IEC 60364: low-voltage electrical installations

What IEC 60364 is

IEC 60364, Low-voltage electrical installations, is the International Electrotechnical Commission’s series of standards for the electrical installations of buildings and similar sites, written by technical committee 64. It sets out how to protect people, livestock and property from shock, fire and overcurrent, how to select and install equipment, and how to verify the result. It applies to installations supplied at up to 1000 V AC or 1500 V DC.

Two things make it different from a code such as the NEC. First, it is a series, not one book: each part is a separate publication with its own edition and revision cycle. Second, it is rarely enforced directly. It is a model that regional and national bodies adopt, adapt and publish, and the national version is what an inspector checks.

How the series is organised

The numbering is the same logic you will see in BS 7671: part, then section, then clause. Part 4 says what protection is needed; Part 5 says how to choose and install the equipment that provides it. The current parts, as listed in the IEC webstore on October 14, 2026:

The newest major revision is Part 1, whose sixth edition appeared in September 2025 after twenty years. IEC’s summary says it was restructured and renumbered, with its scope widened to include safety services, energy efficiency and prosumer installations. On the working parts, the protection parts 4-42, 4-43 and 4-44 were all revised between 2023 and 2024, Part 5-52 gained an amendment in 2024, and Part 8-82 an amendment in 2026. Every reference in the table links to IEC’s catalogue entry, where the full edition history and any work in progress are shown.

Part 7: special installations and locations

Part 7 sections supplement or replace the general rules where the risk is different: wet locations, temporary installations, places where people are unusually vulnerable, or new technologies. Each section is numbered 7-7xx, and the numbers carry straight into national standards, so Section 722 of BS 7671 corresponds to IEC 60364-7-722. The sections currently listed by IEC, with their edition years:

IEC also published a technical specification in 2026, IEC TS 60364-7-725, on resilient power supplies that must keep working in a disaster. Edition years vary widely: the sauna section dates from 2004, while the PV section was revised in 2025 and the sections for temporary installations and mobile units in 2026.

Reading an IEC 60364 reference

Because every part moves on its own, a reference has to say exactly which text it means, and the IEC catalogue uses a compact notation for that:

• IEC 60364-5-52:2009 is Part 5-52 in the edition published in 2009. The part number is the topic; the year after the colon is the edition.
• /AMD1:2024 is an amendment: a separate document, here the first, that changes the base edition. Read the two together.
• +AMD1:2024 CSV is a consolidated version, with the base edition and its amendments merged into one text. It is the easiest way to read a part that has been amended.
• RLV is a redline version, which marks what changed from the previous edition: useful when a part is revised and you want the differences.
• COR is a corrigendum, a correction of errors rather than a technical change.
• IEC TS marks a technical specification, published where the subject is still developing; it may later become a full standard.

Each catalogue page also shows a stability date, the date until which IEC expects to leave the publication unchanged, and any revision under way. National standards built on the series usually state in their foreword which European or IEC texts they implement, which is the quickest way to see how far a national rule book lags or leads the IEC parts. When a calculator, a design report or a test certificate cites IEC 60364, it should name the part and its edition, just as an NEC calculation should name its edition.

How countries adopt it

In Europe, CENELEC takes each IEC part and issues it as a Harmonization Document in the HD 60364 series, sometimes with common European modifications. An HD has to be announced in every member country, and conflicting national standards withdrawn, but unlike a European Norm it need not be published word for word: a country may keep its own national standard on the subject provided it is equivalent in technical content. That is how Germany’s DIN VDE 0100 series, France’s NF C 15-100, Ireland’s I.S. 10101 and the UK’s BS 7671 can look so different on the page yet rest on the same requirements.

Outside Europe, countries take one of three routes: adopt IEC 60364 parts directly, build a national code on them, or write their own rules that borrow IEC concepts, as Australia and New Zealand do with AS/NZS 3000. The codes by country page lists the main ones. North America is the exception: the United States and Canada have their own codes, the NEC and the CEC.

