Heat Release Rates of 

Electrical Enclosure 

Fires (HELEN-FIRE)

Draft Report for Comment

Office of Nuclear Regulatory Research

NUREG/CR-7197
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Heat Release Rates of

Electrical Enclosure 

Fires (HELEN-FIRE)

Draft Report for Comment

Manuscript Completed: February 2015

Date Published: April 2015

Prepared by:

Kevin McGrattan

Scott Bareham

National Institute of Standards and Technology

Engineering Laboratory; Fire Research Division

Gaithersburg, MD 20899

David Stroup, NRC Project Manager

Prepared for:

Division of Risk Analysis

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

NUREG/CR-7197

 
 
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iii 

1 ABSTRACT 

2 This report documents an experimental program to quantify the heat release rate and burning 

3 behavior of electrical enclosures commonly found in nuclear power plants. Electrical enclosures 

4 are a potential source of fire in nuclear power plants because they contain both combustible 

5 materials and live electrical circuits. These fires have the potential to disrupt power, 

6 instrumentation, and control in the plant. Key parameters affecting fire in an enclosure include its 

7 size, openings, electrical voltage, and combustible load. 

 8 

 9 

v 

CONTENTS 

ABSTRACT .................................................................................................................................. iii

CONTENTS................................................................................................................................... v

LIST OF FIGURES .................................................................................................................... vii

LIST OF TABLES ....................................................................................................................... ix

EXECUTIVE SUMMARY ....................................................................................................... xiii

ACKNOWLEDGMENTS .......................................................................................................... xv

ABBREVIATIONS ................................................................................................................... xvii

1 INTRODUCTION ................................................................................................................. 1

1.1 Background ................................................................................................................... 1

1.2 Previous Studies ............................................................................................................ 1

1.2.1 Sandia National Laboratories Experiments ....................................................... 1

1.2.2 VTT Experiments .............................................................................................. 1

1.2.3 IRSN Experiments ............................................................................................. 1

1.3 Current Practice ............................................................................................................ 2

1.4 Objective ....................................................................................................................... 2

2 DESCRIPTION OF ENCLOSURES .................................................................................. 3

2.1 Survey of Electrical Enclosures .................................................................................... 3

2.2 Enclosures used in the Experiments ............................................................................. 9

2.2.1 Enclosure 1 ...................................................................................................... 10

2.2.2 Enclosure 2 ...................................................................................................... 12

2.2.3 Enclosure 3 ...................................................................................................... 14

2.2.4 Enclosures 4 and 5........................................................................................... 16

2.2.5 Enclosure 6 ...................................................................................................... 18

2.2.6 Enclosure 7 ...................................................................................................... 20

2.2.7 Enclosure 8 ...................................................................................................... 22

3 CABLE PROPERTIES ...................................................................................................... 25

3.1 Properties of Cables used in Enclosure Fire Experiments .......................................... 25

4 EXPERIMENTAL PROCEDURE .................................................................................... 33

4.1 Oxygen Consumption Calorimeter ............................................................................. 33

4.2 Ignition Sources .......................................................................................................... 36

4.2.1 Cartridge Heaters ............................................................................................. 36

4.2.2 Propane Line Burners ...................................................................................... 37

4.2.3 Liquid Fuel Pan Fires ...................................................................................... 37

5 FULL-SCALE MEASUREMENTS .................................................................................. 39

5.1 Description .................................................................................................................. 39

5.2 General Observations ................................................................................................ 157

5.2.1 Ignition .......................................................................................................... 157

5.2.2 Fire Spread .................................................................................................... 158

5.2.3 Ventilation ..................................................................................................... 158

5.2.4 Peak Heat Release Rate ................................................................................. 158

5.2.5 Growth Time ................................................................................................. 158

6 CONCLUSIONS AND FUTURE WORK ...................................................................... 161

7 REFERENCES .................................................................................................................. 163

APPENDIX A TEMPERATURE DATA ............................................................................ A-1

vii

LIST OF FIGURES 

Figure 2-1. Photographs of enclosures typically found near the main control room. ............... 4

Figure 2-2. Photographs of enclosures typically found near the main control room. ............... 5

Figure 2-3. Photographs of the internal wiring of typical switchgear enclosures. .................... 6

Figure 2-4. Photographs of the internal wiring of typical motor control centers. ..................... 7

Figure 2-5. Photographs of Enclosure 1. ................................................................................. 10

Figure 2-6. Sketch of Enclosure 1. .......................................................................................... 11

Figure 2-7. Photographs of Enclosure 2. ................................................................................. 12

Figure 2-8. Sketch of Enclosure 2. .......................................................................................... 13

Figure 2-9. Photographs of Enclosure 3. ................................................................................. 14

Figure 2-10. Sketch of Enclosure 3. .......................................................................................... 15

Figure 2-11. Photographs of Enclosures 4 and 5. ...................................................................... 16

Figure 2-12. Sketch of Enclosures 4 and 5. ............................................................................... 17

Figure 2-13. Photographs of Enclosure 6. ................................................................................. 18

Figure 2-14. Sketch of Enclosure 6. .......................................................................................... 19

Figure 2-15. Photographs of Enclosure 7. ................................................................................. 20

Figure 2-16. Sketch of Enclosure 7. .......................................................................................... 21

Figure 2-17. Photographs of Enclosure 8. ................................................................................. 22

Figure 2-18. Sketch of Enclosure 8. .......................................................................................... 23

Figure 3-1. Photograph of Cables 805-835.............................................................................. 25

Figure 3-2. Photograph of Cables 836-842.............................................................................. 26

Figure 3-3. Photograph of Cables 843-845.............................................................................. 26

Figure 3-4. Photograph of a circuit card installed in Enclosure 3. .......................................... 27

Figure 4-1. Schematic diagram of the small calorimeter. ........................................................ 33

Figure 4-2. Schematic diagram of the small calorimeter underneath the large hood 

at the CBD test facility. ......................................................................................... 34

Figure 4-3. Two 300 W cartridge heaters. One has an in-line circuit breaker. ....................... 36

Figure A-1. Enclosure temperatures, Tests 1-4. ..................................................................... A-1

Figure A-2. Enclosure temperatures, Tests 5-10. ................................................................... A-2

Figure A-3. Enclosure temperatures, Tests 11-16. ................................................................. A-3

Figure A-4. Enclosure temperatures, Tests 17-22. ................................................................. A-4

Figure A-5. Enclosure temperatures, Tests 23-28. ................................................................. A-5

Figure A-6. Enclosure temperatures, Tests 29-34. ................................................................. A-6

Figure A-7. Enclosure temperatures, Tests 35-40. ................................................................. A-7

Figure A-8. Enclosure temperatures, Tests 41-46. ................................................................. A-8

Figure A-9. Enclosure temperatures, Tests 47-52. ................................................................. A-9

Figure A-10. Enclosure temperatures, Tests 53-58. ............................................................... A-10

Figure A-11. Enclosure temperatures, Tests 59-64. ............................................................... A-11

Figure A-12. Enclosure temperatures, Tests 65-70. ............................................................... A-12

Figure A-13. Enclosure temperatures, Tests 71-76. ............................................................... A-13

Figure A-14. Enclosure temperatures, Tests 77-82. ............................................................... A-14

Figure A-15. Enclosure temperatures, Tests 83-88. ............................................................... A-15

 
viii

Figure A-16. Enclosure temperatures, Tests 89-94. ............................................................... A-16

Figure A-17. Enclosure temperatures, Tests 95-100. ............................................................. A-17

Figure A-18. Enclosure temperatures, Tests 101-106. ........................................................... A-18

Figure A-19. Enclosure temperatures, Tests 107-112. ........................................................... A-19
ix

LIST OF TABLES 

Table 3-1. Manufacturers’ descriptions of the cables. ........................................................... 28

Table 3-2. Cable properties. ................................................................................................... 30

Table 4-1. Propane burner heat release rate values. ............................................................... 37

Table 5-1. Summary of enclosure fire measurements ............................................................ 40

Table 5-2. Summary of Test 1 ................................................................................................ 45

Table 5-3. Summary of Test 2 ................................................................................................ 46

Table 5-4. Summary of Test 3 ................................................................................................ 47

Table 5-5. Summary of Test 4 ................................................................................................ 48

Table 5-6. Summary of Test 5 ................................................................................................ 49

Table 5-7. Summary of Test 6 ................................................................................................ 50

Table 5-8. Summary of Test 7 ................................................................................................ 51

Table 5-9. Summary of Test 8 ................................................................................................ 52

Table 5-10. Summary of Test 9 ................................................................................................ 53

Table 5-11. Summary of Test 10 .............................................................................................. 54

Table 5-12. Summary of Test 11 .............................................................................................. 55

Table 5-13. Summary of Test 12 .............................................................................................. 56

Table 5-14. Summary of Test 13 .............................................................................................. 57

Table 5-15. Summary of Test 14 .............................................................................................. 58

Table 5-16. Summary of Test 15 .............................................................................................. 59

Table 5-17. Summary of Test 16 .............................................................................................. 60

Table 5-18. Summary of Test 17 .............................................................................................. 61

Table 5-19. Summary of Test 18 .............................................................................................. 62

Table 5-20. Summary of Test 19 .............................................................................................. 63

Table 5-21. Summary of Test 20 .............................................................................................. 64

Table 5-22. Summary of Test 21 .............................................................................................. 65

Table 5-23. Summary of Test 22 .............................................................................................. 66

Table 5-24. Summary of Test 23 .............................................................................................. 67

Table 5-25. Summary of Test 24 .............................................................................................. 68

Table 5-26. Summary of Test 25 .............................................................................................. 69

Table 5-27. Summary of Test 26 .............................................................................................. 70

Table 5-28. Summary of Test 27 .............................................................................................. 71

Table 5-29. Summary of Test 28 .............................................................................................. 72

Table 5-30. Summary of Test 29 .............................................................................................. 73

Table 5-31. Summary of Test 30 .............................................................................................. 74

Table 5-32. Summary of Test 31 .............................................................................................. 75

Table 5-33. Summary of Test 32 .............................................................................................. 76

Table 5-34. Summary of Test 33 .............................................................................................. 77

Table 5-35. Summary of Test 34 .............................................................................................. 78

Table 5-36. Summary of Test 35 .............................................................................................. 79

Table 5-37. Summary of Test 36 .............................................................................................. 80

Table 5-38. Summary of Test 37 .............................................................................................. 81

Table 5-39. Summary of Test 38 .............................................................................................. 82

Table 5-40. Summary of Test 39 .............................................................................................. 83

Table 5-41. Summary of Test 40 .............................................................................................. 84
x

Table 5-42. Summary of Test 41 .............................................................................................. 85

Table 5-43. Summary of Test 42 .............................................................................................. 86

Table 5-44. Summary of Test 43 .............................................................................................. 87

Table 5-45. Summary of Test 44 .............................................................................................. 88

Table 5-46. Summary of Test 45 .............................................................................................. 89

Table 5-47. Summary of Test 46 .............................................................................................. 90

Table 5-48. Summary of Test 47 .............................................................................................. 91

Table 5-49. Summary of Test 48 .............................................................................................. 92

Table 5-50. Summary of Test 49 .............................................................................................. 93

Table 5-51. Summary of Test 50 .............................................................................................. 94

Table 5-52. Summary of Test 51 .............................................................................................. 95

Table 5-53. Summary of Test 52 .............................................................................................. 96

Table 5-54. Summary of Test 53 .............................................................................................. 97

Table 5-55. Summary of Test 54 .............................................................................................. 98

Table 5-56. Summary of Test 55 .............................................................................................. 99

Table 5-57. Summary of Test 56 ............................................................................................ 100

Table 5-58. Summary of Test 57 ............................................................................................ 101

Table 5-59. Summary of Test 58 ............................................................................................ 102

Table 5-60. Summary of Test 59 ............................................................................................ 103

Table 5-61. Summary of Test 60 ............................................................................................ 104

Table 5-62. Summary of Test 61 ............................................................................................ 105

Table 5-63. Summary of Test 62 ............................................................................................ 106

Table 5-64. Summary of Test 63 ............................................................................................ 107

Table 5-65. Summary of Test 64 ............................................................................................ 108

Table 5-66. Summary of Test 65 ............................................................................................ 109

Table 5-67. Summary of Test 66 ............................................................................................ 110

Table 5-68. Summary of Test 67 ............................................................................................ 111

Table 5-69. Summary of Test 68 ............................................................................................ 112

Table 5-70. Summary of Test 69 ............................................................................................ 113

Table 5-71. Summary of Test 70 ............................................................................................ 114

Table 5-72. Summary of Test 71 ............................................................................................ 115

Table 5-73. Summary of Test 72 ............................................................................................ 116

Table 5-74. Summary of Test 73 ............................................................................................ 117

Table 5-75. Summary of Test 74 ............................................................................................ 118

Table 5-76. Summary of Test 75 ............................................................................................ 119

Table 5-77. Summary of Test 76 ............................................................................................ 120

Table 5-78. Summary of Test 77 ............................................................................................ 121

Table 5-79. Summary of Test 78 ............................................................................................ 122

Table 5-80. Summary of Test 79 ............................................................................................ 123

Table 5-81. Summary of Test 80 ............................................................................................ 124

Table 5-82. Summary of Test 81 ............................................................................................ 125

Table 5-83. Summary of Test 82 ............................................................................................ 126

Table 5-84. Summary of Test 83 ............................................................................................ 127

Table 5-85. Summary of Test 84 ............................................................................................ 128

Table 5-86. Summary of Test 85 ............................................................................................ 129

Table 5-87. Summary of Test 86 ............................................................................................ 130
xi

Table 5-88. Summary of Test 87 ............................................................................................ 131

Table 5-89. Summary of Test 88 ............................................................................................ 132

Table 5-90. Summary of Test 89 ............................................................................................ 133

Table 5-91. Summary of Test 90 ............................................................................................ 134

Table 5-92. Summary of Test 91 ............................................................................................ 135

Table 5-93. Summary of Test 92 ............................................................................................ 136

Table 5-94. Summary of Test 93 ............................................................................................ 137

Table 5-95. Summary of Test 94 ............................................................................................ 138

Table 5-96. Summary of Test 95 ............................................................................................ 139

Table 5-97. Summary of Test 96 ............................................................................................ 140

Table 5-98. Summary of Test 97 ............................................................................................ 141

Table 5-99. Summary of Test 98 ............................................................................................ 142

Table 5-100. Summary of Test 99 ............................................................................................ 143

Table 5-101. Summary of Test 100 .......................................................................................... 144

Table 5-102. Summary of Test 101 .......................................................................................... 145

Table 5-103. Summary of Test 102 .......................................................................................... 146

Table 5-104. Summary of Test 103 .......................................................................................... 147

Table 5-105. Summary of Test 104 .......................................................................................... 148

Table 5-106. Summary of Test 105 .......................................................................................... 149

Table 5-107. Summary of Test 106 .......................................................................................... 150

Table 5-108. Summary of Test 107 .......................................................................................... 151

Table 5-109. Summary of Test 108 .......................................................................................... 152

Table 5-110. Summary of Test 109 .......................................................................................... 153

Table 5-111. Summary of Test 110 .......................................................................................... 154

Table 5-112. Summary of Test 111 .......................................................................................... 155

Table 5-113. Summary of Test 112 .......................................................................................... 156

xiii 

1 EXECUTIVE SUMMARY 

2 Electrical enclosures are a potential source of fire in nuclear power plants because they contain 

3 both combustible materials and live electrical circuits. These fires have the potential to disrupt 

4 power, instrumentation, and control in the plant. Key parameters affecting fire in an electrical 

5 enclosure include its size, openings, electrical voltage, and combustible load. 

