And the series of questions about arc flash warning labels continues...

Do you think arc flash warning labels should be on automatic transfer switches?

• Yes
• No
• It depends

Since we are discussing what equipment needs to be labeled with this latest round of questions, I have something that has troubled me.

Most of us are familiar with the NFPA 70E language about what needs labeled:

"...likely to require examination, adjustment, servicing, or maintenance while energized,"

Here is my thought - If you have electrical equipment that does NOT require examination, adjustment, servicing or maintenance while ENERGIZED, how do you know it is not energized? We need to check the voltage according to NFPA 70E. From what I have always understood, the act of checking voltage is live work that requires PPE until the circuit has been proven dead. The rating of the PPE is found on the label of the equipment.

With this logic, it seems to me that EVERY piece of equipment > 50 volts needs an arc flash warning label even equipment that will never be serviced etc. while energized. Did I miss something or is the interpretation that easy? (..and I just felt the scope and cost of arc flash studies spiral further out of control)

It depends if the switch "...likely to require examination, adjustment, servicing, or maintenance while energized." Or if not, can both sources to the transfer switch be verified to be de-energized? If both sources cannot be verified to be de-energized, then you will have to test at the switch to check the voltage before working on it.

Another "it depends" is whether you would interpret manual operation of the switch (most automatic transfer switches include the ability to manually transfer) to constitute an arc flash hazard. You are interacting with the switch, but manual operation could be interpreted as a "normal operating condition". Then again, manual operation is not "examination, adjustment, servicing, or maintenance", so does it require a label? The task tables include opening breakers with HRC > 0, so this would indicate that someone thought there was a potential arc flash hazard.

So doesn't this mean the language about what equipment that needs to be labeled should change to: "...likely to require examination, adjustment, servicing, or maintenance while energized," with the last 2 words deleted since proving de-energized, IS energized work and needs PPE (label to define PPE)