Heat Release Rates of 

Electrical Enclosure 

Fires (HELEN-FIRE)

Final Report

Office of Nuclear Regulatory Research

NUREG/CR-7197

Heat Release Rates of

Electrical Enclosure

Fires (HELEN-FIRE)

Final Report

Manuscript Completed: February 2015

Date Published: April 2016

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

 

iii 

ABSTRACT 

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

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

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

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

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

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

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 ..................................................................................... 36

4.2.3 Liquid Fuel Pan Fires ...................................................................................... 38

4.2.4 Combustible Loading ...................................................................................... 38

5 FULL-SCALE MEASUREMENTS ....................................................................................... 41

5.1 Description .................................................................................................................. 41

5.2 Summary of Individual Experiments ........................................................................... 54

5.3 General Observations ............................................................................................... 167

5.3.1 Ignition .......................................................................................................... 167

5.3.2 Fire Spread ................................................................................................... 167

5.3.3 Ventilation..................................................................................................... 168

5.3.4 Peak Heat Release Rate .............................................................................. 168 
vi

6 CONCLUSION AND FUTURE WORK .............................................................................. 169

7 REFERENCES .................................................................................................................. 171

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 medium voltage switchgear ........................ 7

Figure 2-5. Photographs of the internal wiring from typical motor control centers ................... 8

Figure 2-6. Photographs of Enclosure 1 ................................................................................ 10

Figure 2-7. Sketch of Enclosure 1 ......................................................................................... 11

Figure 2-8. Photographs of Enclosure 2 ................................................................................ 12

Figure 2-9. Sketch of Enclosure 2 ......................................................................................... 13

Figure 2-10. Photographs of Enclosure 3 ................................................................................ 14

Figure 2-11. Sketch of Enclosure 3 ......................................................................................... 15

Figure 2-12. Photographs of Enclosures 4 and 5 .................................................................... 16

Figure 2-13. Sketch of Enclosures 4 and 5 .............................................................................. 17

Figure 2-14. Photographs of Enclosure 6 ................................................................................ 18

Figure 2-15. Sketch of Enclosure 6 ......................................................................................... 19

Figure 2-16. Photographs of Enclosure 7 ................................................................................ 20

Figure 2-17. Sketch of Enclosure 7 ......................................................................................... 21

Figure 2-18. Photographs of Enclosure 8 ................................................................................ 22

Figure 2-19. Sketch of Enclosure 8 ......................................................................................... 23

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

Figure 3-2. Photograph o 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 4-4. Photograph of 30 cm (12 in) propane line burner ................................................ 38

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 conditions ....................................................................... 42

Table 5-2. Summary of enclosure fire measurements .......................................................... 49

Table 5-3. Summary of Test 1 .............................................................................................. 55

Table 5-4. Summary of Test 2 .............................................................................................. 56

Table 5-5. Summary of Test 3 .............................................................................................. 57

Table 5-6. Summary of Test 4 .............................................................................................. 58

Table 5-7. Summary of Test 5 .............................................................................................. 59

Table 5-8. Summary of Test 6 .............................................................................................. 60

Table 5-9. Summary of Test 7 .............................................................................................. 61

Table 5-10. Summary of Test 8 .............................................................................................. 62

Table 5-11. Summary of Test 9 .............................................................................................. 63

Table 5-12. Summary of Test 10 ............................................................................................ 64

Table 5-13. Summary of Test 11 ............................................................................................ 65

Table 5-14. Summary of Test 12 ............................................................................................ 66

Table 5-15. Summary of Test 13 ............................................................................................ 67

Table 5-16. Summary of Test 14 ............................................................................................ 68

Table 5-17. Summary of Test 15 ............................................................................................ 69

Table 5-18. Summary of Test 16 ............................................................................................ 70

Table 5-19. Summary of Test 17 ............................................................................................ 71

Table 5-20. Summary of Test 18 ............................................................................................ 72

Table 5-21. Summary of Test 19 ............................................................................................ 73

Table 5-22. Summary of Test 20 ............................................................................................ 74

Table 5-23. Summary of Test 21 ............................................................................................ 75

Table 5-24. Summary of Test 22 ............................................................................................ 76

Table 5-25. Summary of Test 23 ............................................................................................ 77

Table 5-26. Summary of Test 24 ............................................................................................ 78

Table 5-27. Summary of Test 25 ............................................................................................ 79

Table 5-28. Summary of Test 26 ............................................................................................ 80

Table 5-29. Summary of Test 27 ............................................................................................ 81

Table 5-30. Summary of Test 28 ............................................................................................ 82

Table 5-31. Summary of Test 29 ............................................................................................ 83

Table 5-32. Summary of Test 30 ............................................................................................ 84

Table 5-33. Summary of Test 31 ............................................................................................ 85

Table 5-34. Summary of Test 32 ............................................................................................ 86

Table 5-35. Summary of Test 33 ............................................................................................ 87

Table 5-36. Summary of Test 34 ............................................................................................ 88

Table 5-37. Summary of Test 35 ............................................................................................ 89

Table 5-38. Summary of Test 36 ............................................................................................ 90

Table 5-39. Summary of Test 37 ............................................................................................ 91

Table 5-40. Summary of Test 38 ............................................................................................ 92

Table 5-41. Summary of Test 39 ............................................................................................ 93

Table 5-42. Summary of Test 40 ............................................................................................ 94

Table 5-43. Summary of Test 41 ............................................................................................ 95

Table 5-44. Summary of Test 42 ............................................................................................ 96

Table 5-45. Summary of Test 43 ............................................................................................ 97
x

Table 5-46. Summary of Test 44 ............................................................................................ 98

Table 5-47. Summary of Test 45 ............................................................................................ 99

Table 5-48. Summary of Test 46 .......................................................................................... 100

Table 5-49. Summary of Test 47 .......................................................................................... 101

Table 5-50. Summary of Test 48 .......................................................................................... 102

Table 5-51. Summary of Test 49 .......................................................................................... 103

Table 5-52. Summary of Test 50 .......................................................................................... 104

Table 5-53. Summary of Test 51 .......................................................................................... 105

Table 5-54. Summary of Test 52 .......................................................................................... 106

Table 5-55. Summary of Test 53 .......................................................................................... 107

Table 5-56. Summary of Test 54 .......................................................................................... 108

Table 5-57. Summary of Test 55 .......................................................................................... 109

Table 5-58. Summary of Test 56 .......................................................................................... 110

Table 5-59. Summary of Test 57 .......................................................................................... 111

Table 5-60. Summary of Test 58 .......................................................................................... 112

Table 5-61. Summary of Test 59 .......................................................................................... 113

Table 5-62. Summary of Test 60 .......................................................................................... 114

Table 5-63. Summary of Test 61 .......................................................................................... 115

Table 5-64. Summary of Test 62 .......................................................................................... 116

Table 5-65. Summary of Test 63 .......................................................................................... 117

Table 5-66. Summary of Test 64 .......................................................................................... 118

Table 5-67. Summary of Test 65 .......................................................................................... 119

Table 5-68. Summary of Test 66 .......................................................................................... 120

Table 5-69. Summary of Test 67 .......................................................................................... 121

Table 5-70. Summary of Test 68 .......................................................................................... 122

Table 5-71. Summary of Test 69 .......................................................................................... 123

Table 5-72. Summary of Test 70 .......................................................................................... 124

Table 5-73. Summary of Test 71 .......................................................................................... 125

Table 5-74. Summary of Test 72 .......................................................................................... 126

Table 5-75. Summary of Test 73 .......................................................................................... 127

Table 5-76. Summary of Test 74 .......................................................................................... 128

Table 5-77. Summary of Test 75 .......................................................................................... 129

Table 5-78. Summary of Test 76 .......................................................................................... 130

Table 5-79. Summary of Test 77 .......................................................................................... 131

Table 5-80. Summary of Test 78 .......................................................................................... 132

Table 5-81. Summary of Test 79 .......................................................................................... 133

Table 5-82. Summary of Test 80 .......................................................................................... 134

Table 5-83. Summary of Test 81 .......................................................................................... 135

Table 5-84. Summary of Test 82 .......................................................................................... 136

Table 5-85. Summary of Test 83 .......................................................................................... 137

Table 5-86. Summary of Test 84 .......................................................................................... 138

Table 5-87. Summary of Test 85 .......................................................................................... 139

Table 5-88. Summary of Test 86 .......................................................................................... 140

Table 5-89. Summary of Test 87 .......................................................................................... 141

Table 5-90. Summary of Test 88 .......................................................................................... 142

Table 5-91. Summary of Test 89 .......................................................................................... 143

Table 5-92. Summary of Test 90 .......................................................................................... 144

Table 5-93. Summary of Test 91 .......................................................................................... 145

Table 5-94. Summary of Test 92 .......................................................................................... 146

Table 5-95. Summary of Test 93 .......................................................................................... 147

Table 5-96. Summary of Test 94 .......................................................................................... 148
xi

Table 5-97. Summary of Test 95 .......................................................................................... 149

Table 5-98. Summary of Test 96 .......................................................................................... 150

Table 5-99. Summary of Test 97 .......................................................................................... 151

Table 5-100. Summary of Test 98 .......................................................................................... 152

Table 5-101. Summary of Test 99 .......................................................................................... 153

Table 5-102. Summary of Test 100 ........................................................................................ 154

Table 5-103. Summary of Test 101 ........................................................................................ 155

Table 5-104. Summary of Test 102 ........................................................................................ 156

Table 5-105. Summary of Test 103 ........................................................................................ 157

Table 5-106. Summary of Test 104 ........................................................................................ 158

Table 5-107. Summary of Test 105 ........................................................................................ 159

Table 5-108. Summary of Test 106 ........................................................................................ 160

Table 5-109 Summary of Test 107 ........................................................................................ 161

Table 5-110. Summary of Test 108 ........................................................................................ 162

Table 5-111. Summary of Test 109 ........................................................................................ 163

Table 5-112. Summary of Test 110 ........................................................................................ 164

Table 5-113. Summary of Test 111 ........................................................................................ 165

Table 5-114. Summary of Test 112 ........................................................................................ 166

xiii 

EXECUTIVE SUMMARY 

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

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

power, instrumentation, and control in the plant. Fire growth in an electrical enclosure can be 

influenced by its size, openings, electrical voltage, and combustible load. 

