(D) Class I Temperature
Informational Note: For information regarding autoignition temperatures of gases and vapors, see NFPA 497-2017, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas; and ISO/IEC 80079-20-1-2017, Explosive atmospheres — Part 20—1: Material characteristics for gas and vapour classification — Test methods and data.
Electrical equipment designed for use in the ambient temperature range between -20°C and +40°C shall require no ambient temperature marking.
Electrical equipment that is designed for use in a range of ambient temperatures other than -20°C to +40°C is considered to be special; and the ambient temperature range shall then be marked on the equipment, including either the symbol "Ta" or "Tamb" together with the special range of ambient temperatures, in degrees Celsius.
Informational Note: As an example, such a marking might be "-30°C to +40°C."
Exception No. 1: Equipment of the non-heat-producing type, such as conduit fittings, and equipment of the heat-producing type having a maximum temperature of not more than 100°C (212°F) shall not be required to have a marked operating temperature or temperature class.
Exception No. 2: Equipment identified for Class I, Division 1 or Division 2 locations as permitted by 505.20(A), (B), and (C) shall be permitted to be marked in accordance with 505.8(C) and Table 500.8(C).
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