Key concepts

Installation reference methods

A cable’s current-carrying capacity depends on how well it can lose heat, so Part 5-52 rates cables for a set of reference installation methods and maps every real-world arrangement onto one of them:

• A1: Single-core (insulated) conductors in a conduit buried inside a thermally insulated wall.
• A2: A multi-core cable in a conduit buried inside a thermally insulated wall.
• B1: Single-core (insulated) conductors in conduit or trunking fixed on, or within 0.3 × conduit diameter of, a wall.
• B2: A multi-core cable in conduit or trunking fixed on a wall.
• C: Sheathed single- or multi-core cable clipped directly to a wall (within 0.3 × cable diameter), or on an unperforated tray.
• D1: Cable pulled into a duct or conduit buried in the ground (2.5 K·m/W soil, 0.7 m deep).
• D2: Sheathed cable laid directly in the ground, with or without added mechanical protection.
• E: Multi-core cable in free air or on perforated tray/ladder/brackets, held at least 0.3 × diameter off the wall.
• F: Single-core cables touching each other (flat or trefoil) in free air or on perforated tray/ladder.
• G: Single-core cables (or bare/insulated conductors on insulators) spaced at least one cable diameter apart in free air.

The tabulated capacity is then corrected for ambient temperature (Ca), grouping with other circuits (Cg) and, where relevant, thermal insulation or soil conditions. For example, 2.5 mm² copper PVC cable with two loaded conductors clipped direct (method C) is rated 27 A in the reference conditions. At 40 °C ambient (factor 0.87) and bunched with two other circuits (factor 0.7), it can carry 16.4 A. The cable size calculator runs this for every method.

Overload coordination

Part 4-43 ties the cable to its protective device with two conditions: the design current Ib must not exceed the device rating In, which must not exceed the corrected capacity Iz; and the current that reliably operates the device, I2, must not exceed 1.45 × Iz. Circuit-breakers to IEC 60898 meet the second condition automatically when In ≤ Iz. Fuses operate reliably only at about 1.6 × In, so for them the rating must stay below about 0.91 × Iz.

Earthing systems and automatic disconnection

IEC 60364 classifies supplies as TN-S, TN-C, TN-C-S, TT or IT, explained with diagrams in earthing systems. The main protection against indirect contact is automatic disconnection of supply: the fault loop impedance must be low enough that the protective device opens in time. At 230 V, Part 4-41 sets 0.4 s for TN and 0.2 s for TT on final circuits up to 32 A, and 5 s and 1 s for distribution circuits and larger final circuits. RCDs of 30 mA give additional protection for socket-outlet circuits.

The adiabatic check

A protective conductor must survive the fault current until the device opens. For faults lasting up to 5 s the heat is assumed to stay in the conductor, which gives S ≥ √(I²t) / k, where k depends on the conductor material and the insulation’s starting and limiting temperatures. For copper in 70 °C PVC insulation k works out at 115; a 1,000 A fault cleared in 0.2 s then needs at least 3.89 mm², so a 4 mm² conductor. The CPC size calculator does the check with the k values for each material and insulation.

Voltage drop

Clause 525 of Part 5-52 asks for the voltage at equipment to be adequate, and Annex G recommends limits from the origin of the installation: 3% for lighting and 5% for other uses on a public supply, 6% and 8% where the installation has its own transformer, with a small allowance for runs over 100 m. The background and worked examples are in voltage drop.

How IEC 60364 compares with the NEC

The physics is identical; the way each family packages it is not.

The vocabulary differs too: a protective conductor is an equipment grounding conductor, an RCD is close to a GFCI, and earthing is grounding. The codes by country page has a fuller list, and grounding and bonding covers the NEC side of earthing.

Which of our calculators follow IEC 60364

• Cable size: Part 5-52 Annex B capacities and correction factors, or the BS 7671 tables in UK mode.
• Voltage drop: IEC 60364 and BS 7671 modes alongside the NEC.
• CPC size: the adiabatic equation with k values for each material and insulation.
• Earth fault loop impedance: automatic disconnection checks against device characteristics.
• Prospective fault current: fault current at the origin and along a circuit.

Physics calculators such as Ohm’s law and three-phase power work in any system. Our IEC data follows Part 5-52 as published in 2009; IEC issued Amendment 1 to that part in November 2024, and we are checking whether it changes any value the calculators use.