Source: https://guthlabs.ai/docs/instruments/wire-ampacity-calculator/
instrument / verified-clean
# Wire Ampacity Calculator
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## 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**: t7-068
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The supplied honest label is appropriate but incomplete. Before implementation, require material, code edition and jurisdiction, current-carrying-conductor count, terminal temperature rating, conductor installation method, and an explicit distinction between NEC and IEC calculation engines. No interpolation is used in these vectors; every lookup lands exactly on a cited table row or factor.
### Formula and scope findings
- NEC Table 310.16 is not sufficient by itself: its ampacities assume no more than three current-carrying conductors in a raceway or cable, 30 °C ambient, and the applicable conductor material and insulation temperature column.
- The input schema omits conductor material. AWG/kcmil ampacity differs substantially between copper and aluminum, so the material must be an explicit input or a documented default.
- Conductor count is not necessarily current-carrying conductor count. Equipment grounding conductors, some neutrals, and certain control or balanced-circuit conductors may be excluded under NEC rules; the calculator must either request current-carrying conductor count or clearly state its counting convention.
- Ambient-temperature correction and conductor-count adjustment are multiplicative factors, but the result must also be limited by conductor terminal temperature ratings and other applicable code limits.
- Conduit fill is generally a separate physical-fill calculation, not an ampacity derating factor. It may affect how many conductors can be installed and therefore the current-carrying-conductor count, but it should not be applied as an independent ampacity multiplier.
- The formula must specify the insulation rating used for adjustment, normally the 90 °C column for THHN/THWN-2 adjustment, while final allowable ampacity is limited by the applicable 60 °C or 75 °C terminal rating.
### Unit assumptions
- All currents are in amperes, conductor sizes are AWG, and ambient temperature inputs are degrees Celsius.
- The test vectors assume copper conductors, because material is absent from the supplied input schema.
- THHN is treated as having a 90 °C insulation rating for adjustment calculations; final ampacity is limited to the 75 °C terminal column.
- The NEC convention used is NEC 2020: Table 310.16 values at 30 °C ambient and no more than three current-carrying conductors; ambient correction factors from Table 310.15(B)(1); conductor-count adjustment factors from Table 310.15(B)(3)(a); and small-conductor limits from 240.4(D).
- The reported code_max_allowable_ampacity_A is min(adjusted 90 °C ampacity, terminal-temperature ampacity, any applicable small-conductor limit).
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
An ambient temperature such as 200 C lies outside the NEC correction-factor table and has no defined derating result. The calculator must reject it; extrapolating a factor or returning a numeric ampacity would be a hazard. The convention probe also shows that the conductor-count field needs an explicit current-carrying-versus-total definition.
## 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": {
"material": "copper",
"size": "12 AWG",
"insulation": "THHN",
"ambient_C": 30,
"current_carrying_conductors": 3,
"terminal_rating_C": 75
},
"expected_outputs": {
"base_ampacity_90C_A": 30,
"adjusted_ampacity_90C_A": 30,
"terminal_limited_ampacity_A": 25,
"code_max_allowable_ampacity_A": 20
},
"reference_data": {
"table_310_16_copper_12_AWG": {
"60C_A": 20,
"75C_A": 25,
"90C_A": 30,
"source_convention": "NEC 2020 Table 310.16"
},
"ambient_correction_90C_at_30C": {
"factor": 1,
"source_convention": "NEC 2020 Table 310.15(B)(1)"
},
"current_carrying_adjustment_for_3": {
"factor": 1,
"source_convention": "NEC 2020 Table 310.15(B)(3)(a)"
},
"small_conductor_limit_12_AWG": {
"maximum_A": 20,
"source_convention": "NEC 2020 240.4(D)"
}
},
"working": "Base 90 °C ampacity = 30 A. Ambient factor at 30 °C = 1.00. Three current-carrying conductors require no adjustment, factor = 1.00. Adjusted ampacity = 30 × 1.00 × 1.00 = 30 A. The 75 °C terminal limit is 25 A, so terminal-limited ampacity = min(30, 25) = 25 A. NEC 240.4(D) limits 12 AWG copper to 20 A, so final code maximum = min(25, 20) = 20 A."
}
````
## 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`