Airflow & Ductwork
Static pressure, CFM, duct sizing, returns and filters.
400 CFM per Ton: Where the Rule Comes From and When It's Wrong
Why 400 CFM per ton is the default cooling airflow, when to set airflow lower or higher, and how to check what a system is actually moving.
Total External Static Pressure: How to Measure It and What's Normal
Measure total external static pressure with a manometer, compare it to the equipment's rating, and use it to find airflow restrictions.