NATE Air Distribution

Question 1

What does external static pressure (ESP) measure in an HVAC duct system?

Accepted Answer

Total resistance to airflow the blower must overcome, measured in inches of water column

Answer

ESP is the sum of supply and return static pressures and indicates how hard the blower works against the duct system resistance.

Question 2

What tool is used to measure air velocity in a duct or at a register?

Accepted Answer

Anemometer or flow hood

Answer

An anemometer measures air velocity in feet per minute (FPM); a flow hood captures total CFM at a register directly.

Question 3

What is Manual J used for in residential HVAC design?

Accepted Answer

Calculating heating and cooling loads for a structure

Answer

ACCA Manual J is the industry-standard load calculation procedure that determines the BTU capacity required to heat and cool a home.

Question 4

What is the purpose of a balancing damper in a duct branch?

Accepted Answer

Adjust airflow to individual zones to balance the system and deliver correct CFM to each room

Answer

Balancing dampers restrict airflow in over-supplied branches, diverting more air to under-supplied areas for proper room-by-room comfort.

Question 5

What condition does a very high return static pressure typically indicate?

Accepted Answer

Restricted return airflow due to clogged filter, blocked return grilles, or undersized return duct

Answer

High return static pressure means the system is starved for return air, which reduces airflow and increases strain on the blower.

NATE - North American Technician Excellence Practice Test