Is there an accepted method to determine the Arc Flash energy for a single phase 277V disconnect?

[bdn2004]

A 200A, 480/277V switchgear with no main, is fed from a 200A fused switch upstream that's 1000' away.

They've installed a 30A fused disconnect switch, next to this switchgear, like 5' away to feed some fluorescent lights. It's connected directly to the bus.

This like a tap rule NEC violation but they are asking for an arc flash label.

How would you handle this ?

 

[dpc]

IEEE 1584 says to calculate it as if it were a three-phase system. This should be conservative. Effectively, it will probably have about the same hazard as the switchgear bus if you do this.

 

[jraef]

Do they know what it is at the 490V switchgear now? If not, it's not your job to do that for them as part of this project (unless you want to and get paid for it). If so, it would not be substantially different; 50ft of wire is not enough to bring it down in a meaningful way.


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