connections.
> 
> So I don't know which type is giving the problem (messages indicate problem with heat pump, pump, tees, tempering valves and tank) , and I don't know if type 661 can help in this situation. Somebody can help me please or give me some idea of what is happening? I can't detect the problem since two weeks! 
> 
> Thank you in advance! And sorry about this too large text! 
> 
> 
> -- 
> Alejandra Vargas Cáceres
> Estudiante Ingeniería Civil Mecánica
> Facultad de Ciencias Físicas y Matemáticas
> Universidad de Chile 
> <Diagram.JPG>
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at lists.onebuilding.org
> http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20180702/db42e110/attachment.html>