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| If 130.7(A) Note 3 - 40 cal/cm2 is removed - Then What? https://brainfiller.com/arcflashforum/viewtopic.php?f=33&t=3843 |
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| Author: | Jim Phillips (brainfiller) [ Sun Jan 17, 2016 9:27 am ] |
| Post subject: | If 130.7(A) Note 3 - 40 cal/cm2 is removed - Then What? |
Last weeks' question regarding the possible elimination of Informational Note 3 of NFPA 70E 130.7(A) and the 40 cal/cm2 reference in the 2018 Edition of NFPA 70E had very mixed responses. So, on to the follow up question. Keep in mind, the goal is to always place systems in an electrically safe working condition for voltages 50 volts and greater when possible. If the 40 cal/cm2 reference is removed in 2018, how will that affect your (clients) electrical safety practices? No change - still prohibit work above 40 cal/cm2 No change - we already permit some work above 40 cal/cm2 Not sure - We'll have to evaluate the impact of the change We will probably begin permitting some work above 40 cal/cm2 Something else - please elaborate |
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| Author: | engrick [ Mon Jan 25, 2016 10:08 am ] |
| Post subject: | Re: If 130.7(A) Note 3 - 40 cal/cm2 is removed - Then What? |
As a consultant, I am not in the business (nor an expert) to determine if 39.9 is safe or if 40.0 is dangerous (absolute life safety). I only report the findings and the standard. Until there is more defined I can only recommend what has been published. |
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| Author: | Larry Stutts [ Mon Feb 15, 2016 8:47 am ] |
| Post subject: | Re: If 130.7(A) Note 3 - 40 cal/cm2 is removed - Then What? |
It really depends on the time. There is a big difference between 40 cal/cm^2 over 20 seconds and 40 cal/cm^2 over 20 milliseconds. |
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| Author: | arcad [ Tue Feb 16, 2016 12:15 pm ] |
| Post subject: | Re: If 130.7(A) Note 3 - 40 cal/cm2 is removed - Then What? |
Larry Stutts wrote: It really depends on the time. There is a big difference between 40 cal/cm^2 over 20 seconds and 40 cal/cm^2 over 20 milliseconds. Time factor seems to be the best kept secret in arc flash. The issue of neglecting the factor in arc flash boundary calculations has been raised on this forum before, see topics below for more information: http://www.arcflashforum.com/viewtopic.php?f=33&t=3840 http://www.arcflashforum.com/viewtopic.php?f=33&t=3822 http://www.arcflashforum.com/viewtopic.php?f=34&t=3648 http://www.arcflashforum.com/viewtopic.php?f=23&t=3540 http://www.arcflashforum.com/viewtopic.php?f=34&t=2221 |
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