Positive Value for MechVentEnergy

Hi everyone,

I’m trying to simulate the cooling/heating energy of a lab room. The value of mechanical ventilation energy in July is positive according to results. It sounds to me there is a problem with my model, but I can’t figure out the reason. I’d appreciate some clues about the factors that affect the MechVent energy and should be modified to acquire reasonable results.

Here is the summary of my model (ideal air loads is considered instead of HVAC systems):

Monthly Energy Balance Chart:

Sample Zone _ Energy.gh (939.0 KB)

My guess that is because in July when outdoor air temperature is higher than your room cooling setpoint, ventilation system is bringing warmer humid outdoor air to inside, which requires cooling system needs to do extra work to cool it down and dehumidify.

Thank you @MingboPeng. I can see it, but the point that I can’t realize is that it is necessary to alter certain operant parameters to prevent the result (may occur).

I mean, for example, in case of natural ventilation, the similar result (positive value) shows that the outdoor air is heating the simulated zone instead of cooling it down. So we have to set appropriate indoor and outdoor temperature limits for natural ventilation considering our cooling and Heating setpoints.

I wonder if there are some necessary limits\considerations in term of mechanical ventilation that I’m not aware of.