What it is and what it does
The Siemens SENTRON 3VA2440-5HN32-0CC0 is a molded case circuit breaker (MCCB) designed for line protection in low-voltage distribution panels. Rated 400 A continuously across the full ambient range from 40 °C to 70 °C, it holds its full current rating without derating up to 70 °C — a practical advantage for panels running warm near furnaces or in sealed enclosures. Three poles, with a symmetrical breaking capacity of 187 kA at 240 V and 121 kA at 415 V, dropping to 75.6 kA at 500 V and 9 kA at 690 V. That 187 kA at 240 V is the headline number — it handles high available fault current on 240 V delta or 277/480 V wye services where the transformer is close.
Panel fit and integration
Footprint: 138 mm wide, 248 mm tall, 110 mm deep. That 110 mm depth (4.33 in) clears most standard enclosures with room for the rear bus. Comes with an undervoltage release (UVR) and two auxiliary switches HQ. The UVR is factory-installed; verify coil voltage against your control circuit before wiring. No ground-fault monitoring built in — that's an external add-on if needed. Maximum power loss of 66 W at rated load. That's moderate for a 400 A frame — factor it into your enclosure thermal budget if the panel is sealed and unventilated.