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

Laboratory. Eight electrical enclosures were acquired from Bellefonte Nuclear Generating 

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

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

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

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

be found in a typical plant. 

The key experimental parameters are as follows: 

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

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

“horseshoe” control panel. 

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

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

through its top. 

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

burner and various size pans of acetone were used. 

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

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

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

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

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

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

to monitor internal temperatures. 

Of the 112 experiments, the peak HRR, over that of the ignitor itself, varied from 0 kW to 

576 kW. The mean was 43 kW; the median was 19 kW. Eleven fires peaked at greater than 

100 kW. 

xv 

ACKNOWLEDGMENTS 

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

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

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

composition and typical installation practice. 

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

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

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

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

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

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

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

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

and Anthony Chakalis of the NIST Large Fire Research Facility. 

Finally, a draft of this report was Noticed in the Federal Register for public comment on 

May 1, 2015 (80 FR 24981) by the NRC. The authors thank the Office of Nuclear Reactor 

Regulation and those members of the public, specifically Victoria K. Anderson, Nuclear Energy 

Institute; and James Barstow and Richard Gropp, Exelon Generation; who provided comments 

during the public comment period. 

Disclaimer 

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

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

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

equipment identified are necessarily the best available for the purpose. 

xvii

ABBREVIATIONS 

ASTM American Society for Testing and Materials 

AWG American Wire Gauge 

CAROLFIRE Cable Response to Live Fire 

CBD Chesapeake Bay Detachment 

CDRS Conductors 

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

CPE Chlorinated Polyethylene 

CSPE Chloro-Sulfonated Polyethylene 

DEG C Degrees Celsius 

DIR BUR Direct Burial 

EPR Ethylene-Propylene Rubber 

EPRI Electric Power Research Institute 

FR Flame Retardant 

HRR Heat Release Rate 

IEEE Institute of Electrical and Electronics Engineers 

ISO International Organization for Standardization 

NEC National Electric Code 

NFPA National Fire Protection Association 

NIST National Institute of Standards and Technology 

NPP Nuclear Power Plant 

NRC Nuclear Regulatory Commission 

NRL Naval Research Laboratory 

NRR NRC Office of Nuclear Reactor Regulation 

OIL RES Oil Resistant 

PE Polyethylene 

PMMA Polymethyl Methacrylate 

PRA Probabilistic Risk Assessment 

PVC Poly-vinyl Chloride 

Q Qualified 

RES NRC Office of Nuclear Regulatory Research 

SIS Synthetic Insulated Switchboard 

SNL Sandia National Laboratories 

SP Swedish National Testing and Research Institute 

SR Silicone Rubber 

SUN RES Sun Resistant 

TC Thermocouple or Tray Cable 

TC-ER Tray Cable - Exposed Run 

TC/NCC Tray Cable/Nickel Coated Copper 

Tefzel® DuPont ETFE (Ethylene-Tetrafluoroethylene) Resin

TFN Thermoplastic Fixture wire Nylon jacketed 

TP Thermoplastic 

TPE Thermoplastic Elastomer 

TS Thermoset 

UL Underwriters Laboratories 

UQ Unqualified 

VNTC Vinyl Nylon Tray Cable 
xviii

XHHW Cross-linked High Heat Water resistant 

VTT Valtion Teknillinen Tutkimuskeskus (Technical Research Centre, Finland) 

XLPE, XLP or XPE Cross-Linked Polyethylene 
1

1 INTRODUCTION 

1.1 Background 

Electrical enclosures are a potential source of fire in nuclear power plants (NPPs) because they 

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

disrupt power, instrumentation, and control in the plant. Parameters that affect fire growth in an 

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

1.2 Previous Studies 

Heat release rate (HRR) measurements for electrical enclosure fires have been conducted at 

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

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

Sûreté Nucléaire (IRSN) in France (Plumecocq et al., 2011; Coutin et al., 2012). In these 

studies, various configurations of electrical enclosure sizes, combustible loads and ventilation 

conditions were tested to determine the HRRs and thermal conditions in and around the 

enclosures. 

1.2.1 Sandia National Laboratories Experiments 

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

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

either benchboard or vertical enclosures containing qualified1 or unqualified cable can be 

ignited, but that fires burning unqualified cable spread more rapidly and to a greater extent than 

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

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

1.2.2 VTT Experiments 

VTT conducted 22 fire experiments that are reported in three separate reports: Mangs and 

Keski-Rahkonen (1994; 1996), Mangs (2004), and a paper summarizing the findings (Mangs et 

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

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

experiments was to determine maximum HRRs, minimum igniter strengths, and the effect of 

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

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

1.2.3 IRSN Experiments 

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

analysis with the goal of developing a simplified model of fire behavior within an electrical 

enclosure. This model is based on the assumption that the ventilation within the enclosure is 

limited and that the HRR can be inferred from the limited oxygen supply. Experiments were 

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

experiments were performed with actual electrical components and cabling. 

 

1 “Qualified” typically means that the cable has passed the IEEE-383 flame spread test. 
2

1.3 Current Practice 

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

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

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

fire probabilistic risk assessments (PRAs) in commercial NPP applications. Appendix G of 

NUREG/CR-6850 expresses the peak HRR for five different categories of electrical enclosures 

in the form of gamma distributions. The enclosures are categorized by their combustible load 

(one vs multiple cable bundles), flammability of materials (qualified vs unqualified cable), and 

ventilation (door open vs door closed). The distributions were developed by a panel of experts 

who considered actual fire events in NPPs and other industrial facilities, and the experimental 

data cited above. 

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

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

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

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

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

were designed to answer specific questions like whether it is possible to propagate a fire on 

qualified cables with a particular kind of igniter, or whether it is possible to spread a fire from 

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

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

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

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

results. The nearest substitute would be to invoke the database of actual fire events in NPPs 

(Wachowiak and Lindeman, 2013), but in these cases, human intervention prevented the 

relatively small fires from spreading. It would be impossible to recreate the fires in the events 

database and allow them to progress with no suppression. 

1.4 Objective 

The objective of the current study is to measure the HRRs of fires in electrical enclosures 

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

sources. The enclosures used in the experiments have been acquired from an NPP built in the 

late 1970s but never operated. As received, these enclosures contain wiring typical of those 

built after the Browns Ferry fire of 1975. In addition, these enclosures were refurbished after an 

initial set of experiments so that they resembled other types of enclosures found in other plants. 

The procedure for refurbishing is described in the next chapter. 
3

2 DESCRIPTION OF ENCLOSURES 

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

(NPPs). 

2.1 Survey of Electrical Enclosures 

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

during plant visits to several operating and decommissioned NPPs. These and other 

photographs were used as guidance in developing the wiring configurations that were simulated 

in the experiments. This should not be considered a comprehensive survey of all enclosures in 

all plants, but rather a collection of typical combustible loads and ventilation configurations. 

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

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

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

Figure 2-3 and Figure 2-4 displays photographs of switchgear enclosures. In general, these 

types of enclosures contain less wiring than the enclosures in the control room. These 

enclosures are also relatively large with large amounts of open volume inside. 

Figure 2-5 displays photographs of motor control centers (MCCs). These enclosures contain 

relatively small compartments containing a variety of wiring and equipment. It is difficult to 

characterize these compartments in general terms other than to say that each “bucket” is 

relatively self-contained and isolated from its neighbors. 

 
4

 

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

 

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

 

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

 

Figure 2-4. Photographs of the internal wiring of medium voltage switchgear. 
8

 

Figure 2-5. Photographs of the internal wiring from typical motor control centers. 
9

2.2 Enclosures used in the Experiments 

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

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

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

The enclosures appear to have been manufactured in the late 1970s. All were constructed of 

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

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

typical characteristics of other types of electrical enclosures found throughout a plant. In the 

initial set of experiments, the enclosures were tested as is; that is, in the condition that they 

were received from the plant. After these initial experiments, cables of different amounts and 

configurations were added to the enclosures such as to mimic photographs collected from a 

variety of existing and decommissioned U.S. plants. In some cases, the amount and 

configuration of the cables did not resemble any of the photographs in the collection. 

As previously stated, electrical cables used in commercial NPPs can be grouped into one of two 

categories; thermoplastic (TP) or thermoset (TS). TS cables are typically harder to ignite than 

TP cables, but can reach peak HRRs similar to TP cables once ignited. Some electrical cables 

will have a TS jacket to improve its flammability properties while the individual conductors within 

the cable will have TP insulation. For some of the experiments conducted during this test 

series, some amount of cable jacket was removed to expose the individual insulated 

conductors. While the conductors may or may not have remained twisted, all the associated 

packing material was removed from around the individual conductors. This was done to 

increase the amounts and types of potential fuels, i.e., electrical cables, available for use in the 

experiments. The stripping of the cable jacket was not intended to provide any significant 

information relative to the installation practice in operating plants. 

