Temperature classes, as defined by standards such as CENELEC, IEC, and NEC 505, categorize electrical equipment based on their maximum surface temperature during normal operation. These classes provide guidelines for the selection and installation of electrical equipment in hazardous locations where the risk of fire or explosion due to the presence of flammable gases, vapors, or combustible dusts exists. The temperature classes help ensure that electrical equipment used in these environments does not exceed safe temperature limits and minimize the risk of ignition.
The temperature classes are typically designated by a letter followed by a temperature rating, indicating the maximum surface temperature that the equipment can reach under specified conditions. Here are the common temperature classes along with their corresponding temperature ratings:
- T1: Maximum surface temperature not exceeding 450°C (842°F).
- T2: Maximum surface temperature not exceeding 300°C (572°F).
- T3: Maximum surface temperature not exceeding 200°C (392°F).
- T4: Maximum surface temperature not exceeding 135°C (275°F).
- T5: Maximum surface temperature not exceeding 100°C (212°F).
- T6: Maximum surface temperature not exceeding 85°C (185°F).
The selection of the appropriate temperature class depends on the specific characteristics of the hazardous environment and the potential ignition sources present. It is essential to choose electrical equipment with temperature ratings suitable for the specific hazardous area classification to ensure safety and compliance with regulatory requirements.
It's worth noting that these temperature classes are commonly used in conjunction with hazardous area classification systems such as those outlined in standards like ATEX (Europe), NEC (United States), and IECEx (International Electrotechnical Commission Explosive). These standards provide comprehensive guidelines for the safe installation and use of electrical equipment in hazardous locations.
