Is the simbology defined by IEC 81346-2 compulsory?

Last edit: 03/08/2023

IEC 81346-2 Standard: compulsory symbology and codes?


Is it compulsory to apply IEC 81346-2 Standard and possibly change habits and switch to a new symbology in your wiring diagrams? Is it compulsory to apply IEC 81346-2 Standard and possibly change habits and switch to a new symbology in your wiring diagrams?


IEC 81346-2 Standard, named “Industrial systems, installations and equipment and industrial products — Structuring principles and reference designations Classification of objects and codes for classes” accurately defines various classification and identification schemes of different devices and their associated letter codes. The Standard is primarily intended for designers of electrical schemes and P&IDs. However, many designers follow different in-house guidelines and internal formats.

The adjustment of a schematic symbology to IEC 81346-2 Standard, therefore, depends on the Standard to which the final product must conform.For example, in EN 61439-1 at section 6.3 “Device and/or component identification “ it is written:

Inside the ASSEMBLY, it shall be possible to identify individual circuits and their protective devices.  Identification tags shall be legible, permanent and appropriate for the physical environment. Any   designations  used shall be in compliance with IEC 81346-1 and IEC 81346-2 and identical with those used in  the wiring diagrams, which shall be in accordance with IEC 61082-1.

Therefore, the electrical drawing of a switchboard, like a Power Center, shall correctly identify the components using the simbology and the codes defined by IEC 81346-2. For example, a circuit breaker is designated with the code Q or QA, as normally happens. A designation that, however, can have a significant impact concerns the power contactor for which the code Q or QA is used, while normally the code K or KM is used. For control contactors, on the other hand, K or KF is used.

The doubt is whether this Standard should also be used for industrial control panels. The answer lies in EN 60204-1 which refers to IEC 81346-2 only in an informative way. In facts, in its 2016 edition, it defines IEC 81346-2 as a “Recommended standard”. This voice is in “Table I.1 Documentation/Information that can be applicable” in turn found in Annex I (which is informative only).


It is only necessary to comply with the symbols and/or codes defined by IEC 81346-2 if the Standard to which your product must conform establishes it as compulsory. If you design switchboards, you must follow the symbology defined by that standard. This is not compulsory if you design industrial control panels.

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