 
10

2.2.1 Enclosure 1 

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

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

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

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

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

Figure 2-6. Photographs of Enclosure 1. 
11

Figure 2-7. Sketch of Enclosure 1. 
12

2.2.2 Enclosure 2 

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

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

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

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

Figure 2-8. Photographs of Enclosure 2. 
13

Figure 2-9. Sketch of Enclosure 2. 
14

2.2.3 Enclosure 3 

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

front section contained a rack for holding circuit cards, as seen through the polymethyl 

methacrylate (PMMA) or Plexi-glass® window in Figure 2-10. The middle section (upper right 

photo) contained a large amount of relay wire. The rear section contained little combustible 

material. There was a relatively large access opening on the left side of the enclosure. There 

was also a relatively large opening in the floor. 

Figure 2-10. Photographs of Enclosure 3. 
15

Figure 2-11. Sketch of Enclosure 3. 
16

2.2.4 Enclosures 4 and 5 

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

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

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

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

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

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

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

by the exhaust hood. An exploratory test was conducted to verify this effect, but it is not 

documented in this report. 

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

Figure 2-13. Sketch of Enclosures 4 and 5. 
18

2.2.5 Enclosure 6 

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

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

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

Figure 2-14. Photographs of Enclosure 6. 
19

Figure 2-15. Sketch of Enclosure 6. 
20

2.2.6 Enclosure 7 

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

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

significant amount of combustible materials. 

Figure 2-16. Photographs of Enclosure 7. 
21

Figure 2-17. Sketch of Enclosure 7. 
22

2.2.7 Enclosure 8 

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

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

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

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

enclosure to collect the exiting cables. 

Figure 2-18. Photographs of Enclosure 8. 
23

Figure 2-19. Sketch of Enclosure 8. 

25

3 CABLE PROPERTIES 

3.1 Properties of Cables used in Enclosure Fire Experiments 

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

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

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

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

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

constituent parts – jacket, filler, insulators, and conductors. Note that the “Class” of cables, 

either TS for thermoset or TP for thermoplastic, refers to the broad classification of the two main 

types of cables used in plants. 

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

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

 836 837 838 839 840 841 842 

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

 843 844 845 

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

Figure 3-4. Photograph of a circuit card installed in Enclosure 3. 
28 

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

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 
29 

Cable No. SOURCE MANUFACTURER* DATE CABLE MARKINGS 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 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 

*Certain commercial equipment, instruments, or materials are identified in this report to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials 

or equipment identified are necessarily the best available for the purpose. 
30 

Table 3-2. Cable properties. 

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 17.1 3.06 1.74 0.44 0.52 0.33 0.13 0.02 831 SIS TS TS 1 3.6 0.00 1.25 0.03 0.65 0.00 0.35 0.00 832 Unknown Unknown Unknow

n 

1 6.8 0.98 2.34 0.08 0.41 0.37 0.21 0.01 

833 Unknown Unknown Unknow

n 

1 4.7 N/A 1.74 0.05 0.63 0.00 0.37 0.00 

834 XLPE No Jacket TS 1 4.0 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 XLPE CSPE TS 2 8.6 2.60 1.48 0.11 0.31 0.46 0.13 0.10 837 XLPE CSPE TS 4 16.9 2.86 1.48 0.38 0.19 0.53 0.07 0.20 838 XLPE CSPE TS 6 18.4 2.86 1.48 0.46 0.24 0.55 0.09 0.12 839 XLPE CSPE TS 8 19.8 2.86 1.48 0.55 0.29 0.53 0.11 0.07 840 XLPE CSPE TS 10 23.4 3.65 1.48 0.77 0.24 0.63 0.08 0.05 
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 

841 TPE TPE TP 3 13.5 2.08 1.19 0.12 0.29 0.50 0.15 0.06 842 Unknown Unknown Unknow

n 

40 1.2 N/A N/A 0.08 -- -- -- -- 

843 Unknown Unknown Unknow

n 

352 36.1 N/A N/A 2.86 -- -- -- -- 

844 PVC PVC TP 3 10.2 01.80 0.76 0.17 0.47 0.33 0.18 0.03 845 EP TS TS 1 5.9 0 2.10 0.08 0.60 0.40 0.00 0.00 

33

4 EXPERIMENTAL PROCEDURE 

4.1 Oxygen Consumption Calorimeter 

The measurements of the heat release rate (HRR) of the enclosure fires were performed at the 

Chesapeake Bay Detachment of the Naval Research Laboratory2. This facility has a large-scale 

calorimeter that is nominally 6.1 m by 6.1 m (20 ft by 20 ft), designed to measure the HRR of 

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

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

enclosure experiments. For this reason, a smaller calorimeter (see Figure 4-1) was built to fit 

underneath the large 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 46 cm (18 in) duct was instrumented with a Rosemount 

Annubar® to measure the volume flow, four thermocouples to measure the gas temperature, 

and a gas extraction tube to measure the oxygen concentration of the exhaust gases. The 

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

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

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

the CBD test facility. 

The HRR of the fire is given by the following formula under the assumption that both oxygen 

and carbon dioxide are measured in the exhaust duct (SFPE Handbook, 2008, chapter 

Calorimetry): 

ܳሶ ൌ ܧ ߮

1൅߮ሺߙെ1ሻ

݉ሶ e

Oమܯ

aܯ

൫1 െ ܺHమO a െ ܺCOమ

a ൯ܺOమa Equation 4-1 

with: 

߮ ൌ

ܺOమ

a ൫1 െ ܺCOమe ൯െܺOమe ൫1 െ ܺCOమa ൯

൫1 െ ܺOమ

e െ ܺCOమe ൯ܺOమa Equation 4-2 

where ܳሶ Heat release rate (kW) 

 ܧ Heat release per unit mass of oxygen consumed (13100 kJ/kg) 

 ߮ Oxygen depletion factor 

 ߙ Volumetric expansion factor (1.105) 
35

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

 ܯOమ Molecular mass of oxygen (32 g/mol) 

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

 ܺHమO a Volume fraction of water vapor in the ambient air 

 ܺCOమ

a Volume fraction of carbon dioxide in the ambient air 

 ܺOమ

a Volume fraction of oxygen in the ambient air 

 ܺCOమ

e Volume fraction of carbon dioxide in the exhaust duct 

 ܺOమ

e Volume fraction of oxygen in the exhaust duct 

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

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

ideal gas law: 

ൌ ߩ

ഥܹ ݌

ܴ ܶത Equation 4-3 

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

gases (assumed to be that of air, 29 g/mol), ܴ is the universal gas constant (8.3145 J/(mol·K)), 

and ܶത is the average of the four thermocouple measurements. The volume flow rate is 

calculated: 

ܸሶ ൌ ܣܥdඨ2 ∆݌

ߩ

Equation 4-4 

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

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

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

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

straightened and developed to the extent recommended by the manufacturer of the Annubar®. 

The uncertainty in the HRR 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, and the oxygen depletion, 

ܺOమ

a െ ܺOమe . Janssens (SFPE Handbook, 2008, chapter Calorimetry) states that ܧ equals 

13100 kJ/kg with a relative standard uncertainty of 5 %. The uncertainties of the mass flow rate 

and oxygen concentration measurements were not evaluated independently because the flow 

coefficient, ܥ, was selected based on calibration fires rather than an isothermal flow test. 

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

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

provided a second set of calibration burns. Five experiments were performed in which 1 L of 

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

produce approximately 22.7 MJ of energy. The mean energy release for the five test burns was 

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

aleatoric uncertainty of the HRR measurement is approximately 7 % when the fuel stoichiometry 

is known. However, for general combustibles this estimate of the uncertainty must then be 

combined via quadrature with the uncertainty in the value of ܧ, the heat of combustion based on 

oxygen consumption. The combined relative standard deviation in the HRR is thus estimated to 

be approximately 9 % (Taylor and Kuyatt, 1994). 
36

4.2 Ignition Sources 

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

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

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

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

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

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

4.2.1 Cartridge Heaters 

A cartridge heater is a cylindrical rod approximately 15 cm (6 in) in length and 1 cm (0.4 in) in 

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

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

determine the exact dimensions and power requirements for reliable, reproducible ignition. A 

bundle of cables, each 15 mm in diameter, was ignited with a 300 W heater and spark igniter. 

However, the heaters were used only for a single full-scale experiment because they were 

prone to shorting following ignition and the spark igniter drew too much power from the existing 

electrical circuit in the laboratory. Consequently, the cartridge heaters were abandoned for the 

remainder of the program. 

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

4.2.2 Propane Line Burners 

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

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

constructed of the same type of copper tubing and was 30 cm (12 in) long (see Figure 4-4). The 

smaller burner produced flames with HRRs in the range of 0.5 kW to 2 kW. The larger burner 

produced flames in the range of 4 kW to 10 kW. The propane flowing to the burners was 
37

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

and the expected HRR for each. Each flow meter was calibrated for air (29.0 g/mol) at 24 °C 

(297 K, 70 °F). The average temperature over the five months of testing was 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, was multiplied by a 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 is the volumetric flow rate of propane corrected for molecular weight and temperature. 

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

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 is the density of propane at the 

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

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 

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

meter, which is given as 5 % of the calibrated range. 
38

Figure 4-4. Photograph of 30 cm (12 in) propane line burner. 

4.2.3 Liquid Fuel Pan Fires 

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

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

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

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

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

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

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

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

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

oxygen consumption calorimeter. 

