Many high voltage DC contactors, switches and circuit breakers are only able to perform to their specifications if the current is flowing in the expected direction. This is because they include magnets which push the arc away from the switching element and into an arc chute or other plasma management device. A wire carrying a current through a magnetic field experiences a force (this is how motors work!) and this is particularly effective in the case of an arc because the "wire" is actually made of ionized gas. The problem comes when you reverse the direction of the current -- the "blow out" magnets suddenly become "blow in" magnets and the switch catches fire.
RISE did some testing of polarized DC circuit breakers intended for solar power and the results were quite spectacular. Do wait for the 40A tests towards the end!
Consult the manufacturer's datasheet to ensure your switches are correctly installed!
I tested a few circuit breakers rated for AC using my car's 250V DC battery. I used my load tester to limit the current to about 27A. I found that with a resistive load, the breakers successfully interrupted the current but failed safely after 5 or 10 switching cycles. Since I didn't have the equipment to limit the current to 50 or 100A, I used one of the windings in an isolation transformer to make the load more inductive and sort-of simulate a higher fault current situation. With this additional resistance, the current dropped to 23A. The results were quite scary:
A Vynckier Series E circuit breaker interrupted the current once and caught fire on the second attempt. The fire only went out because I used my (400V 250A DC rated) contactor to turn off the current, you can see the flash on the left when it switches off.
A People DZ47-63 circuit breaker interrupted the current but destroyed itself in the process. Inside you can see the switching element is significantly shortened and the casing burnt:
It's important to note these tests represent abuse of the circuit breakers, if you ask them to switch AC they will likely give years of trouble free operation. The key is that 50Hz AC current falls to zero for long enough that the plasma cools, when the voltage rises during the next cycle, the arc can't re-establish without the plasma. With DC, the current doesn't stop and the arc just keeps burning.