6 To better quantify the heat release rate and burning behavior of electrical enclosures, 112 full7 scale experiments were conducted at the Chesapeake Bay Detachment of the Naval Research 

8 Laboratory. Eight electrical enclosures were acquired from Bellefonte Nuclear Generating 

9 Station, a plant owned by the Tennessee Valley Authority located in Hollywood, Alabama. The 

10 enclosures were installed in the early 1980s, but the plant was never operated. The enclosures 

11 were originally low voltage control cabinets, but in the experiments they were reconfigured with 

12 various amounts and types of electrical cable to represent other kinds of enclosures that would be 

13 found in a typical plant. 

14 The key experimental parameters are as follows: 

15 1. Combustible load, i.e., the amount and type of electrical cables or other materials in the 

16 enclosure that can burn. Cables typically fall into two categories: thermoplastic and 

17 thermoset. The former typically burn more readily than the latter. 

18 2. Ventilation, mainly via opening or closing the enclosure doors. Some of the enclosures 

19 had a false bottom which could be removed. One enclosure had vertical conduits through 

20 its top. 

21 3. Ignition strength, i.e., the amount of energy necessary to start the fire. A small propane 

22 burner and various size pans of acetone were used. 

23 4. Enclosure geometry. Six of the enclosures were vertically oriented with various size 

24 doors and base area. Two of the enclosures were sections of the main control room 

25 “horseshoe” control panel. 

26 An oxygen consumption calorimeter was built on site to measure the heat release rate (HRR) of 

27 the fire as a function of time. Of particular interest is the peak HRR, the time to peak, and the 

28 total energy released. Thermocouples were positioned at various heights within the enclosures to 

29 monitor internal temperatures. 

30 Of the 112 experiments, the peak HRR varied from 0.3 kW to 576 kW. The mean was 43 kW; 

31 the median was 19 kW. Eleven fires peaked at greater than 100 kW. The mean time to peak was 

32 16 min; the median was 13 min. 

 33 

xv

1 ACKNOWLEDGMENTS 

2 The work described in this report was supported by the Office of Nuclear Regulatory Research 

3 (RES) of the US Nuclear Regulatory Commission (USNRC). This program was directed by 

4 David Stroup. Gabriel Taylor and Nicholas Melly provided additional information on the cable 

5 composition and typical installation practice. 

6 The large-scale experiments described in this report were conducted at the Chesapeake Bay 

7 Detachment of the Naval Research Laboratory. The facility is directed by John Farley and 

8 logistical support was provided by Clarence Whitehurst. Data acquisition support was provided 

9 by staff members of Hughes Associates, Inc., Joshua Dinaburg and Andrew Wolf. 

10 Technical support for the experiments was provided by NIST Fire Research Division staff 

11 members Michael Selepak and Mariusz Zarzecki. Roy McLane and Jay McElroy supervised the 

12 construction and dismantling of the small calorimeter. Edward Hnetkovsky and Scott Bareham 

13 designed the calorimeter, with support from Matthew Bundy, Doris Rinehart, Laurean DeLauter, 

14 and Anthony Chakalis of the NIST Large Fire Research Facility. 

 15 

 16 

17 DISCLAIMER 

18 Certain commercial equipment, instruments, or materials are identified in this report to foster 

19 understanding. Such identification does not imply recommendation or endorsement by the 

20 National Institute of Standards and Technology, nor does it imply that the materials or equipment 

21 identified are necessarily the best available for the purpose. 

 22 

xvii

1 ABBREVIATIONS 

2 ASTM American Society for Testing and Materials 

3 AWG American Wire Gauge 

4 CAROLFIRE Cable Response to Live Fire 

5 CBD Chesapeake Bay Detachment 

6 CDRS Conductors 

7 CHRISTIFIRE Cable Heat Release, Ignition, and Spread in Tray Installations 

8 CPE Chlorinated Polyethylene 

9 CSPE Chloro-Sulfonated Polyethylene 

10 DEG C Degrees Celsius 

11 DIR BUR Direct Burial 

12 EPR Ethylene-Propylene Rubber 

13 EPRI Electric Power Research Institute 

14 FR Flame Retardant 

15 HRR Heat Release Rate 

16 IEEE Institute of Electrical and Electronics Engineers 

17 ISO International Organization for Standardization 

18 NEC National Electric Code 

19 NFPA National Fire Protection Association 

20 NIST National Institute of Standards and Technology 

21 NPP Nuclear Power Plant 

22 NRC Nuclear Regulatory Commission 

23 NRL Naval Research Laboratory 

24 NRR NRC Office of Nuclear Reactor Regulation 

25 OIL RES Oil Resistant 

26 PE Polyethylene 

27 PMMA Polymethyl Methacrylate 

28 PRA Probabilistic Risk Assessment 

29 PVC Poly-vinyl Chloride 

30 RES NRC Office of Nuclear Regulatory Research 

31 SIS Synthetic Insulated Switchboard 

32 SNL Sandia National Laboratories 

33 SP Swedish National Testing and Research Institute 

34 SR Silicone Rubber 

35 SUN RES Sun Resistant 

36 TC Thermocouple or Tray Cable 

37 TC-ER Tray Cable - Exposed Run 

38 TC/NCC Tray Cable/Nickel Coated Copper 

39 Tefzel® DuPont ETFE (Ethylene-Tetrafluoroethylene) Resin

40 TFN Thermoplastic Fixture wire Nylon jacketed 

41 TP Thermoplastic 

42 TPE Thermoplastic Elastomer 

43 TS Thermoset 

44 UL Underwriters Laboratories 

45 VNTC Vinyl Nylon Tray Cable 
xviii

1 XHHW Cross-linked High Heat Water resistant 

2 VTT Valtion Teknillinen Tutkimuskeskus (Technical Research Centre, Finland) 

3 XLPE, XLP or XPE Cross-Linked Polyethylene 

 4 
1

1 1 INTRODUCTION 

2 1.1 Background 

3 Electrical enclosures are a potential source of fire in nuclear power plants because they contain 

4 both combustible materials and live electrical circuits. These fires have the potential to disrupt 

5 power, instrumentation, and control in the plant. Key parameters affecting fire in an electrical 

6 enclosure include its size, openings, electrical voltage, and combustible load. 

7 1.2 Previous Studies 

8 Heat release rate measurements for electrical enclosure fires have been conducted at Sandia 

9 National Laboratories (Chavez, 1987; Chavez and Nowlen, 1988), VTT Technical Research 

10 Centre of Finland (Mangs et al., 2003), and the Institut de Radioprotection et de Sûreté Nucléaire 

11 (IRSN) in France (Plumecocq et al., 2011; Coutin et al., 2012). In these studies, various 

12 configurations of electrical enclosure sizes, combustible loads and ventilation conditions were 

13 tested to determine the heat release rates and thermal conditions in and around the enclosures. 

14 1.2.1 Sandia National Laboratories Experiments 

15 Sandia conducted 22 full-scale fire experiments in the mid-1980s, with an emphasis on control 

16 room and switchgear room configurations. The test report (Chavez, 1987) concludes that fires in 

17 either benchboard or vertical enclosures containing qualified or unqualified cable can be ignited, 

18 but that fires burning unqualified cable spread more rapidly and to a greater extent than fires with 

19 qualified cable. The report also concludes that these fires are not severe enough to ignite 

20 combustibles in adjacent enclosures or outside the enclosure of origin. 

21 1.2.2 VTT Experiments 

22 VTT conducted 22 fire experiments that are reported in three separate reports: Mangs and Keski23 Rahkonen (1994; 1996), Mangs (2004), and a paper summarizing the findings (Mangs et al., 

24 2003). The enclosures contained a variety of electronic components, including relays, 

25 connectors, bundled wiring, circuit boards, and (mostly) PE/PVC cable. The purpose of the 

26 experiments was to determine maximum heat release rates, minimum igniter strengths, and the 

27 effect of opening area on the burning rate. A small propane line burner, typically 10 cm in length 

28 and varying between 0.5 kW and 7.5 kW was used to ignite the fires. 

29 1.2.3 IRSN Experiments 

30 Plumecocq et al. (2011) and Coutin et al. (2012) conducted experiments and performed analysis 

31 with the goal of developing a simplified model of fire behavior within an electrical enclosure. 

32 This model is based on the assumption that the ventilation within the enclosure is limited and 

33 that the heat release rate can be inferred from the limited oxygen supply. Experiments were 

34 performed using gas burners and PMMA (polymethyl methacrylate, a common plastic). A few 

35 experiments were performed with actual electrical components and cabling. 
2

1 1.3 Current Practice 

2 In 2005, the US Nuclear Regulatory Commission (NRC) and the Electric Power Research 

3 Institute (EPRI) jointly published NUREG/CR-6850/EPRI TR-101989, EPRI/NRC-RES Fire 

4 PRA Methodology for Nuclear Power Facilities. This report contains methods and data for 

5 conducting fire probabilistic risk assessments (PRAs) in commercial NPP applications. 

6 Appendix G of NUREG/CR-6850 expresses the peak HRR for five different categories of 

7 electrical enclosures in the form of gamma distributions. The enclosures are categorized by their 

8 combustible load (one vs multiple cable bundles), flammability of materials (qualified vs 

9 unqualified cable), and ventilation (door open vs door closed). The distributions were developed 

10 by a panel of experts who considered actual fire events in NPPs and other industrial facilities, 

11 and the experimental data cited above. 

12 Since the publication of NUREG/CR-6850, it has been noted that there is a considerable gap 

13 between the database of actual fire events and the experimental data. The reason for this gap is 

14 that the experiments cited in Section 1.2 were not intended to mimic the distribution of actual 

15 fire events. The VTT and IRSN experiments were aimed at validating empirical models that 

16 predict the peak HRR as a function of ventilation and enclosure geometry. The Sandia 

17 experiments were designed to answer specific questions like whether it is possible to propagate a 

fire on qualified1 18 cables with a particular kind of igniter, or whether it is possible to spread a fire 

19 from one side of an enclosure to another. In all of these studies, the aim was to determine the 

20 largest possible fire as opposed to the typical fire. The latter question is more difficult to answer 

21 because it would be extremely difficult to mimic realistic electrical malfunctions in operating 

22 electrical enclosures in such a way as to generate a statistically significant sample of test results. 

23 The nearest substitute would be to invoke the database of actual fire events in NPPs (Wachowiak 

24 and Lindeman, 2013), but in these cases, human intervention prevented the relatively small fires 

25 from spreading. It would be impossible to recreate the fires in the events database and allow 

26 them to progress with no suppression. 

27 1.4 Objective 

28 The objective of the current study is to measure the heat release rates of fires in electrical 

29 enclosures containing a wide variety of cable types, geometries, ventilation configurations, and 

30 ignition sources with the aim of producing a more realistic distribution of heat release rates than 

31 that of previous studies. The enclosures used in the experiments have been acquired from a 

32 nuclear power plant built in the late 1970s but never operated. These enclosures contain wiring 

33 typical of those built after the Brown’s Ferry fire of 1975. In addition, these enclosures shall be 

34 refurbished after an initial set of experiments so that they resemble other types of enclosures 

35 found in other plants. 

 36 

 

1

 “Qualified” typically means that the cable has passed the IEEE-383 flame spread test. 
3

1 2 DESCRIPTION OF ENCLOSURES 

2 This chapter contains a survey of electrical enclosures commonly found in nuclear power plants. 

3 2.1 Survey of Electrical Enclosures 

4 On the following pages are different types of electrical enclosures that were photographed during 

5 plant visits to several operating and decommissioned NPPs. These and other photographs show 

6 typical wiring configurations that were simulated in the experiments. This should not be 

7 considered a comprehensive survey of all enclosures in all plants, but rather a collection of 

8 typical combustible loads and ventilation configurations. 

9 Figure 2-1 and Figure 2-2 display photographs of enclosures in and around the main control 

10 room. These enclosures typically contain tight bundles of relatively small diameter insulated 

11 wiring and a large number of connection points. Racks of circuit boards are also common. 

12 Figure 2-3 displays photographs of switchgear enclosures. In general, these types of enclosures 

13 contain less wiring than the enclosures in the control room. These enclosures are also relatively 

14 large with large amounts of open volume inside. 

15 Figure 2-4 displays photographs of motor control centers. These contain relatively small 

16 compartments containing a variety of wiring and equipment. It is difficult to characterize these 

17 compartments in general terms other than to say that each “bucket” is relatively self-contained 

18 and isolated from its neighbors. 

19 
4

 

1 Figure 2-1. Photographs of enclosures typically found near the main control room. 
5

 

1 Figure 2-2. Photographs of enclosures typically found near the main control room. 
6

 

1 Figure 2-3. Photographs of the internal wiring of typical switchgear enclosures. 
7

 

1 Figure 2-4. Photographs of the internal wiring of typical motor control centers. 

9

1 2.2 Enclosures used in the Experiments 

2 The electrical enclosures used in the experiments were acquired from Bellefonte Nuclear 

3 Generating Station, a plant owned by the Tennessee Valley Authority located in Hollywood, 

4 Alabama. The enclosures were installed in the early 1980s, but the plant was never operated. All 

5 of the enclosures were low voltage control cabinets, but they were reconfigured to take on typical 

6 characteristics of other types of electrical enclosures found throughout a plant. 

7 The enclosures appear to have been manufactured in the late 1970s by one or two manufacturers. 

8 All were constructed of steel with a thickness of approximately 3 mm (1/8 in). 

9 
10

1 2.2.1 Enclosure 1 

2 Enclosure 1 was classified as a “protection system auxiliary cabinet.” When removed from 

3 Bellefonte NPP, there were a relatively large number of multi-conductor cables connected to a 

4 panel dividing the front of the enclosure from the back. There were 432 connection points, 

5 divided among 6 levels. The floor opening was covered by a steel plate. As installed, the cables 

6 would be routed through the floor or access openings on one side. 

7 Figure 2-5. Photographs of Enclosure 1. 
11

1 

2 Figure 2-6. Sketch of Enclosure 1. 
12

1 2.2.2 Enclosure 2 

2 Enclosure 2 was very similar to Enclosure 1 on the exterior. The interior of Enclosure 2 was 

3 dedicated primarily to racks for circuit cards. There were a number of bundles containing 

4 relatively small wires running both vertically and horizontally. Plastic conduits (labelled 

5 “Panduit”) was used to route the wire to the switches. 

6 Figure 2-7. Photographs of Enclosure 2. 
13

1 

2 Figure 2-8. Sketch of Enclosure 2. 
14

1 2.2.3 Enclosure 3 

2 Enclosure 3 was labelled a “solid state control system.” It was divided into three sections. The 

3 front section contained a rack for holding circuit cards, as seen through the plexi-glass window in 

4 Figure 2-9. The middle section (upper right photo) contained a large amount of relay wire. The 

5 rear section contained little combustible material. There was a relatively large access opening on 

6 the left side of the enclosure. There was also a relatively large opening in the floor. 

7 Figure 2-9. Photographs of Enclosure 3. 
15

1 

2 Figure 2-10. Sketch of Enclosure 3. 
16

1 2.2.4 Enclosures 4 and 5 

2 Enclosures 4 and 5 were bolted together and served as part of the “reactor protection system.” 

3 Both enclosures had similar exterior and interior features, including metal racks for circuit cards. 

4 Most of the circuit cards were removed prior to delivery, and the enclosure was reconfigured to 

5 mimic other types of enclosures. There was a small amount of amount of miscellaneous wire left 

6 in the enclosure, but not enough to constitute a significant combustible load. The fans on the tops 

7 of the enclosures were functional, but it was decided not to operate them during testing because 

8 each would drive smoke downward and out the bottom, and this smoke would not be captured by 

9 the exhaust hood. 

