DC-rated MCB for 880 V photovoltaic and industrial circuits
The Siemens SENTRON 5SY5408-7CC is a 4-pole miniature circuit breaker rated for 880 V DC with a 10 kA breaking capacity per IEC 60947-2, making it a fit for DC-side protection in photovoltaic arrays, battery banks, and industrial DC bus systems where standard AC-rated MCBs would arc and fail to interrupt. The C-curve trip characteristic means it holds through inrush up to 5–10× rated current — appropriate for capacitive loads like inverter DC links or LED drivers — before tripping magnetically on a hard fault. At 8 A rated current, this breaker protects a single string or branch circuit; the 4-pole design switches both positive and negative conductors simultaneously, which is required by many DC code sections to ensure complete isolation during maintenance.
What the DC ratings mean for fit
AC-only MCBs cannot extinguish a DC arc at these voltages — the arc sustains and welds contacts. The 5SY5408-7CC uses a dedicated DC arc chamber and contact geometry rated for that duty. The maximum DC operating voltage is listed at 1 000 V, giving headroom above the 880 V nominal rating.
Mounting position is unrestricted, so it can go sideways or upside-down in a tight enclosure without derating. Height is 90 mm. Neutral conductor is not switched — this is a 4-pole breaker for DC, not a 4-pole AC unit with a switched neutral.