Generator Sizing Calculator (backup power)

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab

Tranche

tranche-7

Evidence ID

t7-126

Ledger rows

1

No ledger note is attached.

Review findings

The running-total and one-at-a-time incremental-surge calculations in the vectors are standard planning estimates. The specification needs revision before implementation: define whether starting_w is absolute or multiplier-derived, define simultaneous-start behavior, and provide a recommendation policy such as reserve margin, kW versus kVA handling, rounding increments, and environmental derating. Until those are defined, the calculator can report running and estimated peak-starting watts but cannot honestly compute a unique recommended generator size.

Formula and scope findings

• The stated starting-power formula is ambiguous when inputs already contain starting watts: it should use each load's absolute starting wattage, or explicitly derive it as running watts multiplied by a documented multiplier.
• For non-simultaneous starts, the standard planning calculation is Ppeak = sum(running watts) + max over loads of (starting watts - running watts), not simply a multiplier applied to the largest motor unless that motor is proven to produce the largest incremental surge.
• The formula does not define whether multiple motors can start simultaneously. If simultaneous starting is allowed, peak demand may require summing the relevant starting watts rather than adding only one surge.
• The recommended generator size has no formula. A reserve margin, rounding increment, power factor/kVA policy, and environmental derating policy are missing.
• The spec says the multiplier table is optional, but does not define behavior when a load has starting watts, a multiplier, or neither.

Unit assumptions

• All wattage values are real power in W; kW inputs must be converted using 1 kW = 1000 W before summation.
• The test vectors assume one load starts at a time and that the generator must cover the running load of all other loads.
• Starting watts are treated as absolute startup demand. If a multiplier is supplied, starting watts = multiplier × running watts.
• The 120 V and 10 A example assumes single-phase unity power factor, so W = V × A × PF.
• No generator-size recommendation can be computed without a documented reserve margin, rounding rule, and derating policy.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The specification does not define overflow handling, has no explicit unit-normalization rule, and does not state the recommended-size margin. Extreme inputs can become non-finite, while the same unit-ambiguous entry can produce 5000 W or 504.5 W.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "loads": [
      {
        "name": "resistive heater",
        "voltage_v": 120,
        "current_a": 10,
        "power_factor": 1,
        "running_w": 1200,
        "starting_w": 1200
      }
    ]
  },
  "expected_outputs": {
    "total_running_w": 1200,
    "peak_starting_w": 1200,
    "recommended_generator_size_w": null
  },
  "reference_data": {
    "nominal_single_phase_voltage_v": 120,
    "source_convention": "ANSI C84.1 nominal U.S. utilization-voltage convention",
    "unity_power_factor": 1,
    "source_convention_pf": "ideal resistive-load convention; not a lookup-table uncertainty"
  },
  "working": "Running power = V × I × PF = 120 V × 10 A × 1 = 1200 W. Total running = 1200 W. Incremental startup surge = starting - running = 1200 - 1200 = 0 W. Peak starting = total running + maximum incremental surge = 1200 + 0 = 1200 W. Recommended size is undefined because the specification gives no reserve or rounding rule."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche7/tranche7-results.json
• BOUNDARY_HAZARD_CATALOG.json