Exaust air damper control in Guideline36 model (Modelica Buildings Library)

asked 2020-10-10 15:44:10 -0500

solutionlx gravatar image

updated 2020-10-11 08:23:09 -0500

I had a question regarding the exhaust air damper control in Modelica Buildings Library Buildings 7.0.0/Examples/VAVReheat/Guideline36.mo. According to the GP36, the engineer must select among control logic options for relief/exhaust as follows:

  • AHUs using actuated relief dampers without a fan (maintain 0.05 '' building static pressure by modulating the relief damper)
  • AHUs using actuated relief dampers with relief fan(s)
  • For AHUs using a return fan with direct building pressure control
  • For AHUs using a return fan with airflow tracking control
  • For AHUs using non-actuated barometric relief only

It seems that in the current GP36 model in the library, there is no return fan and the exhaust damper is not controlled and always open. In the five-zone model, each zone has also infiltration leakage linked to the outside. Thus, the relief airflow through the economizer mixing boxes seems not to be controlled and calculated through the mass balance from the system.

I wonder if there is a numerical issue to implement one of the relief airflow controls to ensure the building positive pressure. Is it feasible to add a control loop for the relief damper to the model? Or, is it possible to add a return fan in this model? One of my colleagues told me that he once listened to Dr. Wetter's report that it is not numerically feasible to add a return fan to this model.

Thanks! Any hint or help will be appreciated.

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