FANS Internal Gains

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Fans do contribute to internal heat gain, but this heat is introduced only when HVAC units are operating. You can check this heat gain component during both heating and cooling. For instance, during heating if your report out Air System Fan Air Heating Energy and Heating Coil Heating Energy variables you will notice that the heating coil supplies less energy than needed, since, fan contributes to the air stream heat gain (provided that the fan system is a blow through fan with fraction of motor in the airstream set to 1).

During zone thermal load prediction calls EnergyPlus predicts the zone thermal loads considering regular internal gains (electric equipment, occupants etc.). HVAC calls are made in a proceeding call, and fans only contribute to changing the airstream supply temperature to the HVAC units - increasing cooling demand from system during cooling scenarios and reducing heating demand from system during heating scenarios (assuming that fans are placed upstream to the flow-loop).