What this MCCB carries — and what it doesn't
The Siemens 3VA2225-7HL32-0AJ0 is a SENTRON molded case circuit breaker (MCCB) sized for 250 A continuous duty in a line-protection role. Three poles, ETU320 electronic trip unit, and a breaking curve that starts at 330 kA at 240 V and holds 242 kA through 440 V before dropping to 6.3 kA at 690 V. That 330 kA at 240 V tells you this is built for high-fault panels — think transformer secondaries or large motor control centers where the available fault current is serious. The ETU320 is a basic electronic trip; no voltage trigger, no ground-fault monitoring, no communication module. It's a workhorse breaker, not a smart one. 2 auxiliary switches plus 1 trip alarm switch (HP type) come built in.
Thermal derating — the real ampacity
Rated continuous current Iu is 250 A, and it holds that full 250 A up to 50 °C ambient. At 55 °C it's 241 A; at 60 °C, 232 A; at 65 °C, 222 A; at 70 °C, 213 A. That's a clean, linear derate — no cliff. If your panel hits 60 °C (common in enclosed MCCs with transformer heat), you're working with 232 A continuous, not 250. Plan the branch circuit load accordingly. Maximum power loss is 48 W — that's the heat the breaker dumps into the enclosure at full load, so factor it into your thermal budget.