As I mentioned in my original message, anything larger than coffee maker i.e., machines that can cause harm requires an estop; a small 3d printers would fall in the coffee maker category, the only harm a 3d printer can cause is burn to your pinky.Since you are from Germany before selling or letting some else use the machine you refurbished double check your country machine wiring regulation.
Many years ago, I was assigned the design of the electrical controls of a machine for export to Germany. My hair went white trying to decipher the German DIN Electrical standard. DIN is the most rigid standard in the world, it even tells you if toilet paper hung under or over)image missing /media/kunena/emoticons/smile.png.
In your case a simple Estop/reset might not be sufficient, you might need a CE certified safety relay, if bought new it will cost you more than 7i92+7i77.
Don’t let those macho cowboys tell you otherwise, liability can ruin you all the way to your grave. In law, ignorantia juris non excusat which means "Ignorance of the Law excuses not" is a legal term holding that a person who is unaware of a law may not escape liability.
