Siemens 5SP3720-2KK01 — SENTRON 1-Pole MCB, E-Curve, 25 kA
The Siemens 5SP3720-2KK01 is a 1-pole SENTRON main miniature circuit breaker (SHU) with an E tripping characteristic, rated 230 V AC at 50 Hz and a 25 kA breaking capacity per EN 60898. The 1.5 modular-width unit (27 mm) mounts on a 40-mm busbar system per DIN 43870 Part 2, with the supply feed stipulated for the lower section of the meter panel.
The 25 kA breaking capacity at 230 V AC (per EN 60898) is the headline number — it tells you this MCB can safely interrupt a fault current up to 25,000 A without welding its contacts or exploding the arc chamber. That's a high-interrupting rating for a domestic-metering form factor; most standard MCBs top out at 10 or 16 kA. The E tripping characteristic means the magnetic release is set higher than a B or C curve — typically 10–20× In — so it's deliberately slow on short-circuit to coordinate with upstream fuses or a main breaker. If you're feeding a sub-distribution board or a transformer, this is the curve that keeps the lights on during a downstream fault. Rated insulation voltage (Ui) is 690 V, and the overvoltage category is IV — that's the highest category for mains-connected equipment, meaning it's designed for the meter side of the installation where surge levels are worst. Terminal capacity accepts 2.5 to 50 mm² solid or stranded — that's a wide range, from a 2.5 mm² lighting circuit up to a 50 mm² main feeder. The outgoing feeder uses a spring-loaded terminal; the infeed is a box terminal. Both are sealable via a locking slide with provision for a lock, wire seal, cable ties, or Antilux seal — important for utility metering panels where tamper evidence is required. Mechanical service life is 20,000 operating cycles typical. Vibration resistance is 2 g per IEC 60068-2-6; shock resistance is 30 g, 3 impacts, 11 ms duration.