How should I wire the E-stop button? NC or NO?

I would recommend wiring the E-Stop to an input terminal via an NC connection. This is the industry standard. It requires a NC (Normally connected) circuit for the machine to be operational, and when the circuit breaks, the machine shuts off. This is better than having a circuit NO (normally open), open circuit that requires a circuit to be created to have the machine shut off for safety. Having en E-Stop run through the mains line would only work for a single circuit (or use multiple E-stops, which defeats the purpose). The E-stop connected to the input terminal would shut off all machine functions. Additional Information: 100% agree. When we have our automatic fire suppression systems wired in, we always do them NC (Normally Connected/Normally Closed). You can see more at www.reactonfire.com/what-we-protect/cnc-fire-suppression/ If you're doing a fire system (ours or others) be sure to shut down the machine and mist collectors) Additional Information: 100% agree. When we have our automatic fire suppression systems wired in, we always do them NC (Normally Connected/Normally Closed). You can see more at www.reactonfire.com/what-we-protect/cnc-fire-suppression/ If you're doing a fire system (ours or others) be sure to shut down the machine and mist collectors)