The T4 classification specifies that electrical devices must operate with a maximum surface temperature of no more than 135°C. Products with a T6 rating are applicable across various temperature groups, whereas T4 devices are compatible with T4, T3, T2, and T1 conditions.
Temperature group of electrical equipment | Maximum allowable surface temperature of electrical equipment (℃) | Gas/vapor ignition temperature (℃) | Applicable device temperature levels |
---|---|---|---|
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 |
The reason T6 is not typically used is that many devices, particularly those requiring high power or consisting of purely resistive circuits, are unable to achieve the stringent low-temperature conditions stipulated by the T6 classification.