FC FC Ductwork & Air Distribution

Question 1

What is the purpose of a static pressure test on a forced-air furnace system?

Accepted Answer

To measure airflow resistance in the duct system and verify proper system operation

Answer

Static pressure testing reveals duct restrictions, undersized ductwork, or dirty filters that reduce airflow and system efficiency.

Question 2

What is the maximum total external static pressure (TESP) typically allowed for a residential furnace?

Accepted Answer

0.5 inches W.C.

Answer

Most residential furnaces are rated for a maximum TESP of 0.5 inches W.C.; exceeding this restricts airflow and causes overheating.

Question 3

What is the primary cause of high static pressure in a residential duct system?

Accepted Answer

Restrictive air filter, undersized ducts, or excessive elbows

Answer

Clogged filters, undersized supply or return ducts, and numerous sharp elbows are the most common causes of excessive static pressure.

Question 4

Which type of duct fitting creates the least resistance to airflow?

Accepted Answer

Long-radius swept 90-degree elbow

Answer

A long-radius swept elbow allows air to change direction gradually, creating far less turbulence and pressure drop than sharp elbows.

Question 5

Return air duct sizing should be based on which primary factor?

Accepted Answer

System airflow (CFM) requirements of the equipment

Answer

Return ducts must be sized to carry the full system CFM with acceptable velocity and pressure drop to ensure adequate airflow to the blower.

(FC) Furnace Installation and Maintenance Certification Practice Test