What this MCCB is and what the ratings mean for fit
The Siemens 3VA2340-7HN32-0AJ0 is a SENTRON molded case circuit breaker (MCCB) sized for line protection in distribution panels. It carries a continuous rated current of 400 A at 40 °C — that's the current it can pass continuously without tripping on thermal overload. The 400 A rating holds steady up to 50 °C; above that it derates to 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C. If your panel ambient runs hot, the 55 °C figure is the one that governs the actual load you can feed through it. Breaking capacity is the other headline: 330 kA at 240 V AC, 242 kA at 415 V, and 187 kA at 500 V. At 690 V it drops to 7.5 kA — still enough for most industrial service-entrance duties, but if your fault current at 690 V exceeds that, you need a different frame. These numbers tell you this breaker can sit at the main disconnect where fault currents are highest, and coordinate downstream without blowing up. Three poles, line-protection design (not motor-protection — no overload relay built in). It ships with 2 auxiliary switches plus a trip-alarm switch (HP type), so you get remote status indication without adding an external block. The basic switch is order code 3VA2340-7HN32-0AA0; this variant adds the auxiliary and alarm contacts.
Panel fit and integration
Dimensions: 248 mm high, 138 mm wide, 110 mm deep. That's a 3-pole frame that fits standard MCCB mounting footprints — no oddball cutout. The 110 mm depth means it clears most shallow backpan enclosures, but check your gland-plate clearance if the panel is tight. Power loss is 96 W maximum at rated load; plan for ventilation or derating if the breaker is in a sealed enclosure with other heat sources.
How it compares to a sibling: 3VA2116-5HL32-0AK0
The 3VA2116-5HL32-0AK0 is a smaller-frame MCCB — 160 A continuous, lower breaking capacity, and a different accessory layout. If your panel was designed around that 160 A frame, the 3VA2340-7HN32-0AJ0 will not drop in without rewiring: the mounting hole pattern and bus-bar spacing differ between frame sizes. The 400 A version is physically larger (248 mm vs. a shorter frame) and needs more clearance for the higher interrupting ratings. Stick with the frame size your panel was built for unless you're doing a full re-design.