I tested my reprap and managed to short something out. I didn't notice it first but after a couple of seconds I saw smoke coming from under my table. The wire connecting my power supply and power system had almost liquefied and was giving out tons of smoke. I unplugged it and it stopped.
My other power source - the battery, had 10A one what went out right away. Next job - make sure that every power wire is fused. The lesson for today - use fuses. There is never enough of them! Next time when making a project, add some. And if you want to protect ICs then self resettable fuses/PTCs.