The resistance to airflow a blower works against outside its own cabinet.
External static pressure is measured across the equipment (supply side and return side) with a manometer, usually in inches of water column or pascals. Compared with the blower table in the manufacturer's data, it tells you roughly how much air the system is moving. High static, from undersized ducts, dirty filters or restrictive coils, reduces airflow, which affects capacity, coil temperature and comfort.
Exam work areas
C · Planning installs and retrofits E · Commissioning and start-up