The OSHA construction standard for electrical safety-related work practices states: “No employer shall permit an employee to work in such proximity to any part of an electric power circuit that the employee could contact the electric power circuit in the course of work, unless the employee is protected against electric shock by deenergizing the circuit and grounding it or by guarding it effectively by insulation or other means.”

The general industry standard states: “Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. Live parts that operate at less than 50 volts to ground need not be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.”

Two footnotes accompany the standard. The first cites examples of “additional hazards.” They are “interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment, or removal of illumination for an area.” The second addresses “infeasibility.” These include “testing of electric circuits that can only be performed with the circuit energized and work on circuits that form an integral part of a continuous industrial process in a chemical plant that would otherwise need to be completely shut down in order to permit work on one circuit or piece of equipment.”

The following scenario was submitted to OSHA for interpretation as to whether deenergizing the 110-volt control circuit as described would be considered “infeasible.”

“Workplace motor control centers have boxes with 480 volts disconnects and 110-volt control power with the same box. The 480-volt load circuits are deenergized, but the 110-volt control circuits must remain energized for the following reasons:

1. Programmable Logic Controllers shut off in some instances and there is no power backup

2. Control power is off on a large number of machines. This could be literally hundreds of machines

3. Hoppers and transitions could plug up with product

4. All fluidizing lines would have to be purged in order to prevent plugging of the line

5. Hot glue machines would be shutdown and the glue would set

6. Hundreds of motors would be shut off

7. Eight to 10 hours of start-up time could be required to re-load processing bins, fluidizing lines and processing transitions

8. When the system is put back into production there is a chance of many more hazards developing that would have to be addressed.”

OSHA replied that deenergizing the 110-volt control circuit appeared to be infeasible. However, it further qualified its response by noting infeasibility is determined on a case-by-case basis.

This situation focuses on the concept of additional hazards, where working hot is not justified. During a state fire inspection, a community college ice rink was cited for lack of emergency lighting due to a bad inverter. To avoid being shut down, emergency lighting needed to be in place within 24 hours. There were three options: fix the inverter, install temporary emergency lighting or have individuals stand flashlight watch at a cost of $70 per night. The inverter repair would take a week, while temporary light installation needed to be scheduled with maintenance.

The manager told the fire inspector and safety director he would hire personnel for the watch, avoiding a shutdown and the loss of $5,000 per day. After the inspector and director left, the manager contacted plant operations for temporary lights.

The safety director was called back to review the results of a short circuit and determined there were no “additional hazards” to justify working hot. It was daylight, so maintaining emergency lighting was not necessary to avoid hazards associated with illumination loss. Work was scheduled to be performed safely and personnel were written up for the event.

Justification for working hot may still seem elusive. However, there is one resource left, the OSHA fatal accident investigation record. OSHA stated in the investigation report: “An electrician was working on a 277-volt lighting circuit without de-energizing it. He contacted an energized conductor as he was making a connection in a switch box and was electrocuted.” Think carefully on how you justify working hot and the procedures to be used. A great deal is at risk. EC

O’CONNOR is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or [email protected].