10 Figure 2-11. Photographs of Enclosures 4 and 5. 
17

1 

2 Figure 2-12. Sketch of Enclosures 4 and 5. 
18

1 2.2.5 Enclosure 6 

2 Enclosure 6 was a section of the main control room “horseshoe.” Its two side panels were 

3 beveled at angles of 22.5° to achieve a 45° turn near the apex of the horseshoe. The enclosure 

4 was well-ventilated via louvers on its front, rear, and top. Additionally, its floor was largely 

5 open. 

6 Figure 2-13. Photographs of Enclosure 6. 
19

1 

2 Figure 2-14. Sketch of Enclosure 6. 
20

1 2.2.6 Enclosure 7 

2 Enclosure 7 was a straight section of the main control room “horseshoe”. Its interior was similar 

3 to that of Enclosure 6. Much of it was compartmentalized, and, as delivered, there was not a 

4 significant amount of combustible materials. 

5 Figure 2-15. Photographs of Enclosure 7. 
21

1 

2 Figure 2-16. Sketch of Enclosure 7. 
22

1 2.2.7 Enclosure 8 

2 Enclosure 8 was labelled a “SEAMS Multiplexer”. SEAMS means “Support Equipment 

3 Acquisition Management System.” The notable feature of this enclosure were the conduits used 

4 for routing cable out the top and, presumably, into cable trays overhead. To mimic this 

5 configuration, a 1.2 m (4 ft) section of cable tray was mounted 45 cm (18 in) above the enclosure 

6 to collect the exiting cables. 

7 Figure 2-17. Photographs of Enclosure 8. 
23

1 

2 Figure 2-18. Sketch of Enclosure 8. 

25

1 3 CABLE PROPERTIES 

2 3.1 Properties of Cables used in Enclosure Fire Experiments 

3 The tables on the following pages contain a general description of the cables that were used to 

4 mock up different enclosure configurations. Note that the “Cable No.” is merely an identifier and 

5 has no relevance beyond this project. Photographs of the cables are shown in Figure 3-1 through 

6 Figure 3-3. The cable markings are listed in Table 3-1. The cable properties are listed in Table 

7 3-2. The property data was obtained by dissecting 20 cm (8 in) cable segments into their 

8 constituent parts – jacket, filler, insulators, and conductors. 

9 

10 805 807 809 813 814 817 818 830 831 832 833 834 835

11 Figure 3-1. Photograph of Cables 805-835. 
26

1 

2 836 837 838 839 840 841 842 

3 Figure 3-2. Photograph of Cables 836-842. 

 4 

5 

6 843 844 845 

7 Figure 3-3. Photograph of Cables 843-845. 
27

 1 

2 

3 Figure 3-4. Photograph of a circuit card installed in Enclosure 3. 

 4 
28 

Table 3-1. Manufacturers’ descriptions of the cables. 1 

Cable 

No. Source Manufacturer* Date Cable Markings 

805 CAROLFIRE #12 Cable USA Unknown No Markings 807 CAROLFIRE #15 General Cable 2006 GENERAL CABLE® BICC® BRAND SUBSTATION CONTROL CABLE 7/C #12AWG 600V 30 MAY 2006 809 CAROLFIRE #9 First Capitol No Markings 813 CAROLFIRE #13 Rockbestos 2006 12/C 18 AWG COPPER ROCKBESTOS-SURPRENANT(G) 600V 90 DEG C WET OR DRY FIREWALL(R) III SUN RES DIR BUR OIL RES II NEC TYPE TC (UL) FRXLPE CSPE I57-0120 2006 6C-399 814 CAROLFIRE #6 General Cable 2006 GENERAL CABLE® BICC® BRAND (WC) VNTC 12C 18AWG (UL) TYPE TC- ER TFN CDRS SUN RES DIR BUR 600V 09 MAR 2006 817 CAROLFIRE #7 Rockbestos 2006 

2/C 16 AWG COPPER ROCKBESTOS-SURPRENANT (G) 600V 90 DEG C WET 

OR DRY FIREWALL(R) III SUN RES DIR BUR OIL RES II NEC TYPE TC (UL) 

FRXLPE SHIELDED CSPE I46-0021 2006 6C-191 

818 Brookhaven Rockbestos 1981 ROCKBESTOS® RSS-6-104 1981 830 Sandia Unknown 8 AWG 3/C XLP/CPE 600V 90C TC TYPE SNRS DE6 6WC-03 831 Purchased Unknown Unknown 14 AWG (UL) XHHW-2 OR SIS VW-1 600V E7088 CSA SIS 600V FTI FT2 LL25850 832 Brookhaven # 32 

Boston Insulated 

Wire and Cable 

Corp. 

1980 BOSTON INSULATED WIRE AND CABLE CORP BOSTON, MASS. 1980 

833 Brookhaven #308 and Sandia # 6 Okonite Unknown No Markings 834 

1/C 12 AWG 

XLPE Removed 

from 37/C 

XLPE/CSPE 

Rockbestos - 

Surprenant Unknown No Markings 

835 Brookhaven #39 Rockbestos - Surprenant Unknown No Markings 836 Installed in CB 1 TVA Unknown BIW, TVA # 77K5-820991 MARK WVA # 16 AWG, 2/C 600V 837 Installed in CB 1 TVA Unknown BIW, TVA # 77K5-820991 MARK WWZ-2 # 16 AWG, 2P 600V 838 Installed in CB 1 TVA Unknown BIW, TVA # 77K5-820991 MARK WWZ-3 # 16 AWG, 3P 600V 839 Installed in CB 1 TVA Unknown BIW, TVA # 77K5-820991 MARK WWZ-4 # 16 AWG, 4P 600V 840 Installed in CB 1 TVA Unknown BIW, TVA # 77K5-820991 MARK WWZ-5 # 16 AWG, 5P 600V 
29 

Cable 

No. Source Manufacturer* Date Cable Markings 

841 Received from NRL Houston Wire & Cable Company Unknown HOUFLEX 16-3 SE00 WA 105°C (-40°C) WATER RESISTANT E54864 DRC 105 P-241-3 MSHA CSA LL39753 16-3ST 105C FT2 842 Installed in CB-6 Unknown Unknown No Markings 843 Installed in CB-2 Unknown Unknown No Markings 844 Purchased Carol Brand of General Cable Unknown 14/3 BUS DROP CABLE 600V 554567-8 (UL) 845 Brookhaven # 29 Rockbestos 1976 Rockbestos® Firewall® EP 10 AWG 600V (UL) TYPE RHH Rockbestos 1976 

 1 *Certain commercial equipment, instruments, or materials are identified in this report to foster understanding. Such identification does 2 

not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials 3 or equipment identified are necessarily the best available for the purpose. 4 

5 
30 

Table 3-2. Cable properties. 1 

Cable No. 

Insulation 

Material 

Jacket 

Material 

Class. 

Conductors 

Diameter 

(mm) 

Jacket 

Thickness 

(mm) 

Insulator 

Thickness 

(mm) 

Mass per 

Length 

(kg/m) 

Copper Mass 

Fraction 

Jacket Mass 

Fraction 

Insulation 

Mass 

Fraction 

Filler Mass 

Fraction 

805 Tefzel® TP 7 10.2 0.76 0.45 0.29 0.74 0.08 0.15 0.02 807 PE PVC TP 7 14.0 1.54 0.27 0.37 0.59 0.24 0.15 0.01 809 SR Aramid Braid TS 7 14.5 1.21 1.10 0.35 0.62 0.08 0.31 0.01 813 XLPE CSPE TS 12 12.7 1.46 1.18 0.25 0.37 0.33 0.29 0.01 814 PVC PVC TP 12 11.3 1.15 0.54 0.19 0.56 0.03 0.40 0.00 817 XLPE CSPE TS 2 7.8 1.64 0.92 0.11 0.24 0.58 0.15 0.00 818 PE PVC TP 1 6.3 1.35 1.41 0.06 0.38 0.40 0.07 0.15 830 XLP CPE TS 3 17.12 3.06 1.74 0.44 0.52 0.33 0.13 0.02 831 SIS TS TS 1 3.58 0.00 1.25 0.03 0.65 0.00 0.35 0.00 832 Unknown Unknown Unkn

own 

1 6.78 0.98 2.34 0.08 0.15 0.37 0.21 0.01 

833 Unknown Unknown Unkn

own 

1 4.70 N/A 1.74 0.05 0.63 0.00 0.37 0.00 

834 XLPE No Jacket TS 1 3.97 N/A 1.98 0.04 0.73 0.00 0.27 0.00 835 SR Aramid Braid TS 1 3.64 0.44 1.47 0.02 0.46 0.13 0.41 0.00 836 TVA Type MXPSJ TVA Type MXPSJ TS 2 8.57 2.60 1.48 0.11 0.24 0.46 0.13 0.10 837 TVA Type MXPSJ TVA Type MXPSJ TS 4 16.9 2.86 1.48 0.38 0.13 0.53 0.07 0.20 838 TVA Type MXPSJ TVA Type MXPSJ TS 6 18.4 2.86 1.48 0.46 0.17 0.55 0.09 0.12 
31 

Cable No. 

Insulation 

Material 

Jacket 

Material 

Class. 

Conductors 

Diameter 

(mm) 

Jacket 

Thickness 

(mm) 

Insulator 

Thickness 

(mm) 

Mass per 

Length 

(kg/m) 

Copper Mass 

Fraction 

Jacket Mass 

Fraction 

Insulation 

Mass 

Fraction 

Filler Mass 

Fraction 

839 TVA Type MXPSJ TVA Type MXPSJ TS 8 19.8 2.86 1.48 0.55 0.20 0.16 0.13 0.06 840 TVA Type MXPSJ TVA Type MXPSJ TS 10 23.4 3.65 1.48 0.77 0.25 0.31 0.17 0.04 841 TPE TPE TP 3 13.46 2.08 1.19 0.12 0.29 0.50 0.15 0.06 842 Unknown Unknown 40 1.2 Unknow

n 

Unknow

n 

0.08 Unknow

n 

Unknow

n 

Unknow

n 

Unknow

n 

843 Unknown Unknown Unkn

own 

352 36.1 N/A Unknow

n 

2.86 Unknow

n 

Unknow

n 

Unknow

n 

Unknow

n 

844 PVC PVC TP 3 10.2 01.80 0.76 0.17 0.06 0.06 0.04 0.01 845 EP TS TS 1 5.9 0 2.10 0.08 0.5 0 0.3 0 

33

1 4 EXPERIMENTAL PROCEDURE 

2 4.1 Oxygen Consumption Calorimeter 

3 The measurements of the heat release rate of the enclosure fires were performed at the 

Chesapeake Bay Detachment of the Naval Research Laboratory2 4 . This facility has a 6.1 m by 

5 6.1 m (20 ft by 20 ft) large-scale calorimeter that is designed to measure the heat release rate of 

6 fires ranging from approximately 100 kW to 10 MW. However, its instruments are not sensitive 

7 enough to measure accurately the HRR of the small fires that were expected in many of the 

8 enclosure experiments. For this reason, a smaller calorimeter was built to fit underneath the large 

9 hood (see Figure 4-2). The smaller hood was 2.4 m by 2.4 m (8 ft by 8 ft), and 2.4 m (8 ft) off 

the floor. Its 45 cm (18 in) duct was instrumented with a Rosemount Annubar® 10 to measure the 

11 volume flow, four thermocouples to measure the gas temperature, and a gas extraction tube to 

12 measure the oxygen concentration of the exhaust gases. The instruments were located 

13 approximately 4 m (13 ft) from the vertical centerline of the hood. 

14 

15 Figure 4-1. Schematic diagram of the small calorimeter. 

 

2

 The experiments were conducted at the Naval Research Laboratory because the Large Fire Facility of NIST was 

undergoing renovation at the time the program was conducted. 
34

1 

2 Figure 4-2. Schematic diagram of the small calorimeter underneath the large hood at the 

3 CBD test facility. 

4 The heat release rate of the fire is given by the following formula under the assumption that both 

5 oxygen and carbon dioxide are measured in the exhaust duct (SFPE Handbook, 2008): 

ܳሶ ൌ ܧ ߮

1 ൅ ߮ሺߙെ1ሻ

݉ሶ e

Oమܯ

aܯ

൫1 െ ܺHమO a െ ܺCOమ

a ൯ܺOమa Equation 4-1 

6 with: 

߮ ൌ

ܺOమ

a ൫1 െ ܺCOమe ൯ െ ܺOమe ൫1 െ ܺCOమa ൯

൫1 െ ܺOమ

e െ ܺCOమe ൯ܺOమa Equation 4-2 

where ܳሶ 7 Heat release rate (kW) 

8 ܧ Heat release per unit mass of oxygen consumed (12800 kJ/kg) 

9 ߮ Oxygen depletion factor 
35

1 ߙ Volumetric expansion factor (1.105) 

 ݉ሶ e 2 Mass flow rate in the exhaust duct (kg/s) 

 ܯOమ 3 Molecular mass of oxygen (32 g/mol) 

 ܯa 4 Molecular mass of the ambient air (29 g/mol) 

 ܺHమO a 5 Volume fraction of water vapor in the ambient air 

 ܺCOమ

a 6 Volume fraction of carbon dioxide in the ambient air 

 ܺOమ

a 7 Volume fraction of oxygen in the ambient air 

 ܺCOమ

e 8 Volume fraction of carbon dioxide in the exhaust duct 

 ܺOమ

e 9 Volume fraction of oxygen in the exhaust duct 

The mass flow rate of the exhaust gases, ݉ሶ e 10 , is the product of their density, ߩ, and their volume 

flow rate, ܸሶ 11 . The density was determined from the four thermocouple measurements via the ideal 

12 gas law: 

ൌ ߩ

ഥܹ ݌

ܴ ܶത Equation 4-3 

13 where ݌ is the pressure (assumed to be 101325 Pa), ܹഥ is the average molecular weight of the 

14 gases (assumed to be 29 g/mol), ܴ is the universal gas constant (8.3145 J/(mol·K)), and ܶത is the 

15 average of the four thermocouple measurements. The volume flow rate is calculated: 

ܸሶ ൌ ܣܥdඨ2 ∆݌

ߩ

Equation 4-4 

where ܣd 16 is the cross sectional area of the duct, and ∆݌ is the pressure difference across the 

Annubar® 17 . The flow coefficient, ܥ, was set to 0.75 rather than the recommended value of 0.61. 

18 This decision was based on initial calibration fires using propane as the fuel. Because the duct of 

19 the smaller hood was required to fit under the larger hood, the flow was not sufficiently 

straightened to the extent recommended by the manufacturer of the Annubar® 20 . 

21 The uncertainty in the heat release rate measurement is primarily due to the value of the heat of 

combustion based on oxygen consumption, ܧ, the mass flow rate in the duct, ݉ሶ e 22 , and the oxygen 

depletion, ܺOమ

a െ ܺOమe 23 . Tewarson (SFPE Handbook, 2008) estimates that ܧ equals 12800 kJ/kg 

24 with a relative standard uncertainty of 7 %. The uncertainties of the mass flow rate and oxygen 

25 concentration measurements were not evaluated independently because the flow coefficient, ܥ, 

26 was selected based on calibration fires rather than an isothermal flow test. 

