250 A MCCB with ETU850 — what the ratings decide
The Siemens SENTRON 3VA2225-5KP42-0AE0 is a 4-pole molded case circuit breaker rated 250 A continuous at 40 °C, carrying the same 250 A rating through 50 °C before it begins to derate — 238 A at 55 °C, 225 A at 60 °C, 213 A at 65 °C, and 200 A at 70 °C. That thermal profile means the breaker holds its full ampacity in most ventilated enclosures; only above 50 °C ambient does the installer need to check the derating curve against the connected load. The ETU850 electronic trip unit provides LSIG protection — long-time, short-time, instantaneous, and ground-fault — with adjustable curves via the communication interface. The breaker ships with four HQ auxiliary switches and an onboard communication function, so it integrates directly into a plant-wide power monitoring scheme without a separate add-on module. Breaking capacity is 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 4.5 kA at 690 V.
Dimensions are 86 mm depth, 140 mm width, and 181 mm height — a 4-pole frame that occupies roughly the same footprint as other SENTRON 3VA 250 A breakers. The width is the critical dimension for multi-breaker lineup spacing; 140 mm per pole set means a 4-pole unit needs 140 mm of DIN-rail or mounting-plate width, not 4 × 35 mm. Rated insulation voltage Ui is 800 V, and the operating temperature range is -25 °C to 70 °C with storage from -40 °C to 80 °C. Maximum power loss is 48 W — a figure the panel thermal designer needs for enclosure heat rise calculations, especially when several breakers are ganged.