Left Hand Rule or Right Hand Rule for operating disconnects in the event of an arc flash?

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Some folks want to change the Left Hand Rule to the Right Hand Rule. We would differ. What about the one-hand-rule? The “Left Hand Rule” came about when all disconnect handles were on the right side so the left hand rule kept you out of the line of fire.

Now our training says:
Use the “One-Hand-Rule”
1. Stand out of the line-of-fire
2. Take a deep breath and hold it.
3. Turn your head away.

We get into this debate all the time. I usually prefer the unhinged side.

1. Yes if you are not in FR you MIGHT be a little bit better off on the hinged side if this prevents clothing ignition. (Why in the heck are you still wearing non-FR?)
2. The hinged side of a small disconnect isn’t likely to break bones. A bigger disconnect or a switchgear might.
3. I prefer the side because MOST of the time the arc comes out. It is a good gamble.
4. I prefer the unhinged side because I want to wear the RIGHT PPE and not use the door as a potentially “bone breaking” shield.

Here is an article by a very wise Dave Smith on the One-Hand-Rule. Dave uses some of our training materials for CSA Z462 and NFPA 70E Training

Hugh Hoagland

does research and testing of PPE exposed to electrical arcs and is an arc flash expert. Hugh is a Sr. Consultant at ArcWear and Sr. Partner at e-Hazard. Read more about Hugh.

This Post Has 4 Comments

  1. Chris Cooney

    I would like to hear about one single accident where a disconnect — perhaps fused — exploded when actuated. Not working on a live panel. Not an arc flash demonstration where a short was intentionally caused in an open disconnect box. A properly maintained disconnect that (the disconnect) exploded and hurt someone.


    Arc Flash Hazard. (definition)
    …. Under normal operating conditions, enclosed energized
    equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.

    130.7 Personal and Other Protective Equipment.
    Informational Note No. 2: It is the collective experience of
    the Technical Committee on Electrical Safety in the Workplace that normal operation of enclosed electrical equipment, operating at 600 volts or less, that has been properly installed and maintained by qualified persons is not likely to expose the employee to an electrical hazard.

    1. Hugh Hoagland

      You have all the right quotes from NFPA 70E.

      All our partners have had employees or friends suffer this fate. Bill Shinn had two under his watch in less than a month when electrical safety chair at a large metals company.

      I was there when these were all formulated. There was substantial debate and it barely passed. The language is correct but most people read but fail to understand the words.

      “properly maintained by qualified persons” is a really tough phrase to meet. I have rarely seen a properly maintained disconnect. Most people don’t know that the part of NFPA 70B (if they have even read it) for maintaining a disconnect is about a page long. I find that almost NO ONE maintains disconnects to NFPA 70B or the manufacturers instructions. Newer disconnects are really tough to blow up if the phase isolators are intact (that’s the good news). Older disconnects or any without phase isolators can and do fail. I would want to be standing to the side in the right PPE. Some electricians and some managers believe it will never happen to them and it might not. I won’t want to be one of those people. I operate a 480V disconnect at the lab about every day. I follow the left hand rule when I do and I wear an arc rated shirt. Never want to be the poster child for arc flash. Rather be the one who purposely fails a disconnect and shows what can happen (knowing that it doesn’t always happen).

  2. Mandie

    Is there a specification for this practice in the standard? No one at work believes me and I would like to show them in black & white.

    1. Ken Sellars

      OSHA does not specifically require the left or right-hand rule, however, the OSHA General Duty clause expects employers to provide a workplace free from recognized hazards. Educating personnel who operate switches per best-practice is an acceptable way to meet this requirement. Of course, using the left or right-hand rule concept certainly does keep the employee out of the line of fire, and this is to key to most injury-avoidance tactics.

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