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For the IEC 60417 symbols in UL/CSA IEC 62368-1, such as the IEC 60417- 5041 symbol, is there any minimum size requirements for the symbol or the text adjacent to the symbol such as "HOT SURFACE"?

In IEC 62368-1,  the only normative mention of legibility is in Annex F, sub-clause F.3.9, Durability, legibility and permanence of markings '“ it states, 'œIn general, all markings required to be on the equipment shall be durable and legible, and shall be easily discernable under normal lighting conditions.'; and 'œCompliance is checked by inspection.'  (There are no CAN/US National Differences on the topic in CSA UL 62368-1.)


IEC TC108 did not provide more specificity due to the hundreds (probably thousands) of product and component types covered under IEC 62368-1, making it impractical to provide '˜minimum size requirements for all applications.  During a product investigation, an NCB may call into question a marking that appears not legible or not easily discernable under normal lighting conditions, but the level of concern also would hinge on whether the marking is an instructional safeguard (e.g., caution marking) or informational (e.g., nameplate).  Over the years, there have been nameplate markings accepted on AV/ICT products (including grey-black nameplate ratings on external power supplies (bricks) and nameplate ratings on small power adapters) that some may consider as marginally meeting the 'œlegible' and 'œeasily discernable under normal lighting conditions' criteria.  However, this concern has not been problematic with instructional safeguards (caution markings).


If a manufacturer wants more guidance on the topic than IEC 62368-1, they may consider reviewing the ANSI Z535 series standards (including Z535.4) for additional help https://www.nema.org/standards/z535/ansi-z535-brief-description-of-all-six-standards-and-safety-color-chart .

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