My question concerns the use of Green and Red lamps used to designate whether a motor control circuit has been energized. I am working to get my Electricians license and in my Motor control theory class our instructor casually mentioned we would be wiring indicator lamps based on NEMA standards. He said that they required Red lamps to be used for “ON” or “Running” and Green lamps were to be used for “OFF” or “Safe”. The GREEN “ON” pushbutton turns on the Red lamp and the RED “OFF” button turns on the Green lamp. This just does not make sense to me. Does anybody have information or a Site which indicates that this is correct?
NFPA 79 - the standard for industrial machinery for the National Fire Protection Agency, says that red indicators are only to be used when the machine is in a state that requires immediate action by the operator to prevent either a safety hazard or to prevent damage to equipment or property. Green indicators are for condition Normal. This is not unique to NFPA 79 or even the US. The european nations have the same deal (EN60204 - European standard for Industrial Equipment).
Red is to be used for only emergency off(EMO) buttons. Green can be used for ON I believe (I’m at home, NFPA 79 is at work) and the OFF buttons should be black, white, or grey.
You should ask the instructor for a quote. Could be he’s been at it for so long, the standards may have changed, or maybe he’s just full of it and makes stuff up as he goes. Please post back when you get the quote. I want to see it.
A few minor corrections:
Red can be used for OFF and Emergency Off but black white and grey are also permitted for OFF.
NFPA 79 - 2002 - Table 10.3.2 explains the meaning of different colors of indicator lights. For personnel safety, the colors are as you mentioned in your first post, for machine status, they are as I posted yesterday. The standard however, requires you use the colors as they relate to machine status (10.3.2), not personnel safety.
Although I don’t work with the NEMA standards, I would be suprised to see such a direct conflict bewteen a NEMA standard and NFPA 79.
A little back ground on the applicability of NFPA standards. The National Electric Code (NEC) is the standard NFPA 70. For industrial tools, NFPA 79 is the most commonly accepted electrical safety standard, at least with Oregon, Washington, and Idaho electrical inspectors. UL508 is also commonly accepted but it does not specify indicator or pushbutton colors other than to say the red is to be used for OFF, STOP, or Emergency OFF/STOP.
Thanks for the info. I mentioned it to him and showed him the references and he said “If you went to work for me and I told you to wire the Red light as on and the green light as off, how are you going to do it?” What an Ass. Oh well, thanks again for the confirmation.