Lenwood Ireland
Ireland Electric Co.

Is it off? This is a common question that many technicians pose concerning the electrical status of a machine before commencing work. Usually the question is asked to a co-worker or other responsible individual engaged in the work at hand. Upon hearing the answer “yes,” the technician will begin to loosen electrical connections, remove wire nuts, cut wires and or perform a host of other tasks that he or she would not have engaged in had the machine still been on.

Here are some questions to consider:  Is “off” the movement of a breaker actuator from the “on” to the “off” position? Is it just the indication of the disconnect handle that has been pulled to its most downward position? Is “off” the selection of a rotated to position on a pilot device or the pressing of a pushbutton labeled the same? Or by whatever physical, electronic or other latent manner, has the action to achieve “off” really accomplished “off”?

I would submit to you that the answer may be NO. Many years ago, a technician turned to “off” a disconnect feeding a generator. Unbeknownst to him, the machine had a circuit on the terminal strip fed by a transformer that was “on.” A short fireball later, a number of buildings tripped offline and the “zombie” like technician headed to the hospital emergency room.  Not knowing this, the fire department searched the debris for a body. Thankfully, the technician survived.

I will spare you the unsightly details of his burns and the painful learning experience that ensued. 

Rest assured that the use of multimeters to confirm “off” became a new practice for me, because I was that technician.

There are many ways to confirm that a device really is “off”; that could be a lengthy technical article.  This is meant to provide some “food for thought” when you’re in a similar situation. 

Here are some additional tips to keep in mind:

• It’s not off unless your lock is on the disconnect, which is clearly labeled with the same name as the label on the machine; and
• It’s not off unless you have first verified your Class III meter is working by testing it on a known live circuit; and
• It’s not off until you have retested your Class II (or Class III as appropriate) meter on a known live circuit – after you have tested the target circuit.
• You should also know the equipment maximum equipment voltage and the associated proper personal protective equipment.

So, the next time you pull a handle, turn a switch, push a button or activate a computer click to accomplish “off,” is it really off?  That may not always be the case. When your life or the life of another depends on it, confirm that the device is off.

Categories: Safety

Tags: Safety Lock-out & tag-out

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