4.2.4 Combustible Loading 

Typical electrical enclosures will contain a variety of combustible materials including electrical 

cables, circuit cards, electrical components, and combustible insulation. This test series utilized 

a variety of electrical cables with various flammability properties in different configurations to 

represent the combustible loading. To intentionally vary the flammability properties of the 

cables or conductors, some cables were stripped of their outer jacket and filler material to 

expose the individual conductors. During the first and some subsequent experiments, the 

combustible loading in the enclosures also included circuit cards and other combustible 

components that were in the enclosures when they were originally manufactured. 
39

The combustible loading in the original enclosures was not determined. For subsequent tests, 

the combustible load was determined based on the amount of cable that was placed inside the 

enclosure. Depending on the cable configuration, the total length of cable was translated into a 

combustible mass using the mass per unit length (kg/m) and the mass fraction values in Table 

3-2. The mass fraction of copper was removed from all cable load calculations and the jacket 

mass fraction was removed for cases were the cables were stripped. In cases where limited or 

no significant burning took place during one test, a subsequent test was often conducted in the 

same enclosure with the existing combustible load. The remaining combustible load for the 

subsequent test was estimated based on review of the test data and video records. 

Finally, the electrical cables used for this test series were stored in an unheated trailer prior to 

use in a particular test. While some tests utilized acetone or other methods to raise the interior 

temperature of the enclosure, the cables were typically at temperatures around 0 oC (32 oF) at 

the start of a test. The impact of the difference between typical operating temperatures and the 

test conditions on electrical cable flame spread has not been evaluated. 

41

5 FULL-SCALE MEASUREMENTS 

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

5.1 Description 

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

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

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

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

the enclosures were not powered. For some a experiments, a pan of ethanol or acetone was 

placed at the base of the enclosure away from the combustibles to raise the interior enclosure 

temperature. These same pans of alcohol were sometimes used to ignite the combustibles 

directly. In the description of each experiment, therefore, there is a distinction made between 

“Ignition Source” and “Preheating Source.” Table 5-1 shows the conditions for each test. A 

summary of measurements obtained during each test is presented in Table 5-2. The 

temperatures measured 0.15 m (6 in) below the top of the test enclosure during each test are 

shown in Appendix A. 

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

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

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

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

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

igniter. 

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

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

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

system. Rather, the burner position and heat release rate (HRR) were varied as would be 

expected in actual fire events. The cables and wiring were not installed in a particularly 

systematic way either. Typically, bundles of cables would be hung using wires on either the left 

or right side of the enclosure, as had been observed in enclosures found on the plant visits. 

Sometimes the cables and/or individual conductors would be tightly bundled using plastic wire 

or “zip ties,” and at other times they would be left to hang in no particular arrangement. It was 

observed that “loose” or non-bundled cables or wires led to higher HRRs, even though bundling 

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

fire spread. The total combustible mass (“Comb. Mass”) refers to the mass of cable jacketing 

and insulation material derived from the measured length of cable multiplied by the mass of 

non-metallic materials per unit length found in Table 3-2. 
42

Table 5-1. Summary of enclosure conditions (continued) 

Test Date 

Test 

Condition Change 

National 

Weather 

National 

Weather 

Start Temp. 

(Low) 

Temp. 

(High) 

(min) (°C) (°C) 

1 October 30, 

2013 0 6 21 

2 October 31, 

2013 0 2 16 

3 October 31, 

2013 0 2 16 

4 October 31, 

2013 0 2 16 

5 October 31, 

2013 0 2 16 

6 October 31, 

2013 0 2 16 

7 October 31, 

2013 0 2 16 

8 November 

1, 2013 0 2 16 

9 November 

1, 2013 0 2 16 

10 November 

4, 2013 0 1 16 

11 November 

4, 2013 0 1 16 

12 A November 

4, 2013 0 1 16 

12 B November 

4, 2013 40 Door opened briefly 1 16 

12 C November 

4, 2013 80 Door opened and left open 1 16 

13 November 

5, 2013 0 6 19 

14 A November 

5, 2013 0 6 19 

14 B November 

5, 2013 20 Door opened and propane blowtorch used 6 19 

15 A November 

5, 2013 0 6 19 

15 B November 

5, 2013 37 Door closed 6 19 

16 November 

5, 2013 0 6 19 
43

Table 5-1. Summary of enclosure conditions (continued) 

Test Date 

Test 

Condition Change 

National 

Weather 

National 

Weather 

Start Temp. 

(Low) 

Temp. 

(High) 

(min) (°C) (°C) 

17 November 

5, 2013 0 6 19 

18 November 

5, 2013 0 6 19 

19 November 

6, 2013 0 11 20 

20 November 

6, 2013 0 11 20 

21 November 

6, 2013 0 11 20 

22 November 

6, 2013 0 11 20 

23 November 

6, 2013 0 11 20 

24 November 

6, 2013 0 11 20 

25 November 

7, 2013 0 8 20 

26 November 

7, 2013 0 8 20 

27 A November 

7, 2013 0 8 20 

27 B November 

7, 2013 40 Door opened and cables moved with crowbar 8 20 

28 A November 

7, 2013 0 8 20 

28 B November 

7, 2013 19 Door opened briefly and cables moved with crowbar 8 20 

28 C November 

7, 2013 40 Door opened briefly and cables moved with crowbar 8 20 

29 December 

11, 2013 0 0 9 

30 December 

11, 2013 0 0 9 

31 December 

12, 2013 0 0 7 

32 A December 

12, 2013 0 0 7 

32 B December 

12, 2013 16 Door opened and left open 0 7 

33 December 

12, 2013 0 0 7 
44

Table 5-1. Summary of enclosure conditions (continued) 

Test Date 

Test 

Condition Change 

National 

Weather 

National 

Weather 

Start Temp. 

(Low) 

Temp. 

(High) 

(min) (°C) (°C) 

34 December 

12, 2013 0 0 7 

35 December 

13, 2013 0 -4 7 

36 A December 

13, 2013 0 -4 7 

36 B December 

13, 2013 12 Door opened and left open -4 7 

37 December 

13, 2013 0 -4 7 

38 December 

13, 2013 0 -4 7 

39 December 

16, 2013 0 1 13 

40 December 

16, 2013 0 1 13 

41 A December 

16, 2013 0 1 13 

41 B December 

16, 2013 11 Front panel burned through creating 

an open door configuration 1 13 

42 December 

16, 2013 0 1 13 

43 December 

16, 2013 0 1 13 

44 December 

17, 2013 0 1 10 

45 December 

17, 2013 0 1 10 

46 December 

17, 2013 0 1 10 

47 December 

18, 2013 0 -1 13 

48 December 

18, 2013 0 -1 13 

49 December 

18, 2013 0 -1 13 

50 December 

19, 2013 0 -1 4 

51 December 

19, 2013 0 -1 4 

52 December 

19, 2013 0 -1 4 
45

Table 5-1. Summary of enclosure conditions (continued) 

Test Date 

Test 

Condition Change 

National 

Weather 

National 

Weather 

Start Temp. 

(Low) 

Temp. 

(High) 

(min) (°C) (°C) 

53 A December 

19, 2013 0 -1 4 

53 B December 

19, 2013 0 Blow torch used to ignite cables -1 4 

54 December 

19, 2013 0 -1 4 

55 December 

19, 2013 0 -1 4 

56 February 4, 

2014 0 -6 2 

57 February 4, 

2014 0 -6 2 

58 February 4, 

2014 0 -6 2 

59 A February 4, 

2014 0 -6 2 

59 B February 4, 

2014 20 Cable bundle loosened with a crowbar -6 2 

60 February 4, 

2014 0 -6 2 

61 February 6, 

2014 0 -12 4 

62 February 6, 

2014 0 -12 4 

63 February 6, 

2014 0 -12 4 

64 February 7, 

2014 0 -12 2 

65 February 7, 

2014 0 -12 2 

66 A February 

10, 2014 0 -2 4 

66 B February 

10, 2014 23 -2 4 

67 A February 

10, 2014 0 -2 4 

67 B February 

10, 2014 13 -2 4 

68 February 

10, 2014 0 -2 4 

69 February 

10, 2014 0 -2 4 
46

Table 5-1. Summary of enclosure conditions (continued) 

Test Date 

Test 

Condition Change 

National 

Weather 

National 

Weather 

Start Temp. 

(Low) 

Temp. 

(High) 

(min) (°C) (°C) 

70 February 

10, 2014 0 -2 4 

71 February 

10, 2014 0 -2 4 

73 February 

11, 2014 0 -3 3 

74 February 

11, 2014 0 -3 3 

75 February 

19, 2014 0 -16 1 

76 February 

19, 2014 0 -16 1 

77 A February 

19, 2014 0 -16 1 

77 B February 

19, 2014 16.5 Door was opened and left open -16 1 

78 A February 

19, 2014 0 -16 1 

78 B February 

19, 2014 12.5 Door was opened and left open -16 1 

79 A February 

19, 2014 0 -16 1 

79 B February 

19, 2014 14 -16 1 

80 A February 

20, 2014 0 -18 -7 

80 B February 

20, 2014 18 Door was opened and left open -18 -7 

81 February 

20, 2014 0 -18 -7 

82 A February 

20, 2014 0 -18 -7 

82 B February 

20, 2014 22 Door was opened and left open -18 -7 

83 February 

20, 2014 0 -18 -7 

84 February 

24, 2014 0 -13 2 

85 February 

24, 2014 0 -13 2 

86 A February 

24, 2014 0 -13 2 
47

Table 5-1. Summary of enclosure conditions (continued) 

Test Date 

Test 

Condition Change 

National 

Weather 

National 

Weather 

Start Temp. 

(Low) 

Temp. 

