DC-rated MCB for solar, UPS, and battery-bank circuits
The Siemens 5SL5204-7RC is a 2-pole miniature circuit breaker from the SENTRON 5SL series, purpose-rated for DC circuits at 440 V with a 10 kA breaking capacity and C-curve tripping characteristic at 4 A. That 440 V DC rating is the headline here — most 2-module MCBs in this footprint top out at 72 V DC, so this one handles ungrounded DC bus voltages common in photovoltaic combiners, UPS battery strings, and DC distribution in telecom shelters.
What the DC rating means in practice
DC arcs don't self-extinguish at current zero like AC does, so a breaker's DC voltage rating is the real constraint. At 440 V DC, this 2-pole unit uses both poles in series to stretch and cool the arc — that's why it's a 2-pole design even though it's switching a single ungrounded DC circuit. The 10 kA interrupting capacity at that voltage is verified for fault currents from battery banks or large capacitor banks. If you're used to seeing 6 kA on typical residential AC MCBs, the 10 kA here gives more headroom for high-fault installations.
Same 76 mm depth, 36 mm width, 90 mm height as the 5SL6220-7 (which is an AC-rated 2-pole C-curve). If a panel was laid out for the 5SL6220-7 but the circuit needs DC protection, the 5SL5204-7RC swaps in without moving the DIN rail or changing the enclosure depth. Same sealable design, same IP20 with conductors, same mounting position any orientation. The difference is purely electrical: 440 V DC vs 400 V AC, and 10 kA vs 6 kA breaking capacity.