CT Fire Alarm flashcards
CT Fire Alarm · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- NFPA 72 pathway Class A
- A supervised circuit that continues to operate with a single open or ground fault; the redundant path allows all devices to remain functional.
- NFPA 72 pathway Class B
- A supervised circuit where a single open fault causes loss of function beyond the fault but does not affect devices ahead of it; no redundant path.
- NFPA 72 pathway Class X
- A supervised circuit that continues to operate during a single open, short, or ground fault; requires isolation at each device or segment.
- Record of completion
- A document required by NFPA 72 that records the installed system configuration, sequence of operations, and acceptance test results, signed by the contractor and owner.
- Smoke detector spacing rule
- On a smooth ceiling, spot smoke detectors are spaced at 30 ft (9.1 m) with 21 ft (6.4 m) between detectors on a row and 10.6 ft (3.2 m) from walls.
- Intelligibility requirement
- Voice alarm systems must achieve a common intelligibility scale (CIS) or speech transmission index (STI) of at least 0.45 in each occupiable area.
- Primary power supply
- A dedicated 120 VAC branch circuit for the fire alarm system, marked "FIRE ALARM CIRCUIT CONTROL," with disconnecting means accessible only to authorized personnel.
- Secondary power supply
- Batteries sized for 24 hours of standby plus 5 minutes of alarm (or 4 minutes for voice systems), per NFPA 72 Table 10.6.7.2.1.
- Battery capacity formula
- Required Ah = (standby current × standby hours + alarm current × alarm hours) × 1.25, using the manufacturer's end-of-life derating.
- Voltage drop formula
- Vdrop = 2 × L × I × R, where L is one-way distance in feet and R is resistance per foot; the end-of-line voltage must exceed the appliance minimum.
- Ohm's law and power
- V = IR; P = VI = I²R = V²/R. A 24 VDC appliance drawing 0.5 A dissipates 12 W and presents 48 Ω.
- Ground fault annunciation
- The control unit must annunciate a ground fault on any supervised circuit conductor; a single ground must not cause an alarm.
- Battery recharge requirement
- The charger must restore the battery to 85% capacity within 24 hours after a full discharge; float voltage for a 24 V lead-acid bank is about 27.6 V.
- Ionization smoke detector
- A detector using a radioactive source to ionize air; it responds better to flaming, fast fires with small particles than to smoldering fires.
- Photoelectric smoke detector
- A detector using light scattering or obscuration; it responds better to smoldering fires with larger particles than to flaming fires.
- Rate-of-rise heat detector
- A heat detector that triggers when temperature rises faster than about 15°F per minute, independent of the absolute temperature reached.
- Duct smoke detector
- A detector installed in an air-handling system rated over 2,000 cfm to shut down the unit and close dampers; sampling tubes must span the duct width.
- Manual pull station location
- Pull stations must be within 5 ft (1.5 m) of each exit door, mounted 42-48 in. (1.07-1.22 m) above the floor, and unobstructed.
- Projected-beam detector spacing
- Maximum 60 ft (18.3 m) between units and 30 ft (9.1 m) from walls; the beam path must be unobstructed and the detector listed for the ceiling height.
- Heat detector spacing
- On a smooth ceiling, 50 ft (15.2 m) for 135°F units and 30 ft (9.1 m) for 194°F units, with the first detector within half the spacing of a wall.
- Audible signal level
- At least 15 dBA above average ambient or 5 dBA above maximum ambient, whichever is greater, measured 5 ft (1.5 m) from the floor.
- Maximum audible level
- Public mode audible signals must not exceed 110 dBA at minimum hearing distance; above 105 dBA ambient, visible-only notification may be permitted.
- Visible appliance candela
- Candela ratings are selected from NFPA 72 Chapter 18 tables based on room size and mounting height; 15 cd minimum for a 20 ft × 20 ft room.
- Strobe synchronization
- Visible appliances in the same field of view must flash in phase within 10 milliseconds; a listed sync module or the control unit provides synchronization.
- Strobe flash rate
- Strobes must flash at 1-2 Hz with a pulse duration of at least 0.1 second, maintained for the life of the appliance.
- Notification appliance circuit
- A supervised circuit (Class A or B) supplying audible and visible appliances; an end-of-line resistor detects open, short, and ground faults.
- Wall-mounted strobe height
- Wall-mounted visible appliances are installed 80-96 in. (2.03-2.44 m) above the floor; ceiling-mounted units are at the center of the room.
- Plenum-rated cable
- CMP cable is required in environmental air-handling spaces unless installed in metallic conduit; CMR cable is used in vertical shafts.
- Acceptance testing scope
- NFPA 72 Chapter 14 requires testing 100% of initiating devices, 100% of notification appliances, and all control unit functions for new installations.
- Smoke detector sensitivity testing
- Sensitivity must be tested within 1 year of installation and every 5 years thereafter, using a listed test method; the detector must be within its listed range.
- Cable support interval
- Fire alarm cables must be supported at intervals not exceeding 10 ft (3 m) and within 12 in. (300 mm) of boxes.
- ITM frequencies
- Monthly for control unit indicators and batteries, quarterly for alarm and supervisory devices, annually for all initiating and notification devices, every 5 years for smoke sensitivity.