Mixed mode ventilation control doesn't seem to work

asked 2020-09-28 04:25:49 -0500

updated 2020-09-28 10:20:52 -0500


I'm working on design builder to model a pool which can be naturally ventilated when favourable conditions occur to provide natural moisture evacuation. I have trouble understanding the way natural ventilation and mixed mode ventilation controls work.

I tried natural ventilation with enthalpy control + mixed mode with enthalpy control, with a maximum outside enthalpy of 75 000 J/kg, and minimum of 20 000 J/kg, a natural ventilation setpoint of 29,5°C, heating setpoint at 29°C and cooling setpoint at 32°C.

The results for "AFN infiltration air change rate" are not logical: sometimes all the conditions should be met and the air change rate is 0, sometimes some of the conditions don't seem to be met (for example zone mean air temperature < 29,5°C) and there is natural ventilation. Furthermore, heating demand (zone ideal loads supply air heating rate) is occuring wheareas internal temperature is higher than 29°C. What could make this happen? Is the natural ventilation setpoint in the activity tab still used when mixed mode ventilation is turned on?

I also tried to regulate the mixed mode ventilation using dewpoint temperature, but i get zero natural ventilation airflow, whereas in numerous moments the conditions are clearly met (internal dewpoint T > external dewpoint T and other conditions are also OK). Has anybody an idea of why it never activates?

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