droberts45 said:
...must have a master start/stop circutit that kills power to the estop circuit...
...I was told that you must have a hard wired Master start stop circuit to shut down any equipment in addition to an E-Stop...
Apart from whether this "Master" is required or not, those statements contradict each other. This "Master" is either supposedly removing the power to an emergency stop circuit, or removing the power to a circuit that an emergency stop circuit also removes the power from. Which is it?
I'm always open to learning new things, especially with regard to safety specifications and regulations.
A properly designed, and required, emergency stop circuit should not, in good practice, have the power to it's own safety circuit removed for any reason other than a scheduled isolation. I have a feeling that this isn't what you/they meant though?
I would ask the person that told you this what exactly they mean?
Ask them where did they hear, or read it from?
What makes it a "Master" over anything else?
What manner of safety device is it?
Why, and how does it "start" and "stop"?
Auxiliary safety circuits to an emergency stop circuit, again, properly designed, and required, may indeed remove the power to the same circuit(s) that the emergency stop removes. But what, by its design, makes it a Master over any other safety circuit that removes power to the same hazard?
Basic safety functions are usually complimentary, not hierarchical.
George