What it is and what it does
The Siemens 3VA2140-7HM42-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. It carries a continuous rated current of 40 A across the full ambient temperature range from 40 °C to 70 °C, with no derating needed up to that ceiling — a solid pick for a warm enclosure or a tightly packed switchboard. Four poles give you the ability to switch all three phases plus neutral in a single package, which simplifies wiring in three-phase four-wire systems where neutral protection is required. The adjustable thermal-magnetic trip unit is set for line protection — meaning it's tuned for cable and busbar protection, not motor overload curves. Breaking capacity is the headline here: 330 kA at 240 V AC, 242 kA at 415 V and 440 V, 187 kA at 500 V, and still 3.7 kA at 690 V. Those numbers mean this breaker can sit at the main incoming position in a high-fault installation and still clear a bolted fault without welding its contacts shut — the 330 kA figure at 240 V is well into industrial-grade SCCR territory.
Ground-fault monitoring and integration
This variant includes ground-fault monitoring via summation current formation on the L + N conductors — it measures the vector sum of phase and neutral currents to detect leakage to earth. That's a built-in residual current detection function without needing a separate RCD module, which saves a DIN-rail slot and reduces wiring complexity in the panel. Physical footprint: 181 mm tall, 140 mm wide, 86 mm deep. The 140 mm width is standard for a 4-pole MCCB in this frame size — it'll drop into a SENTRON 3VA panelboard or a DIN-rail mounting base without surprises. No undervoltage release and no communication function on this variant, so it's a straight electromechanical breaker with no auxiliary electronics to fail.
Lifecycle and sourcing reality
Power loss is rated at a maximum of 1.6 W — negligible for thermal budgeting in a panel, but worth noting if you're stacking a dozen of these in a sub-distribution board. Storage temperature range from -40 °C to 80 °C covers most warehouse and shipping conditions without special handling.
What the 40 A rating means in practice
The 40 A continuous rating is flat from 40 °C to 70 °C ambient — no thermal derating curve to chase. That's unusual for an MCCB; many competitors start derating above 40 °C. For a panel sitting in a hot plant environment or near a furnace line, this breaker holds its full ampacity without needing to oversize the frame. The adjustable trip range spans 60 A minimum to 480 A maximum — those are the magnetic pickup settings, not the continuous rating. The 16 A initial value is the thermal trip calibration at the low end.