Source: https://guthlabs.ai/docs/instruments/inrush-current-fuse-breaker-sizing-estimator/implementation/

instrument implementation / implementation-contract

# Inrush Current / Fuse & Breaker Sizing Estimator implementation

A source-bound implementation contract for Inrush Current / Fuse & Breaker Sizing Estimator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-099

**Effect**: Computation or source lookup only

## Input and validation requirements

The estimator has hazardous boundary behavior unless it validates inputs: zero current produces a meaningless zero rating, negative current can produce invalid negative ratings under a literal signed interpretation, and a very large transformer current causes the inrush calculation to overflow to infinity. The transformer multiplier is also only specified as a 10–15x range, so the selected table endpoint must be documented.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "steady_current": 10,
    "steady_current_unit": "A",
    "load_type": "motor",
    "safety_margin": 1
  },
  "expected_outputs": {
    "recommended_rating_A": 12.5,
    "inrush_current_estimate_A": 60
  },
  "reference_data": {
    "continuous_current_factor": 1.25,
    "continuous_current_factor_source_convention": "NEC-style rule of thumb; widely tabulated 125% sizing heuristic, not a universal NEC device-rating table entry",
    "inrush_multiplier": 6,
    "inrush_multiplier_source_convention": "widely tabulated standard engineering rule-of-thumb value for a typical across-the-line induction motor"
  },
  "working": "1. Continuous-current basis = 1.25 × 10.0 A = 12.5 A.\n2. Apply safety margin = 12.5 A × 1.00 = 12.5 A.\n3. Estimated inrush = 6.0 × 10.0 A = 60.0 A.\n4. Provisional outputs: recommended rating = 12.5 A; inrush estimate = 60.0 A."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/inrush-current-fuse-breaker-sizing-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/inrush-current-fuse-breaker-sizing-estimator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/inrush-current-fuse-breaker-sizing-estimator/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`