What this MCCB is and what it does
The Siemens 3VA2140-7KP42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection, with a continuous current Iu of 40 A across the full ambient range from 40 °C to 70 °C — no derating needed up to that ceiling. It carries an ETU850 electronic overcurrent release, which means the trip curve is programmable and the breaker can communicate status over a network — the communication function is built in, so you get remote monitoring without an add-on module. Four poles handle three-phase plus neutral, and the interrupting ratings are substantial: 330 kA at 240 V, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 3.7 kA at 690 V. That covers most industrial fault-current scenarios without needing a current-limiting upstream device.
Mounting and integration
The breaker measures 181 mm high, 140 mm wide, and 86 mm deep. It mounts on a DIN rail or can be screw-fixed into a panel. The front face carries an IP40 rating, so it is fine for a clean indoor enclosure but not washdown areas. An optional motor drive is available as a field-installable accessory, which lets you remote-reset or remote-trip the breaker from a PLC or SCADA system.
What the ratings mean for your panel
The 40 A rating is flat from 40 °C to 70 °C — no thermal derating curve to worry about in a warm cabinet. The ETU850 release gives you adjustable long-time, short-time, instantaneous, and ground-fault protection (though ground-fault monitoring is not built in on this variant). With a rated insulation voltage Ui of 800 V, the breaker is suitable for 690 V systems. The interrupting capacity at 690 V drops to 3.7 kA — still adequate for most secondary-side faults in a 690 V distribution board, but verify against your available fault current. Storage temperature range is -40 °C to 80 °C, operating -25 °C to 70 °C. Maximum power loss is 1.6 W, negligible for panel thermal budgeting.