Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
There are 2 methods for controlling HVAC systems, specifically the coils. One is load based, the other set point based. If you are trying to simulate a change in supply air temperature with a corresponding change in supply air flow rate, the set point based method may better represent your intent.
Regardless of the method used, coil performance is a function of the inlet air condition, which is represented through performance curves. As the coil air inlet air condition (wet-bulb temperature) increases, the cooling capacity increases while the energy use decreases (a result of higher refrigerant suction temperature/pressure). You should see this result in the hourly simulation output.
However, there is a well known mantra that the load is the load is the load. If you are seeing similar results, I suspect that the zone temperatures are similar, which means you are meeting the same load (and also should see similar coil entering air conditions). If this load is met using a higher supply air temperature, at the expense of added fan power and fan heat, the question is then what optimal combination works best.
Without seeing very specific system sizing results it is very hard to provide more specific guidance.
