Total External Static Pressure Testing - T.E.S.P.

1. TESP is the measure of resistance the blower must overcome outside (external) to the air handler or furnace cabinet. (ductwork, coil, grilles, dampers, filters, etc...)
2. Static probes should be positioned into the direction of airflow. The holes in the probes are perpendicular to the airflow.
3. If individual readings are taken for TESP
   • Add the two readings together for TESP
4. 0.50” w.c. is usually the max TESP recommended by most manufacturers using multi speed blowers.
   • Variable speed blowers can be slightly higher.
5. Most manufacturers TESP numbers are based on a wet coil.
   • A dry coil will have a lower TESP
6. Static probes can be place on each side of a piece of equipment (coil, filter etc.) to get the pressure drop (resistance) across that specific piece of equipment.
   • Subtract the low reading from the high reading when testing individual components for pressure drop.
7. Always remember to read the notes on the bottom of the manufacturer’s blower performance table for specifics in testing their equipment.

Upflow Gas Furnace with a Return Drop

Downflow Gas Furnace

Horizontal Furnace

Horizontal Heat Pump or Air Handler