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#62623 - 02/22/06 10:27 AM indicator lites  
Dr. Electron  Offline
Junior Member
Joined: Jan 2006
Posts: 2
Willmar MN USA
motor control circuits containing red and green indicator lites:, why red for run and green for stop?

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#62624 - 02/22/06 10:48 AM Re: indicator lites  
NJwirenut  Offline
Joined: Sep 2001
Posts: 806
Bergen County, NJ
The thinking probably was that a stopped motor is a "safe" (green) condition, while a running motor is a "caution" (red) condition.

#62625 - 02/22/06 01:24 PM Re: indicator lites  
RODALCO  Offline
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
Yep,NJwirenut We have red for on and green for off on the OCB's in our substations.

Same reason for the colours is that red is a colour for danger live !!

Although I have seen on Melin Gerin switchgear that the colours are the opposite way, green for on, red for off, talk about confusion!

Cheers Ray

The product of rotation, excitation and flux produces electricty.

#62626 - 02/22/06 01:48 PM Re: indicator lites  
ghost307  Offline
Joined: May 2005
Posts: 921
Chicago Illinois USA
The colored lights aren't for the motor, they're for the people.
I usually get a few folks who thing that the pilot lights should be traffic signals for the motor.
BTW, when I was working for GE, I went through their training program for 12 weeks. We had 1 guy who INSISTED that the pilot lights should be like traffic signals. After a few instances of "fixing" the training equipment to match his interpretation of reality, he got dragged into the Director's office and was told:
1. You're wrong; everybody needs to be on the same page.
2. Changing the colored bezels is dangerous to the other students and can get someone killed.
3. If I hear about ONE more incident, you're fired before you even graduate.
I don't necessarily have an issue with any convention, but everybody needs to respect it when it's made. Electrons go the wrong way, 3-way switches go in 2 places, single phase can have 1 hot or 2; we don't need to be 100% correct, but we need to agree to disagree or someone will get hurt.


#62627 - 02/22/06 01:56 PM Re: indicator lites  
Bill39  Offline
Joined: Nov 2001
Posts: 75
Indianapolis, IN, USA
It's similar to the color codes of wiring...there are many different standards.

Pilot light len's colors differ according to industry. See NFPA-79 for some examples. It has a complete list. Ones I can think of are:
Amber = Running
Red = Stopped or abnormal condition
White = Status

#62628 - 02/22/06 04:45 PM Re: indicator lites  
rad74ss  Offline
Joined: Apr 2004
Posts: 156
Pryor, OK USA
The equipment built where I work (HVAC equipment) uses green for run and red for fail. We also tag all lights and put the lens color on the prints. I guess it comes down to paying attention to what you are working on.

#62629 - 02/22/06 04:54 PM Re: indicator lites  
frank  Offline
Joined: May 2001
Posts: 376
windsor ontario canada
Dr. Electron,I know exactly what you mean.We have a new plant with Square D Model 6 mcc's Just the standard manual/off/auto selector switch and one red pilot light that comes on when the starter closes.If you press the pilot light cover with the selector switch in the off position it will light up for a self test.I haven't checked to see if can be wired as a momentary contact but thats what people take it for and believe they jogging the motor when they press it.Also a burnt out light can easily be mistaken for a stopped motor.
I'm almost positive that Allen Bradly at one time or still does used Green for start and red for stop.Could be Westinghouse though.
When i worked in a panel shop we color coded the lights as bill described but if we had more than one light they all got permanently tagged.
I have to agree with amber or green for running and red for stopped simply because every operator/maintenance guy knows a red button means stop and logically surmises a red light to be stopped.Green means go and amber caution so...In fact i have seen fwd/rev motor starter buss pluggs come factory wired like a stop light ready to be racked and wired.
It's not so much for us as them because the day you trust idiot light could be your last when trouble shooting an unfamiliar machine.
Just MHO.

[This message has been edited by frank (edited 02-22-2006).]

#62630 - 02/24/06 06:29 AM Re: indicator lites  
Steve Miller  Offline
Joined: Aug 2001
Posts: 325
Loudoun Cty, VA
They aren't always that way. It's not too unusual for the colors to be reversed. In our system we have them both ways. I've seen the plans and the dern engrs have speced them both ways. Plans approval people approve them and the confusion begins. Same for lighting contactors.

#62631 - 02/24/06 06:46 AM Re: indicator lites  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,223
SI,New Zealand
Majority of Control gear that I've wired down here use:

  • Red= Normal Run
  • Amber= Out on Fault
  • Green= System Stopped
  • Blue= Over-current Device tripped
  • White Flashing= PLC Fault

I did my time as an Industrial Electrician in a Meat-Works here.
All under computer control, sure we now have SCADA systems to do most of it, but back then it wasn't like that, it wasn't around. [Linked Image]

#62632 - 02/24/06 08:30 AM Re: indicator lites  
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
Norfolk, England
I seem to recall reading several threads elsewhere (maybe the Engineering Tips forum?) on this subject, and the conclusion being that there is no particular standard for red and green equating to run and stop/on or off. Different industries and plants seem to use different schemes.

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