Tag

nfpa-72

• July 28, 2026 · 6 min read

  NFPA 72 Secondary Power: The 24-Hour Standby Rule Explained

  Why NFPA 72 wants 24 hours of standby plus 5 minutes of alarm (15 for voice), how that feeds the battery calc, and when a generator fits instead.

• July 13, 2026 · 6 min read

  Building a Fire Alarm Device Matrix (With a Real Example)

  A walkthrough of a real device matrix: addresses, circuits, currents, and the annunciation and supervision columns a plan reviewer actually checks.

• June 29, 2026 · 5 min read

  Battery Calc Differences: Potter vs Fire-Lite vs Silent Knight

  How Potter, Fire-Lite, and Silent Knight structure battery worksheets differently: where to find the numbers and how each handles the derating factor.

• June 26, 2026 · 5 min read

  Sizing a NAC Circuit: Current Limits and Voltage Drop

  How to add up horn/strobe current draw, apply NAC de-rating, and know when voltage drop forces a circuit split or booster.

• June 25, 2026 · 5 min read

  Duct Smoke Detector Requirements Without the Guesswork

  CFM thresholds, sampling tube sizing, remote station placement, and the IMC vs NFPA 72 overlap that catches fire alarm techs off guard.

• June 24, 2026 · 4 min read

  Class A vs Class B Fire Alarm Wiring: When and Why

  Understand the survivability difference between Class A and Class B fire alarm wiring, where AHJs actually require Class A, and the real cost tradeoff.

• June 23, 2026 · 5 min read

  Fire Alarm Candela and Strobe Spacing, Explained

  How to read the NFPA 72 candela tables for wall and ceiling strobes, pick the right cd rating for a real room, and avoid the sync gotcha.

• June 21, 2026 · 8 min read

  NFPA 72 Battery Calculation: A Step-by-Step Walkthrough for Working Contractors

  Walk through the 24-hour standby and 5-minute alarm battery calc from NFPA 72 using real numbers from a Potter panel swap, including the 1.2x derating factor.

• June 21, 2026 · 8 min read

  Fire Alarm Voltage Drop Calculation: The Real Numbers (and Why Most Submittals Show Zero)

  How the fire alarm voltage drop calc actually works, why the panel maker's form almost always shows zero, and when you really need real wire-run numbers.

• June 21, 2026 · 10 min read

  What Goes in a Fire Alarm AHJ Submittal Package? (Based on 47 Real Approved Jobs)

  A practical checklist of every component in approved fire alarm permit packages, with notes on which AHJs want each one, from 47 real completed jobs.