Arc Flash Boundaries and Equipment

[MD88]

Hello there,

I've started reading NFPA 70E about arc flash boundaries and stuff... I see how they apply to personnel and PPE, but what about other equipment? If I have a MCC across an aisle from a transformer, (let's just assume the boundary is 4ft for each equipment) should I put 8 ft between them? It seems like a kind of subjective thing, so can I anyone give some suggestions based on what they usually do?

Thanks!

 

[jim dungar]

The physical separation of devices is not part of NFPA70E, it is covered under the working clearance sections of the NEC.

Arc Flash, and other NFPA70E, boundaries define the area in which you must be wearing the correct PPE.

It is not required that you 'combine' arc flash boundary distances unless you wish to provide a 'clear' zone between them.

 

[WDeanN]

Just to echo what jim said,
The arc flash boundary is not a separation boundary, it is the boundary at which arc flash ppe must be worn.
In your example, you must put on arc flash ppe if you get within 4 feet of the equipment and an arc flash hazard exists in the equipment, ie exposed energized parts, and/or equipment operation/interaction (work).