Plan Reading, System Layout, Wiring Methods, and Battery Calculations
What the exam tests
Plan reading, layout, wiring methods, and battery calculations test whether you can turn a design into a code-compliant installation and prove the standby power will work.
Core rules
- Read the legend, scale, north arrow, riser diagram, device schedule, and circuit schedule before counting devices.
- Layout must respect detector spacing, notification coverage, exit access, and access for testing.
- Wiring methods follow Article 760: PLFA cable listings, Chapter 3 raceways, separation from power, support, firestopping, and survivability where required.
- Battery calculation: standby current times standby hours plus alarm current times alarm hours, then multiply by 1.25 for capacity and aging.
- Verify voltage drop on notification appliance circuits so the last appliance receives its listed operating voltage.
Worked example
A panel draws 0.40 A standby for 24 hours and 2.0 A alarm for 5 minutes. Standby = 0.40 times 24 = 9.6 Ah. Alarm = 2.0 times 5/60 = 0.167 Ah. Total = 9.767 Ah. Multiply by 1.25 = 12.2 Ah. Select a listed battery of at least 12.2 Ah, then confirm the charger can recharge it within the code time.
Traps
Using alarm current for the full standby period; forgetting the 1.25 factor; ignoring auxiliary loads; mixing PLFA and NPLFA wiring; and selecting a battery without checking the charger's recharge rating.