400 A MCCB with ETU860 — selectivity and communication in one frame
The Siemens 3VA2340-5KQ42-0AA0 is a SENTRON molded case circuit breaker rated for 400 A continuous current at 40-50 °C ambient, with a 4-pole configuration and the ETU860 electronic trip unit. The 187 kA breaking capacity at 240 V AC means this breaker can safely interrupt fault currents up to that level without cascading upstream — critical for high-fault panels where selectivity with downstream devices must hold through a bolted fault. The 800 V rated insulation voltage confirms it is suitable for 480 V and 600 V class systems with margin.
Breaking capacity across the voltage range
At 415 V and 440 V the breaker delivers 121 kA; at 500 V it still holds 75.6 kA; at 690 V it drops to 7.5 kA. For a site electrical engineer building a selective coordination study, the 121 kA at 415 V is the figure that governs most industrial main and feeder applications in 400 V class systems — it gives headroom for high-capacity transformer secondaries without needing a current-limiting fuse upstream.
Thermal derating and operating envelope
The 400 A rating holds flat through 50 °C. Above that it derates: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. Operating ambient range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. For a panel OEM wireman, the flat rating to 50 °C means no derating is needed in most ventilated enclosures — only tightly packed or unventilated panels above that threshold require a current reduction.
ETU860 trip unit and protection features
The ETU860 electronic trip unit provides adjustable N-conductor protection from OFF to 20-100%, ground-fault monitoring via summation current formation on L+N, and a communication function for integration into plant monitoring systems. No undervoltage release or voltage trigger is fitted as standard. The trip indicator is absent — fault status is read through the communication interface or local LEDs on the trip unit.
Mounting and panel integration
Dimensions are 248 mm height, 184 mm width, 110 mm depth. The IP40 front protection means the breaker face is protected against solid objects over 1 mm but not against moisture — mount in a suitable enclosure for wet or washdown environments. Maximum power loss is 96 W, which should be factored into enclosure thermal calculations for tightly packed switchboards.