MT Fire Alarm flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Smoke detector 30-foot rule

On smooth ceilings up to 10 ft high, spot-type smoke detectors are spaced no more than 30 ft (9.1 m) apart, with the first detector within 15 ft of any wall.

Pull station mounting height

Manual fire alarm pull stations must be mounted 42 to 48 inches above the finished floor to the operating handle, and located within 5 ft of each exit door.

NAC supervision

Notification appliance circuits are supervised for opens, shorts, and grounds; a listed end-of-line resistor matching the panel value terminates the circuit.

Alarm signal priority

NFPA 72 requires alarm signals to take precedence over supervisory and trouble signals; trouble signals must not be silenced by alarm silence functions.

Audible 15 dBA rule

Audible notification must exceed ambient by 15 dBA or exceed the maximum 60-second ambient by 5 dBA, whichever is greater (NFPA 72 18.4.1.1).

Voice intelligibility STI

Voice evacuation requires STI of at least 0.50 (0.45 in rooms with 0.20-0.80 s reverberation), or CIS of at least 0.70, per NFPA 72.

Addressable SLC

A signaling line circuit is a supervised addressable loop where each device reports individually; capacity is set by the panel listing, often 99 to 318 devices.

Four-wire detector circuit

Four-wire detectors receive power on an unsupervised or separately supervised power circuit and report alarm via a supervised relay contact on the signal circuit.

Ohm's law

Voltage equals current times resistance (E = I × R). Power equals voltage times current (P = E × I), also expressed as I²R or E²/R.

Voltage drop formula

For a two-wire circuit, VD = 2 × K × I × L / CM, where K is about 12.9 for copper, I is amperes, L is one-way length, and CM is circular mils.

NEC Article 760

Article 760 governs fire alarm systems, dividing requirements into Part I general, Part II non-power-limited, and Part III power-limited circuits, including cable listing rules.

Class 2 circuit limit

Class 2 circuits are power-limited to 100 VA and specific voltage-current tables under NEC 725.121; Class 3 exceeds those limits but remains power-limited.

Copper ampacity 12 AWG

Per NEC 310.16 at 60°C, 14 AWG copper is 15 A, 12 AWG is 20 A, and 10 AWG is 30 A for small conductors.

Battery standby calculation

NFPA 72 requires standby capacity of 24 hours (60 hours for voice) plus 5 minutes of alarm, with manufacturer derating, typically to 80% end-of-life capacity.

NAC voltage drop limit

Notification appliance circuits should not drop more than 10% of nominal voltage from the panel terminals to the last appliance, per NFPA 72 and listings.

Parallel resistance

In parallel circuits, the reciprocal of total resistance equals the sum of reciprocals of each branch (1/R_T = 1/R1 + 1/R2), and voltage is equal across branches.

Ground fault detection

A ground fault on a supervised circuit creates a current imbalance detected by the panel; typical detection thresholds range from 10 to 50 kΩ depending on the panel.

Montana Electrical Board

Fire alarm installation in Montana is regulated under Title 37, Chapter 68, MCA by the State Electrical Board within the Department of Labor and Industry.

Montana license types

The Montana Electrical Board issues journeyman, master, and electrical contractor licenses; fire alarm work is performed under a licensed electrical contractor.

Montana CE requirement

Montana electricians renew every three years and must complete 24 hours of approved continuing education, including code update hours; verify the current cycle.

Montana NEC adoption

Montana adopts the National Electrical Code by administrative rule; the adopted edition is updated periodically, so confirm the current edition before design.

Unlicensed practice penalty

Under 37-68-201, MCA, practicing without a license is a violation subject to fines and possible misdemeanor prosecution by the State Electrical Board.

Montana apprentice registration

Apprentices must be registered with the Montana Department of Labor and Industry and work under direct supervision of a licensed journeyman or master electrician.

Montana permit authority

Fire alarm permits and plan review are obtained through the local jurisdiction and AHJ, not the State Electrical Board, which handles licensing and inspections.

Montana reciprocity

Montana has limited reciprocity with certain states for electricians; verify eligibility with the State Electrical Board before relying on an out-of-state license.

Lockout/tagout

OSHA 29 CFR 1910.147 requires disconnecting and locking the fire alarm control panel primary and battery power, then verifying zero energy before service.

Arc flash PPE

NFPA 70E requires an incident energy analysis or PPE category selection; energized work needs an energized electrical work permit and appropriate arc-rated PPE.

Lead-acid battery hazards

Lead-acid batteries emit hydrogen gas, so no open flames or sparks are allowed; use insulated tools and eye protection, and recycle batteries per EPA and DOT rules.

Ladder 4-to-1 rule

Extension ladders are set with the base 1 ft out for every 4 ft of working height, maintain three-point contact, and are inspected before each use.

Fall protection threshold

OSHA requires fall protection at 4 ft or more in general industry (29 CFR 1910.28) and at 6 ft in construction work.

Hearing protection threshold

Hearing protection is required when noise exceeds 85 dBA as an 8-hour time-weighted average; fire alarm horns can exceed 110 dBA at close range.

Smoke detector test method

Detectors are tested with canned smoke or manufacturer-approved aerosol; notify the monitoring company and building occupants before any test to avoid false dispatch.