Flash Hazard Boundary question

Status
Not open for further replies.
J

jimioy

Member
NFPA 70E says 4 feet from live parts on 600V or less rated circuits. What is the Flash Hazard Boundary distance on over 600V (12470V)?
 
B

bphgravity

Senior Member
Location
Florida
It will be the distance at which the incident energy equals 1.2 cal/cm? or 1.5 cal/cm? where the fault clearing time is .1 second or faster. See 130.3(A) of the NFPA 70E.

This will be the distance that a survivable burn would occur. Your calculation will likely require distances as low as 6' and perhaps as great as 15'. Check out Annex D for some guidance...
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
jimioy said:
NFPA 70E says 4 feet from live parts on 600V or less rated circuits. What is the Flash Hazard Boundary distance on over 600V (12470V)?
Click to expand...

Remember, the 4' distance only applies if the combination of fault clearing time and available bolted fault current does not exceed 300kA cycles.
 
Status
Not open for further replies.
Top