What this MCCB is and what it does
The Siemens 3VA2340-5JQ32-0AB0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. It carries a full-scale rating of 400 A and a minimum adjustable trip setting of 80 A, with a 3-pole configuration that covers three-phase feeders. Rated for line protection, this MCCB is the primary overcurrent device on a feeder — not a motor-protective breaker with integrated overload class. It sits upstream of branch circuits and downstream of the main transformer or service entrance. The interrupting capacity tells you where it can be installed: 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 7.5 kA at 690 V. At 400 V class (common in industrial panels), the 121 kA rating gives substantial SCCR headroom for high-fault installations.
Thermal derating and continuous current
The 400 A rating holds up to 50 °C ambient. Above that, the breaker must be derated: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel internal ambient runs hot — near a transformer or in a non-ventilated enclosure — the 55 °C derating to 375 A is the figure to spec against, not the 400 A nameplate. Maximum power loss at rated current is 96 W. That heat must be managed within the enclosure; factor it into your thermal budget alongside other devices on the same DIN rail or mounting plate.
Physical fit and panel integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep. The 138 mm width is standard for a 3-pole MCCB in this frame size — check your panel cutout or mounting footprint against those numbers before committing the BOM line. The breaker includes a communication function and comes with 2 auxiliary switches (HP type) pre-installed. No undervoltage release or voltage trip is fitted on this variant. The basic switch variant is 3VA2340-5JQ32-0AA0 if you need the base model without auxiliaries.