External static pressure refers to the resistance that an air handler must overcome to push air through a duct system. This is a critical measurement for our Concealed Duct and Ducted Systems. If the pressure is too high, airflow will be restricted, causing the system to work harder and reducing its lifespan. Most mini-split air handlers are designed for low to medium static pressure, making them ideal for short duct runs. We provide the static pressure capabilities in the Technical Data for all our ducted air handlers. If you are replacing a traditional system, you may need a Multi-Position Air Handler that can handle higher pressure. Ensuring your ductwork is properly sized and clean will help maintain the ideal pressure for your system. It is a technical but vital aspect of ensuring your whole-home cooling works as intended.