The Siemens 5SP3735-2KK03 is a 1-pole SENTRON miniature circuit breaker from the 5SP3 series, rated 35 A at 230 V AC with a tripping characteristic E and a 25 kA breaking capacity per EN 60898. It is designed as a main MCB for residential and infrastructure metering panels, mounting on a 40-mm busbar system per DIN 43870 Part 2.
At 35 A and 230 V AC, it handles the main feed for a residential or light commercial meter panel. The 6 kV surge voltage resistance confirms it can withstand lightning-induced surges at the service entrance. The 1.5 width units (each 18 mm) means it occupies 27 mm on the DIN rail — a standard single-pole MCB is 1 width unit, so this is wider to accommodate the higher breaking capacity and the E-curve mechanism. Verify the panel's width allocation before swapping from a standard 1-pole unit.
Mounts on a 40-mm busbar system per DIN 43870 Part 2, typical in European meter panels. The infeed is at the box terminal (bottom), with the outgoing feeder via a spring-loaded terminal — no screw tightening needed on the load side. The locking slide accepts a padlock, wire seal, cable ties, or Antilux seal — useful for utility-lockable metering panels where tamper evidence is required. The switch position indicator shows OFF = green, ON = red, a visual cue that matches standard European practice. Ambient range -25 to +55 °C covers most utility rooms; storage range -40 to +70 °C covers transport and warehouse.