(High) 

(min) (°C) (°C) 

86 B February 

24, 2014 27.5 Door opened and cables moved with crowbar -13 2 

87 February 

24, 2014 0 -13 2 

88 February 

24, 2014 0 -13 2 

89 February 

24, 2014 0 -13 2 

90 February 

25, 2014 0 -13 -3 

91 February 

25, 2014 0 -13 -3 

92 February 

25, 2014 0 -13 -3 

93 February 

25, 2014 0 -13 -3 

94 February 

25, 2014 0 -13 -3 

95 February 

25, 2014 0 -13 -3 

96 February 

26, 2014 0 -11 6 

97 A February 

26, 2014 0 -11 6 

97 B February 

26, 2014 16.5 Door opened briefly and cables moved with crowbar -11 6 

98 February 

26, 2014 0 -11 6 

99 February 

26, 2014 0 -11 6 

100 February 

26, 2014 0 -11 6 

101 February 

27, 2014 0 -11 6 

102 February 

27, 2014 0 -11 6 

103 February 

27, 2014 0 -4 3 

104 February 

28, 2014 0 -9 1 

105 February 

28, 2014 0 -9 1 
48

Table 5-1. Summary of enclosure conditions (continued) 

Test Date 

Test 

Condition Change 

National 

Weather 

National 

Weather 

Start Temp. 

(Low) 

Temp. 

(High) 

(min) (°C) (°C) 

106 A February 

28, 2014 0 -9 1 

106 B February 

28, 2014 9 -9 1 

107 March 4, 

2014 0 2 6 

108 March 4, 

2014 0 2 6 

109 March 4, 

2014 0 2 6 

110 A March 4, 

2014 0 2 6 

110 B March 4, 

2014 13.5 Door was opened and left open 2 6 

111 A March 4, 

2014 0 2 6 

111 B March 4, 

2014 20 Door was opened and left open 2 6 

112 March 4, 

2014 0 2 6 

 
49

Table 5-2. Summary of enclosure fire measurements (continued)

Test 

Encl.

Ignition Preheat Ambient Comb. Cable Door Peak Total 

Energy 

HRR HRR Temp. Mass Class. Position HRR Release

(kW) (kW) (°C) (kg) (kW) (MJ)

 Note 4 Note 

2 

1 1 0.3 0 17.3 Note 1 Q Open 2 2 

2 2 0.5 0 17.3 Note 1 Q Open 2 1 

3 2 0.5 0 20.1 Note 1 Q Open 2 2 

4 4 0.7 0 20.3 Note 1 Q Open 2 1 

5 4 0.7 0 19.4 Note 1 Q Open 1 1 

6 4 0.7 0 18 Note 1 Q Open 2 1 

7 5 0.7 0 17.5 Note 1 Q Open 9 6 

8 3 0.7 0 19.7 Note 1 Q Open 0 1 

9 3 0.7 0 19.8 Note 1 Q Open 1 1 

10 3 0.7 0 5.8 Note 1 Q Open 1 1 

11 1 0.7 0 6.5 Note 1 Q Open 1 1 

12 

A 1 0.7 0 8.2 Note 1 Q Closed 3 

B 1 0.7 0 Note 3 Note 1 Q Closed 39 120 

C 1 0.7 0 Note 3 Note 1 Q Open 52 

13 8 0.7 0 9.6 Note 1 Q Closed 2 4 

14 

A 8 0.7 0 14 Note 1 Q Closed 2.2 

2 

B 9 0.7 0 Note 3 Note 1 Q Open 4 

15 A 5 0.7 0 12 3.23 Q Open 3 7 

B 5 0.7 0 Note 3 3.23 Q Closed 0 

16 5 0.7 0 12.4 1.89 Q Open 2 2 

17 4 0.7 0 12.1 2.70 Q Open 0 0 

18 4 0.7 0 12.1 1.76 Q Open 3 3 

19 5 0.7 0 19.5 3.23 Q Closed 3 7 

20 5 0.7 0 31.5 1.89 Q Closed 5 9 

21 4 0.7 0 24.2 1.89 Q Closed 4 3 

22 4 0.7 0 23 1.76 Q Closed 4 4 

23 5 0.7 0 24.2 1.56 UQ Open 18 12 

24 5 0.7 0 26.3 0.73 Q Closed 4 4 
50

Table 5-2. Summary of enclosure fire measurements (continued)

Test 

Encl.

Ignition Preheat Ambient Comb. Cable Door Peak Total 

Energy 

HRR HRR Temp. Mass Class. Position HRR Release

(kW) (kW) (°C) (kg) (kW) (MJ)

 Note 4 Note 

2 

25 1 0.7 0 39.1 3.11 Q Closed 4 5 

26 1 0.7 0 40.6 3.034 Q Closed 1 0 

27 

A 1 0.7 14 18.3 2.994 Q Closed 1.7 

9 

B 1 0.7 14 Note 3 2.994 Q Closed 7 

28 

A 1 0.7 16 30.6 2.874 Q Closed 4.7 

B 1 0.7 16 Note 3 2.87 17 4 Q Closed 11.3 

C 1 0.7 16 Note 3 2.874 Q Closed 10 

29 1 18 0 4.5 2.644 Q Closed 82 76 

30 1 18 0 6.1 1.324 Q Closed 72 59 

31 4 5.5 22 0.4 0.73 Q Closed 28 45 

32 

A 4 5.5 25 38.8 0.73 Q Closed 5.6 

35 

B 4 5.5 25 Note 3 0.73 Q Open 11 

33 5 25 0 11.5 1.46 Q Closed 50 40 

34 5 35 0 34.2 1.224 Q Closed 35 46 

35 8 27 0 2.8 11.37 Q Open 146 153 

36 

A 2 4 0 5.1 2.71 Q Closed 2.5 

4 

B 2 4 0 Note 3 2.71 Q Open 4 

37 2 54 0 18.4 5.41 Q Closed 35 27 

38 2 20 0 33.1 4.744 Q Closed 169 95 

39 8 25 0 2.5 5.68 Q Closed 60 65 

40 3 12 0 3.5 Note 1 Q Closed 2 19 

41 

A 3 20 0 5.2 5.00 Q Closed 122 

141 

B 3 20 0 Note 3 5.00 Q Open 232 

42 4 5.5 0 1.6 2.88 Q Closed 34 35 

43 4 16 0 21.1 2.88 Q Closed 18 21 

44 5 5.5 0 3.6 2.88 Q Closed 31 32 

45 5 5.5 22 24.4 2.88 Q Closed 5 34 

46 4 19 0 4.2 5.41 Q Closed 45 68 

47 4 19 0 4.4 2.71 Q Closed 40 49 

48 4 19 0 21 5.41 Q Open 87 89 
51

Table 5-2. Summary of enclosure fire measurements (continued)

Test 

Encl.

Ignition Preheat Ambient Comb. Cable Door Peak Total 

Energy 

HRR HRR Temp. Mass Class. Position HRR Release

(kW) (kW) (°C) (kg) (kW) (MJ)

 Note 4 Note 

2 

49 4 19 0 23.9 5.41 Q Closed 50 76 

50 4 22 0 4.5 2.65 Q Closed 1 21 

51 4 30 0 31.3 1.33 Q Open 31 34 

52 4 5.5 0 18.3 2.17 UQ Open 122 61 

53 

A 4 5.5 0 17.7 2.17 UQ Closed 57 

60 

B 4 5.5 0 Note 3 0.544 UQ Open 85 

54 4 2.2 0 41.7 3.12 UQ Open 94 41 

55 4 10 0 38 3.12 UQ Closed 21 26 

56 5 0.8 22 1.1 1.68 UQ Closed 8 16 

57 5 0.8 24 12.6 1.68 UQ Closed 5 26 

58 5 0.8 21 2.4 2.33 UQ Closed 26 36 

59 A 5 0.8 0 45.4 2.33 UQ Open 5.3 14 

B 5 0.8 0 Note 3 2.33 UQ Open 22 

60 1 0.8 19 1.2 7.39 UQ Closed 88 96 

61 1 0.8 19 1.1 11.84 Q Closed 5 29 

62 1 1.6 19 4.1 11.84 Q Closed 3 33 

63 1 5.5 19 3.5 11.84 Q Closed 92 156 

64 8 0.8 11 1.5 6.05 Q Closed 6 13 

65 8 0.8 11 5.7 6.05 Q Closed 7 15 

66 

A 4 5.5 24 -2.1 3.36 UQ Closed 26 

57 

B 4 5.5 24 Note 3 3.36 UQ Open 26 

67 

A 4 5.5 0 13.1 3.36 UQ Closed 26 

21 

B 4 5.5 0 Note 3 3.36 UQ Open 29 

68 1 0.8 0 0.9 4.74 UQ Closed 216 121 

69 8 1.6 13 0.8 3.53 UQ Closed 10 22 

70 1 1.6 0 1.6 3.11 Q Closed 2 1 

71 1 5.5 0 2.6 3.11 Q Closed 138 99 

73 4 1.6 22 1 2.88 Q Closed 4 26 

74 5 1.6 20 23.4 2.56 Q Closed 5 28 

75 5 5.5 26 9.4 2.88 Q Closed 15 57 
52

Table 5-2. Summary of enclosure fire measurements (continued)

Test 

Encl.

