HVAC Ductwork 4

Question 1

What is 'total external static pressure' (TESP) in an HVAC system?

Accepted Answer

Combined pressure drop across all external components the blower must overcome

Answer

TESP is the sum of all static pressure drops external to the air handler — including ductwork, filters, coils, and grilles — that the blower must overcome to move air.

Question 2

A duct system has a design static pressure of 0.08 in. w.g. per 100 feet. What design method is being used?

Accepted Answer

Equal friction method

Answer

The equal friction method designs all duct sections to have the same friction rate (pressure drop per 100 feet), making it straightforward to size ducts from tables.

Question 3

Fire dampers are required by code to be installed where ducts:

Accepted Answer

Penetrate fire-rated walls or floor-ceiling assemblies

Answer

Fire dampers must be installed wherever ducts penetrate fire-rated construction (walls, floors, ceilings) to prevent fire and smoke from spreading through the duct system.

Question 4

What is the function of a duct sound attenuator (silencer)?

Accepted Answer

Absorb sound energy to reduce noise transmitted through ductwork

Answer

Sound attenuators contain sound-absorbing material (typically fiberglass) that dissipates acoustical energy from fan and airflow noise before it reaches occupied spaces.

Question 5

In a duct system, what causes the 'stack effect' to influence duct airflow in tall buildings?

Accepted Answer

Temperature difference between inside and outside air creating buoyancy-driven pressure differences

Answer

The stack effect occurs when indoor-outdoor temperature differences create buoyancy forces that drive air up or down through vertical shafts, affecting duct pressure and airflow distribution.

HVAC Practice Test

HVAC Practice Test

HVAC Ductwork 4