IEC TC64 Working Group Update: What's Coming in IEC 60364-5-52 Revision

If you work on multinational projects — or use any national standard derived from IEC 60364 — these changes will cascade through your cable sizing methodology. Here is what the working documents indicate.

Simplified reference method coding

The current reference method system (A1, A2, B1, B2, C, D, E, F, G) is functional but has accumulated ambiguity over successive editions. WG3 is proposing:

• A hierarchical coding system: primary method (enclosed, open, buried) with sub-codes for specific configurations
• Explicit mapping between IEC reference methods and national equivalents — a direct response to the confusion engineers face when converting between IEC, BS, and AS/NZS method designations
• New reference methods for installations not well covered by the current system: cables on building facades, cables in ceiling voids with thermal insulation contact on one side, and cables in modular construction assemblies

The intent is that an engineer specifying “IEC Method E” in a project in Singapore and another specifying the same in a project in Brazil will unambiguously mean the same physical installation.

Updated grouping factor methodology

The current grouping factors in IEC 60364-5-52, Table B.52.17 to B.52.21 assume all grouped circuits are simultaneously loaded at rated current. This is conservative to the point of being unrealistic for many installations. WG3 is developing:

• A tiered approach: default grouping factors (conservative, no load data required) alongside a diversity-adjusted grouping method where documented load profiles justify reduced derating
• Specific grouping provisions for circuits with known low duty cycles (intermittent motor circuits, lighting circuits with scheduled dimming, EV chargers with load management)
• Thermal modelling guidance for complex multi-circuit arrangements where tabulated grouping factors do not adequately describe the installation — bridging to the IEC 60287 series for engineered solutions

This is significant. A diversity-adjusted grouping method could reduce cable sizes by 15–30% in installations where load diversity is genuine and documented — data centres, multi-storey residential, industrial facilities with shift-dependent loading.

New cable type inclusions

The current edition’s current-carrying capacity tables are based on PVC and XLPE insulation with copper or aluminium conductors. The revision adds:

• LSZH (Low Smoke Zero Halogen) cables — now the default specification in tunnels, public buildings, and transport infrastructure, but with thermal ratings that differ from standard PVC
• Fire-rated cables (BS 8519, IEC 60331 compliant) with sustained current ratings during fire conditions — essential for emergency circuit design
• DC power cables with specific current ratings that account for the absence of skin effect and proximity effect, relevant for solar PV strings, battery systems, and DC distribution architectures

The current disconnect between IEC 60364-5-52 (prescriptive tables) and IEC 60287 (thermal calculation methods) forces engineers to choose between two systems that should be complementary. The revision aims to bridge this gap:

• Tabulated ratings in IEC 60364-5-52 will be explicitly derived from IEC 60287 thermal models, with the assumed parameters published alongside each table
• Where an installation deviates from the tabulated assumptions (non-standard ambient, unusual soil thermal resistivity, mixed cable types in a group), the standard will provide a clear pathway to IEC 60287 for a calculated rating rather than requiring engineers to interpolate between tables
• Software validation criteria — for the first time, the standard will include benchmark calculations that cable sizing software should reproduce, enabling engineers to verify that their tools (including ECalPro) implement the methodology correctly

Expected publication timeline: Committee Draft (CD) circulated Q4 2026, Committee Draft for Vote (CDV) mid-2027, publication late 2027 or early 2028. National adoptions (including BS, AS/NZS, and EN versions) typically follow 6–18 months after IEC publication.

For engineers working on multi-standard projects today, the implication is clear: the standards are converging. Invest time in understanding the IEC framework now, because your national standard will adopt these changes within two years of publication.

Standards referenced: IEC 60364-5-52:2009+A1:2011 (current edition), IEC 60287-1-1:2023, IEC 60331, BS 8519:2010.