CSLB C-20 HVAC ContractorVentilation and Air DistributionMedium
A technician measures static pressure on a residential air handler: supply plenum reads +0.28 inches w.c. and return plenum reads -0.32 inches w.c. What is the Total External Static Pressure (TESP)?
- A0.28 in. w.c.
- B0.60 in. w.c.
- C0.32 in. w.c.
- D0.04 in. w.c.
Show answer & explanationAnswer & explanation
Correct answer: B. 0.60 in. w.c.
TESP is the sum of the absolute values of supply and return static pressures: 0.28 + 0.32 = 0.60 in. w.c. This combined value is compared to the blower's rated maximum external static pressure to verify proper airflow.
Why the other options are wrong
- A. This reflects only the supply-side reading.
- C. This reflects only the return-side reading.
- D. This is the difference, not the sum, of the two readings.
Total External Static Pressure (TESP)
The sum of static pressures on the supply and return sides of an air handler, used to verify system airflow against blower ratings.
- TESP = |supply| + |return|
- Compared against manufacturer's rated max ESP
- High TESP often indicates restricted duct or dirty filter
Memory trick: Add the pushes, ignore the signs, get your TESP.