I have a contactor, controlled by a PLC, and a motor protection circuit breaker. Does it matter which comes first and if so: why? I don’t think it matters because the contactor’s job is to latch and the MPCB secures the motor against too much current. Also, is a contactor directional? Can a 24V coil contactor be 24V A1 and common to A2 and visa versa? Same for a 230V one? One side L1 the other neutral?
MPCB first then contactor. The reason is any malfunction in the contactor will also be protected by mpcb, or else malfunction in the contactor will trip the whole panel. Secondly, for ac contactors, it doesn’t matter, but for DC 24v contactors it matters, in fact, there will + and - written on it, you can verify physically.
General practice is the contractor on top and overload device below it. The coil question is on 24v coils, some are polarized so you can’t reverse A1/A2, but you can on 220.