Stack Lights and Machine Lights Information

light stick

Stack lights and machine lights are used for alarm and machine status indication. They can be supplied with audible alarms and be used as flashers or steady light configurations.



There is no specific standard in the U.S. regarding stack light colors. However, ANSI under B11.19 section E4. states "Due to lamp failure, visual awareness devices should use multiple lamps such as green for run and red for unsafe." What the exact meaning is of those colors on a stack light should be part of the documented operator and maintenance personnel training for that machine. Colors commonly available for stack lights and machine lights include amber or orange, blue, clear, green, red, and yellow.

Number of Lights

The number of lights in a stack can range from one to six, but sometimes even greater than six lights can be supplied.

Lighting Options

Lighting options for stack lights and machine lights include lamps that are continuously on and lamps that flash at intervals. Mounting options available include pole mount, direct or base mount and wall mount.

Electrical Parameters

Important electrical parameters to consider when specifying stack lights and machine lights include:

  • The DC voltage rating is the maximum DC voltage rating for the light.
  • The AC voltage rating is the rated AC voltage for the light.
  • The power rating is the maximum power rating of the light.
  • The flashing rate is the rate at which the product flashes. Note, however, that this is not applicable for continuous lights.

Safety Approvals

Stack lights and machine lights may come with safety approval ratings. The maximum current or voltage rating for a product given by an approval organization may be different than the supplier’s designed maximums. In some cases, the product may be used safely at an unapproved level. Check with the supplier, however, for specific usage details.

  • UL Listing Mark - This Mark, denotes that Underwriters Laboratories Inc. (UL) has found that samples of the product met UL's safety requirements. These requirements are primarily based on UL's published Standards for Safety.
  • UL Recognized Component Mark (US and Canadian) - These Marks are used only on component parts that are part of a larger product or system. These components may have restrictions on their performance or may be incomplete in construction. Products intended for Canada carry the Recognized Component Mark "C."
  • CSA Mark (US, C and US, NRTL/C) - The CSA Mark may appear alone or with indicators. If it appears alone, it means that the product is certified for the Canadian market, to the applicable Canadian standards. If this Mark appears with the indicator "C and US" or "NRTL/C" it means that the product is certified for both the U.S. and Canadian markets, to the applicable U.S. and Canadian standards.


Features common to stack lights and machine lights include audible alarms, manual operations and outdoors usage.

Image credit:

Rockwell Automation