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.
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.
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. 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
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.
Dimensions are 248 mm height, 184 mm width, 110 mm depth. Maximum power loss is 96 W, which should be factored into enclosure thermal calculations for tightly packed switchboards.