HVAC Diagnostics: External Static Pressure (ESP), Airflow & Delta T

The discussion moves into how different blower motor types respond to airflow problems, from older PSC motors that would simply bypass air when restricted, to constant torque and constant volume ECM motors that ramp up trying to overcome restriction. Ty breaks down why understanding motor behavior matters just as much as the pressure numbers themselves when a system isn’t performing the way it should.

What’s covered in this diagnostics conversation:

• External static pressure basics and where to actually take the reading
• Test port options, from platform taps to drilled holes and specialized bits
• Checking static pressure across filters, coils, and other components
• How PSC, constant torque, and constant volume motors respond to airflow issues
• Setting airflow using manufacturer charts and static pressure readings
• Why blower charts aren’t always accurate, and when to bring out a flow measurement tool
• Proper probe placement for supply and return readings
• Traversing a duct system for a true velocity-based airflow calculation
• Getting an accurate Delta T reading and avoiding common probe placement mistakes

Whether you’re chasing a nagging callback, setting up a new install, or just want to sharpen your diagnostic process, this one is packed with practical tips you can use on your next truck roll.