Both items are rated as IIB for explosion protection, differing only in their temperature classifications.
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 designations T1 through T6 denote the maximum allowable surface temperatures for equipment under specific conditions, progressively decreasing. Lower temperatures signify higher safety.
Consequently, BT1 has a slightly lower explosion-proof rating compared to BT4.