Electrical Safety - When Can You Work on Energized Circuits?

Technicians and maintenance personnel often need to work on exposed live (energized) circuits to troubleshoot or perform maintenance on electrical systems or equipment. 

The Occupational Safety and Health Administration (OSHA) and the National Fire Protection Associated (NFPA) provide guidance on working on exposed live (energized) circuits.  OSHA 29 CFR 1910 requires that work on electrical systems or equipment shall be de-energized unless de-energizing the circuits could create a greater hazard or if it is infeasible to de-energize the circuits.  The requirements identified in NFPA 70E, Standard for Electrical Safety in the Workplace, Articles 130.1(A)(1) and 130.1(A)(2) are similar to the OSHA requirements.

There are at least three classifications of electrical circuits that if they were de-energized could create a greater hazard to other people: emergency circuits, legally required standby circuits, critical operation power system (COPS) circuits.  Emergency, legally required standby, and COPS circuits are defined by NFPA 70, National Electrical Code, in Articles 700, 701, and 708 respectively.  Emergency circuits are identified as those systems that provide safe exit and communication within a building or other areas associated with life safety (e.g. patient rooms, operating rooms, or other areas within a hospital) [1].  Legally required standby circuits are identified as those systems that if stopped could result in general public safety hazards (e.g. sewage treatment facilities, pollution abatement systems, chemical processes, etc.) [1].  COPS circuits are identified as those systems that vital to national security, the economy, and public safety [1].  De-energizing emergency, legally required standby, or COPS circuits could endanger other personnel.  Therefore, technicians and maintenance personnel are allowed to perform work on these systems.

Optional standby systems, and unclassified systems are other types of electrical systems.  However, these systems in general do not pose a greater hazard to other personnel if they are de-energized like emergency, legally required standby or COPS systems.

When working on exposed live (energized) circuits an electrical hot work permit, risk assessment, and job safety meeting are required prior to conducting the work on exposed live (energized) circuits [2].  Items to be considered in the risk assessment are work practices that could result an inadvertent de-energizing of the electrical system due to human error or equipment malfunctions.

There are a number of work practices where it is infeasible for qualified employees to de-energize the electrical system or equipment regardless of their classification.  This includes troubleshooting, measuring, and adjustment of equipment.  Troubleshooting and measuring of electrical systems or equipment often involves measuring voltage, current, power, phase or other electrical quantities that cannot be observed without electrical energy present.  Adjustment of servos, indicators and similar devices also require electrical energy.

When qualified employees are conducting troubleshooting, measurement, or adjustment of electrical systems or equipment in the presence of exposed live (energized) circuits, a risk assessment and a job safety meeting are required prior to conducting the tasks.  As aforementioned, a risk assessment that evaluates the inadvertent de-energizing of the electrical system due to human or equipment malfunctions should be considered.

1.  National Fire Protection Association (NFPA). National Electric Code, 2011.
2.  National Fire Protection Association (NFPA). Standard for Electrical Safety in the Workplace, 2012.