Hello Equest friends,

I am working in the DD Wizard (and trying to not move into Detailed Mode), building the Proposed and Baseline models for a project that is in the middle of design. I took the Proposed model file and did a "Save As" to create the Baseline model, so I know that the two models are starting out the same. My Proposed HVAC system is a Packaged VAV with Electric Heat and my Baseline system is a Packaged Heat Pump Constant Volume. When I only change the system type in the Baseline model from the Proposed Pkgd VAV to the Constant Vol. HP, my annual energy consumption for cooling reduces in the Baseline model (I would expect no change), the heating consumption reduces (this is to be expected), and the fan power goes down in the baseline. I can't figure out, when I change from a VAV to a Constant Volume system why the fan power would ever go down. I was hoping to make up for the HP's better heating efficiency through reduced fan power.

This just doesn't make sense to me. Remember, I'm still in the DD Wizard and only have limited access to changes. Can anyone explain this to me and offer advice on how to achieve more predictable results? Thanks in advance for the help.

Kristy M. Walson, PE, LEED AP