27 As a way of estimating the combined uncertainty of the mass flow rate and oxygen depletion 

28 measurements, the acetone pan fires that were used to preheat the electrical enclosures provided 

29 a second set of calibration burns. Five experiments were performed in which 1 L of acetone was 

30 burned in a small pan. As discussed further in Section 4.2.3, this fire ought to produce 

31 approximately 22.7 MJ of energy. The mean energy release for the five test burns was 23.5 MJ, 

32 with a standard deviation of 1.7 MJ. From this exercise, it is estimated that the aleatoric 

33 uncertainty of the heat release rate measurement is approximately 7 % when the fuel 

34 stoichiometry is known. However, for general combustibles this estimate of the uncertainty must 
36

1 then be combined via quadrature with the uncertainty in the value of ܧ, the heat of combustion 

2 based on oxygen consumption. The relative standard deviation in the heat release rate is thus 

3 estimated to be approximately 10 %. 

4 4.2 Ignition Sources 

5 Three types of ignition sources were used in the experiments: cartridge heaters, line burners, and 

6 pans of liquid fuel. A cartridge heater is a surrogate for an over-heated electrical component or 

7 cable. The line burner is a surrogate for a small fire that could result from an over-heated wire or 

8 component. The pan fire is a surrogate for a relatively large fire whose origin is difficult to 

9 specify exactly, but most likely due to an event such as a high energy arcing fault or similar 

10 malfunction resulting in the ignition of a relatively large amount of combustible material. 

11 4.2.1 Cartridge Heaters 

12 A cartridge heater is a cylindrical rod approximately 15 cm (6 in) in length and 1 cm (0.5 in) in 

13 diameter (Figure 4-3) that can be inserted lengthwise within a bundle of electrical wires or 

14 cables. Bench-scale experiments were conducted prior to the full-scale experiments to determine 

15 the exact dimensions and power requirements for reliable, reproducible ignition. A bundle of 

16 cables, each 15 mm in diameter, was ignited with a 300 W heater and spark igniter. However, the 

17 heaters were used only for a single full-scale experiment because they were prone to shorting 

18 following ignition and the spark igniter drew too much power from the existing electrical circuit 

19 in the laboratory. Consequently, the cartridge heaters were abandoned for the remainder of the 

20 program. 

21 

22 Figure 4-3. Two 300 W cartridge heaters. One has an in-line circuit breaker. 
37

1 4.2.2 Propane Line Burners 

2 Two propane “line burners” were used as the principal ignition sources. The smaller of the two 

was constructed from 3/8 in3 3 (0.95 cm) copper tubing and was 5 cm (2 in) long. The larger was 

4 constructed of the same type of copper tubing and was 30 cm (12 in) long. The smaller burner 

5 produced flames with heat release rates in the range of 0.5 kW to 2 kW. The larger burner 

6 produced flames in the range of 4 kW to 10 kW. The propane flowing to the burners was 

7 controlled by several different flow meters. Table 4-1 summarizes the settings of the flow meters 

8 and the expected heat release rate for each. Each flow meter was calibrated for air (29.0 g/mol) at 

9 24 °C (297 K, 70 °F). The average temperature over the five months of testing was 

10 approximately 10 °C (283 K, 50 °F). To correct for the difference in temperature and molecular 

weight of propane (44.1 g/mol), the reading from the flow meter, ܸሶ

air 11 , was multiplied by a 

12 correction factor of 0.8: 

ܸሶ

p ൌ ܸሶairඨ

ܹa	ܶp

ܹp	ܶa

ൌ ܸሶ

airඨ29.0 g/mol	ൈ	283 K

44.1 g/mol	ൈ	297	K ≅ 0.8 ܸሶ

air Equation 4-5 

where ܸሶ

p 13 is the volumetric flow rate of propane corrected for molecular weight and temperature. 

14 The heat of combustion of propane is taken as 46,300 kJ/kg (SFPE Handbook, 2008, 

15 Appendix C). The HRR of the burner is given by the expression: 

ܳሶ ൌ ܸሶ

p ߩp ∆ܪp Equation 4-6 

where ܳሶ is the HRR (kW), ܸሶ

p is the volumetric flow rate (L/s), ߩp 16 is the density of propane at the 

ambient temperature (kg/L), and ∆ܪp 17 is the heat of combustion of propane (kJ/kg). 

18 Table 4-1. Propane burner heat release rate values. 

Flowmeter 

Manufacturer Units Range Value Burner Size (cm) 

HRR 

(kW) 

Cole-Parmer L/min, Air 0.2-1.0 0.4 ± 0.05 5 0.47 ± 0.06

Cole-Parmer L/min, Air 0.2-1.0 0.6 ± 0.05 5 0.70 ± 0.06

Dwyer Instruments ft3/h, Air 0.3-3.0 1.5 ± 0.15 5 0.83 ± 0.08

Dwyer Instruments ft3/h, Air 0.3-3.0 3.0 ± 0.15 5 1.6 ± 0.08 

Dwyer Instruments ft3/h, Air 4-40 10 ± 2 30 5.5 ± 1.1 

19 The uncertainty in the HRR of the propane burners is primarily due to the uncertainty in the flow 

20 meter, which is given as 5 % of the calibrated range. 

21 4.2.3 Liquid Fuel Pan Fires 

22 The pan fires served two purposes. In some cases, they served only to pre-heat the enclosure to 

23 temperatures comparable to those expected in an actual NPP. In other cases, they served to ignite 

24 the combustibles directly. Two liquid fuels were used – ethanol and acetone. A variety of pan 

 

3

 The copper tubing is listed specifically in inches. 
38

1 sizes were used; most typically a 15 cm by 23 cm (6 in by 9 in) steel baking pan. It was 

2 approximately 10 cm (4 in) deep. Most often, 1 L of acetone was used as the fuel. This fire 

3 burned for approximately 20 min at a rate of 20 kW, but the duration and rate depended on the 

4 ambient temperature and pan size. Acetone has a density of 0.792 kg/L and a heat of combustion 

5 of 28,600 kJ/kg (SFPE Handbook, 2008, Appendix C). Thus, 1 L releases approximately 

6 22,650 kJ of energy. This fire also served as a convenient means to calibrate the oxygen 

7 consumption calorimeter. 

 8 

 9 
39

1 5 FULL-SCALE MEASUREMENTS 

2 This chapter presents the results of 112 full-scale electrical enclosure fire experiments. 

3 5.1 Description 

4 The experiments were conducted from late October of 2013 through early March of 2014, in the 

5 large fire calorimeter of the Naval Research Laboratory Chesapeake Bay Detachment (CBD). 

6 The facility was not heated, and temperatures ranged from approximately 0 °C (32 °F) to 20 °C 

7 (68 °F). Typically, electrical enclosures are operated at 32 °C (90 °F), but in the experiments, the 

8 enclosures were not powered. Instead, a variety of heaters were used to pre-heat the interior of 

9 the enclosures prior to or at the beginning of each experiment. The most effective way to do this 

10 was to place a pan of ethanol or acetone at the base of the enclosure away from the combustibles. 

11 These same pans of alcohol were sometimes used to ignite the combustibles directly. In the 

12 description of each experiment, therefore, there is a distinction made between “Ignition Source” 

13 and “Preheating Source.” 

14 The order of experiments was determined largely for practical reasons. All of the vertical 

15 enclosures (1, 2, 3, 4, 5 and 8) were outfitted with heavy-duty caster wheels to enable their easy 

16 movement to and from under the calorimeter hood. Typically, as one enclosure was being tested, 

17 other enclosures could be refurbished with new cables or wiring. Sometimes additional 

18 experiments would be conducted on a given enclosure if the fires did not spread beyond the 

19 igniter. 

20 The propane line burner was typically positioned within a bundle of cable as if it were just 

21 another cable. Wire was used to hold the burner firmly in place. The exact placement of the 

22 burner varied from test to test, and there was no particular emphasis on a “standard” ignition 

23 system. Rather, the burner position and heat release rate were varied as would be expected in 

24 actual fire events. The cables and wiring were not installed in a particularly systematic way 

25 either. Typically, bundles of cables would be hung using wires on either the left or right side of 

26 the enclosure, as had been observed in enclosures found on the plant visits. Sometimes the cables 

27 and/or individual conductors would be tightly bundled using plastic wire or “zip ties,” and at 

28 other times they would be left to hang in no particular arrangement. It was observed that “loose” 

29 or non-bundled cables or wires led to higher heat release rates, even though bundling was 

30 necessary to accumulate enough combustible mass in the vicinity of the igniter to facilitate fire 

31 spread. 

 32 
40

1 Table 5-1. Summary of enclosure fire measurements 

Test Encl. 

Ignition 

HRR 

(kW) 

Preheat 

HRR 

(kW) 

Fuel 

Mass 

(kg) 

Cable

Class. 

Door 

Position 

Peak 

HRR 

(kW) 

Note 2 

Time 

to 

Peak 

HRR 

(min) 

Total 

Energy

Release

(MJ) 

1 1 0.3 0 Note 1 Q Open 2 40 2 

2 2 0.5 0 Note 1 Q Open 2 1 1 

3 2 0.5 0 Note 1 Q Open 2 15 2 

4 2 0.7 0 Note 1 Q Open 2 14 1 

5 2 0.7 0 Note 1 Q Open 1 15 1 

6 4 0.7 0 Note 1 Q Open 2 13 1 

7 5 0.7 0 Note 1 Q Open 9 8 6 

8 3 0.7 0 Note 1 Q Open 0 1 1 

9 3 0.7 0 Note 1 Q Open 1 2 1 

10 3 0.7 0 Note 1 Q Open 1 1 1 

11 1 0.7 0 11.2 Q Open 1 13 1 

12 1 0.7 0 11.2 Q Closed 52 85 120 

13 8 0.7 0 Note 1 Q Closed 2 36 4 

14 8 0.7 0 Note 1 Q Closed 4 27 2 

15 5 0.7 0 3.4 Q Open 3 34 7 

16 5 0.7 0 1.9 Q Open 2 23 2 

17 4 0.7 0 2.7 Q Open 0 6 0 

18 4 0.7 0 1.8 UQ Open 3 15 3 

19 5 0.7 0 3.4 Q Closed 3 51 7 

20 5 0.7 0 1.9 Q Closed 5 52 9 

21 4 0.7 0 1.9 Q Closed 4 22 3 

22 4 0.7 0 1.8 Q Closed 4 22 4 

23 5 0.7 0 1.6 UQ Open 18 13 12 

24 5 0.7 0 0.7 Q Closed 4 35 4 

25 1 0.7 0 3.1 Q Closed 4 22 5 
41

Test Encl. 

Ignition 

HRR 

(kW) 

Preheat 

HRR 

(kW) 

Fuel 

Mass 

(kg) 

Cable

Class. 

Door 

Position 

Peak 

HRR 

(kW) 

Note 2 

Time 

to 

Peak 

HRR 

(min) 

Total 

Energy

Release

(MJ) 

26 1 0.7 0 3.1 Q Closed 1 1 0 

27 1 0.7 14 3.1 Q Closed 1 2 9 

28 1 0.7 16 3.1 Q Closed 3 6 17 

29 1 18 0 3.1 Q Closed 82 13 76 

30 1 18 0 3.1 Q Closed 72 8 59 

31 4 5.5 22 0.7 Q Closed 28 13 45 

32 4 5.5 25 0.7 Q Closed 6 4 35 

33 5 25 0 1.5 Q Closed 50 6 40 

34 5 35 0 1.5 Q Closed 6 7 46 

35 8 27 0 11.7 Q Closed 146 8 153 

36 2 4 0 2.8 Q Closed 4 13 4 

37 2 54 0 5.5 Q Closed 35 6 27 

38 2 20 0 5.5 Q Closed 169 9 95 

39 8 25 0 5.8 Q Closed 60 13 65 

40 3 12 0 0.1 Q Closed 2 25 19 

41 3 20 0 5.0 Q Closed 232 15 141 

42 4 5.5 0 2.9 Q Closed 34 18 35 

43 4 16 0 2.9 Q Closed 18 10 21 

44 5 5.5 0 2.9 Q Closed 31 19 32 

45 5 5.5 22 2.9 Q Closed 5 16 34 

46 4 19 0 2.8 Q Closed 45 19 68 

47 4 19 0 1.4 Q Closed 40 17 49 

48 4 19 0 2.8 Q Open 87 18 89 

49 4 19 0 2.8 Q Closed 50 15 76 

50 4 22 0 1.4 Q Closed 1 13 21 

51 4 30 0 1.4 Q Open 31 6 34 
42

Test Encl. 

Ignition 

HRR 

(kW) 

Preheat 

HRR 

(kW) 

Fuel 

Mass 

(kg) 

Cable

Class. 

Door 

Position 

Peak 

HRR 

(kW) 

Note 2 

Time 

to 

Peak 

HRR 

(min) 

Total 

Energy

Release

(MJ) 

52 4 5.5 0 2.8 Q Open 122 4 61 

53 4 5.5 0 2.8 Q Closed 79 39 60 

54 4 2.2 0 1.6 UQ Open 94 17 41 

55 4 10 0 3.1 UQ Closed 21 17 26 

56 5 0.8 22 1.7 UQ Closed 8 6 16 

57 5 0.8 24 1.7 UQ Closed 5 13 26 

58 5 0.8 21 3.4 UQ Closed 26 6 36 

59 5 0.8 0 3.4 UQ Open 22 28 14 

60 1 0.8 19 7.4 UQ Closed 88 28 96 

61 1 0.8 19 12.1 Q Closed 5 17 29 

62 1 1.6 19 12.1 Q Closed 3 18 33 

63 1 5.5 19 12.1 Q Closed 92 25 156 

64 8 0.8 11 6.0 Q Closed 6 14 13 

65 8 0.8 11 6.0 Q Closed 7 16 15 

66 4 5.5 24 3.4 UQ Closed 26 17 57 

67 4 5.5 0 3.4 UQ Closed 25 9 21 

68 1 0.8 0 4.5 UQ Closed 216 11 121 

69 8 1.6 13 3.5 UQ Closed 10 13 22 

70 1 1.6 0 3.1 Q Closed 2 4 1 

71 1 5.5 0 3.1 Q Closed 138 14 99 

72 4 0.8 0 2.9 Q Closed 10 13 7 

73 4 1.6 22 2.9 Q Closed 4 5 26 

74 5 1.6 20 2.4 Q Closed 5 13 28 

75 5 5.5 26 2.9 Q Closed 15 12 57 

76 5 22 0 2.9 Q Closed 9 9 25 

77 5 5.5 24 2.4 Q Closed 13 17 53 
43

Test Encl. 

Ignition 

HRR 

(kW) 

Preheat 

HRR 

(kW) 

Fuel 

Mass 

(kg) 

Cable

Class. 

Door 

Position 

Peak 

HRR 

(kW) 

Note 2 

Time 

to 

Peak 

HRR 

(min) 

Total 

Energy

Release

(MJ) 

78 5 5.5 0 2.4 Q Closed 54 13 27 

79 4 5.5 0 6.1 Q Closed 65 28 63 

80 4 5.5 19 2.8 Q Closed 79 29 92 

81 5 30 0 2.9 Q Closed 24 18 48 

82 1 1.6 19 7.4 UQ Closed 43 30 112 

83 1 0.8 0 4.5 UQ Open 577 13 152 

84 7 0.8 20 3.3 Q Open 37 19 51 

85 7 0.8 0 2.0 Q Closed 2 13 2 

86 7 5 0 2.0 Q Open 19 37 15 

87 7 0.8 21 3.3 Q Closed 29 12 35 

88 7 0.8 0 1.1 UQ Closed 147 6 18 

89 7 0.8 0 1.1 UQ Closed 25 16 10 

90 7 0.8 16 23.4 Q Closed 12 20 33 

91 7 1.6 20 2.1 Q Closed 3 15 26 

92 7 5.5 20 2.1 Q Closed 15 6 37 

93 7 5.5 0 3.1 UQ Closed 59 10 27 

94 7 5.5 0 4.9 Q Closed 37 13 23 

95 7 5.5 0 5.4 UQ Closed 30 16 27 

96 6 5.5 21 5.4 UQ Closed 33 9 47 

97 6 5.5 0 4.6 UQ Closed 89 20 120 

98 6 20 0 7.7 Q Closed 121 8 126 

99 6 5.5 0 3.3 UQ Open 3 9 7 

100 6 5.5 0 6.2 UQ Closed 34 27 42 

101 6 20 0 6.2 UQ Closed 66 10 70 

102 6 23 0 3.6 Q Open 10 6 17 

103 6 5.5 0 1.1 UQ Closed 42 13 50 
44

Test Encl. 

