Arc Flash Labeling

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Brad Ems

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St. Louis, MO
We're at the conclusion of an arc flash reduction project, and we're presented with a dilemma.

We installed a switchboard with circuit breakers having a "maintenance" mode that lowers the instantaneous trip pickup when engaged, reducing the AF Hazard Category from 3 to 1. Here's the quandary:

When we relabel the equipment to reflect the changes, do we:

1 - Label based on the higher hazard category?
2 - Label based on the lower hazard category?
3 - Both?
4 - One or the other with an advisory label?
5 - Something else?
 
I would go with both, and include some way of informing the person reading the labels which one would apply when the maintenance switch is in which position.
 
i am not familiar with that setup, but

if this type of setup is not normally seen across the industry (not common), then i would label it to represent the higher hazard mode.

does "maintenance" mode present dual AF hazards at the same time? if so i would label it to represent the higher hazard mode.
 
FionaZuppa said:
i am not familiar with that setup, but

if this type of setup is not normally seen across the industry (not common), then i would label it to represent the higher hazard mode.

does "maintenance" mode present dual AF hazards at the same time? if so i would label it to represent the higher hazard mode.
Click to expand...

it would be pointless to have the maint mode without labeling it that way.
 
both

both

Initiation of a maintenance switch for a reduction of the incident energy level at a given piece of equipment is addressed in NEC 240.87 B(3) and it is required that there be a local status indicator.
Install two labels with one clearly identified as the Maintenance Mode Label and the local status indicator is then used to determine which label is applicable. Often times a rotating blue light is used as indication, but it could be as simple as selection of an instantaneous setting on a breaker that causes the breaker to flash giving indication of the maintenance-mode selection. New breakers are so equipped.
 
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I always label worst case only. It makes things simple. Then, if a knowledgeable operator uses the maintenance mode, make the full power system study available foe them to understand the impact. Leases you less liable also.
 
Thanks, everyone, for your replies. We have a remote operator control enclosure with mode switches in them, local to the MCC that is being AF-reduced...no specific feedback like a beacon or pilot light at the MCC.

I'll see if we can squeeze the mode verbiage onto the AF labels, and post both on the MCC. Barring that, I'll create a third label explaining what AF category is present and when.
 
FionaZuppa said:
i am not familiar with that setup, but

if this type of setup is not normally seen across the industry (not common), then i would label it to represent the higher hazard mode.

does "maintenance" mode present dual AF hazards at the same time? if so i would label it to represent the higher hazard mode.
Click to expand...

Fiona,

No, only one AF hazard category is present at one time, depending on whether the feeder breaker at the source switchboard is in the normal or maintenance mode. We're using Square-D equipment, and they call it ERMS (Energy Reduction Something-Something).
 
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