Increase in cooling setpoint -> substantial drop in reheat energy
I am running the prototype building energy models for medium size office buildings in energyplus. In the parametric study, I am testing the change in energy consumption with respect to increase in cooling setpoint (72 to 77F) while keeping the heating setpoint constant 68F.
For an increase in cooling setpoint, I see the drop in cooling energy which is expected, however, most of the HVAC savings are coming from a drop in terminal electric heating energy. For example, for San Francisco, the increase in cooling setpoint from 72F to 77F is resulting in 68% drop in reheat coil energy. Am I missing something?
isn't this the expected behavior? higher supply air temperature means less heating of air is needed for zones that are calling for heating.
Thanks Matthew. True, the return air temperature will be higher but, the central cooling coil will the cool the (recirculated + OA) supply air to 55F anyway. Therefore the high return air temperature should not have any impact on the reheat coil. Reheat coil should kick in only if the zone temperature falls below the heating setpoint 68F and that does not change in any of the cases I am running. Therefore I am trying to understand how the change in cooling setpoint affects the reheat coil operation if the supply temperature from central cooling coil is kept at 55F.