Observe Polarity of DC Switches!

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!