What this MCCB carries — and what it means for your panel
The Siemens 3VA1225-6GF42-0AH0 is a SENTRON molded case circuit breaker rated 250 A continuous at 40 °C through 50 °C — no derating needed in a typical ventilated enclosure up to that ambient. Above 50 °C it steps down: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, 223 A at 70 °C. That thermal curve is the one you watch when the panel sits next to a furnace line or a hot motor drive. Four poles, line-protection design, fitted with a TM240 thermal-magnetic overcurrent release. No undervoltage release, no ground-fault monitoring, no communication module — this is a straight feeder or main breaker for a distribution panel where you need a clean interrupting curve and no auxiliary electronics to fail.
Interrupting capacity — the real number depends on your system voltage
At 240 V it clears 220 kA. At 415 V that drops to 154 kA, at 440 V to 75.6 kA, at 500 V to 30 kA, and at 690 V to 17 kA. The 240 V figure is the headline number, but the 415 V and 440 V ratings are the ones that matter for most European and Asian 400 V-class distribution — 154 kA at 415 V still covers high-fault utility feeds without cascading upstream. Rated insulation voltage is 800 V, so the breaker is rated for 690 V line-to-line applications. The 57 W maximum power loss at rated current is what the enclosure ventilation needs to shed — not trivial in a sealed stainless panel.
Physical fit — dimensions and panel integration
Width 140 mm, height 158 mm, depth 70 mm. That's a 4-pole frame that fits standard MCCB panel cutouts in the 250 A class. The 70 mm depth means it clears most shallow gland-plate enclosures — no need to upsize the box for this one. Trip indicator is present; auxiliary switch configuration is 2 auxiliary switches plus 1 trip alarm switch (HQ design). The supplied basic switch order code is 3VA12256GF420AA0 — that's the internal switch mechanism, not a field-replaceable part.