What this 4-pole RCCB carries and where it fits
The Siemens 5SM1656-6 is a SENTRON 5SM1-series residual current circuit breaker (RCCB), 4-pole, rated 63 A at 40 °C and 45 °C, with a 300 mA Type A tripping characteristic and a 10 kA short-circuit current rating. It mounts on DIN rail (REG), occupies 4 width units (about 72 mm), and installs 55 mm deep — a standard panel footprint for a 4P RCCB. Type A means it detects sinusoidal AC residual currents plus pulsed DC residual currents up to 6 mA of smooth DC superimposed — the common choice for circuits with single-phase rectifiers, switched-mode power supplies, or variable-speed drives downstream. Instantaneous design (no short-time delay) means it trips within 40 ms at rated residual; use it where selectivity against upstream delayed RCCBs is not required. Rated supply voltage is 500 V AC, overvoltage category III, so it handles the utility-side transient environment typical of main distribution boards and sub-distribution panels. Finger and back-of-hand safe per the protection-against-electrical-shock listing — the terminals are shrouded enough for live-panel work with the deadfront on.
Thermal derating — the real continuous current
Full 63 A holds up to 45 °C ambient. Above that, derate: 60.48 A at 50 °C, 57.96 A at 55 °C, 55.44 A at 60 °C, 52.92 A at 65 °C, 50.4 A at 70 °C. Operating ambient range is -25 to +45 °C; storage range is -40 to +60 °C. If the panel internal temperature exceeds 45 °C — common in a crowded enclosure with upstream breakers — the 50 °C derating line is the one to design against. Mounting position is unrestricted (any orientation), which helps in tight gland-plate layouts. Terminal torque spec is 2.5 to 3 N·m, accepting solid or stranded conductors from 1.5 mm² up to 25 mm² — covers the full range for a 63 A circuit on standard PVC copper. Supply can enter from top or bottom; no polarity restriction on the line/load side for this electromechanical RCCB.
Lifecycle and sourcing reality
For a BOM freeze or a line-down spare, the 5SM1656-6 is a straight drop-in for any panel originally specified with a 4P 63 A Type A RCCB in the SENTRON 5SM1 family. The closest functional peer from the same brand is the 5SQ2670-2YA63 — same poles, same current, same Type A residual — but the 5SQ series carries a different internal construction (short-time delayed vs instantaneous). Verify the selectivity requirement before swapping; the 5SM1656-6 is instantaneous, so it will trip ahead of a delayed upstream device.
Approvals and compliance paperwork
The 5SM1656-6 is silicon-free, which matters for potting or conformal-coating processes in high-vibration or corrosive environments. IP20 protection applies once the distribution board is installed with conductors connected — the RCCB itself is not sealed against dust ingress until enclosed. Mechanical endurance is rated at 10 000 switching cycles typical; the I²t let-through is 70 000 A²·s, and surge current withstand is 1 kA.