Even if you leave the switch open, it can fail and leave some parts of the units you're working on turned on. Also, some manual motor controller switches have been found installed backward, which means the power is ON when the switch is labeled OFF.

With manual motor controllers (or motor starter circuits), only one conductor is opened. For lockout/tagout – to prevent anyone turning on equipment while repair or maintenance is done – an approved disconnect switch must open all conductors on the power supply and must be able to be locked open. Turning a motor starter switch to OFF is not an acceptable method for lockout/tagout, because that does not guarantee that a machine is turned off.

OSHA does not accept motor starter circuits as complying with its Lockout/Tagout Standard. (See OSHA letter of interpretation http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=20354) The circuits are not an acceptable way to disconnect equipment under the OSHA Construction Standard.

This paper appears in the eLCOSH website with the permission of the author and/or copyright holder and may not be reproduced without their consent. eLCOSH is an information clearinghouse. eLCOSH and its sponsors are not responsible for the accuracy of information provided on this web site, nor for its use or misuse.

eLCOSH | CDC | NIOSH | Site Map | Search | Links | Help | Contact Us | Privacy Policy