400 A MCCB with ETU320 — what the ratings mean for your panel
The Siemens 3VA2440-6HL32-0DC0 is a 3-pole SENTRON molded case circuit breaker rated for 400 A continuous current at 40 °C, with full current hold through 50 °C and a gradual thermal derating curve down to 360 A at 70 °C — meaning it carries its nameplate rating across typical panel ambient without forced derating until you push past 55 °C. Breaking capacity is 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 40 kA at 690 V — that 242 kA figure at 240 V covers high-fault utility feeds and transformer secondaries where available fault current is highest; the 40 kA at 690 V still clears a substantial industrial fault on 600 V class systems. The ETU320 electronic trip unit provides adjustable long-time, short-time, and instantaneous protection with a line-protection profile — no ground-fault or phase-failure detection onboard, so this is a straight feeder or main breaker for distribution panels where you need selective coordination downstream.
Undervoltage release and auxiliary contacts
Factory-fitted with an undervoltage release (UVR) — part number 3VA9608-0BB25 for the integrated auxiliary trip — and two HQ auxiliary switches. The UVR drops the breaker on loss of control voltage, which is standard for emergency-stop chains and safety-related machine feeds where you need the main power to drop when the E-stop circuit opens. No communication function or voltage trigger on this variant — it is a pure power breaker with local status indication via the aux switches. If you need remote monitoring or undervoltage time delay, you step up to the 3VA2 with communication options.
Panel fit — dimensions and mounting
Width 138 mm, height 248 mm, depth 110 mm — this is a full-frame 400 A MCCB that mounts on a DIN rail or bolted directly to a mounting plate. The 110 mm depth means it fits standard 400 mm deep enclosures with clearance for rear bus connections and cable bending radius. Maximum power loss of 66 W at rated current — factor that into enclosure thermal rise calculations, especially in sealed NEMA 4X or IP65 cabinets where natural convection is limited.