Good to Know

Color Coding for pushbuttons, indicator (pilot) lights, and illuminated pushbuttons

( NFPA 79 Industrial Machinery)

Color
Device Type
Typical Function
Examples
RED
Pushbutton Emergency Stop, Stop, Off Emergency Stop button, Master Stop button, Stop of one or more motors.
Pilot Light Danger or alarm, abnormal condition requiring immediate attention. Indication that a protective device has stopped the machine, e.g. overload.
Illuminated Pushbutton Machine stalled because of overload, etc. (the color RED for the emergency stop actuator shall not depend on the illumination of its light).

YELLOW (AMBER)
Pushbutton Return, Emergency Return, Intervention – suppress abnormal conditions. Return of machine elements to safe position, override other functions previously selected. Avoid unwanted changes.
Pilot Light Attention, caution/marginal condition. Change or impending change of conditions. Automatic cycle or motors running; some value (pressure, temperature) is approaching its permissable limit. Ground fault indication. Overload that is permitted for a limited time.
Illuminated Pushbutton Attention or caution/Start of an operation intended to avoid dangerous conditions. Some value (pressure, temperature) is approaching its permissable limit; pressing button to override other functions previously selected.

GREEN
Pushbutton Start-On General or machine start; start of cycle or partial sequence
Pilot Light Machine Ready; Safety Indication of safe condition or authorization to proceed. Machine ready for operation with all conditions nornal or cycle complete and machine ready to be restarted.
Illuminated Pushbutton Machine or Unit ready for operation/Start or On Start or On after authorization by lights; start of one or more motors for auxiliary functions; start or energization of machine elements.

BLACK
Pushbutton No specific function assigned Shall be permitted to be used for any function except for buttons with the sole function of Stop or Off; inching or jogging.

WHITE or CLEAR
Pushbutton Any function not covered by thee above. Control or auxiliary function not directly related to the working cycles.
Pilot Light Normal Condition Confirmation Normal pressure, temperature.
Illuminated Pushbutton Confirmation that a circuit has been energized or function or movement of the machine has been started/Start On, or any preselection of a function Energizing of auxiliary function or circuit not related to the working cycle; start or preselection of direction of feed motion or speeds.

BLUE or GRAY
Pushbutton Any function not covered by the above colors
Pilot Light Any function not covered by the above colors
Illuminated Pushbutton Any function not covered by the above colors

Standard nominal three-phase system voltages per ANSI C84.1-1989

Voltage Class

Three-wire Four-wire

 Low Voltage

208 Y/120

240

240/120

480

480 Y/277

600

 Medium Voltage

2,400

4,160

4,160 Y/2400

4,800

6,900

8,320 Y/4800

12,000 Y/6,930

12,470 Y/7,200

13,200 Y/7,620

13,800

13,800 Y/7,970

20,780 Y/12,000

22,860 Y/13,200

23,000

24,940 Y/14,400

34,500

34,500 Y/19,920

46,000

69,000

 High Voltage

115,000

138,000

161,000

230,000

 Extra-High Voltage

345,000

500,000

765,000

 Ultra-High Voltage 1,100,000