Stale Arc Flash Label and a Racked Bucket

No - it fails on two independent grounds.

1. Against the existing label alone. The label says 12.0 cal/cm² at the working distance. Arc-rated clothing must have a rating at or above the incident energy. His shirt and pants are 8 cal/cm², so the garment layer over the torso and legs is under-rated by 4 cal/cm². A 12 cal/cm² face shield does not compensate: a layered system is limited by the lowest-rated layer in the exposure path, and the face shield protects the face, not the torso.
2. The label is stale. Incident energy at a fixed working distance scales with arcing current, which in turn depends on available bolted fault current. Going from 22 kA to 34 kA raises the arcing current in most 480 V configurations and can push the equipment into a different arcing regime entirely. Nothing in the new letter supports continuing to assume 12.0 cal/cm².

Also check: the label's working distance (18 in) versus the actual racking stance; Class 00 rubber gloves are rated 500 V AC maximum use, which covers 480 V for shock, but rubber insulating gloves are not arc-rated - the leather protector and any over-glove must be evaluated as part of the arc-rated system, not as a substitute for it.

Answer: inadequate. Do not rack the bucket in this PPE.

First: stop work and treat the incident energy as unknown, not as 12 cal/cm².

Then, in order of preference:

• Eliminate the exposure. Open and lock the upstream device that feeds the MCC bus, then verify absence of voltage at the bucket line-side stabs. If the bus can be de-energized, the racking becomes a non-energized task and the arc-rated clothing question largely disappears (shock PPE and voltage verification still apply).
• If the bus cannot be de-energized, get the arc flash study re-run with the 34 kA contribution. Until then, apply a conservative incident energy based on the higher fault current; do not interpolate downward from the old label.
• Reduce the exposure time/distance: remote racking operator, a maintenance switching arrangement, or a temporary upstream device. Racking is one of the highest-risk tasks on a MCC because the stabs part under load and the worker is directly in front of the bucket.
• Update the label once the new study is complete, and record that the old label is superseded so the next crew does not rely on it.

Do not accept the argument that "the main is open, so it's fine." The label governs the task, and the label is wrong.

No. An open main removes one source; it does not prove the bus is dead.

The stabs are fed from the MCC bus. The bus may still be energized from a tie breaker, a back-fed generator, a UPS, or a second service - and a locked-open main is a mechanical statement, not an electrical one. A breaker can also fail to open all poles (welded contact, open pole) while the handle indicates OPEN.

Verification procedure:

1. Use a meter or detector rated for the system voltage and for the environment (CAT III or better at 480 V; the meter's CAT rating must match the location, not just the nominal voltage).
2. Prove the tester on a known live source before the test.
3. Test all combinations: A-B, B-C, C-A, A-N, B-N, C-N, and each phase to ground, at the point of work.
4. Prove the tester again after the test (live-dead-live).
5. Apply lockout/tagout to every identified source, including backfeed sources, before touching anything.

Anticipate: a bus fed from the opposite end of a double-ended lineup, a control power transformer backfeed, and capacitive charge on long cable runs (ground and re-test). If any reading is ambiguous, treat the conductor as energized.