When is De-Energized Equipment Not Actually De-Energized and Safe to Work On?
By George T. Cole, Contributor
Some readers may be wondering about the apparent contradiction or confusion with the title of this article but as we progress, the accuracy will become clear.
The term “de-energized” is common among electrical workers but understanding its significance can vary greatly depending on the person you speak with. However, did you know it’s actually defined by OSHA and NFPA 70E?
Both OSHA and 70E define de-energized as “Free from any electrical connection to a source of potential difference and from electrical charge; not having a potential difference from that of earth.” Another word for ‘potential difference’ or ‘difference of electric potential’ is ‘voltage,’ so de-energized is state that’s free of voltage.
When standards and codes define words, the intent is to ensure all readers will have the same understanding of its meaning, parameters, and limitations. This helps reduce confusion and personal interpretation between individuals while navigating the codes or standards. However, even with technical definitions provided, they must be further understood within the full context of the standard.
Most electricians and technicians will agree working on electrical equipment that has been “de-energized,” i.e. no voltage, offers the greatest level of safety from electric shock and arc flash hazards. And while true, it’s only true in part.
Take for example, the relatively common activity of changing out a 277-volt ballast in a fluorescent lighting fixture. Obviously, removing the wire nuts with the power on is inherently riskier than doing so with the wall switch turned off. Moving the wall switch or circuit breaker to the “off/open” position, should remove voltage from the luminaire. Technically speaking the ballast is “de-energized” according to the definition but is the lighting fixture actually ‘de-energized’ according to safety regulations? This is where we must temporarily exchange our electrician’s hard hat with one from a safety consultant.
To answer this question, we need to look at OSHA 29CFR 1910.333(b) – Working on or near exposed deenergized parts, for a better understanding, especially as we progress to 1910.333(b)(1) – Application, which states: “This paragraph applies to work on exposed deenergized parts or near enough to them to expose the employee to any electrical hazard they present. Conductors and parts of electric equipment that have been deenergized but have not been locked out or tagged in accordance with paragraph (b) of this section shall be treated as energized parts, and paragraph (c) of this section applies to work on or near them,” emphasis added.
This section applies to “exposed de-energized parts” in the first sentence then throws a curve ball in the preceding second sentence. So even when no voltage is present at the lighting ballast because of the status of the wall switch or breaker with the lamps extinguished, unless the lighting circuit has been LOTO according to 1910.333(b)(2), it can’t be considered nor treated as “de-energized”.
But before applying our LOTO, we have other mandatory actions that must be fulfilled according to 1910.333(b)(2)(iii) (A) through (D) for the process of “de-energizing the equipment” that requires:
(A) Procedures to de-energize the equipment must be in place.
(B) The equipment to be disconnected (isolated) from all sources from electrical energy. Prohibits the use of switches, push buttons, control circuits, etc. as isolation devices.
(C) All stored electrical energy in capacitors must be discharged, shorted, and grounded.
(D) All stored non-electrical energy needs to be blocked or relieved.
With these four prerequisite actions completed we can now attach our LOTO to the isolation point(s), but before proceeding to the actual task of changing the ballast, a final two-step verification must also be accomplished pursuant to 1910.333(b)(iv)(A) and (B).
(A) States: “A qualified person shall operate the equipment operating controls or otherwise verify that the equipment cannot be restarted.”
For a lighting fixture this can be flipping the switch to the ‘on’ position to see if the lamps illuminate or pushing the ‘start’ button on a three-phase induction motor. But keep in mind, the attempt to restart the equipment may be adequate for a non-electrical worker such as the mechanic who is tasked with changing the coupling between the motor and gear box, but for the qualified electrical worker who is about to place his hands on the exposed “de-energized” wires of the ballast or inside the motor’s termination box, this must never be the last step. It’s for this reason we’re provided with sub-step (B).
(B) States: “A qualified person shall use test equipment to test the circuit elements and electrical parts of equipment to which employees will be exposed and shall verify that the circuit elements and equipment parts are deenergized. The test shall also determine if any energized condition exists as a result of inadvertently induced voltage or unrelated voltage backfeed even though specific parts of the circuit have been deenergized and presumed to be safe. If the circuit to be tested is over 600 volts, nominal, the test equipment shall be checked for proper operation immediately after this test.”
The directive of “B” means, the circuit must be tested using a voltmeter to verify with 100% certainty that no hazardous voltage still exists on the exposed parts about to be touched. It’s impossible for a human to detect electrical potential using his five sensory systems of sight, sound, taste, smell, and touch. However, one may argue “touch” can be used but it could be your last touch.
Therefore, from a position of compliance with electrical safety regulations but more importantly worker protection, the ballast can’t be treated as “de-energized” unless all the actions listed above have been accomplished.
The apparent paradoxical conditions of the word “de-energized” by OSHA can bring about much confusion and ambiguity between different workers who failed to understand all of 1910.333 in its entirety.
But for those who desire excellence in their electrical safety practices that goes beyond mere compliance alone, NFPA 70E paints a clearer picture that provides a more practical method to this end.
70E moves away from the use of the subjective word “de-energized” to a phrase consisting of four key words, an “Electrically Safe Work Condition” (ESWC) to remove any confusion. While similar to OSHA’s multi-step, albeit disordered process for an electrical circuit to be “de-energized,” NFPA 70E takes a logical and prescriptive approach through a detailed eight step process that must be performed in the specific order.
The ESWC is found in article 120.5 and is foundational for the elimination of electric shock and arc flash hazards as the top priority of NFPA 70E according to article 110.1.
Verification that an ESWC exists mandates all eight of the following steps have been accomplished in the prescribed order, if feasible:
- Determine all possible sources of electrical supply to the specific equipment by checking up-to-date drawings.
- Properly interrupting the load current then open the disconnecting device(s) for each source.
- Visually verify that all blades of the disconnecting devices are fully opened or that drawout-type circuit breakers are withdrawn to the fully disconnected position.
- Release stored electrical energy.
- Block or relieve stored nonelectrical energy so parts cannot be unintentionally reenergized.
- Apply lockout/tagout devices in accordance with procedures.
- Use a rated portable test instrument to test each conductor or circuit part for the absence of voltage by testing both phase-to-phase and phase-to-ground. Before and after each test, verify the test instrument is operating satisfactorily on any known voltage source.
- Apply temporary protective grounds to develop and equipotential zone if induced voltages, reaccumulation of stored energy or a possibility of contact with other energized parts.
As you can see, an ESWC not only contains all the OSHA obligations for a circuit to be treated as “de-energized” but also houses additional prerequisites and lays them out in a logical systematic order with sufficient details for each step. By doing so, 70E purges any confusion by replacing the subjective word “de-energized” as used by OSHA with a distinct term ESWC that can’t be misunderstood.
In conclusion, when speaking of the health and safety of employees, a combination of critical actions is required to ensure electrical hazards are eliminated prior to starting work. Therefore, rather than using the ambiguous word “de-energized” to describe the safe condition of electrical equipment, if we change the paradigm in our workplaces and start incorporating the term Electrically Safe Work Condition, then there will be no misinterpretation between all parties.
George Cole is an electrical safety consultant and instructor for E-Hazard (https://e-hazard.com). He has over 30 years of experience in the electric utility industry and is currently the electrical safety consultant and subject matter expert at the largest nuclear power plant in the U.S. Cole holds credentials as a Certified Electrical Safety Compliance Professional (CESCP) and a Certified Electrical Safety Worker (CESW) from the NFPA and serves as a member of NFPA’s Certification Advisory Group (CAG) for the CESCP and CESW.
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