Siemens SENTRON 5SU1646-6FP16 RCBO — 4-pole, Type B, 16 A
The Siemens 5SU1646-6FP16 is a 4-pole RCBO (residual current circuit breaker with overcurrent protection) from the SENTRON family, combining earth leakage and overcurrent protection in a single 4-module-width unit. It carries a type B tripping characteristic — the magnetic release operates between 3 and 5 times In, so it handles moderate inrush from resistive and lightly inductive loads without nuisance trips, while still clearing a hard short fast. Rated 16 A at 30 °C ambient, 400 V AC, with a 6 kA breaking capacity per EN 60898 (also rated 6 kA per IEC 60947-2). That 6 kA covers most domestic and light commercial distribution boards; if your fault level upstream is higher, you need a current-limiting upstream MCB or fuse to keep the let-through within the 6 kA rating.
Thermal derating and ambient limits
The 16 A rating holds at 30 °C. At 40 °C it derates to 15.2 A; at 50 °C to 14.3 A; at 60 °C to 13.4 A; at 70 °C to 12.5 A. If the panel ambient runs warm — say a crowded enclosure near a drive or transformer — use the 40 °C or 50 °C column for your continuous load calculation. The device itself is rated for ambient from -40 °C to 70 °C, so it can sit in an unheated enclosure in cold climates, but the current must be backed off as temperature rises. Humidity up to 95% is within spec, though the IP20 rating (with distribution board installed and conductors connected) means it is not for wet washdown areas.
Mounting and integration
Snaps onto DIN rail in any orientation — mounting position is unrestricted. The 72 mm width (4 modular units) and 70 mm installation depth fit standard distribution board cutouts. Supply can enter from top or bottom; the spring-cage terminals accept solid or ferruled stranded conductors. Pollution degree 3 and overvoltage category III mean it is rated for the fixed-installation environment inside a panel, not for clean-room or surge-suppressed locations. The 4-pole design switches all three phases plus neutral; the neutral pole is switched and protected, so this unit works in TN-S or TN-C-S systems where the neutral must be broken with the phases.