Appliances, Part 1

State of the Art Review and Fire

Tests, Volume I

Richard D. Peacock

Efrain Ruiz

Roberto Torres-Pereira

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

November 1980

Final Report

Prepared for: -qc

100

.056

i/Vashington, DC 20585

.S. Department of Energy

80-2140

1980

c.2

National Bureau of Standards

Library, E-01 Admin. Bldg.

NBSIR 80-2140 MAfi 1 •

1

/ 34 o

' Ct * ^ FIRE SAFETY OF WOOD-BURNING

APPLIANCES, PART 1:

STATE OF THE ART REVIEW AND FIRE

TESTS, VOLUME I

Richard D. Peacock

Efrain Ruiz

Roberto Torres-Pereira

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

November 1980

Final Report

Prepared for: U.S. Department of Energy

Washington, DC 20585

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary

Jordan J. Baruch, Assistant Secretary for Productivity, Technology, and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

PREFACE

The U.S, Department of Energy, as part of a program to facilitate the

increased use of wood as an alternate energy source, has sponsored studies

at the Center for Fire Research of the National Bureau of Standards to

investigate the fire safety of wood-burning appliances. This report, the

first presenting information from the Department of Energy sponsored experimental program, details the results of fire tests performed on a number of

wood-burning appliances.

The report is separated into two volumes:

Volume I , which includes the text of the report with figures and tables

and presents a review of previous work, details the test program and provides

an analysis of the test results; and

Volume II , which includes the two appendices to the report that present

detailed graphs of the measurements made during the 18 room experiments

(appendix A) and calculated averages and maximums taken from the data in

appendix A (appendix B)

iii
TABLE OF CONTENTS

Page

PREFACE iii

LIST OF FIGURES vi

LIST OF TABLES vii

NOMENCLATURE viii

EXECUTIVE SUMMARY ix

Abstract 1

VOLUME I

1. INTRODUCTION 1

2. REVIEW OF PREVIOUS WORK 3 2.1 Fire Incidents Involving Wood-Burning Appliances 3

2.2 Clearances in Existing Codes and Standards 4 2.3 Temperatures Developed in Heating Appliances 5 2.4 Limiting Safe Temperatures on Combustible Surfaces 6 2.5 Theoretical Prediction of Adjacent Wall Surface Temperatures 7 2.5.1 Configuration Factor for Fuel Pipe Surfaces 7 2.5.2 Configuration Factor for Appliance Surfaces 8

3. SCOPE OF WORK 8

4. DESCRIPTION OF EXPERIMENTAL FACILITIES AND INSTRUMENTATION .... 9

4.1 Test Enclosure 9 4.2 Instrumentation 9 4.3 Data Recording and Instrumentation Accuracy 10

5. TEST PROGRAM 11

5.1 Test Procedure 11

5.2 Appliances 12

6. TEST RESULTS 13

6.1 Appliance Temperatures 13

6.2 Wall Temperatures 13

6.3 Floor Temperatures 14

7. ANALYSIS OF RESULTS 14

7.1 Appliance Temperatures 14

7.2 Wall Temperatures 15

7.3 Floor Temperatures 17

7.4 Wall Insulation 18

7.5 Tests With Front Wall 19

7.6 Log Tests 19

7.7 Measurement Technique 20

8. THEORETICAL TEMPERATURE PREDICTION 21

8.1 Heat Transfer From Flue Pipe Surface 22

8.2 Heat Transfer From Appliance Surface 23

IV
TABLE OF CONTENTS (continued)

Page

9. CONCLUSIONS 24

10. ACKNOWLEDGEMENTS 26

11. REFERENCES 27

VOLUME II

APPENDIX A A-l

APPENDIX B B

Volume II is in microfiche form

in the back of this volume.

v
LIST OF FIGURES

Page

Figure 1. Breakdown of fire incidents by equipment type as recorded

in NFIRS solid fuel fire incident data 31

Figure 2. Construction of test enclosure used in room experiments . . 32

Figure 3. Instrumentation locations for appliance measurements

in room experiments 33

Figure 4. Instrumentation locations for test enclosure measurements

in room experiments 36

Figure 5. Construction of "brands" used in room experiments . ... 37

Figure 6. Flue gas temperatures measured during tests of several

wood-burning appliances 38

Figure 7. Flue pipe surface temperatures measured during tests of

several wood-burning appliances 39

Figure 8 . Maximum measured steady state wall temperatures during

tests of appliance 1 40

Figure 9. Maximum measured steady state wall temperatures during

tests of appliance 2 41

Figure 10. Maximum measured steady state wall temperatures during

tests of appliance 3 42

Figure 11. Maximum measured steady state wall temperatures during

tests of appliance 4 43

Figure 12. Maximum measured steady state wall temperatures during

tests of appliance 5 44

Figure 13. Maximum measured steady state wall temperatures during

tests with wall insulation 45

Figure 14. Maximum measured steady state wall temperatures during

tests with front wall 46

Figure 15. Maximum measured steady state floor temperatures during

tests of appliance 1 47

Figure 16. Maximum measured steady state floor temperatures during

tests of appliance 2 48

Figure 17. Maximum measured steady state floor temperatures during

tests of appliance 3 49

Figure 18. Maximum measured steady state floor temperatures during

tests of appliance 4 50

Figure 19. Maximum measured steady state floor temperatures during

tests of appliance 5 51

Figure 20. Maximum measured steady state floor temperatures during

tests with wall insulation 52

vi
LIST OF FIGURES (continued)

Page

Figure 21. Maximum measured steady state floor temperatures during

tests with front wall 53

Figure 22. Effect of appliance/wall clearance on measured wall

temperatures during tests of several wood-burning

appliances 54

Figure 23. A comparison of maximum appliance temperatures for tests

using logs as a fuel source with tests using douglas fir

brands as a fuel source 55

Figure 24. Test apparatus to evaluate thermocouple mounting

techniques 56

Figure 25. Surface/air temperature difference vs. airflow for

different radiant panel temperatures 57

Figure 26. Surface temperatures as measured using different

thermocouple mounting techniques 58

Figure 27. Heat transfer to wall surfaces 59

Figure 28. Predicted wall surface temperature for heat transfer from

flue pipe only 60

Figure 29. Predicted wall surface temperature for heat transfer from

appliance only 61

LIST OF TABLES

Table 1. Instrumentation locations for measurements during room

experiments for appliances and test enclosure 62

Table 2. Physical characteristics of wood-burning appliances tested . . 63

Table 3. Test conditions for room experiments 64

Table 4. Temperatures measured during fire tests of several wood

heating appliances 65

Table 5. Maximum rise above room temperature on wall and floor

surfaces during fire tests of several wood heating

appliances 66

Table 6. Temperatures measured during log tests of several wood

heating appliances 67

Table 7 . Comparison of measured and calculated wall surface

temperatures for heat transfer from flue pipe to wall .... 68

Table 8. Comparison of measured and calculated wall surface

temperatures for heat transfer from appliance to wall .... 69

vii
NOMENCLATURE

d -

e, , e h w

m

n

w

u

distance between stove surface and adjacent wall surface (m)

edge length (height, width) of stove surface (m)

F - configuration factor for an appliance or flue pipe surface with respect

to the adjacent wall surface

h -

2 4/3 convective heat transfer coefficient (W/m K ) length of flue/diameter of flue (dimensionless)

distance of axis of flue from panel/radius of flue (dimensionless)

T

- ambient temperature of surroundings near the opposite side of the wall

(K)

T -

T -

T -

T

-

surface temperature of the opposite side of the wall (K)

temperature of the room surroundings near the wall surface (K)

appliance or flue pipe surface temperature (K)

wall surface temperature (K)

2 conductive heat transfer coefficient (W/m K)

emissivity

2 4 Stef an-Boltzmann constant (W/m K )

viii
EXECUTIVE SUMMARY

The U.S. Department of Energy, as part of a program to facilitate the

increased use of wood as an alternate energy source, has sponsored studies at

the Center for Fire Research of the National Bureau of Standards to investigate the fire safety of wood-burning appliances used for space heating in

single-family dwellings and similar small-scale applications. The program

includes

• a survey of fire incidents involving wood-burning appliances;

• a review of codes and standards dealing with solid-fuel appliances;

• experimental studies to develop information in the areas of clearances

to combustibles, chimney creosoting and chimney fires, fireplace inserts, and

products of combustion; and

• technical input to a public education effort by DOE and other government

agencies

This report, the first presenting information from the DOE sponsored

experimental program on wood-burning safety at NBS, details the results of

fire tests performed on a number of wood-burning appliances. The tests were

conducted to establish typical operating conditions including temperatures on

the appliances, chimneys, and adjacent wall and floor surfaces.

Several generic types of appliances were included to exemplify those

available in the market. A total of 28 tests were conducted. In these tests,

a total of more than one-half million individual readings of temperature, heat

flux, or velocity were obtained. Two series of tests were conducted:

• full-scale room experiments where measurements of appliance temperature

and surrounding surface temperature were obtained using a standard wood brands

as fuel, and

• "log tests" where seasoned oak logs were used as a fuel source to

compare with a standard wood "brand" fuel source. Only appliance surface

temperature and flue gas temperature were monitored in the "log tests."

Some conclusions from these tests were apparent:

• Appliance firebox surface temperatures measured during steady-state

operation were very similar for all five appliances tested. For appliance 5, a jacketed circulating room heater, outside jacket temperatures were lower.

No correlation was found between appliance surface temperature and clearance

between the appliance and wall surfaces.

• The temperature of the lightweight single wall flue pipe used for

testing was more greatly affected by the clearance between the pipe and wall

surface, an effect not noted for the appliance surface temperature measurements .

• Understandably, wall surface temperatures were found to vary inversely

with the clearance between the appliance and wall surface. Wall temperatures

as high as 189°C were recorded (for an improperly installed appliance)

• Appliance design and appliance size were found to affect temperatures

on wall surfaces.

• Due to the small clearances between appliances and flooring,

temperatures developed on unprotected floor surfaces were typically higher

than wall temperatures during the tests.

IX
• Wall surface temperatures and interior wall studding temperatures

were considerably higher during tests with wall insulation or with a front

wall than without.

• Average maximum appliance surface temperatures measured during tests

using seasoned oak logs as the fuel source were similar to those developed

during the "brand" tests.

• Theoretical calculations of wall surface temperature agreed within

an average of 10°C with measured wall temperatures. Individual calculation

agreement, however, ranged from excellent to poor.

These tests provide the basis for future research on proper clearances

between combustible surfaces and wood-burning appliances and on protective

devices used to allow reduced clearances. The research is expected to lead

to recommendations for modifications to the appropriate model codes, to

improved installation guidelines, and to the preparation of manuals of recommended practices for the safe and optimum use of the wood resource.

x
FIRE SAFETY OF WOOD-BURNING APPLIANCES, PART 1:

STATE OF THE ART REVIEW AND FIRE TESTS, VOLUME I

Richard D. Peacock, Efrain Ruiz, and Roberto Torres-Pereira

Abstract

A series of 18 full-scale tests was conducted in an

instrumented test room using five different wood-burning

appliances. These tests were designed (1) to establish

typical operating conditions including temperatures on

the appliances, chimneys, and adjacent combustible surfaces; (2) to study the effects of a variety of combinations of appliance design, clearance to combustibles, and

room construction on temperatures on adjacent combustible

surfaces; and (3) to compare these measured values with

theoretical predictions of wall surface temperature.

Additional tests were conducted to compare a standardized

fuel source with typical oak logs.

A review of literature related to wood-heating safety

included in this study revealed that current codes are based

on data almost 40 years old. The results of these tests

point out some areas where the codes should be modernized

to accurately reflect the newer appliances and construction

techniques

.

