Rule-pack-driven calculation engine
Same project payload, switch the standard, get demonstrably different numbers. Both rulebooks live as code, version-controlled with the engine.
NEC 2023 (NFPA 70-2023)
Articles 220 (load calc), 230 (services), 240 (OCP), 250 (grounding), 310 (ampacity). Hotel / school / hospital lighting demand factors. T220.42, T220.55 Col.C, T220.84(B), T240.6(A), T250.122, T250.66, T310.16.
CEC 2024 (CSA C22.1:24)
Rule 8-200(a)(i) residential basic, 8-202 lighting, 8-210 non-coincident, 8-304(1)(c) receptacle tier, 28-200 motor demand, 14-100 / 14-104 OCP, Section 16 EBC, Table 2 ampacity.
Trace per number
Every kVA, OCP, EGC, conductor size shows the rule that produced it: NEC-220.42 with formula, substitution, and result. Defensible at any plan review.
Switchable standards
Toggle NEC_2023 ↔ CEC_2024 on the same project — different rules fire, different demand emerges, no cross-contamination. Verified by 89 specs.
One state. Every section reactive.
Edit any field anywhere — demand, OCP, conductor, EGC, voltage drop, conduit fill, panel schedule, and single-line diagram all recompute in <300 ms.
Multi-entry-point UX
Start from project metadata, service parameters, panels, loads, or feeder overrides — same single source of truth. Convergence proven in spec.
CSV / Excel import
Paste your existing load schedule. Parser supports CSV and TSV, reports per-row errors, and previews before commit. Default panel auto-fills.
Equipment library
40+ real manufacturer items: Square D / Eaton / Bussmann / Hammond / Baldor / WEG / Siemens / Milbank. Filter by kind, voltage, ampacity, manufacturer.
Templates + branching
Four built-in starts (residential, office, industrial bundle, EVSE retrofit). Branch from any version into a new project. Source untouched.
Warnings, integrity, audit trail
26 warning codes. Force-delete with reason logged forever. Every state mutation tracked back to the engineer.
26 engineering warnings
GFCI / AFCI / continuous-likely / non-linear-neutral / temperature-rating-mismatch / coordination-violation / VD-exceeded / ampacity-insufficient / conduit-fill-exceeded / panel-balance-off — each with affected element IDs.
Element graph + integrity
Delete a panel with active loads — impact report shows what becomes orphan. Force-delete still allowed but the reason is required and recorded permanently.
Immutable change log
Every save / restore / force-delete / status change writes to an append-only audit log with actor email + timestamp + reason. No API to mutate it.
Single-line diagram
Engine-driven SVG. Conductor labels, OCP, EGC, SPD callouts pulled from the same numbers as the report. Live preview + one-page A3 PDF export.
What the engine actually computes
Real engineering math, every number traceable to its rule. Verified against rulebook golden values.
- Load calc — connected, demand, design current. Per-category aggregation, occupancy-aware demand factors (residential / multifamily / office / hotel / school / hospital), spare-growth allowance, continuous-load 125% multiplier.
- Service sizing — OCP, conductor, EGC, GEC. Next-standard OCP per NEC
T240.6(A)/ CEC14-104. Conductor fromT310.16(75 °C Cu/Al). EGC perT250.122. GEC perT250.66. Engineer overrides supported. - Voltage drop — NEC Annex D K/CM method, per-feeder length. Per-load
lengthMdrives a real VD calc, not a 25 m default. Limits configurable: branch ≤3%, feeder ≤2%. - Conduit fill — NEC Chapter 9 Table 1. Smallest EMT / RMC / PVC that fits L1+L2+L3+N+EGC at ≤40% fill. Reports actual fill percentage. Flags when cable set exceeds the largest standard size.
- Panel schedule — per-panel kVA + 3-φ leg balance. Connected/demand kVA, feeder count, A/B/C leg distribution, imbalance percentage. Warning fires above 10% imbalance.
- LPD check — ASHRAE 90.1 / NECB 2017. Aggregate W/m² compared against the occupancy allowance.
LPD_EXCEEDEDfires when above the table value, with both numbers visible. - Coordination check — downstream OCP ≤ upstream. Override a feeder OCP higher than service OCP → coordination violation flagged immediately, recorded in the audit trail. The override stands; the platform never silently corrects.
- Free-tier verdict — residential ≤ 300 m² (basement included). The engine computes eligibility per project. Above the cap or non-residential occupancy → subscription gate before save / export.
Every output from one calculation
Permit-shaped PDF report
Cover with project photo, sections 1–9 mirroring the EE_Calc_Report template, engineer-of-record signature block, full disclaimer appendix.
Single-page SLD PDF
A3 landscape, scaled SVG, title block with project / engineer / date / sheet number. Reference-only watermark; not a substitute for a sealed permit drawing.
Versioned snapshots
Every save creates a new versioned snapshot with derived state cached. Restore any version via a new snapshot — never destructive.
Team workflow (Pro+)
Per-element comments, status workflow (Draft → Review → Stamped), polling-based collab indicator, optimistic concurrency on every save.