Siemens 5SY4308-7CC — SENTRON 3-pole MCB, C-curve, 8 A
Thermal derating and environmental limits
The 5SY4308-7CC carries a full temperature-derating table from 35 °C to 55 °C, not just a single ambient rating. At 35 °C it holds the full 8 A; at 45 °C it is 7 A; at 55 °C it is 6.25 A. Above 55 °C the humidity limit tightens — max 55% RH at 70 °C, max 35% RH at 75 °C — so a hot, humid environment (e.g., a non-conditioned electrical room in a tropical plant) needs a ventilation or enclosure-sizing check. Energy limitation class 3 indicates it limits let-through energy in a fault, reducing arc-flash stress on downstream components.