Key words: Chimneys; fire models; fire safety; fire tests;

flues; heating equipment; heat transfer; literature reviews;

radiant energy; stoves; wood.

1. INTRODUCTION

The U.S. Department of Energy (DOE), as part of a program to facilitate

the increased use of wood as an alternate energy source, has sponsored studies

at the Center for Fire Research (CFR) of the National Bureau of Standards (NBS)

to investigate the fire safety of wood-burning appliances used for space heating in single-family dwellings and similar small-scale applications. It is

important that the potential fire risks associated with these uses be evaluated

1
and that the appropriate codes, standards, recommended practices, and test

methods be developed and implemented to assure an adequate level of fire safety.

During the first year of the program, an accident survey, literature

review, and codes and standards analysis was performed to establish accident

patterns, to determine the types of risks involved with the use of wood-burning

appliances, and to ascertain the adequacy of existing codes and standards in

addressing the risks associated with wood-burning appliances [1-3] 1

. Overwhelmingly, conditions related to the installation, operation, and maintenance were responsible for the fire incidents studied. Only a small

percentage of the fires were attributed to product design or product defects.

Thus, the safe installation and use of wood-burning appliances is a critical

requirement for preventing fire accidents involving the equipment. Existing

criteria for the installation of wood-burning appliances are based on data

developed nearly 40 years ago and do not provide information on materials

of construction or appliances available in the current market or allow for

variations based on the use of alternate materials.

Accordingly, the plan proposed for a continued experimental program

stresses the installation, operation, and maintenance of wood-burning appliances with some specific objectives for the work during the second and third

years of the program:

• perform necessary experimental studies to develop and quantify safe

but reasonable limits for important fire safety parameters including clearances

to combustibles, chimney creosoting and chimney fires, and products of

combustion;

• provide the technical input to a public education program to be

developed in conjunction with public education efforts at NBS , DOE, and other

government agencies;

• interface with the appropriate model code agencies and consensus

standards groups to initiate the prompt adoption of changes that are desirable

for the safe and optimum use of the wood resource.

This report, the first presenting information from the DOE sponsored

experimental program on wood-burning safety at NBS, presents the results of

fire tests performed on a number of wood-burning appliances. The tests were

Numbers in brackets refer to literature references listed in section 11 at

the end of this report.

2
conducted to establish typical operating conditions including temperatures on

the appliances, chimneys, and adjacent wall and floor surfaces. The data

gathered from these tests will be used to design and confirm laboratory scale

experiments to study minimum acceptable clearances to combustibles and to

study various methods to protect combustibles from the heat generated by

wood-burning appliances.

2. REVIEW OF PREVIOUS WORK

2.1 Fire Incidents Involving Wood-Burning Appliances

An analysis of fire incidents involving solid fuel heating appliances

was conducted by NBS during the first year of the project with fire incident

data from the following sources:

• U.S. Fire Administration;

• National Electronic Injury Surveillance System;

• Massachusetts State Fire Marshal's Office;

• Oregon State Fire Marshal's Office;

• National Fire Protection Association;

• Flammable Fabrics Accident Case and Testing System.

Product malfunctions, construction defects, design deficiencies, or worn

out equipment were attributed to be the cause in only 13% of the solid fuel

related fires recorded in the U.S. Fire Administration data base [1,2],

Overwhelmingly, conditions related to the installation, operation, or maintenance of the appliances were reported as responsible for the fires.

Shelton [3,4] supports this conclusion with studies in the state of

Massachusetts and from an insurance company in Wisconsin. A further analysis

of the data presented in references [1] and [2] is presented in figure 1.

The breakdown of solid fuel related fire incidents by probable cause and by

equipment type indicates that except for improper maintenance, the appliances themselves were involved in most of the fires rather than chimneys or chimney connectors--over 70% in these cases. However, under the category of

improper maintenance, appliances were involved in only 26% of the recorded

fires. Improper maintenance is the significant problem associated with

3
chimneys and chimney connectors while improper installation and operation is

more important with appliances.

2.2 Clearances in Existing Codes and Standards

Recommendations for minimum acceptable clearances to combustible

materials for the installation of chimneys, chimney connectors, and appliances

are specified in the various model codes and recommended practices manuals [1

5-13]. For simplicity and ease of enforcement, a single, hopefully conservative clearance is given for each type of appliance installed without protection.

No allowance is made for the size, heat output, heat transfer characteristics

or other features unique to individual models. Similarly, only a few, specific

methods of protection employed to allow reduction of these clearances are

recommended. Shelton [4] illustrates the effect of appliance size on minimum

safe clearances with theoretical calculations for two radiant room heaters.

Assuming equal surface temperatures, a small heater [surface area of the side

2 2 parallel to a wall of about 930 cm (1 ft ) ] is equally safe at a clearance of

0.5 m (20 in) as a larger heater [surface area of the side parallel to a wall

2 2 of about 0.51 m (5.5 ft ) ] at a clearance of 0.91 m (36 in).

Typically, 0.91 m (36 in) of clearance is specified between radiant

heaters and unprotected combustible construction. For circulating heaters,

clearances of 0.61 m (24 in) from the front of the appliance and 0.30 m (12 in)

from the sides and back of the appliance are recommended [13] . For single wall

metal chimney connectors [13], 0.46 m (18 in) is usually recommended as a minimum clearance.

Several experimental studies have been carried out to determine minimum

acceptable clearances to combustible materials. Voigt, in a 1933 publication,

recommends a minimum clearance of 0.30 m (12 in) for chimney connectors 0.23 m

(9 in) in diameter [14] . A more extensive study, performed by Underwriters

Laboratories in 1943, presents minimum safe clearances for both unprotected

surfaces and surfaces protected by various methods. Distances at which a maximum temperature rise of 50 °C (90 °F) above room temperature is reached are

presented as a function of the temperature of the exposed face of a heat producing appliance. The relative protection afforded by various materials used

as heat barriers between the appliance and combustible surface is also examined

[15] . Lawson, Fox, and Webster [16] and Lawson and Sims [17] have studied the

heating of wall panels and wood by radiation. With experimentation and theoretical predictions, they present safe clearances between flue pipes and wall

surfaces as a function of the pipe diameter and the pipe surface temperature.

To maintain a maximum wall temperature of 100°C (212°F), a 0.15 m (6 in) pipe

4
should not exceed 350°C (660°F) in surface temperature at a clearance of 0.46 m

(18 in) [16]

.

2.3 Temperatures Developed in Heating Appliances

Tests made with prefabricated porcelain-enameled metal chimneys for

solid or liquid fuel furnaces established a limiting temperature rise of 190 °C

(375°F) on the outer surface of the chimney for a flue gas temperature of 540°C

(1000°F) . With this limitation, wood framing spaced 5 cm (2 in) or more away

from the chimney was considered safe. Satisfactory insulation of the chimneys

to reduce the outer surface temperatures to acceptable levels was obtained with

asbestos paper plies totaling about 4.5 cm (1-3/4 in) in thickness. Some

asbestos-cement pipe coverings were also found to be capable of reducing heat

transmission to the extent required for safety to nearby combustibles [18,19].

To establish performance requirements for lightweight prefabricated

chimneys, tests were conducted with lined and unlined masonry chimneys having

10 cm (4 in) thick walls. Hazardous conditions on wood framing spaced 5 cm

(2 in) away from the chimney were noted with a continued flue gas temperature

of 480°C (900°F) for the unlined chimney and 590°C (1100°F) for the lined

chimney. However, these hazardous conditions were not reached in the lined

chimney tests until after 13 hours [20]. As a comparison with typical fuels,

a number of firing tests were conducted with heating appliances known to give

high flue gas temperatures, using wood and soft coal as . fuels. With a coalfired, jacketed type heater, flue gas temperatures at the floor level above

the heater of 650°C to 705°C (1200°F to 1300°F) were obtained for an hour

or more [20]

.

Lawson, et al. [16] present the results of tests to measure surface

temperatures of flue pipes to validate theoretical predictions. Measured for

a variety of flue systems using solid f uels--mostly coal and coke —they report

temperatures of about 148°C (300°F) under "normal conditions" and temperatures

as high as 815°C (1500°F) under overload conditions.

Fox and Whittaker [21] report temperatures on metal flues of several

heating appliances over a range likely to be encountered in normal use. Maximum flue pipe surface temperatures ranged from 700°C to 815°C (1300°F to

1500°F) at the appliance flue outlet, 360°C to 510°C (680°F to 950°F) at a distance of 1 m (3 ft) from the appliance flue outlet and 280°C to 330°C (550°F

to 620°F) at a distance of 2 m (6 ft) from the appliance flue outlet.

5
Larsson [18] concludes that combustible materials will be ignited if

maintained in continued contact with a chimney of 12 cm (4-3/4 in) wall

thickness and with flue gas temperatures of 400°C (750°F)

.

Current test procedures for prefabricated chimneys require testing of

chimney assemblies with hot flue gases [22]. Flue gas temperatures of 540°C

(100 0 °F ) are maintained until steady-state conditions are reached, followed

by 760°C (1400°F) for 1 hour and 925°C (1700°F) for 10 minutes. These

conditions are intended to simulate worst-case conditions.

2.4 Limiting Safe Temperatures on Combustible Surfaces

Listings of heat producing appliances by nationally recognized testing

laboratories and methods for reducing clearances to combustible surfaces are

based on upper limits for temperature on adjacent surfaces of

• 65 °C (117 °F) rise above room temperature on exposed surfaces, and

• 50°C (90°F) rise above room temperature on unexposed surfaces such as beneath the appliance, floor protector, or wall mounted shield [23]

.

While the ignition temperature of wood products is generally quoted to

be on the order of 200°C (400°F), wood that is exposed to a constant heating

over a period of time may undergo a chemical change resulting in a much lowered

ignition temperature and increased potential for self-ignition [24].

Mitchell [25] presents tests on wood fiberboard exposed to moderately

elevated temperatures as low as 109 °C (228 °F) that resulted in ignition after

prolonged exposure. MacLean [26,27] reports charring of wood samples at

temperatures as low as 93°C (200 °F)

.

He concludes that wood should not be

exposed to temperatures appreciably higher than 66 °C (150 °F) for long periods.

McGuire [28], suggests that the maximum safe temperature on the surface of a combustible material adjacent to a constant heat source should be no more than

100°C (212 °F) .

Clearly, the ignition of wood at moderately elevated temperatures is a complex phenomenon. The time of exposure is indeed an important parameter

[29]

.

The ignition and self-heating properties of charcoal may be more

important than that of "natural" wood according to Shelton [4], Still, the

numerous documented fires involving the ignition of wood members near low

pressure steam pipes [30] suggest an upper temperature limit for wood exposed

to long-term low-level heating should not be appreciably higher than 100 °C

(212 °F) . 6
2.5 Theoretical Prediction of Adjacent Wall Surface Temperatures

Under steady-state conditions, the heat gained by the adjacent wall from

an appliance or flue pipe surface will equal the heat lost by the adjacent wall

to the surroundings. Thus, a heat balance for the appliance or flue pipe near

an adjacent wall can be derived:

Net heat absorbed by the wall surface by radiation from the stove

4 4 or flue pipe: ^ Foe (T -T ). ^ s w

Net heat lost by the wall surface to the surroundings by radiation:

(l-F)ae(Tw

4 -T

r

4

)

Net heat lost by the wall surface to the surroundings by convection:

h (T -T ) 4//3. w r

Net heat lost by the wall surface by conduction through to the

opposite side of the wall: U (T -T )

w o

Net heat lost by radiation and convection from the opposite side of

4 4 4 /i the wall: os (T -T )+h(T -T ) '

. o a ' o a'

Balancing the heat gain and heat loss terms gives:

44 44 4/1 4 4 4/3 Fas (T -T )=(l-F)ae(T -T )+h(T -T ) ' +U(T -T )+ae(T -T )+h(T -T ) '

. s w w r wr wo o a oa

Shelton [4]

,

Lawson [16] , and Thulman [31] have also applied the

principles of heat transfer theory to predict temperatures on adjacent surfaces

exposed to heating by stoves and flue pipes . They have developed configuration

factors for radiative heat transfer as described below.

