Arc Flash Calculations

Businesses get advice on avoiding penalties

Key elements of a business storm preparedness plan:
• Check the county hurricane evacuation map. Locate your business facility (or facilities) and its evacuation level (color). Determine if and when you would have to evacuate your business if there is storm surge.
• Remember: All work trailers and most warehouse/storage facilities are extremely vulnerable to hurricane-force winds, regardless of location.
• Decide now, how and when you will communicate with employees if you must evacuate the area. Also determine an alternative work site if your facility is severely damaged or inaccessible.
• Check your disaster supplies kit. Obtain any items you might need for the office, such as a battery-powered National Weather Service weather alert radio.
• Inventory your property. Store with insurance and title papers and other backup documents and video records of inventory in a fireproof safe. Also keep copies elsewhere, in a fireproof safe outside the evacuation area.
• Make sure your address number is clearly marked on your building.
• Review coverage with your insurance agent, regardless of whether you rent or own the business property.

— SOURCE: FPL

Main problem areas:
1) Scaffolding used in construction
2) Fall protection
3) Hazardous communication (right-to-know)
4) Ladders used in construction
5) Respiratory protection
6) Control of hazardous energy (lockout/tagout)
7) Electrical wiring methods
8) Power industrial trucks (forklifts)
9) Electrical systems design
10) Machine guarding

— SOURCE: Occupational Safety and Health Administration

2012 NFPA 70E Doors Open / Doors Closed - Arc Flash Forum

Doors do make a difference no matter what some may think; I’ve seen this first hand more than once. There are even a few test videos out there showing the differences. The problem is no one has come up with a multiplying factor to adjust the calculations or to assist with some type of risk assessment. Everyone continues to treat a fully exposed and a doors or panels closed configuration as the same with regards to “heat exposure”; this has never made sense to me. I agree doors can fly open or projectiles can hit the worker but we’re not calculating impact hazard. I think the problem here is that the rules were written that way because the condition of the doors, missing bolts, bolts not tightened, etc., is unknown and as a result a conservative measure was recommended. More times then not I have found these conditions on customer's equipment. Also, when the doors do open during an arc fault, the heat, may be somewhat less, but at what value do you use for the calculations. It all depends on how long they stay closed. I think the problem here is that the rules were written that way because the condition of the doors, missing bolts, bolts not tightened, etc., is unknown and as a result a conservative measure was recommended. More times then not I have found these conditions on customer's equipment. Also, when the doors do open during an arc fault, the heat, may be somewhat less, but at what value do you use for the calculations. It all depends on how long they stay closed. I think the problem here is that the rules were written that way because the condition of the doors, missing bolts, bolts not tightened, etc., is unknown and as a result a conservative measure was recommended. More times then not I have found these conditions on customer's equipment. Also, when the doors do open during an arc fault, the heat, may be somewhat less, but at what value do you use for the calculations. It all depends on how long they stay closed.

2004 IEEE Industrial and Commercial Power Systems Technical Conference, papers presented at the 2004 Annual Meeting : Sheraton Sand Key, Clearwater Beach, Florida, May 2-6, 2004

IEEE guide for performing arc-flash hazard calculations

Electrical power equipment maintenance and testing

Electrical Wiring Residential, Based on the 2005 National Electric Code

Electric fuses