The Siemens SENTRON 5SP4392-6 is a 3-pole miniature circuit breaker rated 125 A with B-curve tripping characteristic, breaking 10 kA per EN 60898 at 400 V AC. This is the part for a 3-phase 125 A feeder where the upstream fault level stays under 10 kA — the B curve means it trips at 3 to 5 times rated current, so it suits resistive or general-purpose loads where inrush is moderate. Mounts on DIN rail or with screw fixing; tunnel terminals top and bottom accept the conductors. Installation depth is 70 mm; overall depth 76 mm, width 81 mm (4.5 modular width units).
Key ratings and what they mean for fit
The 10 kA breaking capacity per EN 60898 is the standard for domestic and light commercial distribution boards — it safely interrupts a bolted fault up to that level without welding the contacts. The B-curve (3-5× In) provides fast response to short circuits while tolerating the modest inrush of resistive loads, lighting, or small transformers. Rated 400 V AC at 50/60 Hz, 3-pole configuration, so it switches all three phases simultaneously — critical for a 3-phase panel where single-pole interruption could cause single-phasing on a motor load. The 10.9 W power loss per pole at rated current in hot operating state means the breaker dissipates about 33 W total at full load; factor that into enclosure thermal calculations, especially in a tightly packed DIN-rail cabinet. Pollution degree 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation) and overvoltage category III are typical for fixed-installation distribution panels.
Mounting and integration
Fastens via DIN rail or screw fixing — the DIN rail is the standard for panel builders; the screw option helps in retrofit enclosures without a DIN rail. Mounting position any, so vertical or horizontal orientation in the panel is acceptable. The 4.5 modular width units (81 mm) occupy the space of 4.5 standard 18 mm-wide module positions on the rail. Tunnel terminals top and bottom accept the incoming and outgoing conductors; supply cord position is any (line can enter from top or bottom). Sealable — a lead seal can be fitted to the toggle to lock the breaker in the ON or OFF position for lockout/tagout compliance. IP20 with connected conductors, IP40 in the handle area with a distribution cover — not a washdown rating, but suitable for dry indoor panels.
Environmental and compliance
Halogen-free and silicon-free construction — relevant for clean environments or where outgassing could affect contacts or optics. Operating temperature range -40 °C to 75 °C covers cold storage and hot panel conditions. Shock resistance 150 m/s² at 11 ms half-sine per IEC 60068-2-27; vibration resistance 50 m/s² at 25 to 150 Hz and 60 m/s² at 35 Hz per IEC 60068-2-6 — the breaker holds its calibration under typical industrial vibration. Mechanical service life 10 000 operating cycles typical; supplementary devices (auxiliary switches, shunt trips, alarm contacts) can be installed on the side.