2.5.1 Configuration Factor for Flue Pipe Surfaces

For heat transfer from flue pipe surfaces, Lawson [16] presents the

configuration factor for straight sections of flue pipe as seen from a point

directly opposite the midpoint of the pipe as:

F = -

7T mn

[m2 n

2 + [n 2 - l] 2

]

1/ 2

tan

-1 [n2 - l]

1'2

[m2 n

2 + [n 2 - l]

2

]

1/ 2

, 1 . _ -1 m

[n2 - lV/2

7
2.5.2 Configuration Factor for Appliance Surfaces

For heat transfer from appliance surfaces, the configuration factor for an appliance of width ew and height e^ at a distance of d from a parallel wall

can be expressed as:

F = -

U

1 + tan

-1

th/%1

2 ~ wf

1 tan" 1 1

[i + [2d/eh]

;

?

J 1/2 tan

_[eh/ew]

2 +

[

2d/eh]‘

1/2

for the point on the wall directly opposite the center of the appliance surface

[31].

The theoretical model presented here will be used to compare theoretical

predictions with measurements obtained during the experiments reported below.

3. SCOPE OF WORK

The work reported herein consists of a series of tests conducted on several

different wood-burning appliances in a full-scale test room. Several generic

types of appliances were included to exemplify some of the types available in

the marketplace. Tests were conducted on

• three radiant room heaters, including a side-loading unit with a glass

front;

• a "Franklin" type fireplace stove; and

• a circulating or convective type room heater.

The study was primarily designed to provide data on both normal and

overload conditions for the appliances to be used in the development of

laboratory-scale tests of methods employed to allow reduced clearances to

adjacent combustible surfaces. In addition, it was also formulated to obtain

information on several aspects of fire safety of wood-burning appliances.

Areas of interest included:

8
• temperature and heat transfer rates on adjacent combustible surfaces;

• temperatures on appliance surfaces;

• temperatures of flue pipe surfaces and flue gas;

• the effects of changes in room geometry and wall construction on

temperatures developed on combustible surroundings.

4. DESCRIPTION OF EXPERIMENTAL FACILITIES AND INSTRUMENTATION

4.1 Test Enclosure

The appliances were tested in an enclosure approximately 2.4mx2.4mx

2.4m (8 ft x 8 ft x 8 ft)

Three permanent walls were erected and instrumented

as shown in figure 2. A fourth wall, erected with a doorway for some tests,

allowed different room ventilation conditions to be explored. Room construction

followed standard practices. Wall and ceiling linings consisted of 13 mm (1/2

in) gypsum wallboard over 5 cm x 10 cm (2 in x 4 in) wood studding spaced 41 cm

(16 in) apart on center. Flooring used was 1.9 cm (3/4 in) plywood over 5 cm x

10 cm (2 in x 4 in) studding spaced 41 cm (16 in) apart on center.

Wall and ceiling insulation was applied for some tests to study the effects

of typical insulation on temperatures developed in the test enclosure and gain

information on any increased fire risk due to the insulation.

4.2 Instrumentation

The test enclosure, appliances, and flue were instrumented to measure

conditions throughout the tests. All instrument data were automatically

recorded at regular intervals on a high-speed digital data acquisition system.

Data obtained included:

Temperature measurements . 24-gauge chromel-alumel thermocouples were used

to measure temperatures on appliance surfaces, flue pipe surfaces, exposed face

of the test enclosure, and rear surfaces of walls and flooring in contact with

wood studs. During tests where insulation was applied, the temperature of the

insulation was monitored as well as the surface temperature of the opposite

face of the insulated wall. Flue gas temperatures were monitored with shielded

thermocouples mounted in the center of the flue. Thermocouple locations are

indicated in table 1 and figures 3 (appliances) and 4 (test enclosure)

9
Heat flux measurements . Gardon-foil type water-cooled heat flux meters

were used to measure heat flux incident on the wall surface behind the

appliances. Heat flux meter locations are presented in table 1 and figure 4.

Velocity measurements . A bidirectional low-velocity probe was located

in the flue approximately 6 m (20 ft) from the appliance outlet to measure

the velocity of the flue gas. This type of probe was developed by Heskestad

[32] for obtaining low-velocity measurements under fire conditions. McCaffer^

and Heskestad [33] have provided calibration techniques for these probes. The

probe used was 12.7 mm in diameter, with construction details as given in the

above reference. The basic equation for determining velocity is

where AP is the measured differential pressure, p is the gas density (obtained

from temperature readings adjacent to the probe) , u is the gas velocity, and

C(Re) is a constant dependent upon the Reynolds number. For low velocities,

the constant can be taken as C(Re) = 1.08, according to the recommendation of

McCaffrey and Heskestad.

The test series conducted during this phase of the project and reported

herein represents over one-half million individual readings of temperature,

heat flux, and velocity. Data for all channels were recorded automatically

at 1 minute intervals using a digital data acquisition system for the duration

of each test--typically 4. 5-5. 5 hours. Obviously, the voluminous amount of

data collected requires the use of a digital computer for the reduction of the

data into a useable form. A general purpose computer program for the reduction

of data collected by automatic data acquisition systems, documented in reference [34], was used throughout the test series for the reduction and analysis

of the data collected.

The overall accuracy of a system used to measure physical quantities is

an important parameter when studying the significance of scientific data. A

discussion of the accuracy of the measurements taken during this test series

is included below:

u

4.3 Data Recording and Instrumentation Accuracy

10
Temperature measurements . Errors in the measurement of temperature arise

from two sources—the accuracy and repeatability of the thermocouple wire used

and the technique used to convert the thermocouple EMF to engineering units.

For Type K thermocouples and the data system used in these tests, these errors

are ±2°C and ±1°C, respectively, or a total overall error of ±3°C [35,36,37],

Ambient temperatures recorded for all temperature channels prior to each test

and data system calibration checks performed twice during the series were well

within these limits.

Heat flux measurements . The accuracy of the heat flux transducers used

for the tests is stated as ±3% in the manufacturers' specifications.

Calibrations supplied with each meter were verified against a working standard

in a test chamber [38] that had been previously calibrated by the NBS Optical

Radiation Group relative to the NBS standard electrically calibrated thermopile radiometer [39]

Detector precision within 3% was obtained with this

calibration. Including data system error [36,37] yields an overall system

accuracy of ±6%.

Velocity measurements . McCaffery and Heskestad [33] have provided

calibration techniques for the probes used in this study. Accuracy is valid

to about ±5% [33]

5. TEST PROGRAM

A total of 18 experiments were conducted on five different appliances in

the test room described previously. Table 2 provides a description of the

salient features of the appliances tested. Typically, at least two tests were

conducted with each appliance--one test with 0.91 m (36 in) of clearance

between the rear wall of the test enclosure and the appliance and one test

with 0.46 m (18 in) of clearance. Additional tests were conducted with some

appliances when smaller rear wall/appliance clearances could be obtained. In

several tests, the room construction and geometry was changed to study their

effects on test results. Table 3 gives details of the test conditions for

each experiment.

5.1 Test Procedure

Underwriters Laboratories standard 1482 for solid fuel room heaters

provides guidelines for testing wood-burning appliances [23] . Each appliance was installed and instrumented with the specified wall clearance and

the instrumentation checked to verify its proper operation. An experiment

11
consisted of two tests —a "brand fire test," and a "flash fire test" run as

a continuation of the "brand Fire test."

In the "brand fire test," specially constructed, oven-dry douglas fir

brands are added at 75 minute intervals after ignition until it is apparent

that steady-state conditions have been attained. This is indicated by level

temperature profiles on appliance surfaces and on surrounding combustibles.

Figure 5 illustrates the construction of the brands.

The "flash fire test" is conducted as a continuation of the "brand fire

test" to simulate overload conditions. Eight brands (as used for the "brand

fire test") are stacked in the appliance at one time. Data are recorded until

it is apparent that maximum temperatures have been attained.

5.2 Appliances

The five appliances tested were selected by their design and operating

characteristics as being representative of those available in the marketplace.

Obviously, with hundreds of manufacturers, it would be impossible to test every

model. However, the appliances selected were chosen for the range of sizes

and operating features available. A description of each appliance is included

below and summarized in table 2.

Appliance 1 is a small radiant room heater constructed of 6.4 mm (1/4 in)

and 8 mm (5/16 in) plate steel for the top, sides, and bottom of the appliance.

The inside of the fire chamber is lined with fire brick refractory. The door

is cast iron with two draft inlets and draft control knobs to adjust the

intensity of the fire. A 0.15 m (6 in) flue collar projects out the back of

the unit and a sheet steel bottom heat shield is attached to block radiation

from the appliance to the floor surface.

Appliance 2 like appliance 1, is a small radiant room heater constructed

of 6.4 mm (1/4 in) plate steel. The fuel loading door and flue collar are similar to appliance 1 except the door is on the right side of the appliance.

On the front of the appliance is a high temperature glass window 0.15 x 0.44 m

(6 x 17.5 in). Since the appliance is intended for installation on the hearth

of an existing fireplace, the appliance is supported by a plate steel apron on

three sides in lieu of legs to support the appliance. No heat shield is

attached

.

Appliance 3 is a large radiant room heater similar in design and

construction to appliance 1. The hearth area of this appliance is more than

twice that of the smaller appliance 1. No heat shield is attached.

12
Appliance 4 is a free-standing fireplace stove--the traditional "Franklin

stove," constructed of cast iron with double folding doors for the front of the

appliance. A grate is supplied with the unit and was used for all tests. The

flue collar, 0.2 m (8 in) in diameter, could be attached either to the back or

the top of the appliance. For the tests reported herein, the flue collar was

attached to the top of the appliance to allow testing at small wall/appliance

clearances

Appliance 5 is a circulating room heater, a radiant room heater with an

exterior cabinet allowing air circulation around the appliance. The firebox

is constructed of cast-iron with a sheet steel exterior cabinet. A thermostatically controlled damper controls the air supply for combustion. The flue

collar attachment for a 0.15 m (6 in) flue is on the back of the appliance.

6. TEST RESULTS

Test measurements from all instruments used to monitor temperature, heat

flux, and velocity in the 18 room experiments are presented in appendix A.

Groups of measurements such as appliance surface temperature, wall surface

temperature, wall studding temperature, floor surface temperature, sub-floor

studding temperature, flue gas temperature, flue pipe surface temperature,

heat flux, and flue gas velocity are plotted together. Each graph is labeled

with the instrument identification (corresponding to the instrument identification as listed in table 1) and location. The graphs are arranged by test

with a table of contents at the beginning of the appendix.

6.1 Appliance Temperatures

Measurements of appliance surface temperature, flue gas temperature, and

flue pipe surface temperature during steady-state operation (the "brand fire

test") and during overload conditions (the "flash fire test") are presented in

table 4 for the 18 room experiments. Flue gas temperatures and flue pipe

surface temperatures are also presented in figures 6 and 7, respectively, as profiles of temperature through the length of the flue.

