I have been putting on the arc flash labels the upstream protective device that is the tripping device. Recently an electrician told me that does not help him and he would rather see the upstream/fed from bus or panel name on the label. That got me thinking. From my perspective as an engineer it is nice to know which device is responsible for clearing the fault but I can see that the electrician would like to know the bus/panel that it is fed from.

Further, I think the purpose of the label is restricted to the arc flash and shock protection information and that knowing where the device is fed from should be obtained as part of a pre-job brief and electrical work permit.

What do other people put on the label? Bus/panel fed from? Protective device clearing the fault? Neither?

Jim- may be a question of the week item???

Thanks to all

I rarely put 'fed from' or 'tripping' information on my Arc Flash labels.
Equipment identification is so important it should be stand alone. It is much better to have an accurate one-line drawing and a floor plan with equipment locations available than any complex labeling.

I cannot tell you how many times the electricians I am with have no clue as to the 'identification' provided on the arc flash label, most often because it was decided upon by the study entity and often bears no semblance to the facility's operating methodology.

Arc flash label says 'fed from Panel 2'. Once Panel 2 is physically found out to really be Panel Z in the facility, it is missing its panel directory so the controlling device is still a mystery.

The arc flash label must be on the equipment or device where the arc flash can happen. The point of a warning label is to let people know about the danger at the location where that danger exists.

NFPA 70E specifically requires the following types of electrical equipment, in locations other than dwellings, be marked with an arc flash warning label:

• Switchboards
• Panelboards
• Industrial control panels
• Meter socket enclosures
• Motor control centers

Just as a matter of record, NFPA70E does not specify what type of equipment has to be marked with an Arc Flash Label. NEC Article 110.16 specifies that equipment SUCH AS (emphasis added) switchboards, Panelboards, Industrial control panels, Meter socket enclosures, Motor Control Centers. I place emphasis on "such as" because this list was not intended by NFPA70 to be all inclusive. In fact, that's why the words "such as" were added in the last code cycle.

I think including the "upstream" protective device on the arc-flash label is problematic. When doing arc-flash calculations, the upstream device that is tripping may not actually be the closest upstream device. This can be a source of confusion if the electrician is looking for the disconnecting means for this bus.

Also, in many situations, we have to calculate arc-flash energy under a variety of operating scenarios. The "upstream" device listed on the label will be associated with the worst-case arc-flash energy condition not necessarily the upstream device under all (or even normal) operating conditions.

I think including the "upstream" protective device on the arc-flash label is problematic. When doing arc-flash calculations, the upstream device that is tripping may not actually be the closest upstream device. This can be a source of confusion if the electrician is looking for the disconnecting means for this bus.

Also, in many situations, we have to calculate arc-flash energy under a variety of operating scenarios. The "upstream" device listed on the label will be associated with the worst-case arc-flash energy condition not necessarily the upstream device under all (or even normal) operating conditions.