Miniature Circuit Breakers (MCBs) in DC Circuits

It is not recommended. The reason is that the AC MCB utilizes the zero point of AC fault current to extinguish the arc to make the contact separation. If you use it in DC circuit, it fails and introduces hazard.

-MS

MCBs made by most major manufacturers have been tested and are rated for use in DC systems.

The maximum voltage will be considerably less than for AC, perhaps 50V per pole - best to consult manufacturer's datasheets for an exact figure. If you need to operate at a higher voltage, it is possible to connect multiple poles in series.

The current rating of an AC MCB in a DC system should be quite close to, if not the same as its rating in an AC system. The short-circuit current rating will be less in DC operation. Again, consult the manufacturer's datasheets.

Note that some manufacturers have several ranges of MCB, and may have only rated some of them for DC.