Operating d II CT4 devices ensures a lower maximum operating temperature, which increases safety. The term “d” denotes flameproof equipment. The explosion-proof rating for CT4 is superior.
| Temperature Classification for Electrical Equipment | Maximum Permissible Surface Temperature of Electrical Equipment (°C) | Gas/Vapor Ignition Temperature (°C) | Applicable Equipment Temperature Class |
|---|---|---|---|
| T1 | 450 | ＞450 | T1~T6 |
| T2 | 300 | ＞300 | T2~T6 |
| T3 | 200 | ＞200 | T3~T6 |
| T4 | 135 | ＞135 | T4~T6 |
| T5 | 100 | ＞100 | T5~T6 |
| T6 | 85 | ＞85 | T6 |
T4-rated explosion-proof equipment holds a higher standard and can substitute for BT4-rated devices; thus, using CT4 instead of BT4 ensures compliance and enhanced safety.
