NFPA 72 work procedure

NFPA 72 Battery Sizing Workflow

A practical calculation sequence for standby load, alarm load, aging margin, and standard battery size selection.

Guide workflow

Follow the sequence as an engineering workflow: each phase lists the action, tools, and evidence to retain before moving forward.

Phase	Action	Tools	Evidence to keep
Step 1	Collect total standby current for all connected equipment.	Fire Alarm Battery Capacity Calculator	Document the source used to start the NFPA 72 workflow.
Step 2	Collect total alarm current for notification and control loads.	Fire Alarm Battery Capacity Calculator, Fire Alarm NAC Voltage Drop Calculator	Keep calculation notes showing how this step supports: collect total alarm current for notification and control loads.
Step 3	Apply the required standby and alarm durations.	Fire Alarm Battery Capacity Calculator, Fire Alarm NAC Voltage Drop Calculator	Keep calculation notes showing how this step supports: apply the required standby and alarm durations.
Step 4	Apply the aging margin when required by the project basis.	Fire Alarm Battery Capacity Calculator, Fire Alarm NAC Voltage Drop Calculator	Keep calculation notes showing how this step supports: apply the aging margin when required by the project basis.
Step 5	Select the next standard battery size and verify cabinet constraints.	Fire Alarm Battery Capacity Calculator, Fire Alarm NAC Voltage Drop Calculator	Record the reviewed output, warning state, and next review decision.

1NFPA 72 workflow basis and project condition that triggered this guide.
2Input source notes for each calculator used in the sequence.
3Intermediate results, warnings, and pass/fail states from linked tools.
4Final review notes for engineering review, submittal review, field check, or AHJ coordination.

1The sequence starts with project-specific inputs, not untouched default values.
2Each intermediate result is checked before being transferred into the next calculator.
3Warnings or failed screens are resolved or documented before final project use.
4NFPA 72 context and local AHJ requirements remain part of the final review.

1Use this guide as a workflow checklist, not as a sealed design package.
2Start with the related worksheet before treating the guide as complete.
3Open the linked calculators when a step needs a numeric screen.
4Transfer only reviewed values and documented assumptions into project calculations or submittal material.

NFPA 72 Battery Sizing Workflow

1Start from the standard workflow context when the guide controls a design or field-review decision.
2Open the related worksheet before treating the guide as complete.
3Run the related calculator sequence when a step needs numeric screening.
4Retain reviewed inputs, warnings, and handoff notes before final project use.