tigebite

Thanks for the input. In order to bring the system down and not damage anything, things need to happen in a timed sequence. Would I be looking at a safety PLC at that point and not just a "safety" rated relay? Or, would the safety relay still be used but only to safely stop that which can be immediately and allow the PLC to bring the rest of the system down.

I am new to the forum. For design guidlines for our industrial furnaces we follow NFPA 86. Under safety it talks about needing manual emergency switches to initiate a safety shutdown. It doesn't define what a safety shutdown must consist of, or what a manual emergency switch is other than the fact that it must be hardwired outside of the PLC. Does anyone know of a requirement/regulation that would govern how I need to wire the switch and how to physically wire the safety shutdown. I have been poking around the forum looking for sources (by searching safety and NFPA), but am getting burried. I have briefly looked in the viewable NFPA 70 (2005), as someone pointed out. I have NFPA 70 (Newest version) on the way. Is there an OSHA or ANSI code I should be following? Thanks for the help in advance.