SENTRON 3VM1040-4ED32-0AA0 — 400 A MCCB for Line Protection
The Siemens SENTRON 3VM1040-4ED32-0AA0 is a 3-pole molded case circuit breaker rated for a maximum of 400 A, designed specifically for line protection in distribution panels. This is the breaker you spec into a main feeder or heavy branch circuit where you need a single interrupting device that can handle the full load and clear faults fast. The TM210 overcurrent release means it uses a thermal-magnetic trip — thermal for overloads, magnetic for short-circuits — no electronic adjustments, no communication module, just a straightforward, field-reliable trip curve. Rated insulation voltage is 800 V, so it's comfortable on 480 V and 600 V class systems with headroom. The IP40 front protection keeps tools and fingers out of the live terminals but isn't rated for washdown — this lives inside a dry enclosure. Power loss at full load is 14 W, which matters when you're calculating heat rise in a packed panel.
Breaking Capacity — What the Ratings Mean for Selectivity
At 240 V, the interrupting rating is 121 kA. That drops to 76 kA at 415 V, 40 kA at 440 V, and 12 kA at 500 V. These are the numbers your coordination study needs — if your available fault current at the panel is 50 kA at 440 V, this breaker clears it with 10 kA of margin. The 12 kA at 500 V is the limiting case; don't put this on a 500 V bus with more than 12 kA available unless you've got a current-limiting upstream device.
Thermal Derating — Don't Ignore the Cabinet Temperature
Rated 40 A continuous at 40 °C, 45 °C, and 50 °C — no derating needed in that range. At 55 °C it's 39 A, at 60 °C it's 39 A, at 65 °C it's 38 A, and at 70 °C it's 37 A. If your panel ambient runs 65 °C (tight enclosure, solar load, next to a furnace line), you lose 3 A from the nameplate. That's a 7.5% reduction — enough to nuisance-trip if you sized the load right at 40 A. Always size the breaker for the actual cabinet temperature, not the 40 °C rating.
Panel Fit — Dimensions and Mounting
Depth is 70 mm, width is 76.2 mm, height is 130 mm. That's a compact footprint for a 400 A frame — it fits standard distribution panel gutters without crowding the bend radius on incoming cables. Mounts on a DIN rail or directly to the panel backplate via the screw terminals. The 3-pole block takes up about 3 inches of rail space.