Siemens 5SP3220-3 SENTRON Miniature Circuit Breaker – 20 A, 2-Pole, Type E, 25 kA
The Siemens 5SP3220-3 is a 2-pole SENTRON miniature circuit breaker (MCB) rated at 20 A with a 25 kA breaking capacity at 400 V AC, per EN 60898. Its Type E tripping characteristic is designed for residential and infrastructure applications where a delayed magnetic trip is needed to avoid nuisance tripping from inrush currents — common on transformer or long-cable circuits. The 25 kA SCCR at 400 V means it safely interrupts fault currents up to that level without cascading upstream, provided the panel's prospective short-circuit current stays within that envelope. Rated insulation voltage (Ui) is 690 V, with surge voltage resistance rated at 6 kV and overvoltage category IV — suitable for main incoming panels where transient energy is highest. Pollution degree 3 means it tolerates conductive dust and humidity typical of industrial enclosures, not just clean residential environments.
Mounting and Integration
Snaps onto standard DIN rail (35 mm). Occupies 3 modular width units (each 18 mm wide, so 54 mm total). The enclosure depth is 76.3 mm; height is 128 mm. Wire terminals accept solid or stranded conductors from 2.5 mm² up to 50 mm² — saddle terminals are included, and infeed can be at either the box terminal or the saddle. The locking slide is integrated and accepts a padlock, wire seal, or cable tie for lockout/tagout compliance. IP40 protection with conductors connected — adequate for enclosed distribution boards but not for washdown or outdoor exposure. Shock resistance is rated at 30 g for at least 3 impacts of 11 ms duration, so it survives shipping and panel vibration without tripping.
Temperature Derating and Wire Range
Rated 20 A at 30 °C ambient. Derate to 19 A at 40 °C, 18.5 A at 45 °C, 18 A at 50 °C, and 17.5 A at 55 °C — important for panels with high internal heat rise or summer ambient conditions. The wide wire range (2.5 to 50 mm²) covers everything from small control circuits to main feeder tails.