Ignition 

HRR 

(kW) 

Preheat 

HRR 

(kW) 

Fuel 

Mass 

(kg) 

Cable

Class. 

Door 

Position 

Peak 

HRR 

(kW) 

Note 2 

Time 

to 

Peak 

HRR 

(min) 

Total 

Energy

Release

(MJ) 

104 1 0.8 24 4.5 UQ Open 220 33 141 

105 1 5.5 0 6.1 UQ Closed 80 7 25 

106 1 5.5 0 6.1 UQ Closed 33 14 25 

107 1 5.5 19 0.6 Q Open 55 13 51 

108 1 5.5 0 5.5 Q Closed 32 7 15 

109 8 5.5 19 6.1 Q Closed 64 14 61 

110 4 5.5 24 2.2 UQ Closed 7 15 32 

111 5 5.5 20 3.1 UQ Closed 268 23 120 

112 4 5.5 0 2.2 UQ Open 17 11 12 

1 

2 Notes: 

3 1. Experiments 1-10, 13, and 14 were performed in the enclosures as delivered from 

4 Bellefonte NPP. The mass of the combustibles was not measured because these materials 

5 could not be extracted from the enclosure without disrupting the original construction. 

6 2. The Peak HRR is the total HRR minus the Ignition HRR and the Preheat HRR. 

7 
45

1 Table 5-2. Summary of Test 1 

Test: 1 

Enclosure: 1 

Fuel Load: 7/C control cables 

Ignition Source: 300 W cartridge heater 

Ventilation: Door open 

Notes: The fire did not spread beyond its point of 

origin (right side of photos below). The heater 

was turned off at 40 min. 
46

1 Table 5-3. Summary of Test 2 

Test: 2 

Enclosure: 2 

Fuel Load: Vertical bundle of SIS wire 

Ignition Source: 0.5 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread beyond its point of 

origin. The burner was turned off after 

approximately 16 min. 

 2 
47

1 Table 5-4. Summary of Test 3 

Test: 3 

Enclosure: 2 

Fuel Load: Horizontal bundle of SIS wire 

enclosed by plastic conduit 

Ignition Source: 0.5 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread beyond its point of 

origin. The plastic harness charred and 

deformed, but did not appear to add to the heat 

release rate. The burner was turned off after 

approximately 15 min. 

 2 
48

1 Table 5-5. Summary of Test 4 

Test: 4 

Enclosure: 4 

Fuel Load: Vertical bundle of SIS wire enclosed 

by plastic conduit 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread beyond point of 

origin. The burner was turned off at 

approximately 15 min. 

 2 
49

1 Table 5-6. Summary of Test 5 

Test: 5 

Enclosure: 2 

Fuel Load: Horizontal bundle of SIS wire inside 

a plastic conduit 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread beyond point of 

origin. The burner was turned off at 

approximately 15 min. 

 2 
50

1 Table 5-7. Summary of Test 6 

Test: 6 

Enclosure: 4 

Fuel Load: Vertical bundle of SIS wire enclosed 

by plastic conduit 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread beyond point of 

origin. The plastic melted near the burner but 

did not appear to add much to the HRR. The 

burner was turned off at approximately 15 min. 

 2 
51

1 Table 5-8. Summary of Test 7 

Test: 7 

Enclosure: 5 

Fuel Load: Vertical bundle of SIS wire encased 

in plastic jacket 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire spread on the plastic jacket used 

to harness the wires. Some of the jacketing 

material and loose plastic material fell to the 

floor where it continued to burn. The propane 

burner was turned off at 6 min. 

No picture available 

 2 
52

1 Table 5-9. Summary of Test 8 

Test: 8 

Enclosure: 3 

Fuel Load: Circuit boards 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire was ignited between two circuit 

boards at the bottom of a four tier array. Each 

card was approximately 20 cm by 30 cm. The 

fire did not spread upwards, and only scorched 

the boards. The burner was turned off at 

15 min. 

 2 
53

1 Table 5-10. Summary of Test 9 

Test: 9 

Enclosure: 3 

Fuel Load: Assorted bundles of relay wire 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread beyond its point of 

origin (blue bundles in left photo). There was 

only minor scorching of the coating on the 

wires. The propane burner was turned off at 

10 min. 

 2 
54

1 Table 5-11. Summary of Test 10 

Test: 10 

Enclosure: 3 

Fuel Load: Vertical bundle of relay wire bound 

by a rubber harness 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The rubber harness material burned, but 

there was no measureable heat release or 

significant spread. The burner was turned off at 

10 min. 

 2 
55

1 Table 5-12. Summary of Test 11 

Test: 11 

Enclosure: 1 

Fuel Load: Loose collection of control cables that 

were originally installed in the enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire burned some of the cable jackets 

in the immediate vicinity of the propane 

burner, shown at the bottom right of the 

enclosure in the photo on the right. The burner 

was turned off at approximately 20 min. 

 2 
56

1 Table 5-13. Summary of Test 12 

Test: 12 

Enclosure: 1 

Fuel Load: Same cables from Test 11 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The door of the enclosure was initially 

closed, but it was opened at approximately 

40 min to check on progress. The fire flared up 

due, presumably, to the introduction of fresh 

air. The door was closed at about 41 min. The 

cables burned or smoldered for about an hour. 

All that remained was glowing char. 

 2 
57

1 Table 5-14. Summary of Test 13 

Test: 13 

Enclosure: 8 

Fuel Load: Control cables originating at interior 

connection panel and directed through conduits 

at the top of the enclosure into a cable tray 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened at 23 min and then 

closed again. The burner was turned off at 

approximately 31 min. The fire did not spread 

beyond its point of origin. 

 2 
58

1 Table 5-15. Summary of Test 14 

Test: 14 

Enclosure: 8 

Fuel Load: Same as Test 13 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: This experiment was similar to Test 13, 

but the cables were bundled closer together 

about the igniter. There was no measureable 

increase in the HRR for approximately 20 min, 

at which time the door was opened and a 

propane blow torch was used to try to spread 

the fire. The test was ended at approximately 

30 min. 

 2 
59

1 Table 5-16. Summary of Test 15 

Test: 15 

Enclosure: 5 

Fuel Load: 22 cables (#817), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread or grow 

appreciably in 30 min. At approximately 

35 min, the door was closed to determine if 

this might better trap the heat and enhance 

burning. The burner was turned off at 

approximately 41 min. 

 2 
60

1 Table 5-17. Summary of Test 16 

Test: 16 

Enclosure: 5 

Fuel Load: 7 cables (#807), 1.8 m (6 ft) long, 

routed up right side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The holes of the propane burner became 

clogged, and the burner was cleaned at 

approximately 10 min. The fire did not spread 

beyond its point of origin. The burner was 

turned off at 23 min. 

 2 
61

1 Table 5-18. Summary of Test 17 

Test: 17 

Enclosure: 4 

Fuel Load: 7 cables (#830), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire did not spread beyond its point of 

origin. The burner was turned off at 14 min. 

 2 
62

1 Table 5-19. Summary of Test 18 

Test: 18 

Enclosure: 4 

Fuel Load: 30 cables (#845), 1.8 m (6 ft) long, 

routed up right side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The fire spread upwards approximately 

60 cm (2 ft) above the propane burner. The 

burner was turned off at 20 min. 

 2 
63

1 Table 5-20. Summary of Test 19 

Test: 19 

Enclosure: 5 

Fuel Load: 22 cables (#817), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The fire did not spread beyond its point of 

origin. The door was opened at 24 min and at 

40 min. At 40 min, the propane burner was 

increased to 1.7 kW, but the fire still did not 

spread. 

 2 
64

1 Table 5-21. Summary of Test 20 

Test: 20 

Enclosure: 5 

Fuel Load: 7 cables (#807), 1.8 m (6 ft) long, 

routed up right side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The burner was placed above the damaged 

cables left over from Test 16, approximately at 

mid-height. The flames extended about 60 cm 

(2 ft) above the burner. The door was opened 

at 30 min and at 50 min to check progress. The 

fire did not spread beyond 60 cm (2 ft). The 

burner was turned off just short of an hour. 

 2 
65

1 Table 5-22. Summary of Test 21 

Test: 21 

Enclosure: 4 

Fuel Load: 7 cables (#807), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The fire did not spread beyond its point of 

origin. 

 2 
66

1 Table 5-23. Summary of Test 22 

Test: 22 

Enclosure: 4 

Fuel Load: 30 cables (#845), 1.8 m (6 ft) long, 

routed up right side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The fire did not spread beyond the point of 

origin. 

 2 
67

1 Table 5-24. Summary of Test 23 

Test: 23 

Enclosure: 5 

Fuel Load: 10 cables (#841), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door open 

Notes: The cable was cut from old power cords 

that were being discarded. The fire spread 

rapidly upwards after approximately 10 min, at 

which point the bundle fell from its restraining 

harness at piled onto the floor of the enclosure 

where it burned for approximately 20 min. 

 2 
68

1 Table 5-25. Summary of Test 24 

Test: 24 

Enclosure: 5 

Fuel Load: 1.8 m (6 ft) vertical bundle of 37 

insulated conductors (#834) routed up right 

side of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The fire did not spread beyond its point of 

origin. The burner was turned off at 35 min. 

 2 
69

1 Table 5-26. Summary of Test 25 

Test: 25 

Enclosure: 1 

Fuel Load: 768 m (2520 ft) insulated conductors 

(#834) connected to center board and running 

down both sides of enclosure 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: The fire spread approximately 20 cm (8 in) 

above the burner. The door was opened at 

approximately 20 min to check progress. The 

fire did not spread beyond the vicinity of the 

burner. 

 2 
70

1 Table 5-27. Summary of Test 26 

Test: 26 

Enclosure: 1 

Fuel Load: Same as Test 25 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed 

Notes: This test made use of the mostly unburned 

wire from Test 25. The propane burner was 

placed in a different position, near unburned 

wire. The door was opened at approximately 

15 min and the test was ended at 17 min. The 

fire did not spread. 

 2 
71

1 Table 5-28. Summary of Test 27 

Test: 27 

Enclosure: 1 

Fuel Load: Same as Test 25 

Ignition Source: 0.7 kW propane burner 

Preheating Source: 150 mL ethanol pan fire 

Ventilation: Door closed 

Notes: The ethanol was exhausted at 

approximately 7 min, at which time the 

propane burner was lit. The door was opened 

at 27 min and at 40 min. Each time the door 

was opened, the cables were jostled with a 

crowbar. The burner was turned off at 56 min. 

 2 
72

1 Table 5-29. Summary of Test 28 

Test: 28 

Enclosure: 1 

Fuel Load: Same as Test 25 

Ignition Source: 0.7 kW propane burner 

Preheating Source: 300 mL ethanol pan fire 

Ventilation: Door closed 

Notes: The ethanol fire was exhausted at 

approximately 9 min after which the propane 

burner was ignited. At 19 min, the door was 

opened and the wires in the vicinity of the 

burner were jostled with a crowbar. The fire 

then spread upwards, approximately 0.6 m 

(2 ft) above the burner. The process was 

repeated at 40 min. 

 2 
73

1 Table 5-30. Summary of Test 29 

Test: 29 

Enclosure: 1 

Fuel Load: Same as Test 25 

Ignition Source: 500 mL acetone pan fire 

Ventilation: Door closed 

Notes: The bottom ends of 3 bundles, each 

consisting of 37 insulated conductors, were 

placed into the 15 cm by 23 cm (6 in by 9 in) 

steel baking pan at the lower left side of the 

enclosure. The acetone burned for 

approximately 12 min, 30 s. The fire spread up 

one side of the enclosure. 

 2 
74

1 Table 5-31. Summary of Test 30 

Test: 30 

Enclosure: 1 

Fuel Load: Same as Test 25 

Ignition Source: 500 mL acetone pan fire 

Ventilation: Door closed 

Notes: This test was similar to Test 29, where the 

acetone pan was placed on the unburned right 

side of the enclosure. The test was terminated 

at approximately 23 min. 

 2 
75

1 Table 5-32. Summary of Test 31 

Test: 31 

Enclosure: 4 

Fuel Load: 72 insulated conductors extracted 

from Cable #834, loosely bundled, 1.8 m (6 ft) 

along right side of enclosure 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed in the rear of 

the enclosure for the purpose of pre-heating. 

The acetone was exhausted at 20 min. The 

door was opened and the propane burner was 

turned off at 23 min. 

 2 
76

1 Table 5-33. Summary of Test 32 

Test: 32 

Enclosure: 4 

Fuel Load: 72 insulated conductors (#834), 

loosely bundled, 1.8 m (6 ft) along left side of 

enclosure 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone was exhausted at 

approximately 16 min, and the propane burner 

was turned off at 22 min. The fire did not 

spread beyond the vicinity of the propane 

burner. 

 2 
77

1 Table 5-34. Summary of Test 33 

Test: 33 

Enclosure: 5 

Fuel Load: Remnants of Test 31 and 32 

Ignition Source: 5.5 kW propane burner and 1 L 

acetone pan fire at the overlap region of left 

and right side bundles 

Ventilation: Door closed 

Notes: This was an attempt to burn the wiring on 

both sides of the enclosure. The fire spread 

about one-third of the way up the left side, but 

within 10 min the only fuel burning was the 

acetone and propane. The acetone was 

exhausted and the burner turned off just after 

20 min. 

 2 
78

1 Table 5-35. Summary of Test 34 

Test: 34 

Enclosure: 5 

Fuel Load: Remnants of Test 33 

Ignition Source: 2 pans of acetone, 500 mL each 

Ventilation: Door closed 

Notes: This was an attempt to burn wire bundles 

left over from previous tests. The fire spread 

up the left side of the enclosure, and halfway 

up the right. 

 2 
79

1 Table 5-36. Summary of Test 35 

Test: 35 

Enclosure: 8 

Fuel Load: 42 control cables (#807), 1.8 m (6 ft) 

long, routed through vertical conduits on top of 

enclosure into cable tray 45 cm (18 in) above 

Ignition Source: 5.5 kW propane burner within 

the bundled cable and 1 L acetone pan fire 

60 cm (2 ft) below base of cable bundle 

Ventilation: Door closed 

Notes: The door popped open at 3 min, 20 s, due 

to the rapid increase in the HRR. The propane 

burner was turned off at 5 min, 30 s. At 

approximately 20 min the fire spread through 

the 10 conduits and burned the cables in the 

tray above. 

 2 
80

1 Table 5-37. Summary of Test 36 

Test: 36 

Enclosure: 2 

Fuel Load: Bundle of 10 control cables (#807) 

Ignition Source: 4 kW propane burner 

Ventilation: Door closed 

Notes: The fire did not spread beyond its point of 

origin near the base of the bundle. The burner 

was turned off at approximately 14 min. 

