sorry, thought i responded yesterday. i appreciate the attention to the question. I was really trying to confirm my assumption that the switch was designed to prevent restart if the loss and restoration of power was remote from the machine. I figured that was the principal function but I hadn't head the term "no-volt release".
The only question I have about Greg's diagram is the aux side switch. couldn't you also just pick up the same on the main switch for the motor. Currently, this machine taps the leg that would be the very bottom line in Greg's drawing (is there a color or labeling convention that would help to discuss this picture better)at the upstream side of the contactor which if you go back to scott's original drawing which Greg also linked above :
https://www.electrical-contractor.n...Stop_3_wire_AC_motor_con.html#Post148638 is upstream of the motor overloads, so the load for running the contactor is not added to the motor overloads.
What I'm wondering is, couldn't you just pick up the same leg downstream of the contactor but still upstream of the overloads, i.e. at the screw terminal on the contactor. I can't easily get to the contactor to check how this one is wired, appears to have a side terminal for the switch, but no input for that side terminal, so maybe the crossover is internal? Since all is well, I can't really justify the time to pull the contactor box further apart and use a continuity test to reverse engineer what it is up to so though I'd just ask.
I suppose one downside to my simple approach adds the contactor load to the main switch capacity, but while I can see the contactor load possibly affecting overload throw if the overloads are conservative (i.e. allow very little overcurrent) I would think that the contactor would usually have more slack in rating.
And while on the subject of overloads. I assume the meaning of scott's diagram with 3 overloads in series is that these are actually auxilary contacts on the motor overloads so that if an overload trips on any leg, it has the effect of opening the stop switch as well.
The reference to the overload in Greg's drawing is as a single which could be read as a current restrictor on the contactor coil itself.
thanks,
brian
