I am struggling to find a solution for my dilemma, and feel as though it's a common occurrence. My situation involves residential electrical service for single phase 120/240v. I have been in the field of electrical for over 15 years, and I am now an electrical contractor (5 years running). I am more or less the only employee of my company, but I would like to hire employees and have a safety protocol in place before I even consider hiring.
My concern is the practical nature of my career and the regulations which have recently been made known to me through sifting this forum and two others regarding "de-energized parts" for 29 CFR 1910.333.
From my understanding, there is no possible scenario or exception for me or other employees to work near energized parts. Since most of the residential main breaker panels/load centers around my area (Southwest Florida) include all the branch circuit breakers, there would be no way for me to de-energize the electrical panel/load center apart from the local utilities. I also believe that I cannot use the table method or even perform an incident energy exposure calculation, risk hazard assessment, shock hazard assessment, fill out an energized electrical work permit, etc... That is only for times when it is "impracticable" (impossible) to de-energize, correct?
Is this to say that for every installation requiring me to remove the electrical panel cover/dead front requires a disconnect/reconnect from the local utilities?

Thanks.

~ Scott

Scott,

As you've probably determined, the AF standards are relegated to 3 phase systems, so the arc flash risk is minimized (in your case, non-existent in my opinion). Shock is your main concern. What you have outlined is a common problem, however unless you can show there is a justifiable reason to work while energized, it is suggested you de-energize per the standard.

This can sometimes be a charged topic...so I will be interested to see other's responses.

Mike

Thank you for your response.

I will post a letter of clarification regarding 29 cfr 1910.333, from the OSHA website. It deals with my situation for over approximately 80% of my installations.

Scenario: An employee is to perform work inside an electrical panel. The electrical disconnect is open and has been properly locked out. The electrical circuitry below the disconnect has been confirmed to be in a zero energy state by a qualified person using test equipment.

Question 1: Is the panel considered de-energized even though there is voltage to one side of the open disconnect? if the panel is not de-energized, would an employee be required to not only disconnect and lockout the power at the electrical panel, in this case a panel at floor level [Location B], but also to disconnect electrical service on-leg or panel upstream in the electrical system [Location A]?

Response: Section 1910.333(a)(1) establishes prerequisite criteria that live parts to which an employee may be exposed must be de-energized before an employee works on or near them, unless it is infeasible to do so.1 If locking and tagging out the circuit at the point of work (i.e., the panel to be worked on) does not de-energize the live parts an employee may contact, the employer needs to assess, on a case-by-case basis, the feasibility of locking and tagging out the circuit further upstream since doing so would de-energize the live parts. If upstream de-energization is infeasible, then the employer is required to use other safety-related work practices, such as the use of electrical protective equipment (e.g., barriers, rubber insulation blankets, gloves, sleeves, covers, insulated tools or handling equipment, in accordance with §1910.137 and §1910.335). Also, if upstream de-energization creates additional or increased hazards, per §1910.333(a)(1) de-energization is not required, and the employer must use other safety-related work practices. In any event, an employee is not required to lockout more than one panel governing the same circuit, if all exposed electrical components in a panel can be de-energized by locking/tagging out a single energy isolation device (at Location A or Location B) that is upstream from where the work is being performed.

The panel in your scenario may be considered de-energized depending on the design of the equipment and the work to be performed. In your scenario, the panel, while not technically de-energized as there is still power to the supply side of the disconnect, provides adequate employee protection if the design and installation of the panelboard is of dead-front construction — i.e., it prevents, through guarding, accidental contact of the employee or conductive objects with energized parts (e.g., the contact points on the fixed side of the switch designed to receive the contact points on the movable portion of the switch, conductor attachment points, conductors with compromised insulation, etc.). if the panel is not of dead-front construction or if the employee removes the panelboard guard, thus exposing live parts, the panel would be considered energized and thus be subject to the requirements of §1910.333(a)(2) (which requires the use of other safety-related work practices) and §1910.333(c)(2) (which allows only qualified persons to work on energized parts.2

This leaves me with more questions:

How does this apply to a residential main breaker panelboard/load center with the branch circuit breakers in the same enclosure? Remind you, I am never working ON any wiring as it is energized. The installations/repairs would be for adding a circuit, replacing/adding a circuit breaker, or fixing a double tap wiring issue (not at the line side of the main breaker). My primary purpose is to develop a proper safety procedure for employees, along with whatever else is necessary each time the electrical panel cover is taken off. It really should be a standard, since we are essentially put in the exact same scenario each day as residential electricians.

