[TRNSYS-users] Type 966 and Type 954 air heat pumps related problems.

[David BRADLEY]

Jim,

  Your project connections are correct. I think your description of the 
building sounds reasonable too. I can't be 100% sure that the 
implementation is correct as I would need the look in the *.b18 file as 
well.


  The issues that you are running into with the heat pump and building 
are almost always caused by using too long a timestep (this should be on 
the order of 1 to 5 minutes) and/or a heat pump that is not sized 
correctly for the zone that it is serving. I'm not sure how you have 
handled the conditioning in the zones that are not served by the heat 
pump but I would recommend putting them into energy rate control while 
you are adding heat pumps. Each time you add a heat pump to a zone 
you'll want to turn off that zone's automatic/idealized heating and 
cooling. The problem is that if all but one zone is unconditioned, the 
additional load on the one conditioned zone (from all of its 
unconditioned neighbors) causes the heat pump to be undersized until the 
neighboring zones are also conditioned.

kind regards,

  David





On 08/26/2021 15:47, dimitris soukoulis via TRNSYS-users wrote:
> Greetings community.
> I am modelling a multizone building and I have two questions.
> First, I would like to know if I am modelling the geometry correctly 
> (through the TRNbuild wizard). It is a two floor apartment building 
> with two apartments in each floor, so in the floorplan window, I model 
> it as two separate floors (three zones each, with the middle zones 
> representing the hallways)-as shown in the picture- and then 
> connecting the floors  with adjacent floors ( or ceilings). Is that 
> the right way ?
> Secondly, I am constantly running into problems with the air pump 
> system I am using. I have tried both approaches -DOE coefficient and 
> catalog data- type 966 and 954 respectively, but I cant seem to solve 
> the warnings and errors of the simulation. Some common problems i get 
> are: Error 118  (SAT subroutine was called with a temperature below 
> absolute zero), fail of input convergence, controller (Type 166) 
> sticks for a considerable amount of timesteps. I also experience a 
> very slow simulation even with a timestep of 1 hour. I have tried many 
> things like short timestep, calibrating the heat pumps capacity, 
> increasing the zone's thermal capacitance, using the absolute instead 
> of the relative humidity etc.  but when I manage to erase one problem 
> the other appears.
> If anyone has some idea about what might be going wrong in my case I 
> would be reaally grateful, considering the time I have consumed trying 
> to get it right. I attached the .tpf of the simulation for better a 
> understanding of my project. Looking forward for your ideas.
>
> Thanks in advance,
>
> Jim Soukoulis
> National Technical University of Athens.
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI  53703 USA

P:+1.608.274.2577
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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