What this MCCB is and what the ratings mean
The Siemens 3VA2140-8KP42-0AA0 is a SENTRON molded case circuit breaker (MCCB) for line protection, fitted with an ETU850 electronic trip unit. It carries a rated continuous current Iu of 40 A at ambient temperatures from 40 °C up to 70 °C with no derating — that flat thermal curve is unusual and simplifies panel sizing in warm enclosures. The 4-pole design handles three-phase plus neutral, with the N-conductor protection adjustable OFF or from 40 % to 160 % of the phase setting, so it suits both solidly-grounded and impedance-grounded systems. The interrupting ratings are the headline here: 440 kA at 240 V, 330 kA at 415 V and 440 V, 220 kA at 500 V, and 53 kA at 690 V. Those numbers mean this breaker can safely clear a fault at those levels without welding contacts or venting arc gas into the panel — critical for high-fault-current installations like transformer secondaries or large motor control centers. The ETU850 release gives adjustable long-time delay (tr) from 0.5 to 25 seconds, letting you coordinate selectively with downstream breakers.
Dimensions and panel fit
The breaker measures 140 mm wide, 181 mm high, and 86 mm deep. That 86 mm depth is the mounting depth behind the panel face — check your gland plate clearance and busbar stack before committing the cutout. Front IP40 protection means it's splash-resistant on the operator side but not sealed against dust ingress into the enclosure; keep it behind a panel door in dirty environments.