What IEC 60364 is and how it is organised
IEC 60364 is the international standard for low-voltage electrical installations of buildings. It is not a single document but a family of parts, each dealing with one area: fundamental principles, protection for safety, the selection of equipment, and the verification of the finished installation. When an engineer cites 60364-5-52, the numbering itself carries the roadmap — part 5, section 52.
The reason the standard is split this way is practical. A designer rarely needs the whole text at once. A question about cable size lands in Part 5; a question about shock protection lands in Part 4; a question about what must be tested before handover lands in Part 6. Knowing where a rule lives turns a long search into a short one.
It also matters that the parts are revised independently. A requirement can be amended without the rest of the family changing, which is why citing IEC 60364 without a part number is rarely precise enough for design work.
The parts that matter most in daily design
Part 1 sets the scope, the definitions and the fundamental principles — the reasoning that sits behind the individual requirements. Part 4 gathers protection for safety. Part 5 covers the selection and erection of equipment. Part 6 deals with verification, the checks and tests carried out before an installation is put into service.
For most projects the working weight sits in Parts 4 and 5. Part 4 decides how people, conductors and equipment are protected; Part 5 decides which cables, devices and earthing arrangements are actually installed. Reading them together is what turns a set of clauses into a design.
| Part | What it covers |
|---|---|
| Part 1 | Scope, definitions, fundamental principles |
| Part 4 | Protection for safety — shock, thermal, overcurrent, voltage |
| Part 5 | Selection and erection of equipment |
| Part 6 | Verification and initial testing |
Part 4: protection for safety in practice
Part 4-41 covers protection against electric shock. The default strategy is automatic disconnection of supply: a fault current must be cleared fast enough that a dangerous touch voltage does not persist. That is why the continuity of the protective conductor, the system earthing arrangement and the tripping characteristics of the protective device are considered together rather than in isolation.
Part 4-43 covers overcurrent. The requirement forms a chain: the design current of the circuit must not exceed the rating of the protective device, and that rating must not exceed the current-carrying capacity of the cable. A further condition keeps the cable's overload capability and the device's operating curve coordinated, so the conductor is protected up to the point where its insulation would be damaged.
Other sections in Part 4 handle thermal effects and voltage disturbances such as overvoltage and undervoltage. They rarely drive the whole design, but they surface in specific areas — for example when selecting surge protection, or when a motor's starting current has to be tolerated without tripping.
Part 5: cable sizing, earthing and voltage drop
Part 5-52 turns the protection rules into conductor sizes. It provides current-carrying capacities for wiring systems and the correction factors that adjust them for ambient temperature, grouping and installation method. A cable rated at a comfortable current in free air may only be good for a fraction of that once it is bunched with others in a warm enclosure.
Part 5-54 deals with earthing arrangements and protective conductors, and Part 5-53 covers switchgear and controlgear — the devices that switch and protect the circuit. Together they decide what physically appears in the panel and along the route, which is why an early decision about the earthing system saves rework later.
Annex G of Part 5-52 adds guidance on voltage drop. It frequently becomes the limiting criterion once the heating calculation has already passed, particularly on long runs to the far end of a building. Sizing only for heat is a common way to end up with a circuit that is safe but barely usable.
How the standard reaches a real project
In practice the standard is applied in a sequence. First choose the system earthing and the type of protective devices. Then size conductors for current-carrying capacity. Next confirm that the protective device clears a fault within the permitted disconnection time. Finally verify voltage drop over the full length of the circuit, because a cable that passes the heating check can still fail the voltage check on a long run.
Each step feeds the next, and every one of them depends on the same underlying data: lengths, loads, routes and the choice of devices. Change a cable size and the voltage drop changes; move a board and the lengths change with it.
GorkyCAD runs these IEC 60364 checks in the background while the model is being built, so the single-line diagram, the panel layout and the cable schedule all follow from the same set of data. The standard stops being a document you consult and becomes a set of constraints the project is held to.
Common mistakes when reading IEC 60364
The first mistake is treating the standard as one text. Its parts are published and amended separately, so a rule you remember from one edition may have been reworded or moved. Checking the part number, not just the family name, is the difference between a citation and a guess.
The second is overlooking national adoption. Most countries publish a national version that follows IEC 60364 closely but adds local rules, values and exceptions. The international text is the framework; what gets inspected and approved is the national document.
The third is reading guidance values as absolute limits. Many of the numbers in the annexes are recommendations, and where a national or project rule is stricter, the stricter value governs. Treating a guidance figure as a hard pass-fail line leads to both over-design and under-design.
FAQ
Is IEC 60364 a single document?
No. It is a family of parts, each covering a different area and revised separately. Cite the specific part, such as 60364-5-52, when you refer to a rule.
Which part covers cable sizing?
Part 5-52 covers wiring systems, current-carrying capacity and correction factors. Annex G of the same part gives guidance on voltage drop.
Which part covers protection against electric shock?
Part 4-41 covers protection against electric shock, mostly through automatic disconnection of supply, and it sits alongside the overcurrent rules in Part 4-43.
Does national law replace IEC 60364?
Most countries adopt IEC 60364 through a national version that adds local rules and values. The international text is the framework; the national document is what gets inspected.