Dear Users,

I have a tiny and very simple hotel project to apply for LEED. The baseline system is PTAC (for residential) and proposed system is WSHP. When I run the model for both cases, the default supply air flow for the proposed system matches the actual design really well. However, for the Baseline PTAC system, in spaces with similar max cooling and heating load with the Proposed, the automatically generated supply air flow is twice or even three times that of the WSHP (as attached). With exactly the same delta T (20 deg F), I really cannot explain why such a result comes out. I attampted to calculate the supply air flow rate manually (with max load of the space, delta T, air density and Cp), and the result I have got is much smaller, close to that in the Proposed. I am sure there must be something terribly wrong with my Baseline model (attached) air-side setting. If someone could have a closer look into the model and give me some valuable advice, that would be greatly appreciated.

Regards,
Rick
PE, LEED AP