HVAC Systems & Airflow Control Flashcards
7 cards from real FSD practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 HVAC Systems & Airflow Control flashcards as text
Which NFPA standard governs the installation of fire dampers in HVAC duct systems?
Answer: NFPA 90A
NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems, governs fire damper installation in HVAC ductwork.
A combination fire/smoke damper must comply with which UL standard?
Answer: Both UL 555 and UL 555S
Combination fire/smoke dampers must comply with both UL 555 (fire dampers) and UL 555S (smoke dampers) since they perform both functions.
What is the primary purpose of an actuator on a motorized smoke damper?
Answer: Open or close the damper blades upon receiving a control signal
The actuator is the electromechanical device that physically positions the damper blades open or closed in response to a control signal from the fire alarm or building automation system.
In a variable air volume (VAV) HVAC system, why is damper leakage rating especially important?
Answer: Leakage affects the accuracy of zone temperature control and can compromise smoke containment
In VAV systems, damper leakage affects zone temperature accuracy and, critically, can allow smoke migration past a closed smoke damper during an emergency.
A fire damper installed in a rated floor-ceiling assembly must achieve which minimum fire-resistance rating when the assembly is rated at 2 hours?
Answer: 2 hours
Fire dampers must have a fire-resistance rating at least equal to the rating of the assembly in which they are installed; a 2-hour assembly requires a 2-hour damper.
What does the term 'dynamic closure' mean for a smoke damper?
Answer: The damper is rated to close against moving airflow without the system being de-energized first
Dynamic-rated smoke dampers (Class II) are tested and listed to close reliably against airflow while the fan is still running, unlike static-only dampers that require fan shutdown first.
Which component in a fire damper provides the thermal trigger that causes the damper to close?
Answer: Fusible link
The fusible link is a heat-sensitive element that melts at a rated temperature (typically 165°F), releasing the damper blades to close under spring tension.