HD 60364-4-43:2023/FprAA:2026

HD 60364-4-43:2023/FprAA:2026 is a CENELEC draft amendment to the low-voltage electrical installations rules for protection against overcurrent. It updates the guidance for protecting live conductors, PEN conductors, PEM conductors and PEL conductors, and for coordinating overcurrent protective measures in electrical installations.

This draft amendment is being prepared by CLC/TC 64 and, if approved, it will modify HD 60364-4-43:2023. It is aimed at people who design, install, check or specify low-voltage installations and the overcurrent protective devices used in them.

What does HD 60364-4-43:2023/FprAA:2026 specify?

HD 60364-4-43:2023/FprAA:2026 specifies how overcurrent protection devices are positioned for overload and short-circuit protection in low-voltage installations. The amendment also adds national annex material for special national conditions and A-deviations.

The document is organized as:

• amendments to Subclause 431.4, “Protection against overload current”
• amendments to Subclause 431.5, “Protection against short-circuit currents”
• a new normative Annex G on the position of overcurrent protection devices
• annex material for special national conditions and A-deviations

What are the key requirements of HD 60364-4-43:2026?

HD 60364-4-43:2026 ties the placement of overload and short-circuit protective devices to Annex G. In practice, this means designers must check where a device sits in the circuit, not only which device is selected.

Overload protection

For overload protection, devices are generally placed at the origin of each circuit unless an exception applies. Annex G says a device should also be placed where the current-carrying capacity of the conductors is reduced, unless one of the stated exceptions is used. This matters when conductor size, material, insulation, installation method, external influences or grouping change along a run.

The amendment also allows some exceptions where the conductor is already effectively protected upstream, or where the distributor provides overload protection at the origin and agrees that it protects the relevant part of the installation. In IT systems without a neutral conductor, the overload protective device may be omitted in one line conductor if a residual current protective device is installed in each circuit.

Short-circuit protection

For short-circuit protection, the device is normally placed where the conductor’s let-through energy withstand capability, expressed as k2S2, is reduced. Annex G also allows alternative placement when the run section is short, has no branch circuit or socket-outlet, and is installed to minimize short-circuit and fire risk.

A protective device may also be installed on the supply side of the point of reduced k2S2 if its operating characteristic still protects the wiring downstream against short-circuit. This is important for coordination studies and for selecting devices with the right trip behavior.

Safety limits on exceptions

The special positioning exceptions in Annex G do not apply to installations in locations with a fire risk or risk of explosion. That means the more flexible placement rules cannot be used where the consequences of a fault would be more severe.

What the amendment changes in the clauses

The amendment updates Subclause 431.4.1 and Subclause 431.5.1 so that the positioning of overcurrent protective devices must meet Annex G. In practice, Annex G becomes the central reference for deciding where overload and short-circuit protection may be installed.

What terms does HD 60364-4-43:2026 define?

• Overcurrent - current above the intended value in a circuit, which the document treats as the condition that protection must manage.
• Overload current - a type of overcurrent linked to excessive load rather than a fault, so protection focuses on thermal stress.
• Short-circuit current - fault current caused by a low-impedance path, which drives fast protective disconnection.
• Current-carrying capacity - the amount of current a conductor can carry without exceeding its permitted limits.
• Let-through energy withstand capability (k2S2) - the conductor’s ability to withstand the energy from a short-circuit until the protective device operates.
• Residual current protective device - a device used in the document as part of certain overload-protection exceptions in IT systems.
• PEN conductor / PEM conductor / PEL conductor - conductor types explicitly named in the scope and included in the protection rules for live conductors.

Who uses HD 60364-4-43:2026?

HD 60364-4-43:2026 is used by electrical designers, installers, inspectors, and technical reviewers working on low-voltage electrical installations. It is also relevant to manufacturers and specifiers of fuses, circuit-breakers and other overcurrent protection devices.

It matters for building services, industrial installations and electricity supply systems where protection has to be coordinated with conductor sizing, circuit layout and fire or explosion risk. Buyers and quality managers use it to check whether a proposed installation concept places protective devices in acceptable positions.

What changed in HD 60364-4-43:2026 from the previous edition?

The underlying HD 60364-4-43:2023 is described as a technical revision of the third edition published in 2008. The scope states that the document was restructured, that automatic disconnection of supply was designated as the preferred protection measure, that other measures were moved into normative annexes, that a new terms-and-definitions clause was added, and that new requirements were added for neutral or mid-point conductors with and without triplen harmonics.

Which standards are used with HD 60364-4-43:2026?

The amendment refers to IEC 60364-5-53:2019, IEC 60364-5-53:2019/AMD1:2020, HD 60364-5-53:2015/A11:2017, and CEI 0-21. Annex ZB uses CEI 0-21 for Italy’s maximum and minimum prospective short-circuit currents at a grid supply point. The other named documents appear in the national-condition material and related cross-references.

What does the HD 60364-4-43:2026 document contain?

This amendment contains clause-by-clause wording changes, not a full rewrite of the base standard. It includes the revised text for overload and short-circuit protection, plus the new Annex G on device positioning.

It also includes annex material on special national conditions and A-deviations for national implementation. For readers, the practical value is in the placement rules, the exceptions to those rules, and the national notes that can affect application in specific countries.