The only difference might be the safety barriers which from 2017 were included with main breaker electrical panels/load centers.

If there is a barrier, between the line and load sides, you could most likely justify working in the panel "live". If there is no insulated guarding, then the panel would be considered live. My 2 cents...

Mike

Speculating that I was able to work in the electrical panel with the service barrier at the line side lugs, how would I calculate PPE?

In order to even use the arc flash PPE category method of Table 130.7(C)(15)(a), the qualified person must already know several key pieces of information:

The voltage of the equipment being worked on while energized (obvious)
The maximum available fault current at the equipment being worked on (I have the utility provided chart for specific transformer sizes and their respective secondary fault currents @ 240V)
The maximum fault clearing time of the overcurrent device protecting the equipment being worked on (I will need to contact the utilities to confirm, but I do not believe that any of their secondary protection is going to clear a fault in 2 cycles or less - 0.03seconds)
The needed working distance in order to perform the task

If any one of the above are not known, or the information known does not allow you to fall into a specific parameter (specifically the fault clearing times on the secondary), then Table 130.7(C)(15)(a) cannot be used and an incident energy analysis must be performed instead of using the Table.

Am I wrong?

Scott,

The standard is not built around single phase arc flash. As I mentioned in my previous post, it is my opinion the arc flash risk is essentially zero as single phase arcs self extinguish rather quickly (the testing I have read about is with regards to 3 phase arcs, on 208V systems). The point is if 208V, 3 phase systems self extinguish, then single phase arcs most certainly do and may not even really start. I'm sure others on this board more knowledgeable than me will weigh in here...

In my opinion, your main concern is shock protection.

Mike

PS There is a good white paper on 208V arc flash testing from EPRI that talks about real world testing of network protectors with some interesting conclusions. While the testing doesn't fit your application, it is instructive.

I agree with your statement regarding self extinguishing arcs at 240V single phase. Since the standard is not built around single phase 120/240V, does this mean that there is no requirement for arc flash PPE by OSHA regulations? It would not make sense to need Category 1 or Category 2 PPE for single phase 120/240V residential when the arc flash requirements were not designed for single phase 120/240V. Shock protection makes perfect sense, which 500V rated gloves with leather protectors would be provided for situations where the line side of the main breaker cannot be de-energized. Also, is this to say that an EEWP is required each and every time I would have an employee working in the main breaker panel/load center where the line side lugs are still energized? Would there be any difference between a main breaker with the service barrier vs. without?

Thanks. Much appreciated.

~ Scott

I agree on the arc flash question...but you'll probably see a bunch of research coming on single-phase arc flash in the not so distant future.

An EEWP in your instance would be required by NFPA 70E if you were needing to disconnect the line side terminals on the main without the utility pulling the fuse. That is not your example though, and I am not advocating for anyone to do that kind of work.

If you are putting in a new single-pole breaker for instance, for a 20A circuit, doing that after verifying that the bus is de-energized is not energized work if you establish an electrically safe work condition on the load side of the main. See NFPA 70E-2021 120.5. Once the load side of the main is shown to be a safe work condition you can use Table 130.4(E)(a) to see what the restricted approach boundary is....and for 240VAC (as measured line-to-line) it would be 12" meaning that your worker would need to have shock protection gear if they are working within 12" of the exposed line side terminals on the main breaker.

Calculating available fault current for residential systems can often be simplified by your utility. In my area, the local utilities publish a contractor-focused manual that explains how long a feeder needs to be connecting a single-phase transformer to a residence in order to have the maximum available fault current at the breaker panel below 10kA.

Wearing voltage-rated gloves will provide protection for your worker too when they are pulling the panel cover off because their hands would typically be within the 12" restricted approach boundary during that work

Scott, Arc flash as well as shock hazard is still a concern at the main panel board. When we are in this situation and the incoming source is energized, we will utilize rubber insulating blankets to prevent an individual touching the source side of the main breaker. In addtion, we'll document an energized work permit and discuss both the shock risk and potential arc flash risk with the individuals involved.

Depending on what we're doing, we've pulled the meter socket in some cases to remove the incoming source on the main breaker. Your Electrical Safety Program may want to document some Safe Work examples................JD