Ignition Preheat Ambient Comb. Cable Door Peak Total 

Energy 

HRR HRR Temp. Mass Class. Position HRR Release

(kW) (kW) (°C) (kg) (kW) (MJ)

 Note 4 Note 

2 

76 5 22 0 38.2 2.88 Q Closed 9 25 

77 

A 5 5.5 24 29.7 2.56 Q Closed 10 

53 

B 5 5.5 24 Note 3 2.56 Q Open 18 

78 

A 5 5.5 0 18.6 2.56 Q Closed 30 

27 

B 5 5.5 0 Note 3 2.56 Q Open 54 

79 

A 4 5.5 0 14.6 6.12 Q Closed 40 

63 

B 4 5.5 0 Note 3 6.12 Q Open 65 

80 

A 4 5.5 19 6.3 2.77 Q Closed 20 

92 

B 4 5.5 19 Note 3 2.77 Q Open 100 

81 5 30 0 12.5 2.88 Q Closed 24 48 

82 

A 1 1.6 19 10 7.39 UQ Closed 1 

112 

B 1 1.6 19 Note 3 7.39 UQ Open 63 

83 1 0.8 0 16.5 4.74 UQ Open 577 152 

84 7 0.8 20 6.5 3.27 Q Open 37 51 

85 7 0.8 0 45.4 1.96 Q Closed 2 2 

86 A 7 5 0 26.4 1.96 Q Open 0 15 

B 7 5 0 Note 3 1.96 Q Open 24 

87 7 0.8 21 11.4 3.27 Q Closed 29 35 

88 7 0.8 0 26.9 1.15 UQ Closed 147 18 

89 7 0.8 0 45 1.15 UQ Closed 25 10 

90 7 0.8 16 2 3.41 Q Closed 12 33 

91 7 1.6 20 23.6 2.07 Q Closed 3 26 

92 7 5.5 20 24.8 2.07 Q Closed 15 37 

93 7 5.5 0 5.2 3.25 UQ Closed 59 27 

94 7 5.5 0 54 4.78 Q Closed 37 23 

95 7 5.5 0 29.2 5.37 UQ Closed 30 27 

96 6 5.5 21 1 5.37 UQ Closed 33 47 

97 

A 6 5.5 0 53.1 4.87 UQ Closed 9 

120 

B 6 5.5 0 Note 3 4.87 UQ Closed 89 

98 6 20 0 21.7 7.67 Q Closed 121 126 
53

Table 5-2. Summary of enclosure fire measurements (continued)

Test 

Encl.

Ignition Preheat Ambient Comb. Cable Door Peak Total 

Energy 

HRR HRR Temp. Mass Class. Position HRR Release

(kW) (kW) (°C) (kg) (kW) (MJ)

 Note 4 Note 

2 

99 6 5.5 0 26.5 2.30 UQ Open 3 7 

100 6 5.5 0 16.4 6.24 Q Closed 34 42 

101 6 20 0 1.2 6.24 Q Closed 66 70 

102 6 23 0 68.5 3.56 Q Open 10 17 

103 6 5.5 0 19.6 1.15 UQ Closed 42 50 

104 1 0.8 24 -5.2 4.74 UQ Open 250 141 

105 1 5.5 0 -3.3 6.10 UQ Closed 80 25 

106 

A 1 5.5 0 69.8 3.054 UQ Closed 17 

25 

B 1 5.5 0 Note 3 3.054 UQ Open 38 

107 1 5.5 19 -4.9 5.53 Q Open 55 51 

108 1 5.5 0 48 1.384 Q Closed 32 15 

109 8 5.5 19 -4.7 5.98 Q Closed 64 61 

110 

A 4 5.5 24 0.5 3.36 UQ Closed 7 

32 

B 4 5.5 24 Note 3 3.36 UQ Open 11 

111 

A 5 5.5 20 2.8 3.12 Q Closed 49 

120 

B 5 5.5 20 Note 3 3.12 Q Open 268 

112 4 5.5 0 113.9 1.68 UQ Open 22 12 
54

Notes: 

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

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

materials could not be extracted from the enclosure without disrupting the original 

construction. 

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

3. Ambient enclosure temperatures were not relevant during the mid test conditions. 

4. Estimated based on initial loading and review of test videos and pictures. 

5.2 Summary of Individual Experiments 

The following 112 pages contain a brief description of each experiment, including the important 

test parameters, a plot of the HRR, and some illustrative photographs. The HRR plots include 

the peak recorded temperature in the enclosure. The HRR of the ignition or preheating source, 

shown in red on the plots, is estimated either from a gas flow measurement of the propane 

igniters, or from oxygen consumption calorimetry of the pan of liquid fuel. The temperature 

history within the enclosure 0.15 m (6 in) below the top is shown in Appendix A for each 

experiment. 

Four to six shielded thermocouples (TC) were installed at various locations in each enclosure. 

The uppermost TC was typically 15 cm (6 in) from the top, depending on the interior contents. 

This uppermost TC usually recorded the peak temperature of the gases accumulating near the 

enclosure ceiling and provided a single value indicating the overall thermal environment within 

the enclosure. The TCs were not placed in direct proximity of the fire itself. Such a 

measurement would record a flame temperature but would not indicate the extent to which the 

entire enclosure was heated. 

For certain tests, there may be a letter designation written with the number (e.g., 12 (A,B,C)). In 

all tests where this designation is present, the beginning of the test is “A” and the times at which 

the next test “B” or “C” starts is written in the Notes part of the description. These letters refer to 

the designations that are used to characterize a change in fire conditions, i.e., ventilation while a 

test was ongoing. These designations are also noted in the RACHELLE-FIRE report listing of 

these tests. 

 
55

Table 5-3. 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. 
56

Table 5-4. 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. 
57

Table 5-5. 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. 
58

Table 5-6. 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. 
59

Table 5-7. Summary of Test 5 

Test: 5 

Enclosure: 4 

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. 
60

Table 5-8. 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. 
61

Table 5-9. 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 
62

Table 5-10. 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. 
63

Table 5-11. 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. 
64

Table 5-12. 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. 
65

Table 5-13. 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. 
66

Table 5-14. Summary of Test 12 

Test: 12 (A,B,C) 

Enclosure: 1 

Fuel Load: Same unburned cables from Test 11 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed, open at end of test 

Notes: The door of the enclosure was initially 

closed, but it was opened at approximately 

40 min (B) 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 door was opened at 80 min (C) 

and left open. The cables burned or smoldered 

for about an hour. All that remained was 

glowing char. 
67

Table 5-15. 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, opened briefly 

Notes: The door was opened at 23 min for 

approximately a minute and then closed again. 

The burner was turned off at approximately 

31 min. The fire did not spread beyond its point 

of origin. 
68

Table 5-16. Summary of Test 14 

Test: 14 (A,B) 

Enclosure: 8 

Fuel Load: Same as Test 13 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed, opened briefly 

Notes: This experiment was similar to Test 13, 

but the cables were bundled closer together 

around the igniter. There was no measureable 

increase in the HRR for approximately 20 min, 

at which time the door was opened (B) and a 

propane blow torch was used to try to spread 

the fire. The test was ended at approximately 

30 min. 
69

Table 5-17. Summary of Test 15 

Test: 15 (A,B) 

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, then closed 

Notes: The fire did not spread or grow 

appreciably in 30 min. At approximately 35 min 

(B), 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. 
70

Table 5-18. 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. 
71

Table 5-19. 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. 
72

Table 5-20. 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. 
73

Table 5-21. 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, for approximately 1 min each time. At 

40 min, the propane burner was increased to 

1.7 kW, but the fire still did not spread. 
74

Table 5-22. 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, opened briefly 

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, for approximately 1 min 

each time. The fire did not spread beyond 

60 cm (2 ft). The burner was turned off just 

short of an hour. 
75

Table 5-23. 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. 
76

Table 5-24. 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. 
77

Table 5-25. 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 and onto the floor of the enclosure 

where it burned for approximately 20 min. 
78

Table 5-26. 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. 
79

Table 5-27. 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, opened briefly 

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

above the burner. The door was opened at 

approximately 20 min for 1 min to check 

progress. The fire did not spread beyond the 

vicinity of the burner. Based on observation, 36 

cables were consumed 20 cm (8 in) above the 

burner. 
80

Table 5-28. Summary of Test 26 

Test: 26 

Enclosure: 1 

Fuel Load: Same as Test 25 

Ignition Source: 0.7 kW propane burner 

Ventilation: Door closed then opened 

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. Based on observation, 36 

conductors were consumed 10 cm (4 in) above 

the burner. 
81

Table 5-29. Summary of Test 27 

Test: 27 (A,B) 

Enclosure: 1 

Fuel Load: 2.99 kg 

Ignition Source: 0.7 kW propane burner 

Preheating Source: 150 mL ethanol pan fire 

Ventilation: Door closed, opened briefly 

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 (B), for approximately 

1 min. Each time the door was opened, the 

cables were jostled with a crowbar. The burner 

was turned off at 56 min. Based on 

observation, 36 conductors were consumed 

30 cm (1 ft) above the burner. 
82

Table 5-30. Summary of Test 28 

Test: 28 (A,B,C) 

Enclosure: 1 

Fuel Load: 2.87 kg 

Ignition Source: 0.7 kW propane burner 

Preheating Source: 300 mL ethanol pan fire 

Ventilation: Door closed, opened briefly 

Notes: The ethanol fire was exhausted at 

approximately 9 min after which the propane 

burner was ignited. At 19 min (B), the door was 

opened and the wires in the vicinity of the 

burner were jostled with a crowbar, and the 

door was closed. The fire then spread 

upwards, approximately 0.6 m (2 ft) above the 

burner. The crowbar process was repeated at 

40 min (C). 
83

Table 5-31. Summary of Test 29 

Test: 29 

Enclosure: 1 

Fuel Load: 2.64 kg 

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 in 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. Half of the 

combustible material was consumed. 
84

Table 5-32. Summary of Test 30 

Test: 30 

Enclosure: 1 

Fuel Load: 1.32 kg 

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. 
85

Table 5-33. Summary of Test 31 

Test: 31 

Enclosure: 4 

Fuel Load: 37. 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. 
86

Table 5-34. Summary of Test 32 

Test: 32 (A,B) 

