Fused Disconnect Necessary to Protect Panelboard Users?

[Murloc]

For arc flash labeling, if there is no OCP I believe that calculation is generated for 2 seconds. since that is the approximate time it takes for someone to react to an arc flash scenario. The ETAP says FCT not determined due to no OCP present.


Since the Panelboard high side has a large incident energy value. Would it be advisable to placed a fused disconnect before the panel?
49 cal/cm^2 is rather high. Would this value mean if someone were to touch the panel they would need wear that ARC Flash space suit thing just to
flip the breakers by code?

I was told by an engineer the high side has no danger energizing the panel and a fused disconnect wouldn't be necessary since all the breakers downstream would trip. Didn't make much sense to me.

 

[EC Dan]

The high incident energy and arc flash PPE will come into play if someone needs to do live work within the panel, which of course includes verifying de-energization. One of the lessons I've learned is to include external OCPD for panels immediately downstream of transformers for this reason, at least for 208/120 V panels that have a higher likelihood of circuits being added. PPE is not required for normal operation of circuit breakers, assuming all conditions of NFPA 70E 130.2(A)(4) are met.

No idea what that engineer was trying to say.