The Siemens 5SP3820-2 is a SENTRON main miniature circuit breaker (MCB), designed as a 3-pole unit with a rated current of 20 A at AC and a breaking capacity of 25 kA per EN 60898. It carries an E tripping characteristic, which means it's tuned for a specific overload curve — less common than B or C curves, so verify coordination with downstream loads.
That's a high-interrupting rating for a 4.5-module-width MCB, so it's meant for service-entrance or main-switch positions where fault current is high. The E-curve is a slower, more delayed curve than a standard C-curve, designed to ride through inrush from large transformers or capacitor banks without nuisance tripping. Temperature derating is published: 20 A at 30 °C, 19 A at 40 °C, 18 A at 50 °C.