 2 
81

1 Table 5-38. Summary of Test 37 

Test: 37 

Enclosure: 2 

Fuel Load: Two bundles of 10 control cables 

(#807); one on each side of enclosure 

Ignition Source: Two pans of acetone, each 

containing 500 mL 

Ventilation: Door closed 

Notes: The fire spread upwards on the left side 

bundle, but did not spread upwards on the 

right. 

 2 
82

1 Table 5-39. Summary of Test 38 

Test: 38 

Enclosure: 2 

Fuel Load: Same cables from Test 37, with both 

left and right bundles gathered together in front 

of central partition with the ends terminating in 

the fuel pan 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The fire consumed all of the cables within 

the enclosure. Flames extended outside of the 

access openings, reaching a height 

approximately 30 cm (1 ft) above the top of the 

enclosure. The acetone was exhausted at 

21 min. 

 2 
83

1 Table 5-40. Summary of Test 39 

Test: 39 

Enclosure: 8 

Fuel Load: Similar to Test 35, using 21 instead of 

42 control cables (#807) 

Ignition Source: 5.5 kW propane burner within 

the bundled cable and 1 L acetone pan fire 

60 cm (2 ft) below base of cable bundle 

Ventilation: Door closed 

Notes: The fire spread upwards through the 10 

conduits in the top of the enclosure and 

consumed the cables in the tray directly above. 

 2 
84

1 Table 5-41. Summary of Test 40 

Test: 40 

Enclosure: 3 

Fuel Load: Various bundles of fine, coated relay 

wire in middle section of enclosure 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed; side panel open 

Notes: The wire and connectors were stuffed into 

the fuel pan. The fire did not spread beyond the 

pan. The wire coating appeared to blacken but 

did not generate any measurable heat. 

 2 
85

1 Table 5-42. Summary of Test 41 

Test: 41 

Enclosure: 3 

Fuel Load: 36 circuit boards, 28 cm by 23 cm 

(11 in by 9 in) 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The fire spread rapidly through the circuit 

boards, which were arranged in multiple racks 

above the pan. The clear plastic panel in the 

front door burned through at 11 min, and the 

fire grew rapidly afterwards. The coated relay 

wiring on the back side of the partition 

between the front and middle sections burned. 

 2 
86

1 Table 5-43. Summary of Test 42 

Test: 42 

Enclosure: 4 

Fuel Load: 10 cables (#813), 1.8 m (6 ft) long, 

routed up right side of enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed then opened at 10 min 

Notes: The fire spread upwards along the cables 

in the right side of the enclosure. The door was 

opened at approximately 10 min and it was left 

open for the remainder of the test. The burner 

was turned off at 17 min. 

 2 
87

1 Table 5-44. Summary of Test 43 

Test: 43 

Enclosure: 4 

Fuel Load: 10 cables (#813), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 500 mL acetone pan fire 

Ventilation: Door closed 

Notes: Even though the cables were immersed in 

the acetone, the fire did not spread upwards. 

The acetone was exhausted at approximately 

14 min. 

 2 
88

1 Table 5-45. Summary of Test 44 

Test: 44 

Enclosure: 5 

Fuel Load: 10 cables (#813), 1.8 m (6 ft) long, 

routed up right side of enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened at approximately 

14 min. The propane burner was turned off at 

approximately 19 min; turned back on at 

22 min; and finally off at 23 min. This was 

done to test the influence of the burner. 

 2 
89

1 Table 5-46. Summary of Test 45 

Test: 45 

Enclosure: 5 

Fuel Load: 10 cables (#813), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The pan fire was placed away from the 

cables. The acetone was exhausted by 20 min, 

at which time the door was opened. The 

propane burner was turned off and the fire 

sustained itself for a few minutes. 

 2 
90

1 Table 5-47. Summary of Test 46 

Test: 46 

Enclosure: 4 

Fuel Load: Two cable bundles; one on each side. 

Each bundle contained 10 cables (#807), 

stripped 20 cm (8 in) and overlapping near the 

top 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The pan was placed on the right side of the 

enclosure with the base of the cable bundle 

soaked in the liquid fuel. The fire spread 

upwards; across the top, and partially down the 

left side (see photo below right). The door was 

opened at approximately 30 min. 

 2 
91

1 Table 5-48. Summary of Test 47 

Test: 47 

Enclosure: 4 

Fuel Load: Two cable bundles; one on each side. 

Each bundle contained 5 cables (#807), 

stripped 20 cm (8 in) and overlapping near the 

top 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The fire behaved in a similar manner as 

Test 46. The door was opened at 25 min, 

which point the fire had spread to the top of the 

bundle on the right side and was burning the 

top of the left bundle. 

 2 
92

1 Table 5-49. Summary of Test 48 

Test: 48 

Enclosure: 4 

Fuel Load: Two cable bundles; one on each side. 

Each bundle contained 10 cables (#807), 

stripped 20 cm (8 in) and overlapping near the 

top 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door open 

Notes: This test was the same as Test 46, except 

with the door open. 

 2 
93

1 Table 5-50. Summary of Test 49 

Test: 49 

Enclosure: 4 

Fuel Load: Two cable bundles; one on each side. 

Each bundle contained 10 cables (#807), 

stripped 20 cm (8 in) and overlapping near the 

top 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: This test was a repeat of Test 46 because 

there was a concern that the calorimetry might 

have been faulty in Test 46. The door was 

opened at 32 min. The fire spread from the 

right side of the enclosure to the left side 

following overlapping cable bundles. The fire 

burned halfway down the left side. 

 2 
94

1 Table 5-51. Summary of Test 50 

Test: 50 

Enclosure: 4 

Fuel Load: Two cable bundles; one on each side. 

Each bundle contained 10 cables (#805) 

stripped 20 cm (8 in) near the top 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: Even though the cables were immersed in 

the liquid fuel, the fire did not spread upwards. 

The acetone was exhausted at 20 min. 

 2 
95

1 Table 5-52. Summary of Test 51 

Test: 51 

Enclosure: 4 

Fuel Load: The unburned left side bundle from 

Test 50 

Ignition Source: 5.5 kW propane burner and 1 L 

acetone pan fire 

Ventilation: Door open 

Notes: The fire spread halfway to the top of the 

enclosure. The propane burner was turned off 

at 10 min. 

 2 
96

1 Table 5-53. Summary of Test 52 

Test: 52 

Enclosure: 4 

Fuel Load: Two cable bundles; one on each side. 

Each bundle contained 70 insulated conductors 

stripped from Cable #807 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door open 

Notes: The fire spread upwards along the right 

side of the enclosure. The burner was turned 

off at 3 min. The second peak in HRR was due 

to the spread of the fire across a horizontal 

bundle of wire which ignited a fire on the left 

side. 

 2 
97

1 Table 5-54. Summary of Test 53 

Test: 53 

Enclosure: 4 

Fuel Load: Two cable bundles; one on each side. 

Each bundle contained 70 insulated conductors 

stripped from Cable #807 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: This test was a repeat of Test 52, except 

with the door closed. The fire spread rapidly 

along the right side of the enclosure. The 

burner was turned off after 5 min. The door 

was opened at 20 min and then closed. At 

30 min, a blow torch was used to ignite the 

unburned wire on the left side of the enclosure. 

The fire spread upwards with the door 

remaining open

 2 
98

1 Table 5-55. Summary of Test 54 

Test: 54 

Enclosure: 4 

Fuel Load: 2 bundles of surplus power cord 

(#841); one per side; 10 cords per bundle 

Ignition Source: 4 kW propane burner 

Ventilation: Door open 

Notes: The fire spread up the right side of the 

enclosure and then spread along the top of the 

enclosures where the two bundles overlapped. 

The burner was turned off at 10 min. 

 2 
99

1 Table 5-56. Summary of Test 55 

Test: 55 

Enclosure: 4 

Fuel Load: Same as Test 54 

Ignition Source: 4 kW propane burner and 

200 mL of acetone in a stainless steel cup 

10 cm in diameter 

Ventilation: Door closed 

Notes: The two ignition sources were positioned 

beneath the two bundles, but the fire only 

spread upwards on the side of the propane 

burner. The propane burner was turned off and 

the acetone exhausted at 15 min. The door was 

opened at 27 min. 

 2 
100

1 Table 5-57. Summary of Test 56 

Test: 56 

Enclosure: 5 

Fuel Load: 10 cable bundle (#844) routed up 

right side of enclosure 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 500 mL acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire was used for preheating only and burned for about 10 min, at 

which time the propane burner was turned on. 

The propane burner was turned off at 31 min. 

The door was opened several times and the 

cables were jostled with a crowbar (photo, 

lower right). The fire did not spread beyond 

the vicinity of the burner. 

 2 
101

1 Table 5-58. Summary of Test 57 

Test: 57 

Enclosure: 5 

Fuel Load: 10 cable bundle (#844) routed up left 

side of enclosure 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire was used for preheating only and burned for about 18 min. The 

propane burner was lit at the start of the test. 

The propane burner was turned off at 23 min. 

The fire did not spread beyond the vicinity of 

the propane burner. 

 2 
102

1 Table 5-59. Summary of Test 58 

Test: 58 

Enclosure: 5 

Fuel Load: 10 jacketed cables and 10 stripped 

cables (#844). The jacketed cable was left over 

from Tests 56 and 57. 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire burned for about 

17 min, at which point the propane burner was 

turned off. The fire spread to the top of the 

bundle, burning mainly the stripped cable. 

 2 
103

1 Table 5-60. Summary of Test 59 

Test: 59 

Enclosure: 5 

Fuel Load: 10 jacketed cables and 10 stripped 

cables (#844). The jacketed cable was left over 

from Tests 56 and 57. 

Ignition Source: 0.8 kW propane burner 

Ventilation: Door open 

Notes: The propane burner was increased to 2 kW 

after 10 min, 30 s, at which point the fire began 

to spread upwards, extending about 60 cm 

above the burner by 20 min. At 21 min, the 

cable bundle was loosened with a crowbar, and 

the fire spread to the top of the enclosure. The 

burner was turned off at 34 min. 

 2 
104

1 Table 5-61. Summary of Test 60 

Test: 60 

Enclosure: 1 

Fuel Load: 72 cables (#844) of various lengths, 

73 m (240 ft) total 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire was placed in the 

back of the enclosure, behind a steel partition. 

The acetone was exhausted at 22 min, 40 s. 

The propane burner was turned off at 26 min. 

 2 
105

1 Table 5-62. Summary of Test 61 

Test: 61 

Enclosure: 1 

Fuel Load: 60 cables (#807) of various lengths; 

63 m (208 ft) total 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed at the back of 

the enclosure behind a steel partition, and it 

burned for 20 min. At 21 min, the cables were 

jostled with a crowbar. At 25 min, the door 

was opened. The propane burner was turned 

off at 28 min. The fire did not spread beyond 

the vicinity of the propane burner. 

 2 
106

1 Table 5-63. Summary of Test 62 

Test: 62 

Enclosure: 1 

Fuel Load: Same as Test 61 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed at the back of 

the enclosure behind a steel partition, and it 

burned for 20 min. At 30 min, the door was 

opened. The propane burner was turned off at 

31 min. The fire did not spread beyond the 

vicinity of the propane burner. 

No picture available 

 2 
107

1 Table 5-64. Summary of Test 63 

Test: 63 

Enclosure: 1 

Fuel Load: Same as Test 61 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed at the back of 

the enclosure behind a steel partition, and it 

burned for 20 min. The propane burner was 

turned off at 26 min. The door was opened at 

46 min and it was observed that all the cables 

had burned. 

 2 
108

1 Table 5-65. Summary of Test 64 

Test: 64 

Enclosure: 8 

Fuel Load: 21 cables (#813), each 1.8 m (6 ft) 

long, routed through channels in top of 

enclosure and onto a cable tray 30 cm (1 ft) 

above 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 500 mL acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed at the back of 

the enclosure such that the fire did not directly 

impinge on cables. The acetone was exhausted 

at 16 min, at which time the door was opened. 

The propane burner was turned off at 17 min. 

The fire did not spread beyond the propane 

b

 2 
109

1 Table 5-66. Summary of Test 65 

Test: 65 

Enclosure: 8 

Fuel Load: Same as Test 64 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 500 mL acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed at the back of 

the enclosure and the fire did not directly 

impinge on cables. The acetone was exhausted 

at 16 min. The propane burner was turned off 

at 20 min. The fire did not spread beyond 

igniter. 

 2 
110

1 Table 5-67. Summary of Test 66 

Test: 66 

Enclosure: 4 

Fuel Load: 20 cable bundle (#844), 1.8 m (6 ft) 

long, routed up right side of enclosure 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed at the rear of 

the enclosure, out of direct contact with the 

cables. The acetone was exhausted at 17 min, 

and the propane burner was turned off at 

18 min. At 23 min, the door was opened and 

the cables were jostled with a crowbar. The 

fire then spread to within 30 cm (1 ft) of top. 

 2 
111

1 Table 5-68. Summary of Test 67 

Test: 67 

Enclosure: 4 

Fuel Load: 20 cable bundle (#844); 1.8 m (6 ft) 

long, routed up left side of enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The propane burner was turned off at 

9 min. At 13 min, the door was opened and the 

cables were jostled with a crowbar. The fire 

then spread to within 30 cm (1 ft) of the top of 

the bundle. 

 2 
112

1 Table 5-69. Summary of Test 68 

Test: 68 

Enclosure: 1 

Fuel Load: 420 insulated conductors extracted 

from Cable #807; 540 m (1770 ft) total 

Ignition Source: 0.8 kW propane burner 

Ventilation: Door closed 

Notes: The burner was turned off at 4 min, 30 s. 

The door was opened at 15 min and it was 

observed that all the wire had burned. 

 2 
113

1 Table 5-70. Summary of Test 69 

Test: 69 

Enclosure: 8 

Fuel Load: 21 cables, 1.8 m (6 ft) long, routed 

through conduits in top of enclosure onto a 

cable tray 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 500 mL acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was located in the rear of 

the enclosure and did not directly impinge on 

the cables. The acetone was exhausted in 

16 min. The door was opened at 17 min and 

the propane was turned off at 18 min. The fire 

did not spread beyond vicinity of igniter. 

 2 
114

1 Table 5-71. Summary of Test 70 

Test: 70 

Enclosure: 1 

Fuel Load: 420 insulated conductors extracted 

from Cable #834; 540 m (1770 ft) total 

Ignition Source: 1.6 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened at 5 min, 30 s and 

left open. The propane was turned off at this 

time. The fire did not spread beyond the 

vicinity of the igniter. 

 2 
115

1 Table 5-72. Summary of Test 71 

Test: 71 

Enclosure: 1 

Fuel Load: Same as Test 70 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed in the rear of 

the enclosure, behind a steel partition. The 

acetone was exhausted at 18 min. The propane 

was turned off at 18 min. The door was opened 

at 23 min, when it was observed that the cables 

were completely burned. 

 2 
116

1 Table 5-73. Summary of Test 72 

Test: 72 

Enclosure: 4 

Fuel Load: 10 cable bundle (#813), 1.8 m (6 ft) 

long 

Ignition Source: 0.8 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened at 12 min and the 

cables were jostled with a crowbar. The 

propane was turned off at 16 min. The fire did 

not spread beyond the vicinity of the burner. 

The HRR measurement is flawed – there was 

nothing observed that indicates a jump of 

10 kW. It is likely that the HRR was never 

greater than 5 kW. 

