Does UL Certify (List) Circuit Breaker Pad Locking Devices?


Does UL Certify (List) Circuit Breaker Pad Locking Devices?


Yes, UL certifies both circuit breaker lock-on and lock-off devices under the product category Circuit Breaker Accessories (DIHS), located on page 96 of the 2011 UL White Book. These devices are evaluated for compliance with the Standard for Safety for Molded Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures, UL 489. UL 489 requires that a lock-off or lock-on device supplied as a kit for field installation comply with all of the following:

  • Accommodate a padlock that will prevent the operation of the circuit breaker or switch with the padlock in place;
  • Require the use of a tool for removal;
  • Have the necessary mechanical strength to ensure reliable and positive mechanical performance;
  • Not depend on the panel enclosure cover to retain the device in place;
  • Not interfere with the normal intended operation of the circuit breaker or switch;
  • Ensure that the ON-OFF marking for the circuit breaker or switch is clearly visible with the padlocking attachment in place. The marking may appear on the lock-on or lock-off device.
  • Each kit or package of a lock-off or lock-on device is required to be marked with its catalog number and the numbers of the circuit breakers or switches with which it may be used; the name, trade name, or trademark of the manufacturer; and the method of installation unless the construction makes the installation plainly evident.

The Guide Information for Circuit Breaker Accessories (DIHS), can be viewed on UL’s Online Certification Directory at and enter DIHS in the category code search field.