Unitary DX Cooling Sizing

When using the Unitary DX cooling sizing method the Cooling design calculation is made through a detailed EnergyPlus simulation using Compact HVAC Single zone Unitary DX equipment. A diagram of the system layout used is shown in the Unitary Single Zone topic.

 

Each zone has it's own Unitary system with a fan (generating no pickup), a DX cooling coil, an outside air controller and a damper to reduce supply air flow. More specifically:

 

Note: Unitary DX will tend to calculate higher latent loads than the other 3 cooling sizing methods and the zone air humidity will generally be lower. This is because DX coils run colder than water-cooled coils and will condense out more water from the supply air. Unitary DX can often be used to provide a conservative calculation for the latent cooling loads.