liminfoElectrical Code Reference
Free reference guide: Electrical Code Reference
About Electrical Code Reference
The NEC/KEC Electrical Code Reference is a comprehensive quick-reference tool for electrical engineers, covering the Korean Electrical Code (KEC) and the U.S. National Electrical Code (NEC). It includes wire ampacity tables per KEC 232, voltage drop formulas for single-phase and three-phase circuits, circuit breaker sizing rules (MCCB/ACB), earth leakage breaker (ELB) sensitivity ratings, and grounding system requirements under KEC 140.
This reference spans seven categories: Wiring Design (ampacity, voltage drop, feeder/branch circuits, cable tray, conduit sizing), Protection Devices (MCCB selection, ELB, motor circuit protection, breaker coordination, arc-fault prevention), Grounding (KEC 140 grounding systems, grounding conductor sizing, NEC Article 250, lightning protection per KEC 150), Substation (transformer sizing, power factor correction, short-circuit calculations, switchgear specs, single-line diagrams, emergency power), Lighting (illuminance standards per KS A 3011, LED selection, lumen method calculations), Fire Electrical (fire detectors, emergency lighting, exit signs), and Special Equipment (explosion-proof classification per IEC 60079, power quality/harmonics, solar PV design).
Each entry provides practical values, formulas, and sizing tables that engineers reference daily during electrical system design. Whether you are calculating conductor sizes for a feeder circuit, selecting a transformer for a commercial building, or determining the correct ELB sensitivity for wet locations, this tool gives you instant access to the essential standards and calculations without needing to flip through code books.
Key Features
- KEC 232 wire ampacity tables for IV, HIV, and XLPE conductors with temperature ratings at 60C, 75C, and 90C
- Voltage drop formulas for single-phase 2-wire and three-phase 3-wire systems with KEC allowable limits by distance
- Circuit breaker sizing guide covering MCCB frame sizes (100AF to 800AF), breaking capacities, and ACB ratings
- Grounding system reference with KEC 140 unified grounding resistance standards and PE conductor sizing rules
- Transformer selection data including standard kVA ratings, percent impedance values, and oil/dry/amorphous types
- Short-circuit current calculation using percent impedance method with utility, transformer, and cable impedance summation
- Lighting design standards with KS A 3011 illuminance levels and lumen method formula (N = E*A / F*U*M)
- Explosion-proof equipment classification covering IEC 60079 zones, protection types (Ex d/e/i/p/n), and temperature classes
Frequently Asked Questions
What electrical codes does this reference cover?
This reference primarily covers the Korean Electrical Code (KEC), which was revised in 2021, alongside relevant sections of the U.S. National Electrical Code (NEC). It includes KEC 232 for wire ampacity, KEC 140 for grounding systems, KEC 150 for lightning protection, NEC Article 250 for grounding and bonding, and NEC 210.12 for arc-fault protection.
How do I calculate voltage drop using this reference?
The reference provides the standard voltage drop formulas: e = 2*I*L*(R*cos(theta)+X*sin(theta)) for single-phase 2-wire, and e = sqrt(3)*I*L*(R*cos(theta)+X*sin(theta)) for three-phase 3-wire. It also includes KEC allowable limits: 3% for runs under 60m, 5% for under 120m, 6% for under 200m, and 7% for over 200m.
What wire sizing information is available?
The reference includes KEC 232 ampacity tables for common conductor types: IV wire at 60C (e.g., 2.5mm2 = 27A, 4mm2 = 37A), HIV wire at 75C, and XLPE at 90C. It also covers feeder design with demand factor application, branch circuit sizing per KEC, and NEC AWG wire gauge equivalents.
How do I select a circuit breaker using this tool?
The MCCB selection entry specifies that rated current must be at least 1.25 times the load current, and breaking capacity must exceed the prospective short-circuit current. Standard frame sizes from 100AF to 800AF are listed with their adjustable trip ranges. ACB ratings from 800A to 6,300A are also included.
What grounding standards are covered?
The reference covers the KEC 2021 grounding revision including unified grounding resistance of 10 ohms or less, equipotential bonding requirements, PE conductor sizing rules (S for conductors up to 16mm2, 16mm2 for 16-35mm2, S/2 for over 35mm2), and the legacy classification system (Class 1 through Special Class 3). NEC 250 grounding electrode conductor sizing is also included.
Can I use this for transformer and substation design?
Yes. The reference includes transformer capacity calculation formulas (TR[kVA] = equipment capacity * demand factor / (PF * efficiency)), standard kVA ratings from 300 to 3000, percent impedance values by size, and guidance on oil-immersed versus dry-type versus amorphous core transformers. Short-circuit current calculations and power factor correction capacitor sizing (Qc = P*(tan(phi1)-tan(phi2))) are also covered.
What fire safety electrical standards are included?
The reference covers automatic fire detection systems including smoke detector coverage (150m2 per photoelectric detector), heat detector coverage (40-70m2 per differential spot type), mounting height limits (8m for heat, 20m for smoke), emergency lighting requirements (1 lx minimum, 20-minute battery backup), and exit sign specifications.
Does this reference cover solar PV system design?
Yes. The solar PV design entry includes the design sequence from solar irradiance survey (3.5-4.0 kWh/m2/day) through module sizing, inverter selection, wiring design, and grid interconnection review. Module efficiencies for monocrystalline (20-22%) and polycrystalline (17-19%) panels are listed, along with KEC requirements for DC circuit breakers and system/equipment grounding.