We often get questions in the e-Hazard office about allowances to perform “hot work”, aka “energized electrical work.” I’ve heard just about all of the excuses, and I always give the same answer.
99% of the time, energized electrical work is NOT authorized.
Mind you, I am not referring to voltage testing, troubleshooting, or similar functions. What concerns me are the questions, “Can I install a new circuit breaker in an energized panel?” or “Can I install a conduit in an energized electrical enclosure?”
Let me be clear: This activity is inherently dangerous, and the many recorded injuries from arc flash, as well as many unfortunate fatalities from electrocution, prove this point.
In this OSHA letter of interpretation, the questioner wanted to know if workers would be able to work live on a panel that feeds ten pieces of electrical equipment. The individual pieces manufacture integrated circuit components. Please read and take heed of OSHA’s official interpretation, dated December 19, 2006. The following shows most of the letter.
(The standard in question is OSHA’s 1910.333(a)(1), with special attention on Note 2.)
The scenario, question and OSHA’s response
Scenario: The manufacturing of our products involves many discrete pieces of equipment whose individual processes are part of the overall manufacture of integrated circuit components. For example, we have ten pieces of manufacturing equipment fed out of a 480-volt three-phase panel. A new project requires that additional feeders and a 225-ampere circuit breaker be added to the panel to supply a new piece of equipment. To perform the work in a de-energized state, it requires the power to the panel must be disconnected and appropriate LOTO devices applied. This activity would result in the shutdown of the ten pieces of equipment, causing a significant interruption to our ability to manufacture integrated circuits.
Question: Is the panel considered part of a “continuous industrial process,” thus allowing the work to be performed while the panel was energized using electrical safe work practices, as per Note 2 in §1910.333(a)(1)?
Response: It appears that your panel is not part of a “continuous industrial process.” The term “continuous industrial process” was derived from its use in the National Electrical Code (NEC). In the NEC “continuous industrial process” is used in the context of situations where the orderly shut down of integrated processes and equipment would introduce additional or increased hazards.1 Therefore, to qualify for the exception found in Note 2 of §1910.333(a)(1), the employer must, on a case-by-case basis, determine if the orderly shutdown of the related equipment (including the panel) and processes would introduce additional or increased hazards. If so, then the employer may perform the work using the electrical safe work practices found in §§1910.331-1910.335, including, but not limited to, insulated tools, shields, barrier, and personal protective equipment. If the orderly shutdown of the related equipment and processes would not introduce additional or increased hazards, but merely alter or interrupt production, then the de-energization of the equipment would be considered feasible, and the exception found in Note 2 of §1910.333(a)(1) would not apply. Based on the limited information you provided, it does not appear that de-energization of the panel in question would introduce additional or increased hazards. (emphasis added)
1 While the term “continuous industrial process” is used only once in the body of the NEC, the index directs the reader to four locations where the provisions are applicable to “continuous industrial processes.” See NEC 2003, Sections 240-12, 230-95 Ex. 1, 430-44, and 240-3(a)
As always, de-energizing is best practice. Doing live work in order to keep up the pace in manufacturing does not cut it.
There are exceptions to de-energizing, including Note 2 of this standard. Examples of other exceptions include “interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment, or removal of illumination for an area.”
As always, keep this in mind: if you are injured, or even killed at work, how long will the company you work for shut down? If you are an electrical contractor or contract engineer, how long will that client be affected if you meet your demise working on their systems “hot?” We must always remember: That activity you are doing is not worth your health or your life!