6.2 Wall Temperatures

Measurements of wall surface temperatures are presented in table 4 for

the 18 room experiments. Wall surface temperature profiles are presented in

figures 8-12 for the five appliances tested and in figures 13 and 14 for the

13
tests with wall insulation and with a front wall, respectively. These can be

compared with figure 9 (tests with appliance 2 but without wall insulation or

front wall) to see the effect of the insulation and reduced ventilation. Each

graph presents a vertical profile of maximum steady-state temperatures for

thermocouples along the appliance and flue centerline from the floor to the

ceiling

.

6.3 Floor Temperatures

Floor surface temperatures are listed in table 4 for the 18 room

experiments. Figures 15-19 show floor surface temperature profiles for the

five appliances tested. Floor surface temperature profiles for the tests with

wall insulation and with a front wall are plotted in figures 20 and 21,

respectively. Each graph presents a profile of maximum steady-state temperatures for thermocouples along the rear wall-appliance centerline from the rear

wall forward to a distance of 1.22 m (48 in) from the rear wall.

7. ANALYSIS OF RESULTS

7.1 Appliance Temperatures

Appliance surface temperatures during steady-state operation in the 17

"brand fire tests" (not including test CLR10—the "log test") were similar for

all five appliances tested. The steady-state maximum temperatures ranged from

a low of 2 97 °C (567°F) to a high of 436°C (817°F)— a range of only 139°C (250°F).

The average maximum steady-state appliance surface temperature for the 17 "brand

fire tests" was 374°C (706°F) with a coefficient of variation of 6%. Maximum

overload temperatures for the appliance surface averaged 28% higher than the

steady-state readings with an average maximum temperature of 480 °C (896 °F) and

a higher coefficient of variation of 24%.

Appliance 5, the jacketed circulating heater exhibited temperatures on

the outer surface of the jacket significantly lower than the other appliances.

While firebox temperatures measured for appliance 5 were similar to those

measured durxng tests of the other appliances, the jacket temperature, the

suv race radiating heat to surrounding combustibles, averaged only 135°C (275°F).

There was no significant coorelation between appliance surface temperature

and clearance between the appliance and rear wa] l. For some appliances, the

maximum steady-state appliance surface temperature was slightly higher at

smaller clearances while for some appliances slightly lower. However, in all

cases, these differences were small when compared to the maximum temperatures.

14
Flue pipe surface temperatures near the flue outlet of the appliance

were similar to the appliance surface temperature. The average maximum flue

pipe surface temperature for all 17 "brand fire tests" was 375°C (707°F),

practically identical to the average maximum appliance surface temperature.

Maximum average overload temperature was higher for the flue pipe surface

than for the appliance surface--520 °C (970°F). During the overload tests, it

was evident that flames extended into the flue pipe, exposing the flue pipe

to heating similar to the appliance surface. However, the lower mass of the

flue pipe as compared to the appliances allows the flue pipe to react faster

to the high intensity and relatively short duration of the overload test.

Effects related to the light weight of the flue pipe can also be seen

in the flue gas temperatures in figure 6. Flue gas temperatures measured

far downstream from the appliance flue outlet are nearly identical for all

appliances. But for measurements closer to the flue outlet, the temperature

naturally rises and the variation from appliance to appliance becomes greater.

This effect is probably due to two sources. First, the higher temperatures

of the flue pipe surface nearer the appliance are due not only to higher flue

gas temperature but also to conduction down the length of the pipe from the

massive appliance. Second, the lightweight pipe is more greatly affected by

feedback radiation from the hot wall and hot appliance surface. This is

evidenced by higher flue pipe surface temperatures at smaller flue pipe/

wall clearances, an effect not noted in the appliance surface temperature

measurements

7.2 Wall Temperatures

Understandably, the wall surface temperature varied inversely with the

clearance between the appliance and wall surfaces as illustrated in figure 22.

For each appliance, the maximum steady-state wall surface temperature increased

as the appliance/wall clearance decreased. Temperatures ranged from a low of

54°C (129 °F ) for appliance 1 at a clearance of 0.91 m (36 in) to a high of

18 9 °C ( 37 2 °F ) for appliance 4 at a clearance of 0.15 m (6 in). In test CLRll

[appliance 4 at 0.15 m (6 in)] , the wall ignited soon after the beginning of

the overload test charring the wood studding behind the wallboard before the

fire was extinguished. While the appliance, installed at this clearance, was

clearly installed improperly, the result demonstrated the consequences of

insufficient clearances between an appliance and surrounding combustibles.

For tests at an appliance/wall clearance of 0.91 m (36 in), the highest

wall temperatures were noted surrounding the metal thimble used to pass the

single wall flue pipe through the wall. The thimble, 0.46 m (18 in) larger in

15
diameter than the pipe passing through it, still allows the minimum clearance

between the hot pipe surface and the wall surface for large appliance/wall

clearances (see figures 8-12). For appliance/wall clearances less than 0.91 m

(36 in) , the highest wall temperatures were noted behind the rear of the appliance. At these reduced clearances, the combined heating by the lower portion

of the flue pipe and the large surface area of the appliance adjacent to the

wall surface contribute to raising the temperature of the wall surface. For

appliance 4, the added effects of heating by the flue pipe were not noted.

Since the flue outlet on appliance 4 was on the top surface of the appliance,

the flue pipe surface was always further away from the wall than the appliance

surface. Thus, for appliance designs where the flue outlet is in the rear of

the appliance, the clearance between the flue pipe and wall surface is important

in addition to the clearance between the appliance and wall surface.

Two other factors, in addition to the appliance/wall clearance, which are

important to the temperatures attained on wall surfaces are apparent: appliance

design and appliance size.

For the three different designs of appliances tested in this study, the

fireplace stove exhibited the lowest temperatures on the wall surfaces, followed

by the circulating heater and finally the highest temperature by the radiant

room heaters. This ranking by appliance design also corresponds to a ranking by

average flue gas velocity for the different appliance designs. The lowest flue

gas velocities were noted for the radiant appliances (see appendix A—velocity

plots and appendix B —average steady-state velocity, instrument VEL 84) followed

by the circulating heater and finally the highest flue gas velocity with the

tests involving the fireplace stove. This is not a surprising finding since the

higher flue gas velocity is an indicator of the amount of excess air, an important parameter in determining the efficiency of an appliance in delivering heat

to a room [40]

.

| Within a given appliance design, the size of the appliance can have a significant effect on temperatures attained on wall surfaces. For the three

radiant room heaters tested, the wall surface temperatures were directly related

to the size of the appliance as shown in the following data:

16
Appliance Back Surface Areaa Average Steady-State

Temperature*3

(cm ) (°C)

1 2032 65

2 3319

2942

96

3 95

a Area of the back surface of the appliance parallel to the

rear wall of the test enclosure.

Average maximum steady-state rear wall surface temperature

for tests at 0.91 m and 0.46 m.

The difference between maximum steady-state wall temperatures and maximum

overload wall temperatures as indicated in table 4 ranges from as little as

29 °C for test CLR08 with appliance 4 to as much as 253°C (455 °F) when the wall

ignited during test CLRll. The magnitude of the difference depended on the

wall/appliance clearance. Wall temperatures were raised more by the overload

conditions during tests at smaller clearances than during tests at the larger

clearances. As an example, consider tests CLR01, CLR02 , and CLR03 for appliance 1. At clearances of 0.91 m, 0.62 m, and 0.46 m (36 in, 24 in, and 18 in),

the difference between maximum steady-state and maximum overload wall temperatures were 40°C, 64°C, and 99°C (72°F, 115°F, and 178°F) , respectively.

Maintaining proper clearances between appliance surfaces and wall surfaces thus

becomes even more critical at the higher firing rates of the overload tests.

The maximum wall temperatures during steady-state operation and during

overload can also be compared to the generally accepted upper limits for wall

temperatures as noted in section 2.4. Table 5 presents the maximum temperature

rise above room temperature for the 18 room experiments. Wall temperatures at

a clearance of 0.91 m (36 in) were within accepted limits. However, at clearances below 0.91 m (36 in), wall temperatures exceeded the recommended limits.

Temperatures measured on floor surfaces during steady-state operation

varied from appliance to appliance. Like the wall temperatures, two factors

are apparent: 1) appliance/floor clearance and 2) appliance size. Since the

appliance/floor clearance and appliance bottom area did not vary as much as wall clearances and appliance rear surface area, the effects were not as large.

Floor temperatures measured during tests of appliance 1 were considerably lower

than those measured during tests of the other appliances. From table 4,

the average floor surface temperature during steady-state operation of appliance 1 was 6

9 °C (156 °F ) while it was 125°C (257°F) during tests of the other

7.3 Floor Temperatures

17
appliances. Appliance 1 was equipped with a radiation shield between the

bottom surface of the appliance and the floor surface. Clearly, this is an effective method to limit floor temperatures to acceptable levels.

For some appliances, the floor temperature increased as the clearance

between the appliance and rear wall was reduced. However, this effect was not

noted for appliance 1, again pointing out the merits of the radiation shield.

Overload temperatures on floor surfaces averaged only 14 °C (26 °F) higher

than those measured during steady-state operation, with some measurements

actually lower during overload than during steady-state.

7.4 Wall Insulation

The three tests with wall insulation applied, tests CLR14 , CLR15 , and

CLR16 , were conducted to ascertain any effects of the change in room construction and gain information on any increased fire risk due to the use of the

insulation. Wall surface temperatures for tests with and without wal 1 insulation conducted using appliance 2 can be noted from table 4 as:

Temperature Temperature

Clearance Without Insulation With Insulation

(m) (°C)

0.91 74

0.46 117

Wall surface temperatures during

approximately 20 °C (36 °F) higher than

The use of insulation provides a more

without the insulation.

(°C)

96

142

tests with wall insulation were

those measured without the insulation.

severe testing requirement than testing

Temperatures measured on wall studding surfaces show an even larger effect

Temperature Temperature

Clearance Without Insulation With Insulation

(m) (°C) (°C)

0.91 55 80

0.46 64 128

18
7.5 Tests With Front Wall

In two tests, CLR17 and CLR18 , a front wall was erected on the test

enclosure to study conditions in this reduced ventilation environment. An

opening in the wall the size of a standard doorway was provided.

Comparing tests CLR17 and CLR18 with tests CLR15 and CLR16 (tests without

a front wall) , some similarities and some differences are apparent. From table

4, steady-state temperatures on appliance, wall, and floor surfaces were similar

at both clearances of 0.91 m (36 in) and 0.46 m (18 in). Overload temperatures

on wall and floor surfaces were higher in tests CLR17 and CLR18 (with front

wall) than in tests CLR15 and CLR16 (without front wall) . The rapid heat

buildup during the overload tests could not be carried away as quickly with

the reduced ventilation available in tests CLR17 and CLR18

7.6 Log Tests

In order to compare the results of tests conducted with the standardized

douglas fir brands with those utilizing a more realistic fuel source, a test

was designed using seasoned oak logs. While no specific size of logs were

used, the logs were cut to an appropriate length for each appliance--

approximately two-thirds the length of the appliance floor surface. Each

appliance was instrumented with thermocouples in the same configuration as used in the room experiments. Each test was continued until steady-state

conditions were obtained with fuel added at fixed intervals —either 15 minutes or 30 minutes. Maximum temperatures were recorded for each instrument.

Table 6 presents the results of the 10 experiments. Figure 23 compares

the results obtained from the brand test for steady-state and for overload

operation with the results from the 15-minute and 30-minute log test. Several

interesting observations can be made from this figure. Appliance 1 shows a close similarity for all four tests. This indicates that the rate of consumption of the fuel is fairly even. For appliance 2, however, the air inlets can

be opened further permitting more air for combustion than appliance 1. Thus,

the more fuel available in the log tests allowed somewhat higher temperatures

to be attained. For the other three appliances, the log tests resulted in lower

temperatures because of' the limited air supply available for combustion. The

shape and construction of the brands helped them to burn easily and attain

steady-state in a shorter time period.

