Which code applies where
Installation codes are adopted by governments, so the code that applies is set by where the work is done, not where the equipment was made. The main codes in use:
| Where | Installation code | Family |
|---|---|---|
| United States | National Electrical Code (NFPA 70), adopted state by state | NEC family |
| Canada | Canadian Electrical Code, Part I (CSA C22.1), adopted by each province, sometimes as a provincial code | Own code, close to the NEC in practice |
| Philippines | Philippine Electrical Code | Largely based on the NEC |
| United Kingdom | BS 7671, Requirements for Electrical Installations (the IET Wiring Regulations) | IEC 60364 family |
| Ireland | I.S. 10101, National Rules for Electrical Installations | IEC 60364 family |
| European Union | National standards built on the harmonised HD 60364 series, such as DIN VDE 0100 (Germany) and NF C 15-100 (France) | IEC 60364 family |
| Australia and New Zealand | AS/NZS 3000, the Wiring Rules, with cable selection in AS/NZS 3008.1 | Own code, IEC-aligned |
| India | IS 732 and the National Electrical Code of India (SP 30) | IEC-aligned |
| Many other countries | IEC 60364 directly, or a national standard based on it | IEC 60364 family |
Within a country there can still be several editions in force. In the United States each state adopts NEC editions on its own schedule; see the NEC adoption tracker for every state. Codes are also amended locally, so the adopted text, not the model code, is what an inspector enforces.
Two families of codes
The NEC family grew up around 120/240 V split-phase homes and 208Y/120 V and 480Y/277 V commercial systems. Conductors are sized in AWG and kcmil from ampacity tables, usually with 75 °C terminations, adjusted for ambient temperature and the number of current-carrying conductors. Services and feeders are sized from prescribed load calculations, and equipment grounding conductors are sized from the rating of the overcurrent device.
The IEC 60364 family is built around 230/400 V systems. Cables are sized in mm² from current-carrying capacities that depend on the installation method (clipped direct, in conduit, buried and so on), with correction factors for temperature, grouping and thermal insulation. Protection is verified by calculation: the earth fault loop impedance must be low enough for the protective device to disconnect within a set time, and protective conductors are checked with the adiabatic equation. Earthing systems are classified as TN-S, TN-C-S, TT or IT, and 30 mA RCDs are required for most socket-outlets.
The physics underneath is identical. Ohm’s law, voltage drop, three-phase power and transformer currents do not care which code you work to, which is why those calculators on this site work for both, with the code-specific checks layered on top.
NEC and IEC terms side by side
The same things go by different names. A quick translation:
| NEC term | IEC 60364 / BS 7671 term |
|---|---|
| Equipment grounding conductor (EGC) | Protective conductor (PE); circuit protective conductor (CPC) in the UK |
| Grounding electrode conductor | Earthing conductor |
| Grounded conductor | Neutral conductor (N) |
| Ground-fault circuit interrupter (GFCI) | Residual-current device (RCD, RCCB, RCBO) |
| Ampacity | Current-carrying capacity |
| Overcurrent protective device | Protective device |
| Raceway | Conduit, trunking or ducting |
| Service | Origin of the installation, supply intake |
| AWG and kcmil conductor sizes | Cross-sectional area in mm² |
| Available fault current | Prospective fault current |
Codes on this site
Our NEC calculators support the 2017, 2020, 2023 and 2026 editions, with the section references for each, and preselect the edition used in your state. Physics calculators such as Ohm’s law, three-phase power and transformer sizing work in any system. For IEC 60364 and BS 7671 work there are calculators for cable size, earth fault loop impedance, protective conductor size and prospective fault current, and visitors outside the US get them by default. See BS 7671 explained and IEC 60364 explained.
We never reproduce code text. Requirements are summarised in our own words with section numbers, so you can look them up in the edition you work to. See our methodology for how values are sourced and checked.