What it is and what it does
The Siemens SENTRON 3VA2340-5HL42-0AH0 is a 4-pole molded case circuit breaker (MCCB) rated for 400 A continuous current at 40 °C, designed for line protection in distribution panels and switchboards. Its interrupting capacity hits 187 kA at 240 V and 121 kA at 415 V, so it can handle high-fault scenarios like large transformer secondaries or feeder mains without cascading upstream. The breaker carries a 4-pole configuration and ships with 2 auxiliary switches plus a trip alarm switch (HQ), giving you remote status feedback without adding a separate module.
Sizing and derating
The 400 A rating holds flat from 40 °C to 50 °C, then derates linearly to 340 A at 70 °C — useful if the breaker sits in a warm enclosure or near other heat sources. Dimensions are 248 mm high, 184 mm wide, and 110 mm deep — check your enclosure depth before committing, especially on retrofit panels where the backplate clearance is tight. Maximum power loss is 96 W at rated current; factor that into your thermal budget if the panel has limited ventilation or multiple breakers ganged together.