The Siemens 5SL6420-7RC is a SENTRON miniature circuit breaker rated for 20 A at AC, with a C tripping characteristic and a 4-pole (4P) design. It breaks fault currents up to 7.5 kA per EN 60898, which means it safely clears short-circuits in residential and light commercial distribution boards without cascading upstream.
Ratings and what they mean for fit
The C-curve (tripping characteristic class C) means the magnetic trip fires at 5 to 10 times rated current — suited for circuits with moderate inrush, like lighting banks, small motors, and general socket outlets. At 20 A, that's a magnetic trip threshold between 100 A and 200 A instantaneous. Breaking capacity of 7.5 kA at 415 V AC per EN 60898 covers most domestic and light commercial fault levels in European installations. The 4-pole version switches all three phases plus neutral, though the neutral conductor is not switched internally (Neutral Conductor Switching = No), so it's a 4-pole device protecting all four paths, not a switched-neutral design. Rated for multi-phase operation up to 440 V AC maximum, and single-phase at 250 V AC. DC rating is 72 V maximum — usable on DC control circuits but only at that voltage ceiling. Mechanical service life is 10 000 switching cycles typical — adequate for panel isolation and occasional manual switching, not for daily load-break duty.
Where it fits in the panel
Occupies 4 modular width units (72 mm wide) on a DIN rail. Depth is 76 mm, installation depth 70 mm, height 90 mm. Mounting position is any — no derating needed for horizontal or inverted orientation. IP20 with connected conductors, so it's enclosed inside a distribution board or panel; not rated for wet or dusty environments. Sealable design allows locking the toggle in the off position for lockout/tagout procedures. Touch protection is integrated. Halogen-free and silicon-free construction matters if the panel is in a clean room or oxygen-enriched environment. Overvoltage category III and degree of pollution 2 — standard for fixed-installation distribution boards inside buildings. Rated for ambient temperatures from -40 °C to 75 °C, so it handles unheated enclosures in cold climates.
How it compares to the 3-pole sibling
The closest functional peer is the 5SL4363-7 — same SENTRON series, same C-curve, same 20 A rating, same 7.5 kA breaking capacity per EN 60898, same 72 V DC max, same mechanical endurance. The critical difference is pole count: the 5SL6420-7RC is 4-pole (4P) at 72 mm wide (4 MW), while the 5SL4363-7 is 3-pole (3P) at 54 mm wide (3 MW). If your panel was laid out for a 3-pole breaker, the 4-pole version will not drop in without rewiring and a wider DIN slot. The 4-pole is the correct choice when the neutral must be switched or when the circuit requires four protected poles (three phases plus neutral).