There are several calculation methods available to calculate arc flash risk in terms of incident energy, but until recently, there was no clear direction from OSHA about which calculation method was preferred. Because of this, several methods were used. The new final ruling of OSHA 29 CFR Parts 1910 and 1926 provides recommendations for calculation methods to use for incident energy for equipment of different voltages. This webinar summarizes the ruling’s recommendations for incident energy calculations and the impact these recommendations may have on arc flash risk assessments from the perspective of a consultant engineer. View this webinar to learn: -An overview of current incident energy calculation methods -Which incident energy calculation method OSHA recommends for certain equipment -How OSHA recommendations for incident energy calculation methods may be incorporated into arc flash studies

1. An Engineer’s Guide to OSHA’s
New Recommendations
for Arc Flash Studies

2. Before We Start
q This webinar will be available at
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q Q&A at the end of the presentation
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3. Moderator Presenter
Paul Dvorak
Windpower Engineering
& Development
Tahnee Miller
Ulteig

4. An Engineer’s Guide
to OSHA’s New
Recommendations for
Arc Flash Studies
Tahnee Miller, PE
Ulteig
tahnee.miller@ulteig.com

5. Objective
• Explain the impact of a new OSHA filing which affects the
calculation methods of arc flash risk assessment from the
perspective of a consultant engineer.

6. Overview
• Basics of arc flash
• How arc flash is calculated
• Impact of OSHA 29 CFR Parts 1910 and 1926 final ruling
• Incorporating OSHA ruling into arc flash studies

7. Arc Flash Basics
• Defined by NFPA 70E-2015: a dangerous condition
associated with the possible release of energy caused by
an electric arc.
• An arc flash risk assessment must include:
o Incident Energy at a given working distance
o Arc Flash Boundary
o Personal Protective Equipment (PPE) that must be worn inside the AF boundary

8. Calculation Methods
• NFPA 70E-2015
• IEEE 1584
• Ralph Lee Method
• ANSI/IEEE C2 NESC, Section 410
• Etc.

9. OSHA 29 CFR 1910/1926
• Released in April 2014, became effective in July 2014
• Replaces the incorporation of these consensus standards
with a set of recommendations
• Appendix E to Subpart V of Part 1926 summarizes OSHA’s
recommendations for calculation methods for equipment
• Includes detailed comparison of the options
o Summary on following slides

10. NFPA 70E-2012 Annex D
(Lee Equation)
• <= 600 V
o Acceptable for open-air arcs (though not typically used at this voltage)
• > 600 V and <= 15 kV
o Reasonable, but conservative, so PPE will be heaver and bulkier than needed
• > 15 kV
o Should only be used to estimate incident energy if the employee exposure is
calculated to be less than 2 cal/cm2
• Estimates incident energy levels for three-phase arcs

11. Doughty, Neal, and Floyd
• <= 600 V
o Conservative, but reasonable
• > 600 V
o Not acceptable
o Testing was performed exclusively with an electrode spacing of 32 mm at 600 V

12. IEEE Std 1584b-2011
• Refers to IEEE Std 1584-2002 including both amendments
• <= 15 kV
o Reasonably estimates incident energy
o Accounts for differences between single-phase and three-phase arcs and between
arcs in open air or enclosed arcs
• > 15 kV
o Outside the range of the standard and thus not recommended

13. ARCPRO
• Based on tested heat flux data in lab
• <= 15 kV
o Can be used as long as arc is single phase and open air
o Conversion factors for three-phase or enclosed arcs are not verified
• > 15 kV
o Same issues as <= 15 kV, but since there is no reasonable alternative, OSHA
considers this method as a reasonable estimate if the conversion factors are used
• NESC tables in Section 410 based on ARCPRO calculations

14. Incident Energy
Calculation Method
600 V and Less2 601 V to 15kV2 More than 15 kV
1Φ 3Φa 3Φb 1Φ 3Φa 3Φb 1Φ 3Φa 3Φb
NFPA 70E-2012 Annex D
(Lee Equation)
Y-C Y N Y-C Y-C N N3 N3 N3
Doughty, Neal,
and Floyd
Y-C Y Y N N N N N N
IEEE Std 1584b-2011 Y Y Y Y Y Y N N N
ARCPRO Y N N Y N N Y Y4 Y4
Table 1 – Selecting Reasonable Incident-Energy Calculation Method1

15. Table 1 Notes
1Φ: Single-phase arc in open air
3Φa: Three-phase arc in open air
3Φb: Three-phase arc in enclosure (box)
Y: Acceptable: produces a reasonable estimate of incident heat
energy from this type of electric arc
N: Not acceptable: does not produce a reasonable estimate of
incident energy from this type of electric arc
Y-C: Acceptable: produces a reasonable, but conservative, estimate of
incident heat energy from this type of electric arc

16. Incorporating Ruling
• Equipment <= 15 kV
o IEEE Standard 1584b-2011
• Equipment > 15 kV
o ARCPRO calculations adjusted with conversion factors
for three-phase arcs in open air or in an enclosure
o NESC Section 410 tables (based on ARCPRO test data)

17. Thank You
Tahnee Miller, PE
Ulteig
tahnee.miller@ulteig.com

18. Questions?
Paul Dvorak
Windpower Engineering & Development
pdvorak@wtwhmedia.com
Twitter: @windpower_eng
Tahnee Miller
Ulteig
tahnee.miller@ulteig.com

19. Thank You
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