It can also be noticed that the 15-minute feeding interval resulted in

higher temperatures than the 30-minute feeding interval due to the increased

amount of fuel available.

19
7.7 Measurement Technique

Measuring surface temperature is not as simple as it looks. Comparing

floor surface and floor studding temperatures for steady-state operation from

table 4, measured studding temperatures were indicated as higher than floor

surface temperatures in three tests —CLR01, CLRll, and CLR13. Surface thermocouples were mounted in these tests with the bead touching the surface with a small loop in the thermocouple wire to insure good contact with the surface.

Studding temperatures were measured with the thermocouple mounted flat, sandwiched between the floor and stud. Some laboratory tests were conducted to

see how these different mounting techniques affected the readings. A test was

designed for this purpose.

A 10.2 x 10.2 x 1.27 cm (4 x 4 x 1/2 in) plywood specimen was placed

12.7 cm (5 in) in front of a 30.5 x 30.5 cm (12 x 12 in) electric radiant

panel. Both were surrounded by a calcium silicate box to minimize unwanted

drafts. Four thermocouples were placed at the horizontal centerline of the

plywood, separated from each other by 0.63 cm (1/4 in). The radiant panel

with a voltage-controlled blower attached was used to deliver different heating rates and airflows to the specimen (figure 24)

.

The first set of tests were run using different airflows and four

different thermocouple mountings: first, the bead touching the surface in a loop; second, the bead touching the surface completely flat; third, a small

hole was punched into the surface and the bead was placed in it, also in a loop; and finally, the bead was placed in the air, about 0.63 cm (1/4 in)

from the surface. The four thermocouples were mounted identically and a set

of replicates were run for a total of eight individual readings for each test.

The radiant panel was heated to a constant temperature. The specimen was left

in front of the radiant panel until steady-state was achieved with no forced

airflow and the temperatures recorded. Then air was blown at different rates

of 0.05, 0.10, 0.15, and 0.20 m/sec (10, 20, 30, and 40 ft/min) allowing it to

obtain steady-state. This procedure was done with each type of mounting.

More tests were run at different radiant panel temperatures, following the

same procedure. Figure 25 shows the results obtained when the temperature

recorded from the thermocouple mounted flat, in hole and with loop was subtracted from the temperature recorded by the one in the air and plotted against

the different airflows for two different radiant panel temperatures: 260 °C

and 677°C (500°F and 1250°F) . It can be noticed that at low temperatures the

differences are rather small and are not affected very much by the changing

airflow. But at high temperatures, those differences vary between 20 to 50 °C

(70 to 125°F) . Tests run with a radiant panel temperature of 399°C (750°F)

20
showed temperatures similar to those obtained in the brand tests conducted

with the woodstoves. The difference between the thermocouple mounted flat

and the one mounted with a loop ranged from 20 to 40°C (70 to 105°F). This

shows that the temperature indicated by the thermocouple could be affected

significantly by airflows.

Another series of tests were run, but this time the four thermocouples

were mounted two in a loop and two flat to the surface with no airflow. The

radiant panel temperature was raised and the readings obtained from the thermocouple were recorded. The results were plotted and were found linear.

The same arrangement was used again, but the plywood was placed 45.7 cm

(18 in) from the radiant panel. Results were plotted and also were linear but

the slope was nearer to the ideal 1:1 curve. Thus, a calibration curve can be

made by plotting the temperatures mounted flat vs. temperatures mounted with

loop (figure 26) . If the critical range of 70 to 120°C for the thermocouple

mounted with loop is examined in this figure against temperatures measured

with the thermocouple mounted flat, the difference at 12.7 cm (5 in) is between

20 to 45°C (36 to 80°F) while at 0.46 m (18 in), the range is between 15 to

3 0 °C (27 to 54 °F) .

Thus, airflow and mounting technique can significantly affect the

temperature indicated by a surface mounted thermocouple. The thermocouple

mounted flat with no airflow gave the highest indicated temperature and thus

is the most severe and conservative of the techniques tested for use with

standard test methods. However, data collected by different mounting

techniques can easily be compared with the development of calibration curve

comparing the techniques.

8. THEORETICAL TEMPERATURE PREDICTION

A theoretical model for predicting the heat transfer between the

appliance or flue pipe surface and the wall or floor surface can be a useful

tool not only in design of equipment but also in the design of future experiments to study clearances and reduced clearances for wood-burning appliances.

The theoretical models discussed in section 2 are compared below with experimental results obtained during the steady-state brand tests. The following

assumptions apply:

• the system is at steady-state (heat gain equals heat loss);

21
• the appliance and/or flue pipe are at one constant, uniform temperature;

and

• the wall surface, back wall surface and surroundings are each at

constant, uniform temperatures.

Figure 27 illustrates the heat transfer model.

8.1 Heat Transfer From Flue Pipe Surface

Figure 28 presents the results of these calculations for a flue pipe

0.15 m (6 in) in diameter configured similarly to the room experiments.

Calculated wall surface temperatures are presented as a function of clearance

between the flue pipe and wall surface for flue pipe surface temperatures from

100 to 500°C (212 to 932°F). In these calculations, the ambient air temperature and back wall surface temperature were taken to be 25 °C (77 °F) . From

these curves, it is evident that flue pipe surface temperatures higher than

250 to 300°C (480 to 570°F) would lead to wall surface temperatures exceeding

the recommended limits of 50 °C (90 °F) above room temperature at a clearance of

0.46 m (18 in)

.

Table 7 presents a comparison of wall surface temperatures measured

opposite the midpoint of the vertical section of flue pipe with calculated

values. For prediction of wall surface temperatures adjacent to flue pipe

surfaces, the following data were used:

• flue pipe surface temperature: TC 72

• wall surface temperature: TC 20

• wall rear surface temperature: TC 40

• room ambient air: TC 00

• air temperature near wall rear surface: ambient temperature at

beginning of test.

Average steady-state temperatures were taken from appendix B for all data.

Since these calculations assume the wall receives no heat from the

appliance--only from the section of flue pipe adjacent to the wall surface,

it would be expected that predicted values would be low. In fact, predicted

wall temperatures averaged 12% lower than the measured temperatures. This

22
points out three limitations to the calculations: 1) even at points on the

wall opposite the flue pipe, the heat generated by the appliance can affect

the wall temperature; 2) neither the flue pipe nor the wall are in reality

at a uniform temperature; and 3) the calculations are very sensitive to the

clearance between the flue pipe and wall--a change of only 2.5 cm (1 in) in

clearance changes the calculated temperature by about 8%.

8.2 Heat Transfer From Appliance Surface

Figure 29 shows calculated wall surface temperatures as a function of

appliance/wall clearance for a medium size appliance [area of appliance side

2 2 parallel to wall of 0.26 m (400 in )] for appliance surface temperatures

from 100 to 500°C (212 to 932°F). As with the flue pipe calculations, the

ambient air temperature and back wall surface temperature were taken to be

25°C (77 °F) . At an appliance clearance of 0.91 m (36 in), appliance temperatures higher than 300 to 350 °C (570 to 660 °F) would lead to temperatures on

the wall in excess of recommended limit of 50°C (90°F) above room temperature.

A comparison of wall surface temperatures measured opposite the appliance

during the steady-state tests and calculated values are presented in table 8.

For prediction of wall surface temperatures adjacent to appliance surfaces,

the following data were used:

• appliance surface temperatures: average of appliance

surface temperatures

excluding floor and door

• wall surface temperature:

• wall rear surface temperature:

• room ambient air:

TC 15 or TC 18

TC 4 2

TC 00

• air temperature near rear wall surface: ambient temperature at

beginning of test.

Average steady-state temperatures were taken from appendix B for all data.

As with the calculations for the flue pipe, the predicted wall

temperatures assume heat transfer from the appliance to the wall only—with

no contribution from the flue pipe. While the calculated values averaged

2% lower than the measured temperatures, there was considerably more spread

in the variation than in the flue pipe calculations--ranging from 18% low

23
to 18% high. A number of factors could account for this. Perhaps most

importantly, the assumption that the appliance surface is at one uniform

temperature is clearly a gross oversimplification. However, it would be

extremely difficult both to measure the time dependent temperature distribution on the appliance surface as well as to incorporate this into the

calculations.

9. CONCLUSIONS

A total of 28 tests were conducted on five wood-burning appliances of

differing designs. In these tests, a total of more than one-half million

individual readings of temperature, heat flux, or velocity were obtained.

Two series of tests were conducted:

• full-scale room experiments where measurements of appliance temperature

and surrounding surface temperature were obtained using a standard wood brand

as fuel, and

• "log tests" where seasoned oak logs were used as a fuel source to

compare with a standard wood "brand" fuel source. Only appliance surface

temperature and flue gas temperature were monitored in the "log tests".

Some conclusions from these tests were apparent:

• Appliance firebox surface temperatures measured during steady-state

operation were very similar for all five appliances tested. For appliance 5, a jacketed circulating room heater outside jacket temperatures were lower.

No correlation was found between appliance surface temperature and clearance

between the appliance and wall surfaces.

• The temperature of the lightweight single wall flue pipe used for

testing was more greatly affected by the clearance between the pipe and wall

surface an effect not noted for the appliance surface temperature measurements. I

• Understandably wall surface temperatures were found to vary inversely

with the clearance between the appliance and wall surface. Wall temperatures

as high as 189°C were recorded (for an improperly installed appliance)

.

• Appliance design and appliance size were found to affect temperatures

on wall surfaces.

24
• Due to the small clearances between appliances and flooring,

temperatures developed on unprotected floor surfaces were typically higher than

wall temperatures during the tests.

• Wall surface temperatures and interior wall studding temperatures were

considerably higher during tests with wall insulation or with a front wall than

without.

• Average maximum appliance surface temperatures measured during tests

using seasoned oak logs as the fuel source were similar to those developed

during the "brand" tests.

• Theoretical calculations of wall surface temperature agreed within

an average of 10 °C with measured wall temperatures. Individual calculation

agreement, however, ranged from excellent to poor.

Three specific recommendations can be made based on the results of these

tests

• Current codes for the installation of appliances are based in part on

data developed in 1943 by Underwriters Laboratories. Comparing the UL data

with requirements in the NFPA code, the requirements were based on appliance

surface temperatures ranging from 315°C (600°F) for unprotected surfaces to

480°C (900°F) and above for various protection methods. Clearly, the appliances tested here can easily exceed the lower limitation for extended periods

of time. Based on the tests reported herein, a more appropriate limit would

be closer to 400°C (750°F).

• Floor protection is clearly an important area that should be addressed

specifically in the codes.

• Due to the higher temperatures developed during tests with wall

insulation, it may be appropriate to modify current test procedures to include

"typical" insulation of walls in the test enclosure.

This is a report presenting information on research ongoing at the Center

for Fire Research at the National Bureau of Standards related to wood-heating

safety. As such, it provides information on only a part of the research program. Future reports will be forthcoming on other areas of research including

chimney creosoting and chimney fires; reduced clearances with protection and

fireplace inserts.

25
10. ACKNOWLEDGEMENTS

This study was sponsored by the U.S. Department of Energy (DOE). This

support by DOE and by the contract officers, Mr. John D. Ryan, Mr. David Pellish,

and Mr. Jimmie Dollard, is gratefully acknowledged. Thanks are also due to

Mr. T. Maher, Mr. W. Bailey, and the staff of the full-scale fire test facility

at NBS for their assistance in preparation, instrumentation, scheduling,

and experimental work; and to Mr. D. Klein for the development of a computer

software package for automated plotting of data.

