Master Start/Stop ciruit

Is there a regulation that states that you 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 any information would be welcome
Thanks

Here's some reading material

I do not see anything in that regulation that refers to "Master Start or Stop", is there something I am overlooking

droberts45,

NFPA 79 - Electrical standard for industrial machinery.

an emergency stop relay (E-stop) is required for all machinery.
if someone is hung in a machine, the e-stop relay kills the master ******* relay (MCR) which in turn kills the power to all i/o. there are exceptions to killing the i/o, but you must do your homework. the e-stop is then reset by pressing a reset button and then press the power on button.

why would you not have an estop relay circuit? it's an OSHA requirement.

if you build a machine and someone gets hurt / killed, Osha will do an investigation and when they find no e-stop circuit,
it will fall on the company who built the machine, the one who designed the system, and maybe on the one who built the system.

regards,
james

I just posted the Information pertaining to Emergency Stops.
Whether you need a Master Start Stop I am not Sure. Depends on the Machine. Depends on the Risk to Life,Limb and Equipment Damage.

i always have a safety relay for estop but I was told that a master start/stop circuit was also required by code, but can not find it in NEC, NFPA 79, or OSHA

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...

Click to expand...

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

Hi
I recently did a project where the machine was over 3 floors and the e=stop was zoned into 4 areas.. with the safety voltage daisy chained through 4 safety relays. I used a master reset to reset all 4 zones from a common reset button ( e-stop reset for each zone, locally, and an overall master reset

Maybe your scenario is like that

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

Click to expand...

In the bad old days before the modern version of Safety Relays was a gleam in OSHA eyes, Master Control Relays were used as a convenient way to kill power to machines. A Stop button dropped out the relay, which opened power to all of the devices on the machine, including any PLC outputs. Now such a system (without a safety stop relay) would not meet safety standards.