 2 
117

1 Table 5-74. Summary of Test 73 

Test: 73 

Enclosure: 4 

Fuel Load: 10 cable bundle (#813) 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the cables. The acetone was 

exhausted at 19 min, at which time the door 

was opened and the cables were jostled with a 

crowbar. The propane burner was turned off at 

21 min. The fire spread approximately 45 cm 

(18 in) above the burner. 

 2 
118

1 Table 5-75. Summary of Test 74 

Test: 74 

Enclosure: 5 

Fuel Load: 10 cable bundle (#809) 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the cables. The acetone was 

exhausted at 22 min, at which time the door 

was open. The propane burner was turned off 

at 22 min. The fire spread approximately 

60 cm (2 ft) above the burner. 

 2 
119

1 Table 5-76. Summary of Test 75 

Test: 75 

Enclosure: 4 

Fuel Load: 10 cable bundle (#813) 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the cables. The acetone was 

exhausted at 16 min, 30 s. The door was open 

at 18 min and left open. The propane was 

turned off at 22 min, 30 s. The fire spread 

0.9 m (3 ft) above the burner. 

 2 
120

1 Table 5-77. Summary of Test 76 

Test: 76 

Enclosure: 5 

Fuel Load: 10 cable bundle (#813) 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed directly under 

the cable bundle so that the ends of the cables 

were immersed in the liquid. The door was 

opened at 8 min, 30 s and then closed 30 s 

later. The door was opened again at 17 min and 

the cables were jostled with a crowbar. The 

acetone was exhausted at 19 min. The fire 

never spread beyond the vicinity of the acetone 

flames. 

 2 
121

1 Table 5-78. Summary of Test 77 

Test: 77 

Enclosure: 5 

Fuel Load: 10 cable bundle (#809) 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the cables. The door was opened 

at 16 min, 30 s, and was left open until 28 min. 

The propane burner was turned off at 18 min 

and the acetone was exhausted at 18 min, 30 s. 

Over the next 20 min, the fire spread slowly 

upwards, with occasional door openings and 

jostling with a crowbar. 

 2 
122

1 Table 5-79. Summary of Test 78 

Test: 78 

Enclosure: 5 

Fuel Load: 10 cable bundle (#809) 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The fire spread steadily to the top of the 

bundle. The burner was turned off at 15 min. 

 2 
123

1 Table 5-80. Summary of Test 79 

Test: 79 

Enclosure: 4 

Fuel Load: 310 insulated wires stripped from 

Cable #834, arranged in 4 loose bundles 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The propane burner was turned off at 

6 min, 40 s. The door was opened at 12 min. 

The propane burner was relit at 14 min and the 

door was left open. The wires were jostled at 

19 min with a crowbar, after which the fire 

spread to the top of the bundle. The propane 

burner was turned off at 27 min. 

 2 
124

1 Table 5-81. Summary of Test 80 

Test: 80 

Enclosure: 4 

Fuel Load: 70 insulated wires (#834), arranged in 

2 loose bundles along right side of enclosure 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the wires. The propane burner 

was initially set to 1 kW and then increased to 

5.5 kW at 17 min, 30 s. The acetone was 

exhausted at 18 min, and the propane burner 

was turned off at 21 min. The fire spread to the 

top of the bundles. 

 2 
125

1 Table 5-82. Summary of Test 81 

Test: 81 

Enclosure: 5 

Fuel Load: 10 cable bundle (#813) 

Ignition Source: 5.5 kW propane burner and 1 L 

acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire was placed near the 

base of the cable bundle. The acetone was 

exhausted at 18 min. The door was opened at 

19 min and the propane burner was turned off 

at 19 min, 30 s. The fire spread approximately 

30 cm (1 ft) above burner. 

 2 
126

1 Table 5-83. Summary of Test 82 

Test: 82 

Enclosure: 1 

Fuel Load: 72 cables (#844) of various lengths; 

73 m (240 ft) total 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed in the rear of 

the compartment behind a steel partition. The 

acetone was exhausted at 20 min, at which 

time the propane burner was increased from 

0.8 kW to 1.6 kW. The door was opened at 

22 min and left open. The propane burner was 

turned off at 32 min. 

 2 
127

1 Table 5-84. Summary of Test 83 

Test: 83 

Enclosure: 1 

Fuel Load: 420 loose, insulated wires of various 

lengths, stripped from Cable #807. 540 m 

(1768 ft) total 

Ignition Source: 0.8 kW propane burner 

Ventilation: Door open 

Notes: This experiment was similar to Test 68, 

but with the door open. The fire spread rapidly 

upwards after a roughly 10 min warm-up 

period. 

 2 
128

1 Table 5-85. Summary of Test 84 

Test: 84 

Enclosure: 7 

Fuel Load: 36 cable bundle (#818) 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door open 

Notes: The acetone pan fire did not directly 

impinge on the cables. The burner was placed 

within a coiled bundle of cable inside of a 

small box whose front panel had been 

removed. The fire eventually spread upwards 

through access holes in the top of the box. The 

fire reached the top of the enclosure but did not 

spread horizontally. 

 2 
129

1 Table 5-86. Summary of Test 85 

Test: 85 

Enclosure: 7 

Fuel Load: 10 cables (#817) routed up the left 

side of the enclosure, 2.4 m (8 ft) long 

Ignition Source: 0.8 kW propane burner 

Ventilation: Door closed 

Notes: The cables originated in a small box whose 

side panel had been removed. The propane 

burner was tied to the cables inside of the 

enclosure. The burner was increased to 1.6 kW 

at 10 min, 30 s. The burner was turned off at 

15 min. 

 2 
130

1 Table 5-87. Summary of Test 86 

Test: 86 

Enclosure: 7 

Fuel Load: Same as Test 85 

Ignition Source: 500 mL acetone pan fire 

Ventilation: Door open 

Notes: The acetone was poured into a stainless 

steel beaker with a 10 cm (4 in) opening. The 

cables inside the small box burned, but the fire 

did not spread through the conduits at the top. 

 2 
131

1 Table 5-88. Summary of Test 87 

Test: 87 

Enclosure: 7 

Fuel Load: 36 cables (#818), 2.4 m (8 ft) long, 

routed up left right side of enclosure 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the cables. The propane burner 

was turned off at 9 min. The door was opened 

at 21 min, 20 s, at which time the fire was out. 

The cable burned 1.2 m (4 ft) above the burner. 

 2 
132

1 Table 5-89. Summary of Test 88 

Test: 88 

Enclosure: 7 

Fuel Load: 56 insulated conductors extracted 

from Cable #807, 2.4 m (8 ft) long, routed 

from enclosed box up left side of enclosure 

Ignition Source: 0.8 kW propane burner 

Ventilation: Door closed 

Notes: The propane burner was turned off at 

5 min. The fire spread upwards and 

horizontally over all of the wire except a small 

amount hanging down at the end. 

 2 
133

1 Table 5-90. Summary of Test 89 

Test: 89 

Enclosure: 7 

Fuel Load: Same set-up as Test 88, except the 

wires were left tightly bundled in groups of 7 

Ignition Source: 0.8 kW propane burner 

Ventilation: Door closed 

Notes: The burner was turned off at 11 min, 30 s. 

The fire spread more slowly than Test 88, and 

it consumed only the vertical portion of the 

bundles. 

 2 
134

1 Table 5-91. Summary of Test 90 

Test: 90 

Enclosure: 7 

Fuel Load: 10 cables (#809) routed up the left 

side of the enclosure, 2.4 m (8 ft) long 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not impinge upon 

the cables. The propane burner was increased 

to 1.6 kW at 14 min, 40 s. The fire spread 

slowly upwards, but only burned the vertical 

portion of the bundle, approximately 1.2 m 

(4 ft) above the burner. 

 2 
135

1 Table 5-92. Summary of Test 91 

Test: 91 

Enclosure: 7 

Fuel Load: 5.9 kg of SIS wire hung along top and 

right side of enclosure 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the wire. The acetone was 

exhausted and the burner turned off at 20 min. 

There was little damage to the wire. 

 2 
136

1 Table 5-93. Summary of Test 92 

Test: 92 

Enclosure: 7 

Fuel Load: Same as Test 91 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The test set-up was the same as Test 92, 

only with the larger propane burner. The fire 

spread vertically, but did not spread 

horizontally. The acetone was exhausted at 

20 min and the propane burner was turned off 

at 22 min. 

 2 
137

1 Table 5-94. Summary of Test 93 

Test: 93 

Enclosure: 7 

Fuel Load: 72 cables (#833), arranged in 4 

bundles, 2.4 m (8 ft) long, originating in open 

box on right side of enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The propane burner was turned off at 

8 min. The door was opened at 14 min, 30 s, 

and left open after that time. The fire spread 

vertically but not horizontally. A few flames 

were seen extending just beyond the louvers at 

the top of the enclosure. 

 2 
138

1 Table 5-95. Summary of Test 94 

Test: 94 

Enclosure: 7 

Fuel Load: 24 cables (#814) in 4 bundles of 6, 

2.4 m (8 ft) long, routed up the left side and 

across brackets running along the top 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened at 20 min and the 

propane burner was turned off at 21 min. The 

fire spread vertically and approximately 30 cm 

(1 ft) horizontally. 

 2 
139

1 Table 5-96. Summary of Test 95 

Test: 95 

Enclosure: 7 

Fuel Load: 24 cables (#844) in 4 bundles of 6, 

2.4 m (8 ft) long, routed up the left side and 

across brackets running along the top 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The burner was turned off at 16 min. The 

door was opened at 22 min. The fire spread 

vertically and approximately 30 cm (1 ft) 

horizontally. 

 2 
140

1 Table 5-97. Summary of Test 96 

Test: 96 

Enclosure: 6 

Fuel Load: 24 cables (#844), 2.4 m (8 ft) long, 

routed up left side and across brackets running 

along the top 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not impinge upon 

the cables. The propane burner was turned off 

at 9 min and the acetone was exhausted at 

19 min, 30 s, when the door was opened. The 

fire spread vertically but not horizontally. 

 2 
141

1 Table 5-98. Summary of Test 97 

Test: 97 

Enclosure: 6 

Fuel Load: 108 cables (#833), arranged in 6 

bundles, 2.4 m (8 ft) long, originating in a 

junction box in the center of the enclosure, 

running vertically, then horizontally 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened at 16 min, 30 s, and 

the cables were jostled with a crow bar, 

leading to a rapid increase in the HRR and 

spread. The propane burner was turned off at 

21 min, 45 s. The door was opened at 38 min 

and left open. The fire spread both vertically 

and horizontally. 

 2 
142

1 Table 5-99. Summary of Test 98 

Test: 98 

Enclosure: 6 

Fuel Load: 21.9 kg of SIS wire (#831) spread 

over brackets running along the top of 

enclosure 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: A bundle of the wire was placed directly in 

the fuel pan. The acetone was exhausted after 

20 min. The doors were opened at 25 min and 

left open after that time. Most of the wire 

insulation was consumed. 

 2 
143

1 Table 5-100. Summary of Test 99 

Test: 99 

Enclosure: 6 

Fuel Load: 20 coaxial cables (#832), 2.4 m (8 ft) 

long, routed through a narrow, open-topped 

steel duct 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door open 

Notes: This experiment was to determine if a fire 

could propagate from the box at the left of the 

first photo below along the horizontal channel 

to the right. The cables were jostled 

periodically during the test, but the fire did not 

spread beyond the vicinity of the burner, which 

was turned off at 16 min, 20 s. 

 2 
144

1 Table 5-101. Summary of Test 100 

Test: 100 

Enclosure: 6 

Fuel Load: 80 cables (#845), arranged in 8 

bundles of 10, 2.4 m (8 ft) long, running along 

the top of the enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened periodically to check 

on progress. The propane burner was turned 

off at 32 min. The cables were jostled at 

35 min and at 43 min with a crowbar. The fire 

spread approximately 1 m (3 ft) along the top. 

 2 
145

1 Table 5-102. Summary of Test 101 

Test: 101 

Enclosure: 6 

Fuel Load: The unburned right side portion of the 

cables from Test 100, approximately 1.2 m 

(4 ft) of horizontal cable extending downward 

into fuel pan 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The fire spread rapidly upwards and then 

horizontally. The right hand photo below 

shows the fire spreading in the horizontal 

direction when looking through an opening on 

the front side of the enclosure. The door was 

opened at 19 min and left open. The acetone 

was exhausted at 22 min. 

 2 
146

1 Table 5-103. Summary of Test 102 

Test: 102 

Enclosure: 6 

Fuel Load: 60 insulated wires extracted from 

Cable #834, routed through a horizontal duct 

with 20 cm (8 in) square cross section and 

5 cm (2 in) openings every 30 cm (1 ft) 

Ignition Source: 500 mL acetone pan fire 

Ventilation: Door open 

Notes: The acetone pan was placed 5 cm (2 in) 

below an opening in the bottom of the duct 

(below left). The acetone was exhausted by 

10 min, and the fire continued to spread slowly 

inside the duct. The fire spread to the end of 

the duct (below right) but did not burn the wire 

outside the duct. 

 2 
147

1 Table 5-104. Summary of Test 103 

Test: 103 

Enclosure: 6 

Fuel Load: 56 insulated conductors extracted 

from Cable #807, tightly bound in bundles of 

7, 2.4 m (8 ft) long, routed along top of 

enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The propane burner was turned off at 

20 min, 30 s. The doors were opened at 

37 min. The fire spread approximately 2 m 

(6 ft) from left to right along the top of the 

enclosure. The photo at right shows the 

furthest extent of the fire. 

 2 
148

1 Table 5-105. Summary of Test 104 

Test: 104 

Enclosure: 1 

Fuel Load: 420 insulated conductors extracted 

from Cable #807, tightly bound in groups of 7, 

various lengths, 540 m (1768 ft) total 

Ignition Source: 0.8 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door open 

Notes: The acetone pan fire was placed in the 

back of the enclosure, behind a steel partition. 

The burner was increased to 1.6 kW at 17 min. 

The acetone was exhausted at 19 min, but the 

fire had not spread. The cables were jostled at 

24 min with a crowbar, after which the fire 

grew and spread. 

 2 
149

1 Table 5-106. Summary of Test 105 

Test: 105 

Enclosure: 1 

Fuel Load: A variety of cable remnants 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The burner was positioned among the 

cables routed up the right side of the enclosure. 

The fire spread to the top of the enclosure in 

6 min. The burner was turned off at 7 min, 

30 s. The door was opened at 9 min. The fire 

did not spread to the left side of the enclosure. 

 2 
150

1 Table 5-107. Summary of Test 106 

Test: 106 

Enclosure: 1 

Fuel Load: Unburned portion of Test 105 along 

left side of enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The door was opened at 9 min and left 

open. The propane burner was turned off at 

12 min. The cables were jostled with a crowbar 

at 14 min (below right). The fire spread to the 

top of the left side of the enclosure. 

 2 
151

1 Table 5-108. Summary of Test 107 

Test: 107 

Enclosure: 1 

Fuel Load: 280 insulated conductors (#834), 

arranged in 4 bundles, 1.8 m (6 ft) long, 

hanging in front of steel partition 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door open 

Notes: The acetone pan was placed in the back of 

the enclosure behind a steel partition. The 

propane burner was turned off at 10 min. The 

fire consumed the insulation of the two left 

bundles completely, and burned some of the 

right two bundles. 

 2 
152

1 Table 5-109. Summary of Test 108 

Test: 108 

Enclosure: 1 

Fuel Load: Unburned wire from Test 107 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed 

Notes: The propane burner was turned off at 

6 min. The door was opened at 11 min. All of 

the remaining cable insulation from Test 107 

was consumed. 