26
11. REFERENCES

[1] Peacock, R. D., A Review of Fire Incidents, Model Building Codes, and

Standards Related to Wood-Burning Appliances, Nat. Bur. Stand. (U.S.),

NBSIR 79-1731 (April 1979).

[2] Peacock, R. D. , A Review of Fire Incidents Related to Wood-Burning

Appliances, Wood Energy Institute, Proceedings of Wood Heating Seminar

IV, Portland, Oregon, March 21-24, 1979, 43-46.

[3] Shelton, J. W., Analysis of Fire Reports on File in the Massachusetts

State Fire Marshal's Office Relating to Wood and Coal Heating Equipment,

contract to the National Bureau of Standards (U.S.), NBS-GCR-78-149

(November 1978) .

[4] Shelton, J. W. , Wood Heat Safety, (Garden Way Publishing, Charlotte,

Vermont, September 1979) .

[5] The BOCA Basic Building Code/1978, Model Building Regulations for the

Protection of Public Health, Safety and Welfare, Seventh Edition,

Building Officials and Code Administrators International, Homeward,

Illinois (1978) .

[6] The BOCA Basic Mechanical Code/1978, Model Mechanical Regulations for

the Protection of Public Health, Safety and Welfare, Third Edition,

Building Officials and Code Administrators International, Homeward,

Illinois (1978)

[7] The National Building Code, 1976 Edition, American Insurance Association,

New York, New York (1976)

[8] National Fire Codes, Vol. 9, Standard for Chimneys, Fireplaces, and

Vents, NFPA 211-1977, National Fire Protection Association, Boston,

Massachusetts (1978)

[9] Standard Building Code, 1976 Edition, Southern Building Code Congress,

International, Inc., Birmingham, Alabama (1976).

[10]

Amendments to the Standard Building Code, 1977 and 1978 Revisions to the

1976 Edition, Southern Building Code Congress, International, Inc.,

Birmingham, Alabama (1978)

27
[11] Uniform Building Code, 1976 Edition, International Conference Building

Officials (1976) .

[12] 1977 Supplement to the Uniform Building Code, U.B.C. Standards, Uniform

Housing Code, Uniform Code for the Abatement of Dangerous Buildings and

the Uniform Fire Code, International Conference of Building Officials

(1977) .

[13] National Fire Codes, Vol. 14, Manual on Clearances for Heat Producing

Appliances, NFPA 89M-1976, National Fire Protection Association, Boston,

Massachusetts (1978) ,

[14] Voigt, G. Q., Fire Hazard of Domestic Heating Installations, Nat. Bur.

Stand. (U.S.), NBS Research Paper RP596 (September 1933).

[15] Neale, J. A., Clearances and Insulation of Heating Appliances,

Underwriters Laboratories, Inc., UL Bulletin of Research #27 (February

1943) .

[16] Lawson, D. I., Fox, L. L., and Webster, C. T., The Heating of Panels by

Flue Pipes, Fire Research Special Report No. 1, Fire Protection

Association, London, England (1952).

[17] Lawson, D. I. and Simms, D. L., The Ignition of Wood by Radiation,

British Journal of Applied Physics, Vol. 3, 288-292 (September 1952).

[18] Shoub, H., Survey of Literature on the Safety of Residential Chimneys

and Fireplaces, Nat. Bur. Stand. (U.S.), NBS Misc. Pub. 252 (December

1963) .

[19] Prerabricated Metal Chimneys, National Bureau of Standards, Fire Research

Section, unpublished reports to Federal Public Housing Authority (1941-

1945)

.

[20] Temperatures Developed in Chimneys for Low Cost Houses, Nat. Bur. Stand.

(U.S.), Tech. News Bull., 328 (August 1944).

[21] Fox, L. L. and Whittaker, D., Some Measurements of Temperatures of Metal

Flues of Domestic Heating Appliances, Journal of the Institution of

Heating and Ventilation Engineers, Vol. 23, 183-192 (August 1955).

[22] Standard for Chimneys, Factory-Built Residential Type and Building

Appliance--UL 103, Underwriters Laboratories, Inc. (March 1971).

28
[23] Standard for Room Heaters, Solid Fuel Type —UL 1482, First Edition,

Underwriters Laboratories, Inc. (August 1979).

[24] Fire Protection Handbook, 14th Edition, McKinnon, G. P. and Tower, K.

,

Eds. , National Fire Protection Association, Boston, Massachusetts, 3-2/7-

1976.

[25] Mitchell, N. D., New Light on Self-Ignition , NFPA Quarterly, Vol. 45,

No. 2, 165-172 (October 1951).

[26] MacLean, J. D. , Effect of Heat on Properties and Serviceability of Wood:

Experiments on Thin Wood Specimens, Forest Products Laboratory Report No.

R1471 (1945) .

[27] MacLean, J. D. , Rate of Disintegration of Wood Under Different Heating

Conditions, American Wood-Preservers Association (1951)

[28] McGuire, J. H., Limiting Safe Surface Temperature of Combustible Materials,

Fire Technology, Vol. 5, No. 3 (August 1969).

[29] Ignition and Charring Temperatures of Wood, Forest Products Laboratory

Report No. 1464 (January 1958)

[30] Matson, A. F., Dufori, R. E., and Breen, J. F. , Performance of Type B Gas

Vents for Gas-Fired Appliances, Part II, Survey of Available Information

on Ignition of Wood Exposed to Moderately Elevated Temperatures,

Underwriters Laboratories, Inc., Bulletin of Research, No. 51, Northbrook,

Illinois (May 1959) .

[31] Thulman, R. D. , personal communication.

[32] Heskestad, G., Bidirectional Flow Tube for Fire-Induced Vent Flows in

Large-Scale Bedroom Fire Test, July 11, 1973, P. A. Croce and

H. W. Emmons, Eds., FMRC Serial 21011.4, 140-145, Factory Mutual Research,

Norwood, Massachusetts (1974)

[33] McCaffrey, B. J. and Heskestad, G., A Robust Bidirectional Low-Velocity

Probe for Flame and Fire Application, Combustion and Flame, Vol. 26,

125-127 (1976)

[34] Peacock, R. D. and Smith, J. M. , SPEED2 , A Computer Program for the

Reduction of Data from Automatic Data Acquisition Systems, Nat. Bur.

Stand. (U.S.), NBS Tech. Note 1108 (September 1979).

29
[35] Manual on the Use of Thermocouples in Temperature Measurement, American

Society for Testing and Materials, STP 470A (1974) .

[36] Chandler, James M. , How to Make Accurate Low-Level Measurements, Accurex

Corporation, Mountain View, California.

[37] Maintenance Manual, Accurex Autodata Nine, Accurex Corporation,

Mountain View, California.

[38] Adams, C. H. and Davis, S., Development of the Flooring Radiant Panel

Test as a Standard Test Method, Nat. Bur. Stand. (U.S.), NBSIR 79-1954

(January 1980)

.

[39] Kostkowski, H. J. and Lund, M. A., National Bureau of Standards Report

of Calibration, Special Test Detector Responsivity of Three Thermal

Detectors, Test No. 221.12/1B/74 (October 1974).

[40] Maxwell, T. T., Maples, G., Pruitt, T. M. , and Dyer, D. F., Design

Handbook for Residential Wood-Burning Equipment, Department of Mechanical

Engineering, Auburn University (July 1979)

.

30
PROBABLE CAUSE

Ignition of Combustibles

Exterior Fire From Sparks

Chimney Fires

Improper Fueling Technique

Equipment Defect / Design

Use of Flammable Liquids

Other

Improper Maintenance

Improper Construction / Design

Improper Operation

Ignition of Structure

Improper Installation

Improper Chimney

0

Number of Fires

1000 2000 3000

Figure 1: Breakdown of fire incidents by probable cause

and equipment type as recorded in NFIRS fire incident data

EQUIPMENT TYPE

Appliances

Chimneys

Connectors

SOURCE: USFA NFIRS

Data Base

31
46cm><46cm

|18” x

18") i oo i i —-

CM

O

_i S co

>- z C3 <C E S x E E_ES

tn -PG

<ug

•Hp

aja

><; cugoopc

•H

rs

d)wGvpGwoI—I oG

d) Pw

<u -pmOGO

•P

-PoGP

-P

tnGOu

<upG

CG •H

CP

32
©

~©~

©

TOP VIEW

V d

CC- ©

CO

f ^ BOTTOM VIEW

Appliance 1 LOCATION OF THERMOCOUPLES

LEFT SIDE FRONT VIEW RIGHT SIDE BACK VIEW

Appliance 2 LOCATION OF THERMOCOUPLES

Figure 3. Instrumentation locations for appliance

measurements in room experiments.

33
©

ZSI

©

TOP VIEW / “1 © r \_ o

©

© ©

J

\©

L ©

» 17 V 17 V V 17 t

RIGHT SIDE FRONT VIEW LEFT SIDE BACK VIEW ©

©

r \

BOTTOM VIEW

Appliance 3 LOCATION OF THERMOCOUPLES

r-“

T 2T©

7 S7 T

FRONT VIEW

Appliance 4 LOCATION OF THERMOCOUPLES

Figure 3. Instrumentation locations for appliance

measurements in room experiments (con't).

34
Appliance 5

LOCATION OF THERMOCOUPLES

fr

l

l

i ilM.LJ

TOP VIEW (INSIDE)

LEFT SIDE (OUTSIDE)

EZJ

17 ©r

FRONT VIEW (OUTSIDE)

i i

©

i

—

—

tJ

.i ©

i i i :

1 J —Jj

'vJ l_7 \j

LEFT SIDE (INSIDE) FRONT VIEW (INSIDE)

TOP VIEW (OUTSIDE)

o°

o

© o©

17 \j

BACK VIEW (OUTSIDE)

r n

©

L_ j

BOTTOM VIEW (OUTSIDE)

T7 ' X]

RIGHT SIDE (INSIDE)

Lr_ 7—<r-y

right" SIDE (OUTSIDE)

Figure 3. Instrumentation locations for appliance

measurements in room experiments (con't).

35
Figure 4. Instrumentation locations for test enclosure

measurements in room experiments.

i

36
CO

LU

I—

CD

coLUo

>- <i £! °-

Lr Q_

OS

Qu U.

Q_

i . i f *» LU

CO

OS

00

o°

LU Q —

OS LU LU

1— Z O o

H

OS

LU

z Q

1-

00 O

LU

oo °°

1— lu as Q

OS L|_ as CO

Z CO <t — Z CD

LU so z as o o 00 o

Figure 5. Construction of "brands" used in room experiments

37
FLUE

GAS

TEMPERATURES

38

DISTANCE

FROM

APPLIANCE

FLUE

OUTLET

(M)
FLUE PIPE SURFACE TEMPERATURES

DISTANCE

0

FROM FLUE

12

OUTLET (M)

Figure 7. Flue pipe surface temperatures measured during

tests of several wood-burning appliances.

