Automatic Transfer Switch Lights and Alarms

NFPA 110 Requirements for Automatic Transfer Switches in Emergency Power Systems

NFPA 110, 2010 Edition

  • Chapter 6.2.13 – “Indication of Transfer Switch Position” Two pilot lights are required to indicate switch position—normal and emergency.

Note: Most transfer switches also have pilot lights to indicate available source—normal utility or generator. These lights may not be controlled by voltage sensors and therefore may falsely indicate power availability.

  • Chapter 6.2.1 (3) – “Visual Annunciation when “not in automatic” : A means(light) of indicating if the switch is not in the automatic mode. Chapter 6.2.1 (3)

The transfer switch may have other indications that are not code requirements.

  • Digital display that reads in code or script. Keep your operators manual available to decipher the codes and warnings.
    • “Fail to connect” may mean no power from the generator. Go back to my flowchart.
  • “Test” light helps guide you through the manual test mode. See my: “Transfer Switch Controllerspage.
  • “Exercise” light means it is in the automatic exercise mode.
  • Battery Low” This refers to the transfer switch internal battery. Some transfer switch computer controls use batteries to maintain settings or create a start signal when both sources are not available. Some of these are replaceable. In any case, you only have three to ten years of life before the battery fails and transfer switch malfunctions. Typically, the “Authorized Service” company will want to replace the entire control. Ask them if it is just a battery problem.

Our Legal Disclaimer:

All information expressed by Standby Power Solutions, LLC or its officers is strictly the opinion of Standby Power Solutions, LLC.
Standby Power Solutions, LLC disclaims any liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory directly or indirectly resulting from the publication, use of, or reliance on this website or any information derived thereof. Standby Power Solutions, LLC also makes no guaranty or warranty as to the accuracy or completeness of any information contained herein. Anyone using this website should rely on his or her own independent judgment, or as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. ©2021 by Standby Power Solutions, LLC. All rights reserved. Do not reproduce without express written permission.