Enclosure: 4 

Fuel Load: 37 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, then opened 

Notes: The acetone was exhausted at 

approximately 16 min, and the propane burner 

was turned off at 22 min. The door was opened 

at 16 min (B) and remained open. The fire did 

not spread beyond the vicinity of the propane 

burner. 
87

Table 5-35. Summary of Test 33 

Test: 33 

Enclosure: 5 

Fuel Load: 74 insulated conductors (#834), 

loosely bundled, 1.8 m (6 ft) 

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. Based on observation, 37 conductors 

were consumed 0.6 m (2 ft). 
88

Table 5-36. Summary of Test 34 

Test: 34 

Enclosure: 5 

Fuel Load: 62 insulated conductors (#834), 

loosely bundled, 1.8 m (6 ft) long, 1.22 kg 

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. 
89

Table 5-37. 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, then opened 

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. 
90

Table 5-38. Summary of Test 36 

Test: 36 (A,B) 

Enclosure: 2 

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

1.8 m (6 ft) long, 2.71 kg 

Ignition Source: 4 kW propane burner 

Ventilation: Door closed, then opened 

Notes: The fire did not spread beyond its point of 

origin near the base of the bundle. The front 

door was opened at 12 min (B). The burner 

was turned off at approximately 14 min. 
91

Table 5-39. Summary of Test 37 

Test: 37 

Enclosure: 2 

Fuel Load: Two bundles of 10 control cables 

(#807); 1.8 m (6 ft) long, 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. 10 control cables approximately 0.46 m 

(1.5 ft) on the right side were consumed,. 
92

Table 5-40. 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. 4.74 kg 

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. 
93

Table 5-41. Summary of Test 39 

Test: 39 

Enclosure: 8 

Fuel Load: 21 control cables (#807), 1.8 m (6 ft) 

long 

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. 
94

Table 5-42. 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. 
95

Table 5-43. Summary of Test 41 

Test: 41 (A,B) 

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 (B), and 

the fire grew rapidly afterwards. The coated 

relay wiring on the back side of the partition 

between the front and middle sections burned. 
96

Table 5-44. 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. 
97

Table 5-45. 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 then opened 

Notes: Even though the cables were immersed in 

the acetone, the fire did not spread upwards. 

The door was opened at 9.5 min and remained 

open. The acetone was exhausted at 

approximately 14 min. 
98

Table 5-46. 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, then opened 

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. 
99

Table 5-47. 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, then opened 

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. 
100

Table 5-48. Summary of Test 46 

Test: 46 

Enclosure: 4 

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

Each bundle contained 10 cables (#807), 

1.8 m (6 ft) long, 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. 
101

Table 5-49. Summary of Test 47 

Test: 47 

Enclosure: 4 

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

Each bundle contained 5 cables (#807), 1.8 m 

(6 ft) long, 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, at 

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. 
102

Table 5-50. Summary of Test 48 

Test: 48 

Enclosure: 4 

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

Each bundle contained 10 cables (#807), 1.8 

m (6 ft) long, 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. 
103

Table 5-51. Summary of Test 49 

Test: 49 

Enclosure: 4 

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

Each bundle contained 10 cables (#807), 

1.8 m (6 ft) long, 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. 
104

Table 5-52. Summary of Test 50 

Test: 50 

Enclosure: 4 

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

Each bundle contained 10 cables (#805), 

1.8 m (6 ft) long, stripped 20 cm (8 in) near the 

top 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed, then opened 

Notes: Even though the cables were immersed in 

the liquid fuel, the fire did not spread upwards. 

The door was opened at 18 min and remained 

open. The acetone was exhausted at 20 min. 
105

Table 5-53. Summary of Test 51 

Test: 51 

Enclosure: 4 

Fuel Load: The unburned left side bundle from 

Test 50, 10 cables (#805), 1.8 m (6 ft) long, 

stripped 20 cm (8 in) near top 

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. 
106

Table 5-54. 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, 1.8 m 

(6 ft) long 

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. 
107

Table 5-55. Summary of Test 53 

Test: 53 (A,B) 

Enclosure: 4 

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

Each bundle contained 70 insulated 

conductors stripped from Cable #807, 1.8 m 

(6 ft) long 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed, then opened 

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 (B), 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. Approximately, one-fourth of 

the initial fuel remained before the blow torch 

was applied 
108

Table 5-56. Summary of Test 54 

Test: 54 

Enclosure: 4 

Fuel Load: 2 bundles of surplus power cord 

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

1.8 m (6 ft) long 

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. 
109

Table 5-57. Summary of Test 55 

Test: 55 

Enclosure: 4 

Fuel Load: 2 bundles of surplus power cord 

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

1.8 m (6 ft) long 

Ignition Source: 4 kW propane burner and 

200 mL of acetone in a stainless steel cup 

10 cm in diameter 

Ventilation: Door closed, then opened 

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. 
110

Table 5-58. Summary of Test 56 

Test: 56 

Enclosure: 5 

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

side of enclosure, 1.8 m (6 ft) long 

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. 
111

Table 5-59. Summary of Test 57 

Test: 57 

Enclosure: 5 

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

side of enclosure, 1.8 m (6 ft) long 

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. 
112

Table 5-60. Summary of Test 58 

Test: 58 

Enclosure: 5 

Fuel Load: 10 jacketed cables and 10 stripped 

cables (#844), 1.8 m (6 ft) long. 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. 
113

Table 5-61. Summary of Test 59 

Test: 59 (A,B) 

Enclosure: 5 

Fuel Load: 10 jacketed cables and 10 stripped 

cables (#844), 1.8 m (6 ft) long. 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 

(B), 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. 
114

Table 5-62. 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. 
115

Table 5-63. 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. No appreciable 

combustible material lost. 
116

Table 5-64. Summary of Test 62 

Test: 62 

Enclosure: 1 

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

63 m (208 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 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 
117

Table 5-65. Summary of Test 63 

Test: 63 

Enclosure: 1 

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

63 m (208 ft) total 

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. 
118

Table 5-66. 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 burner. No appreciable 

combustible mass lost. 
119

Table 5-67. 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. No appreciable combustible 

mass lost. 
120

Table 5-68. Summary of Test 66 

Test: 66 (A,B) 

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 then opened 

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 (B), the door was opened 

and the cables were jostled with a crowbar. 

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

top. 
121

Table 5-69. Summary of Test 67 

Test: 67 (A,B) 

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, then open 

Notes: The propane burner was turned off at 

9 min. At 13 min (B), 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. 
122

Table 5-70. 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 cable had burned. 
123

Table 5-71. 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. 
124

Table 5-72. 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. No appreciable 

combustible mass lost. 
125

Table 5-73. 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. 
126

Table 5-74. 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, then opened 

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 oxygen measurement malfunctioned 

during this experiment, and it is assumed that 

the HRR is only that of the ignition source. 

The oxygen consumption calorimeter 

malfunctioned. No HRR data available. 
127

Table 5-75. Summary of Test 73 

Test: 73 

Enclosure: 4 

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

long 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed, then opened 

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 door remained open. The 

propane burner was turned off at 21 min. The 

fire spread approximately 45 cm (18 in) above 

the burner. 
128

Table 5-76. Summary of Test 74 

Test: 74 

Enclosure: 5 

Fuel Load: 10 cable bundle (#809), 1.8 m (6 ft) 

long 

Ignition Source: 1.6 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed, then opened 

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 opened and remained open. The propane 

burner was turned off at 22 min. The fire 

spread approximately 60 cm (2 ft) above the 

burner. 
129

Table 5-77. Summary of Test 75 

Test: 75 

Enclosure: 4 

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

long 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed, then opened 

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. 
130

Table 5-78. Summary of Test 76 

Test: 76 

Enclosure: 5 

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

long 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed and opened multiple 

times 

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. 
131

Table 5-79. Summary of Test 77 

Test: 77 (A,B) 

Enclosure: 5 

Fuel Load: 10 cable bundle (#809), 1.8 m (6 ft) 

long 

Ignition Source: 5.5 kW propane burner 

Preheating Source: 1 L acetone pan fire 

Ventilation: Door closed, then opened 

Notes: The acetone pan fire did not directly 

impinge upon the cables. The door was 

opened at 16 min, 30 s (B), 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. 
132

Table 5-80. Summary of Test 78 

Test: 78 (A,B) 

Enclosure: 5 

Fuel Load: 10 cable bundle (#809), 1.8 m (6 ft) 

long 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed, then opened 

Notes: The fire spread steadily to the top of the 

bundle. The burner was turned off at 15 min. 