39
200 H rH tH H

(Oo) s3aniva3dH3i wnwxvw

40

FIGURE

8:

MAXIMUM

MEASURED

STEADY

STATE

WALL

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

1
200

41
003

00

LU

cy

in

cvj

o

OJ

Od

o

I

Od

Ld

>

too

o

inr^ o

in in o in o in o

oj o Is- in oj

x—i vH

Co®) s3aniva3diAGi iwmxvw

10

t—

<

CY

LU

Q_2

LU

I—

<

^ ro lulu

H-o

< z

co^

>-ct

LU Lj_

i— o

00

^ cnh

y cu

CY lu

00

< O

si

X

<

6

\—

I

LU

DC3

CD

Li_

42
200

!i

a

f

I

j

LO

h-LOOLOOLOOLOOin cu o h- in oj

CLo

o

CL

la- idO

<

i

CO3

<

o

CLId>

(Go) S3aniva3dw3i mHixvw

43

FIGURE

11:

MAXIMUM

MEASURED

STEADY

STATE

WALL

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

4
200

(Do) S3ynivy3dw3i wnwxvw

44

FIGURE

12:

MAXIMUM

MEASURED

STEADY

STATE

WALL

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

5
200

(Oo) s3aniva3dW3i lAini^ixvkM

45

FIGURE

13:

MAXIMUM

MEASURED

STEADY

STATE

WALL

TEMPERATURES

DURING

TESTS

WITH

WALL

INSULATION
200

in

OJ

o

oJ

in

m

d

o

in o

in

in o in o in o

oj o h- in oj

CLo

o

e

UJo

z:<

i

CO3

_i<

o

CL

LJ>

(Do) S3aniva3dw3i wnwxvw

46

FIGURE

14:

MAXIMUM

MEASURED

STEADY

STATE

WALL

TEMPERATURES

DURING

TESTS

WITH

FRONT

WALL
150

IT)

IT) o

CL

LJCL2OCL

L_

UO2

<I

CO3

o

in o lo o to o

oj o h- in oj

rH -I

(Oo) s3amva3diN3i wwixvh

47

FIGURE

15:

MAXIMUM

MEASURED

STEADY

STATE

FLOOR

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

1
150

ID

O

IDOJ O ID O ID O

O N- ID OJ

Co.) s3aniva3dW3i kMniAiixvH

48

FIGURE

16:

MAXIMUM

MEASURED

STEADY

STATE

FLOOR

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

2
150

too S3amva3dw3i nnwxviN

49

FIGURE

17:

MAXIMUM

MEASURED

STEADY

STATE

FLOOR

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

3
150

i

[f> O LO O lO O OJ O h- ID CVJ

(Oo) s3amva3cM3i wnwxvw

50

FIGURE

18:

MAXIMUM

MEASURED

STEADY

STATE

FLOOR

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

4
150

10H

IDd

<

DCaCL2o

CL

li_ UO2

<

I

CD*—

Q

O

ID

CO O ID O ID O

h- ID CO

Co) S3amva3di^3i wrwxvw

51

FIGURE

19:

MAXIMUM

MEASURED

STEADY

STATE

FLOOR

TEMPERATURES

DURING

TESTS

OF

APPLIANCE

5
150

£

on<

LJ

ono

on

L_LJo

2

<

I

CO5

(Oo) S3aruva3dw3i wnwxvw

52

FIGURE

20:

MAXIMUM

MEASURED

STEADY

STATE

FLOOR

TEMPERATURES

DURING

TESTS

WITH

WALL

INSULATION
150

T T in

UJ UJ o o z z

< <

QC O'

<c <

UJ UJ dri

< < yy2 Z

_l -J

Q_ CL

CL CL < <

rH (O

O) ->* <

in

OJ oo

in o

in

in o

OJ

(Oo) s3anivy3diAi3i vNnmxvkM FIGURE

21:

MAXIMUM

MEASURED

STEADY

STATE

FLOOR

TEMPERA

DURING

TESTS

WITH

FRONT

WALL
200

I— LJ Z CL U CL <1 I— Z) CL LJ — Q Ld CD O

"t LO

LJ LJ O O

< <

H H

Cl Cl

Cl cl

< <

LJO

<

CL<

LJ

_lO

— C\l oo

LJ LJ LJ UOU z; z; z; < < <

H H H

I I I CL CL CL

Cl CL CL < < <

54

Figure

22.

Effect

of

appliance/wall

clearance

on

measured

wall

temperatures

during

tests

of

several

wood-burning

appliances.
mmnnjinniinn

njiruinnnnnfmruuuuumiin

ii n n n nanrui nri n nn n m 1 1 1 1 imm

iiiiiilllllllHiiiiiiiiiiiiiiiiimiiiiiiiiiiniiiii nimii

[TUT[in.nnn 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 11 1 imnn

CD

1CD

1

CD "T"

CD ~T~

CD

rCD CD CD CD CD CD

LO 00 00 —

LO

Cl

CL<

CL

CL<

CO

CL

CL<

00

CL

CL<

CL

CL<

I— Ld X Q_ Ld CL <£ I— Z) CL Ld CO — Ld CD CD

H H

X X

UD Q

— CO

CD CD O O

_J _1

LUh-

<

I

CO o

<

>- o

a _i

< CL LU Ld

I- >

CO o

55

Figure

23.

A

comparison

of

maximum

appliance

temperatures

for

tests

using

logs

as

a

fuel

source

with

tests

using

douglas

fir

brands

as

a

fuel

source.
56i

1

Figure

24.

Test

apparatus

to

evaluate

thermocouple

mounting

techniques.
150 o

CXI o

LOo w

<up2

-p

fdP

<DQ,e

<U -p

<DC

fda

-Pa

fd •HT3

fdP

-PC

<UP0) m

O—I o

LOooo

LOO LO

CXI hO LO

O

LO OJ

(Do) 30N3d3JJIQ

Uia)p

a)

4-1 4-1

<UP3

+1

fdp

Q)C4£

<u -pp

"H

(d \l)o

td 44p3

ai

in

CM

<up3

tr> •H

Cn

57

AIR

FLOW

(M/SEC)
200 dOOl H1IM CGlNflOW 3dfUVd3dlAI31

w

(1) d

cr

1 •Pc

XXo

a) +>

tnd

•H

-pcdo

B

<u I—

I

ftd

o

o

w

Q)P

d

-p

(0p

<1)

i*

<u -p

a>o

d

M-lP

d

a>

x>

CM

a)p

d

Cn P

ft

58

TEMPERATURE

MOUNTED

FLAT
tivm HonodHi

NoiionaNoo 1 r

59

Figure

27.

Heat

transfer

to

wall

surfaces.
400 CO CO OJ OJ H tH

o

o>o

ooo ^

§

Is

-; O bJ

o

CO ^

o iS

o

LD

o

o

coo

OJ

o

u

Q.

Q_

Ld

Li_

O

(Oo) 3amvd3di^3i tivm I

'

60

FIGURE

28:

PREDICTED

WALL

SURFACE

TEMPERATURE

FOR

MEAT

TRANSFER

FROM

FLUE

PIPE

ONLY
500

i

q

M—

G)

d

ooo

iq

o LU

o

col

<

LlJ

I o

ID

o

qo

CO

o

CLJ o

—

o

o

LJO

CL

CL

<C

o

LD o o

O LD ^ CO

O

O

rO

O

LD

Cvj O

OJ

o

ID O O

LD O

(Oo) 3dniVd3dlAGl T1VM

61

FIGURE

29:

PREDICTED

WALL

SURFACE

TEMPERATURE

FOR

HEAT

TRANSFER

FROM

APPLIANCE

ONLY
TABLE I INSTRUMENTATION LOCATIONS FOR MEASUREMENTS DURING

ROOM EXPERIMENTS FOR APPLIANCES AND TEST ENCLOSURE

INSTRUMENT

ID. DESCRIPTION

TC 00 AMBIENT ROOM AIR TEMPERATURE

TC 01 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 02 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 03 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 04 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 05 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 06 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 07 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 08 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 09 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 10 APPLIANCE SURFACE TEMPERATURE CSEE FIGURE 2D TC 1 1 REAR WALL SURFACE TEMPERATURE 0.3 M FROM FLOOR 0.3 M SOUTH OF FLUE CENTERLINE

TC 12 REAR WALL SURFACE TEMPERATURE 0 .

3

M FROM FLOOR FLUE CENTERLINE

TC 13 REAR WALL SURFACE TEMPERATURE 0.3 M FROM FLOOR 0.3 M NORTH OF FLUE CENTERLINE

TC 1 4 REAR WALL SURFACE TEMPERATURE 0.6 M FROM FLOOR 0.3 M SOUTH OF FLUE CENTERLINE

TC 15 REAR WALL SURFACE TEMPERATURE 0.6 M FROM FLOOR FLUE CENTERLINE

TC 16 REAR WALL SURFACE TEMPERATURE 0.6 M FROM FLOOR 0.3 M NORTH OF FLUE CENTERLINE

TC 17 REAR WALL SURFACE TEMPERATURE 0 9 M FROM FLOOR 0.3 M SOUTH OF FLUE CENTERLINE

TC 18 REAR WALL SURFACE TEMPERATURE 0.9 M FROM FLOOR FLUE CENTERLINE

TC 19 REAR UALL SURFACE TEMPERATURE 0.9 M FROM FLOOR 0.3 M NORTH OF FLUE CENTERLINE

TC 20 REAR WALL SURFACE TEMPERATURE 1 .2 M FROM FLOOR FLUE CENTERLINE

TC 21 REAR WALL SURFACE TEMPERATURE 1 .5 M FROM FLOOR FLUE CENTERLINE

TC 22 REAR UALL SURFACE TEMPERATURE 5 CM FROM THIMBLE SOUTH OF FLUE CENTERLINE

TC 23 REAR UALL SURFACE TEMPERATURE 5 CM FROM THIMBLE NORTH OF FLUE CENTERLINE

TC 24 REAR WALL SURFACE TEMPERATURE 5 CM FROM THIMBLE A80VE FLUE CENTERLINE

TC 25 SIDE WALL SURFACE TEMPERATURE 0 3 M FROM FLOOR 0.3 M WEST OF APPLIANCE CENTERLINE

TC 26 SIDE WALL SURFACE TEMPERATURE 0 3 M FROM FLOOR APPLIANCE CENTERLINE

TC 27 SIDE WALL SURFACE TEMPERATURE 0.3 M FROM FLOOR 0.3 M EAST OF APPLIANCE CENTERLINE

TC 28 SIDE UALL SURFACE TEMPERATURE 0.6 M FROM FLOOR 0.3 M WEST OF APPLIANCE CENTERLINE

TC 29 SIDE WALL SURFACE TEMPERATURE 0.6 W FROM FLOOR APPLIANCE CENTERLINE

TC 30 SIDE WALL SURFACE TEMPERATURE 0 .

6

M FROM FLOOR 0.3 M EAST OF APPLIANCE CENTERLINE

TC 31 SIDE WALL SURFACE TEMPERATURE 0.9 M FROM FLOOR 0.3 M WEST OF APPLIANCE CENTERLINE

TC 32 SIDE UALL SURFACE TEMPERATURE 0.9 M FROM FLOOR APPLIANCE CENTERLINE

TC 33 SIDE UALL SURFACE TEMPERATURE 0 9 M FROM FLOOR 0.3 M EAST OF APPLIANCE CENTERLINE

TC 34 SIDE WALL SURFACE TEMPERATURE 1 . 2 M FROM FLOOR APPLIANCE CENTERLINE

TC 35 SIDE WALL SURFACE TEMPERATURE 1 .5 M FROM FLOOR APPLIANCE CENTERLINE

TC 36 SIDE WALL SURFACE TEMPERATURE 1 .8 M FROM FLOOR APPLIANCE CENTERLINE

TC 37 SIDE WALL SURFACE TEMPERATURE 2.

1

M FROM FLOOR APPLIANCE CENTERLINE

TC 38 REAR WALL STUDDING TEMPERATURE 2. 1 M FROM FLOOR FLUE CENTERLINE

TC 39 REAR WALL STUDDING TEMPERATURE 1 .5 M FROM FLOOR FLUE CENTERLINE

TC 40 REAR UALL STUDDING TEMPERATURE 1 .2 M FROM FLOOR FLUE CENTERLINE

TC 41 REAR WALL STUDDING TEMPERATURE 0 .

