What this MCCB is and where it fits
The Siemens 3VA2040-6JP42-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in low-voltage distribution. It carries 4 poles, a rated continuous current of 40 A, and an ETU550 electronic overcurrent release. The interrupting capacity hits 242 kA at 240 V and 187 kA at 415 V — that's the fault current it can safely clear without welding contacts or venting plasma into the panel. For a 40 A frame, that's serious SCCR headroom; you're not chasing coordination curves because the breaker can handle downstream faults before the upstream device has to move. The ETU550 release is a communicating electronic trip unit — this isn't a thermal-magnetic slug. It gives you adjustable long-time, short-time, instantaneous, and ground-fault protection (though this variant ships without ground-fault monitoring enabled). The communication function means it can talk to a BMS or energy management system over the integrated bus, so you're getting status and trip event data without adding a separate meter. The IP40 on the front is standard for panelboard mounting — it's not a washdown part, keep it inside the enclosure.
Thermal derating: full rated current across the operating range
One thing that sets this 40 A frame apart: the rated current holds at 40 A from 40 °C all the way up to 70 °C ambient (–). No derating curve to calculate. In a crowded panel where internal temperature can push past 50 °C, you don't have to oversize the frame or lose headroom. The maximum operating temperature is 70 °C; storage range runs from -40 °C to 80 °C.
Physical fit and mounting
Dimensions: 181 mm high, 140 mm wide, 86 mm deep (–). That's a 4-pole MCCB footprint — it mounts on a DIN rail or panel-mount base depending on the accessory kit. The 86 mm depth is the body only; allow clearance for the rotary handle or motor operator if fitted. No undervoltage release and no voltage trip on this variant — if you need UVR or shunt trip, that's a different order code in the 3VA2 family.