The door was opened at 12 min 30 sec (B), 

and remained open. 
133

Table 5-81. Summary of Test 79 

Test: 79 (A,B) 

Enclosure: 4 

Fuel Load: 310 insulated wires stripped from 

Cable #834, 1.8 m (6 ft) long, arranged in 4 

loose bundles 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed, then opened 

Notes: The propane burner was turned off at 

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

(B). 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. 
134

Table 5-82. Summary of Test 80 

Test: 80 (A,B) 

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, then opened 

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 door was opened 

at 10 min and a crowbar was used. The door 

was opened again at 20 min. The acetone was 

exhausted at 18 min (B), and the propane 

burner was turned off at 21 min. The fire 

spread to the top of the bundles. 
135

Table 5-83. Summary of Test 81 

Test: 81 

Enclosure: 5 

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

long 

Ignition Source: 5.5 kW propane burner and 1 L 

acetone pan fire 

Ventilation: Door closed, then opened 

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. 
136

Table 5-84. Summary of Test 82 

Test: 82 (A,B) 

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, then opened 

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 (B) and left open. The propane burner 

was turned off at 32 min. 
137

Table 5-85. 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. 
138

Table 5-86. Summary of Test 84 

Test: 84 

Enclosure: 7 

Fuel Load: 36 cable bundle (#818), 2.4 m (8 ft) 

long 

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. 
139

Table 5-87. 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. No appreciable combustible 

mass lost. 
140

Table 5-88. Summary of Test 86 

Test: 86 (A,B) 

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. 

The cables were jostled with a crowbar at 

27 min 30 sec (B), 29 min, and 31 min. 
141

Table 5-89. 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. 
142

Table 5-90. 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, then opened 

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. The door 

was opened at 13 min 30 sec. 
143

Table 5-91. 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, then opened 

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. The door was opened at 20 min 45 

sec and left open. 
144

Table 5-92. 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, opened briefly 

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 door was 

opened at 15 min and again at 23 min. The fire 

spread slowly upwards, but only burned the 

vertical portion of the bundle, approximately 

1.2 m (4 ft) above the burner. 
145

Table 5-93. 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, open briefly 

Notes: The acetone pan fire did not directly 

impinge upon the wire. The door was opened 

at 10 min to check the burner. The acetone 

was exhausted and the burner turned off at 

20 min. No appreciable combustible mass lost. 
146

Table 5-94. 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. 
147

Table 5-95. 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, then opened 

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. 
148

Table 5-96. 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, then opened 

Notes: The door was opened at 20 min and left 

open. The propane burner was turned off at 

21 min. The fire spread vertically and 

approximately 30 cm (1 ft) horizontally. 
149

Table 5-97. 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, then opened 

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

door was opened at 22 min and left open. The 

fire spread vertically and approximately 30 cm 

(1 ft) horizontally. 
150

Table 5-98. 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, then opened 

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. 
151

Table 5-99. Summary of Test 97 

Test: 97 (A,B) 

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 (B), 

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. 
152

Table 5-100. 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, then opened 

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. 
153

Table 5-101. 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. 
154

Table 5-102. 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, opened briefly multiple 

times 

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 

consumed approximately 1 m (3 ft) of the 80 

cables. Roughly half of the combustible load. 
155

Table 5-103. 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. Approximately 3.9 kg. 

Ignition Source: 1 L acetone pan fire 

Ventilation: Door closed, then opened 

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. 
156

Table 5-104. 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. 
157

Table 5-105. 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. 
158

Table 5-106. 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. 
159

Table 5-107. Summary of Test 105 

Test: 105 

Enclosure: 1 

Fuel Load: A variety of cable remnants, 

approximately 6.1 kg 

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. Approximately half of the 

combustible mass was consumed. 
160

Table 5-108. Summary of Test 106 

Test: 106 (A,B) 

Enclosure: 1 

Fuel Load: Unburned portion of Test 105 along 

left side of enclosure, approximately 3.05kg 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed, then opened 

Notes: The door was opened at 9 min and left 

open (B). 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. 
161

Table 5-109. 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. Approximately, threequarters of the combustible material was 

burned. 
162

Table 5-110. Summary of Test 108 

Test: 108 

Enclosure: 1 

Fuel Load: Unburned wire from Test 107, 

approximately 1.38 kg 

Ignition Source: 5.5 kW propane burner 

Ventilation: Door closed, then opened 

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. 
163

Table 5-111. 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, then opened 

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 and left open. The 

fire consumed the cable within the enclosure, 

and scorched approximately 15 cm (6 in) of 

cable outside. 
164

Table 5-112. Summary of Test 110 

Test: 110 (A,B) 

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, then opened 

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 (B). 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. 
165

Table 5-113. Summary of Test 111 

Test: 111 (A,B) 

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, then opened 

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 door was opened at 20 min and 

left open (B). The fire spread rapidly on both 

sides following the door opening. All of the 

cable insulation was consumed. 
166

Table 5-114. 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. 
167

5.3 General Observations 

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

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

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

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

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

fires with qualified cable do not become very large.” 

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

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

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

spread was much wider than with qualified cable.” 

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

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

from the burning cabinet to adjacent cabinets.” 

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

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

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

is not surprising given that the enclosure geometries and cable construction have not 

significantly changed since the early 1980s. 

5.3.1 Ignition 

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

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

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

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

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

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

conductor wiring insulated with thermoplastic materials like polyethylene. Stronger propane 

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

single conductor thermoset wiring. Acetone pan fires, with HRRs on the order of 20 kW, were 

required to ignite jacketed thermoset cable. Chavez (1987) reports similar observations. 

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

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

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

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

5.3.2 Fire Spread 

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

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

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

upwards beyond the flame height of the igniter, but stopped because it could not support itself 
168

without the assist of the heat from the igniter. In cases where the fire spread to the top of the 

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

notes the same phenomenon when he says that the fires were not severe enough to cause 

auto-ignition. In a few instances, the fire spread to the top of the enclosure and burned the top 

end of some of the cables from the opposite side, but in general the fire spread was vertical in a 

vertical enclosure. In bench board enclosures, the fire sometimes spread horizontally near the 

top of the enclosure. 

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

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

to the other. However, enclosure to enclosure spread was not the focus of this test series and 

no conclusions should be drawn from the results. 

5.3.3 Ventilation 

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

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

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

operated during the experiments. Smoke from the fire would have been blown outside of the 

exhaust product collection hood and adversely impacted the HRR measurements. The 

removable plates did not seem to have much of an impact on the fire behavior, probably 

because the variation in the fire dynamics test to test was such that the effect of the plate could 

not be distinguished. Since only two of the fires reached peak heat release rates where 

ventilation would be expected to have a significant influence, this test series has limited value 

for analyzing the impact of ventilation. 

5.3.4 Peak Heat Release Rate 

In an effort to expand the data available for analysis, some test conditions were altered during 

the tests. For example, doors that were initially closed were opened and remained open for the 

duration of a test to examine ventilation effects. A crowbar was used to “jostle some of the 

cable bundles during some tests to examine the impact of cable bundling on peak HRR rate. 

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

sources from the total measured HRR. Of the 112 experiments, the peak HRR varied from 0 kW 

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

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

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

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

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

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

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

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

thermoset rather than thermoplastic insulation. 
169

6 CONCLUSION AND FUTURE WORK 

During the Heat Release Rates of Electrical Enclosure Fires (HELEN-FIRE) program, 112 fullscale experiments were conducted in which the heat release rate of fires in a variety of electrical 

enclosures was measured using oxygen consumption calorimetry. This data can be used in the 

development of energy source terms for fire models used to assess the potential consequences 

of fires within nuclear power plants (NPPs).

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

The 112 experiments in the HELEN-FIRE test program can be used to support development of 

statistical distributions of HRRs that can be input into fire models. However, simplified fire 

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

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

words, even if the HRR of the fire is specified, there is no physical mechanism within the model 

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

and not transported upwards to damage ceiling targets. In the HELEN-FIRE experiments, the 

overall HRR of the fire was inferred from the measured rate of oxygen consumption, but it was 

not possible to measure the fraction of the energy that was absorbed by the steel walls of the 

enclosure and the fraction that was transported into the exhaust duct. 

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

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

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

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

The results of the experiments will be used to develop guidance for applying the HRRs to 

simplified models and to validate CFD models used to assess other enclosure geometries. 

171

7 REFERENCES 

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

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

Regulatory Commission, Washington, DC. 

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

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

US Nuclear Regulatory Commission, Washington, DC. 

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

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

52: 34-45. 

IEEE-383 (1974) Standard for Qualifying Class 1E Electric Cables and Field Splices for Nuclear 

Power Generating Stations, IEEE Standards Association.

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

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

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

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

Finland. 

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

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

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

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

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

Release, Ignition, and Spread in Tray Installations During Fire (CHRISTIFIRE), NUREG/CR7010, Vol. 1, National Institute of Standards and Technology, Gaithersburg, Maryland. 

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

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

Laboratories, Albuquerque, New Mexico. 

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

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

Regulatory Commission, Washington, DC.

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

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

Commission, Washington, DC. 

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

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

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

Protection Association, Quincy, Massachusetts. 
172

Taylor, B.N. and C.E. Kuyatt (1994), Guidelines for Evaluating and Expressing the Uncertainty 

of NIST Measurement Results, NIST Technical Note 1297, National Institute of Standards and

Technology, Gaithersburg, Maryland. 

U.S. NRC and EPRI (2004), Fire PRA Methodology for Nuclear Power Facilities, NUREG/CR6850, U.S. Nuclear Regulatory Commission, Washington, DC. 

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

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

Research Institute, Palo Alto, CA. 
A-1

Appendix A TEMPERATURE DATA 

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

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

below and centered from left to right. 

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

 
A-2

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

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

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

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

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

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

Enclosure temperatures were not measured 

for Test CBD-46. 

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

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

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

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

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

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

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

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

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

Figure A-17. Enclosure temperatures, Tests 95-100. 
A-18

Figure A-18. Enclosure temperatures, Tests 101-106. 
A-19

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





 

 

NUREG/CR-7197

Final

Heat Release Rates of Electrical Enclosure Fires (HELEN-FIRE)