9

M FROM FLOOR FLUE CENTERLINE

TC 42 REAR WALL STUDDING TEMPERATURE 0.6 M FROM FLOOR FLUE CENTERLINE

TC 43 REAR WALL STUDDING TEMPERATURE 0.3 M FROM FLOOR FLUE CENTERLINE

TC 44 REAR WALL STUDDING TEMPERATURE 0.6 M FROM FLOOR 0.8 M SOUTH OF FLUE CENTERLINE

TC 45 REAR UALL STUDDING TEMPERATURE 0.6 M FROM FLOOR 0.4 M SOUTH OF FLUE CENTERLINE

TC 46 REAR WALL STUDDING TEMPERATURE 0.6 M FROM FLOOR 0.8 M NORTH OF FLUE CENTERLINE

TC 47 REAR UALL STUDDING TEMPERATURE 0.6 M FROM FLOOR 0.4 M NORTH OF FLUE CENTERLINE

TC 48

TC 49 TC 50

FLUE GAS TEMPERATURE IN FLUE AT FLUE GAS TEMPERATURE IN FLUE

FLUE GAS TEMPERATURE IN FLUE

APPLIANCE FLUE OUTLET

1 M FROM APPLIANCE FLUE OUTLET

2 M FROM APPLIANCE FLUE OUTLET

TC 51 FLOOR SURFACE TEMPERATURE

TC 52 FLOOR SURFACE TEMPERATURE

TC 53 FLOOR SURFACE TEMPERATURE

TC 54 FLOOR SURFACE TEMPERATURE

TC Si FLOOR SURFACE TEMPERATURE

TC 56 FLOOR SURFACE TEMPERATURE

TC 57 FLOOR SURFACE TEMPERATURE

TC 58 FLOOR SURFACE TEMPERATURE

TC 59 FLOOR SURFACE TEMPERATURE

TC 60 FLOOR SURFACE TEMPERATURE

TC 61 FLOOR SURFACE TEMPERATURE

0.3 M FROM REAR UALL APPLIANCE CENTERLINE

0.46 M FROM REAR WALL APPLIANCE CENTERLINE

0.6 M FROM REAR UALL APPLIANCE CENTERLINE

0.76 M FROM REAR WALL APPLIANCE CENTERLINE

0.9 M FROM REAR WALL APPLIANCE CENTERLINE

I 05 M FROM REAR WALL APPLIANCE CENTERLINE

1.2 M FROM REAR WALL APPLIANCE CENTERLINE

0.8 M SOUTH OF APPLIANCE CENTERLINE

0.4 M SOUTH OF APPLIANCE CENTERLINE

0.4 M NORTH OF APPLIANCE CENTERLINE

0.8 M NORTH OF APPLIANCE CENTERLINE

TC 62 SUB-FLOOR STUDDING TEMPERATURE

TC 63 SUB-FLOOR STUDDING TEMPERATURE

TC 64 SUB-FLOOR STUDDING TEMPERATURE

TC 65 SUB-FLOOR STUDDING TEMPERATURE

TC 86 SUB-FLOOR STUDDING TEMPERATURE

TC 67 SUB-FLOOR STUDDING TEMPERATURE

TC 68 SUB-FLOOR STUDDING TEMPERATURE

TC 69 SUB-FLOOR STUDDING TEMPERATURE

TC 70 SUB-FLOOR STUDDING TEMPERATURE

0.3 M FROM REAR WALL APPLIANCE CENTERLINE

0 46 M FROM REAR WALL APPLIANCE CENTERLINE

0.6 M FROM REAR WALL APPLIANCE CENTERLINE

0.76 M FROM REAR WALL APPLIANCE CENTERLINE

0.9 M FROM REAR WALL APPLIANCE CENTERLINE

0.8 M SOUTH OF APPLIANCE CENTERLINE

0.4 M SOUTH OF APPLIANCE CENTERLINE

0.4 M NORTH OF APPLIANCE CENTERLINE

0.8 M NORTH OF APPLIANCE CENTERLINE

TC 7 1 FLUE PIPE SURFACE TEMPERATURE AT APPLIANCE FLUE OUTLET

TC 72 FLUE PIPE SURFACE TEMPERATURE AT I M FROM APPLIANCE FLUE OUTLET

TC 73 FLUE PIPE SURFACE TEMPERATURE AT 2 M FROM APPLIANCE FLUE OUTLET

TC 74 FLUE GAS TEMPERATURE IN FLUE AT 7 M FROM APPLIANCE FLUE OUTLET

TC 75

TC 76

TC 77 TC 78 TC 79

REAR UALL BACK SURFACE TEMPERATURE

REAR WALL BACK SURFACE TEMPERATURE

REAR WALL BACK SURFACE TEMPERATURE

REAR UALL BACK SURFACE TEMPERATURE

REAR UALL BACK SURFACE TEMPERATURE

2. 1 M FROM FLOOR FLUE CENTERLINE

1 .5 M FROM FLOOR FLUE CENTERLINE

1 .2 M FROM FLOOR FLUE CENTERLINE

0.9 M FROM FLOOR FLUE CENTERLINE

0 .

6

M FROM FLOOR FLUE CENTERLINE

RAO 80 RAD 31 RAD 32

RADIANT HEAT FLUX ON REAR WALL SURFACE 0.3 M FROM FLOOR

RADIANT HEAT FLUX ON REAR WALL SURFACE 0.6 M FROM FLOOR RADIANT HEAT FLUX ON REAR WALL SURFACE 0 9 M FROM FLOOR

VEL 34 FLUE GAS VELOCITY

62
LlI I

GO

LJI—

co

LUo

z:<H

_1

CL

CL<

CDZH

CL

Z)

CQI O

L_O

COOHI

COH

QL

UJ1

O<

CL<Xo

_l<oH

CO

>-X

CL

OJ

LlI _1

CQ<

hO LJ

UJ

iCl

UJ

_l

-J0

Q£

J-ZO

>- -JO < _J HZ _l Ul< CL < XH co O

(0

J J- z H

<0 CL ZH

J- ZCL oa < J“ O < oc< J-UJ z H U.O C0_1 LJ 1- Ck _j oz <U <0 XH SI Hh (OUJ oc X aco <Q UJQC O <H —J H XH O a-i COCO J-< <

LU

CL< X X1— 0

CL 0 < CO

LJX

V-/

® 0 0 (9 s> 10 a> 0) 00 CM h* 00 CM — CM — CM

LUOz<

cl a: o <5; O LlI O

_l _l 'w'

lx.Ox

CO I—X zoo O H ^ H 3

COz

l±J

H

XX ^ H O X OHOUJ ^

LlI

X

OZ< X

HIa

_JOX

CL Z O

CL LlI ^ < _J

LO

(0

r»

co

CO

CO

LO

H

<0 I". a>

CM

"t U)00

cm co a> <0 00 CO

M-10

a>

<0

co10

hiOZ< LlI H CL

_l >- CL I— CL<

O'o z JJ- H 1- H < Z Z z _1 _1 < < < JC H H H z 5 O a < O' < < < O' H

O' O'a u.

O

CL

LlI CQX3Z

CM CO M- IO

63
TABLE

3:

TEST

CONDITIONS

FOR

ROOM

EXPERIMENTS

O _l

cy: <

Li- 3

\ \

OH

I-<

_1

_1 => _l CO < z

15 H

\ \ \ \ \

LJCL

ID

1- <

Z CL

LJ LJ H CL CQ Z

Z LJ < I- ftlMWNWWWWMWNWNNRINWW i/)l/)(0-4--4-|/>6)(0l/)L0(0(M-4-'4-(9 — CD M-

_l LJ

_J O

< z

15 < <D CO CO CO CO CO CO 0) 0) 00 CO CO <o CD CO CO to \ CL C\J CM CM 0) — CM CM CM CM LJ < —i i . i ® © ® ® ® © ® Q ® ® ® ® ® ® ® ® ® ®

Li. O

<3 LJ \ O

U Z

O <

Z CL < <

H LJ

CM CO CO CO to <o LO CO .p- to to CO

0) CO CO a

>

oi Tf* — CD Tf* CO 0) ® ® ® Q ® ® ® ® ® ® Q ® ® ® ® ® ® ®

CL O

a.<

LJo

Z Cl < LJ H L-

_1 CO

CL LJ

CL h- <

CM CM CO CO M- M- M" "tlOinCMCMCMCMCM

L— __ cm CO "T ID CD CD CO ® CM CO LO CO I'' CO (OLJ ® ® ® ® ® ® ® ® ® •— — .

•— <*

cl DC QC O' CL OL CL CL QC CL QC CL a; CL QC QC QC OC

_1 _l —I _l _l _1 _a _i _1 _1 _i _1 _i _J 1- a a CJ CJ o a o o CJ o O CJ o O a O CJ CJ

64

I

!i
TABLE

4

TEMPERATURES

MEASURED

DURING

FIRE

TESTS

OF

SEVERAL

WOOD

HEATING

APPLIANCES

65
TABLE

5:

MAXIMUM

RISE

ABOVE

ROOM

TEMPERATURE

ON

WALL

AND

FLOOR

SURFACES

DURING

^IRE

TESTS

OF

SEVERAL

WOOD

HEATING

APPLIANCES

66
TABLE

6

TEMPERATURES

MEASURED

DURING

LOG

TESTS

OF

SEVERAL

WOOD

HEATING

APPLIANCES

67
TABLE

7:

COMPARISON

OF

MEASURED

AND

CALCULATED

WALL

SURFACE

TEMPERATURES

FOR

HEAT

TRANSFER

FROM

FLUE

PIPE

TO

WALL I i|r

68
TABLE

8=

COMPARISON

OF

MEASURED

AND

CALCULATED

WALL

SURFACE

TEMPERATURES

FOR

HEAT

TRANSFER

FROM

APPLIANCE

TO

WALL

69
N B S' I I 4 A (REV. 9-76)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 80-2140

4. TITLE AND SUBTITLE

FIRE SAFETY OF WOOD-BURNING APPLIANCES, PART 1:

STATE OF THE ART REVIEW AND FIRE TESTS, VOLUME I

5. Publication Date November 1980

Biliili_

7. AUTHOR(S)

Richard D. Peacock, Efrain Ruiz, and Roberto Torres-Pereira

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State, ZIP)

U.S. Department of Energy

Washington, D.C. 20585

13. Type of Report & Period Covered Final Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or

literature survey, mention it here.)

A series of 18 full-scale tests was conducted in an instrumented test room using

five different wood-burning appliances. These tests were designed (1) to establish typical operating conditions including temperatures on the appliances, chimneys, and adjacent combustible surfaces; (2) to study the effects of a variety

of combinations of appliance design, clearance to combustibles, and room construction on temperatures on adjacent combustible surfaces; and (3) to compare these

measured values with theoretical predictions of wall surface temperature.

Additional tests were conducted to compare a standardized fuel source with typical

oak logs.

A review of literature related to wood-heating safety included in this study

revealed that current codes are based on data almost 40 years old. The results of

these tests point out some areas where the codes should be modernized to accurately

reflect the newer appliances and construction techniques.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

Chimneys; fire models; fire safety; fire tests; flues; heating equipment; heat

transfer; literature reviews; radiant energy; stoves; wood.

18. AVAILABILITY [^Unlimited

| | For Official Distribution. Do Not Release to NTIS

Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

' 20402, SD Stock No. SN003-003- L Order From National Technical Information Service (NTIS), Springfield, VA. 22161

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF

PRINTED PAGES

69

22. Price

$7.00

USCOMM-DC*