 2 
153

1 Table 5-110. Summary of Test 109 

Test: 109 

Enclosure: 8 

Fuel Load: 30 cables (#814), 2.4 m (8 ft) long, 

routed through 10 conduits in top of enclosure 

into a tray 45 cm (18 in) above 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan was placed in the back of 

the enclosure, away from the cables. The 

propane burner was turned off at 9 min. The 

door was opened at 20 min. The fire consumed 

the cable within the enclosure, and scorched 

approximately 15 cm (6 in) of cable outside. 

 2 
154

1 Table 5-111. Summary of Test 110 

Test: 110 

Enclosure: 4 

Fuel Load: 10 cables (#844), 1.8 m (6 ft) long, 

routed up right side of enclosure 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed 

Notes: The acetone pan fire did not directly 

impinge upon the cables. The propane burner 

was turned off at 8 min. The door was opened 

at 13 min, 30 s. The acetone was exhausted at 

17 min. The cables were jostled at 20 min and 

at 24 min, at which times the fire spread 

upward, gradually reaching within 30 cm (1 ft) 

of the top. 

 2 
155

1 Table 5-112. Summary of Test 111 

Test: 111 

Enclosure: 5 

Fuel Load: 2 bundles of 20 cables each (#845), 

one on each side of enclosure, 2.4 m (8 ft) long 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed for 20 min, then open 

Notes: The acetone pan was placed on a ledge at 

the mid-height of the enclosure. It did not 

directly impinge upon the cables. The propane 

burner was positioned at intersection of two 

bundles at base of enclosure. It was turned off 

at 17 min. The fire spread rapidly on both sides 

following the door opening. All of the cable 

insulation was consumed. 

 2 
156

1 Table 5-113. Summary of Test 112 

Test: 112 

Enclosure: 4 

Fuel Load: 10 cables (#844), 1.8 m (6 ft) long, 

routed up left side of enclosure 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door open 

Notes: The propane burner was turned off at 

10 min, 30 s. The fire sustained itself, but 

gradually weakened and stopped spreading 

1.2 m (4 ft) above the burner. The cables were 

jostled with a crowbar at 19 min and the fire 

spread approximately 30 cm (1 ft) further. 

2 
157

1 5.2 General Observations 

2 The test report documenting the full-scale electrical enclosure experiments conducted by Sandia 

3 National Laboratories (Chavez, 1987) has five general conclusions. Briefly: 

4 1. “Cabinet fires can be ignited and propagate in either unqualified or qualified cable... 

5 However, the qualified cable is much more difficult to ignite and propagate.” 

6 2. “It is possible to have a rapidly developing cabinet fire in either type of cable... 

7 Although, fires with qualified cable do not become very large.” 

8 3. “Ignition, development rate, and spread of a cabinet fire are dependent on ‘critical’ 

9 ignition sources, in situ fuel type, geometries, cabinet style, and ventilation... However, it 

10 was found that with unqualified cable, the range of values causing ignition and fire 

11 spread was much wider than with qualified cable.” 

12 4. “For the enclosure conditions tested, the thermal environment ... was not severe enough 

13 to cause auto-ignition of materials.... Furthermore, it appears that a fire will not spread 

14 from the burning cabinet to adjacent cabinets.” 

15 5. “For the enclosure conditions tested, dense smoke accumulation ... became a problem 

16 within minutes after ignition, for all fuel types and cabinet configurations.” 

17 These same general conclusions apply to the enclosure fire experiments described above. This is 

18 not surprising given that the enclosure geometries and cable construction have not significantly 

19 changed since the early 1980s. 

20 5.2.1 Ignition 

21 There were three types of ignition sources used in the experiments, although one of these, the 

22 cartridge heater, proved unreliable and was only used for one experiment. The other two, a 

23 propane line burner or an acetone pan fire, were used either separately or together depending on 

24 the type of cables in the enclosure. A propane line burner was used in the VTT experiments 

25 (Mangs), and a bucket of acetone was used in some of the Sandia experiments (Chavez, 1987). 

26 In general, the propane burner with a roughly 1 kW flame could ignite loosely bound single 

27 conductor wiring insulated with thermoplastic materials like polyethylene. Stronger propane 

28 flames, 2 kW to 8 kW, were required to ignite unqualified jacketed cable or loosely bundled 

29 single conductor thermoset wiring. Acetone pan fires, with heat release rates on the order of 

30 20 kW, were required to ignite jacketed thermoset cable. Chavez (1987) reports similar 

31 observations. 

32 Past experimental programs at Sandia, VTT, and IRSN focused on generating relatively large 

33 fires to better understand the fire dynamics. However, in the experiments described above, the 

34 various test parameters (ignition source, fuel load, ventilation, etc.) were varied randomly so that 

35 the resulting distribution of fire sizes would not be skewed towards larger fires. 
158

1 5.2.2 Fire Spread 

2 Regardless of ignition source, the cables in each experiment were heated sufficiently to ignite. 

3 However, in many cases the fire did not spread beyond the point of origin, and the fire generally 

4 self-extinguished when the propane igniter was removed. In some cases the fire spread upwards 

5 beyond the flame height of the igniter, but stopped because it could not support itself without the 

6 assist of the heat from the igniter. In cases where the fire spread to the top of the enclosure, it 

7 typically did not ignite cables on the opposite side of the enclosure. Chavez (1987) notes the 

8 same phenomenon when he says that the fires were not severe enough to cause auto-ignition. In a 

9 few instances, the fire spread to the top of the enclosure and burned the top end of some of the 

10 cables from the opposite side, but in general the fire spread was vertical in a vertical enclosure. 

11 In bench board enclosures, the fire sometimes spread horizontally near the top of the enclosure. 

12 Two vertical enclosures (#4 and #5) were connected together, and there was a fairly wide 

13 opening connecting the two. In none of the experiments did the fire spread from one enclosure to 

14 the other, even though many of these experiments were deliberately set up to test whether this 

15 was possible. 

16 5.2.3 Ventilation 

17 The most obvious way of controlling the ventilation in the enclosures was to either open or close 

18 the door(s). In addition, some enclosures had a removable steel plate covering the bottom, and 

19 some had cooling fans mounted at the top. These fans blew air downwards, and were not 

20 operated during the experiments because the smoke from the fire would have been blown outside 

21 of the exhaust product collection hood. The removable plates did not seem to have much of an 

22 impact on the fire behavior, probably because the variation in the fire dynamics test to test was 

23 such that the effect of the plate could not be distinguished. 

24 5.2.4 Peak Heat Release Rate 

25 The peak HRR is calculated by subtracting off the estimated HRR of the ignition and preheating 

26 sources from the total measured HRR. Of the 112 experiments, the peak HRR varied from 

27 0.3 kW to 576 kW. The mean was 43 kW; the median was 19 kW. Eleven of the 112 fires had a 

28 peak HRR greater than 100 kW. Six had a peak HRR between 100 kW and 200 kW. Four had a 

29 peak HRR between 200 kW and 300 kW. The highest peak HRR was nearly 600 kW in Test 83. 

30 This particular experiment had all the elements that lead to a high HRR: a relatively large fuel 

31 load of relatively thin, unqualified, thermoplastic wiring loosely hung in an open enclosure. This 

32 essentially produced a wall of flame that quickly consumed virtually all of the combustibles. The 

33 experiments with peak HRRs between 100 kW and 300 kW all had relatively large amounts of 

34 loose, thin wiring, but some were performed with the doors closed, and some contained 

35 thermoset rather than thermoplastic insulation. 

36 5.2.5 Growth Time 

37 The mean time to peak was 16 min; the median was 13 min. All but 4 of the 112 fires reached 

38 their peak in 40 min or less. The longest time to peak was nearly 80 min, where a closed cabinet 

39 with a relatively large load of qualified cable was ignited with a small burner and smoldered for 
159

1 over an hour, like an underground coal or tire fire. Most of the other cases with relatively long 

2 times to peak had negligibly small heat release rates. Others were cases where the door was 

3 opened at some arbitrary time, leading to a larger fire. Most of the fires with significant heat 

4 release rates reached the peak in 10 to 15 minutes. This is consistent with current guidance in 

5 NUREG/CR-6850. 

 6 

161

1 6 CONCLUSIONS AND FUTURE WORK 

2 During the HELEN-Fire (Heat Release Rate in Electrical Enclosures) program, 112 full-scale 

3 experiments were conducted in which the heat release rate of fires in a variety of electrical 

4 enclosures was measured using oxygen consumption calorimetry. This data is to be used to 

5 provide the energy source term for fire models used to assess the potential consequences of fires 

6 within nuclear power plants. 

7 Future work in this program is to develop simplified models of fires within electrical cabinets. 

8 The 112 experiments in the HELEN-Fire test program can be used to develop statistical 

9 distributions of heat release rates that can be input into fire models. However, simplified fire 

10 models that rely on empirical correlations of plume and ceiling jet temperatures do not contain 

11 the physical mechanisms to account for the geometry of the electrical enclosure itself. In other 

12 words, even if the heat release rate of the fire is specified, there is no physical mechanism within 

13 the model to account for the fact that a significant fraction of the fire’s heat is trapped within the 

14 enclosure and not transported upwards to damage ceiling targets. In the HELEN-Fire 

15 experiments, the overall heat release rate of the fire was inferred from the measured rate of 

16 oxygen consumption, but it was not possible to measure the fraction of the energy that was 

17 absorbed by the steel walls of the enclosure and the fraction that was transported into the exhaust 

18 duct. 

19 Computational fluid dynamics (CFD) models can account for the geometry of the enclosure, but 

20 even these models require validation. For this reason, experiments are being planned in which a 

21 simple gas burner is to be placed in various locations within a few different kinds of electrical 

22 enclosures and surface and gas temperatures are to be measured on and above the enclosure. The 

23 results of the experiments will be used to develop guidance for applying the HELEN-Fire heat 

24 release rates to simplified models and to validate CFD models used to assess enclosure 

25 geometries not tested in HELEN-Fire. 

 26 

163 

1 7 REFERENCES 

2 Chavez, J.M. (1987). An Experimental Investigation of Internally Ignited Fires in Nuclear Power 

3 Plant Control Enclosures: Part I: Enclosure Effects Tests, NUREG/CR-4527/V1, US Nuclear 

4 Regulatory Commission, Washington, DC. 

5 Chavez, J.M. and S.P. Nowlen (1988). An Experimental Investigation of Internally Ignited Fires 

6 in Nuclear Power Plant Control Enclosures: Part II: Room Effects Tests, NUREG/CR-4527/V2, 

7 US Nuclear Regulatory Commission, Washington, DC. 

8 Coutin, M., W. Plumecocq, S. Melis and L. Audouin (2012). “Energy balance in a confined fire 

9 compartment to assess the heat release rate of an electrical enclosure fire,” Fire Safety Journal, 

10 52: 34-45.

11 Wachowiak, R. and A. Lindeman (2013). The Updated Fire Events Database: Description of 

12 Content and Fire Event Classification Guidance, EPRI Report 1025284, Electric Power 

13 Research Institute, Palo Alto, CA. 

14 Mangs, J., J. and O. Keski-Rahkonen (1994) “Full scale fire experiments on electronic 

15 enclosures,” VTT Publications 186, VTT Technical Research Centre of Finland, Espoo, Finland. 

16 Mangs, J., J. and O. Keski-Rahkonen (1996) “Full scale fire experiments on electronic 

17 enclosures II,” VTT Publications 269, VTT Technical Research Centre of Finland, Espoo, 

18 Finland. 

19 Mangs, J., J. Paananen and O. Keski-Rahkonen (2003) “Calorimetric fire experiments on 

20 electronic enclosures,” Fire Safety Journal, 38: 165-186. 

21 Mangs, J., J. (2004) “On the fire dynamics of vehicles and electrical equipment,” VTT 

22 Publications 521, VTT Technical Research Centre of Finland, Espoo, Finland. 

23 McGrattan, K., A. Lock, N. Marsh, M. Nyden, S. Bareham, M. Price (2012) Cable Heat Release, 

24 Ignition, and Spread in Tray Installations During Fire (CHRISTIFIRE), NUREG/CR-7010, 

25 Vol. 1, National Institute of Standards and Technology, Gaithersburg, Maryland. 

26 Nowlen, S.P. (1989) A Summary of Nuclear Power Plant Fire Safety Research at Sandia 

27 National Laboratories, 1975-1987, NUREG/CR-5384, SAND89-1359, Sandia National 

28 Laboratories, Albuquerque, New Mexico. 

29 Nowlen, S.P. and Wyant, F.J. (2007a). CAROLFIRE Test Report Volume 1: General Test 

30 Descriptions and the Analysis of Circuit Response Data, NUREG/CR-6931/V1, US Nuclear 

31 Regulatory Commission, Washington, DC.

32 Nowlen, S.P. and Wyant, F.J. (2007b). CAROLFIRE Test Report Volume 2: Cable Fire Response 

33 Data for Fire Model Improvement, NUREG/CR-6931/V2, US Nuclear Regulatory Commission, 

34 Washington, DC. 

35 Plumecocq, W., M. Coutin, S. Melis and L. Rigollet (2011). Characterization of closed-doors 
164 

1 electrical enclosure fires in compartments,” Fire Safety Journal, 46: 243-253.

2 SFPE (2008) SFPE Handbook of Fire Protection Engineering, Fourth Edition, National Fire 

3 Protection Association, Quincy, Massachusetts. 

4 U.S. NRC and EPRI (2004). Fire PRA Methodology for Nuclear Power Facilities, NUREG/CR5 6850, U.S. Nuclear Regulatory Commission, Washington, DC. 

 6 
A-1 

1 APPENDIX A TEMPERATURE DATA 

2 Near-ceiling temperature measurements for each experiment are listed on the following pages. 

3 Shown is the measurement nearest to the ceiling of the enclosure, typically about 15 cm (6 in) 

4 below and centered from left to right. 

5 

6 Figure A-1. Enclosure temperatures, Tests 1-4. 

7 
A-2 

1 Figure A-2. Enclosure temperatures, Tests 5-10. 
A-3 

1 Figure A-3. Enclosure temperatures, Tests 11-16. 
A-4 

1 Figure A-4. Enclosure temperatures, Tests 17-22. 
A-5 

1 Figure A-5. Enclosure temperatures, Tests 23-28. 
A-6 

1 Figure A-6. Enclosure temperatures, Tests 29-34. 
A-7 

1 Figure A-7. Enclosure temperatures, Tests 35-40. 
A-8 

Enclosure temperatures were not measured for 

Test CBD-46. 

1 Figure A-8. Enclosure temperatures, Tests 41-46. 
A-9 

1 Figure A-9. Enclosure temperatures, Tests 47-52. 
A-10 

1 Figure A-10. Enclosure temperatures, Tests 53-58. 
A-11 

1 Figure A-11. Enclosure temperatures, Tests 59-64. 
A-12 

1 Figure A-12. Enclosure temperatures, Tests 65-70. 
A-13 

1 Figure A-13. Enclosure temperatures, Tests 71-76. 
A-14 

1 Figure A-14. Enclosure temperatures, Tests 77-82. 
A-15 

1 Figure A-15. Enclosure temperatures, Tests 83-88. 
A-16 

1 Figure A-16. Enclosure temperatures, Tests 89-94. 
A-17 

1 Figure A-17. Enclosure temperatures, Tests 95-100. 
A-18 

1 Figure A-18. Enclosure temperatures, Tests 101-106. 
A-19 

1 Figure A-19. Enclosure temperatures, Tests 107-112. 

2 







NUREG/CR

-7197

Draft

Heat Release Rates of Electrical Enclosure Fires (HELEN-FIRE)