TAMPERE UNIVERSITY OF TECHNOLOGY FIRE LABORATORY RESEARCH REPORT NO. PALO 2133/2012 FLUE GAS TEMPERATURES OF FIREPLACES Tampere 2012
1 (42) 42 pages Financiers Fire Protection Fund Ministry of the Interior Federation of Finnish Financial Services Juhani Lehikoisen säätiö Linnatuli Oy Hormex Oy Ekovilla Oy Paroc Oy Ab Researchers Timo Inha, Lic.Sc. (Tech.) Perttu Leppänen, M.Sc. (Tech.) Martti Peltomäki, B.Sc. (Tech.) Tampere University of Technology Department of Civil Engineering PO.Box 600 Tel. +358 3 311 511 Distribution of report Fire Protection Fund TUT / Department of Civil Engineering / archive
2 (42) Foreword Several fires caused by metal chimney penetrations led to a study on the fire safety of metal chimneys at TUT in 2010. One conclusion of the study was that especially sauna stoves produced hot flue gases. In 2011 Tampere University of Technology (TUT) started a study on the fire safety of fireplaces and metal chimneys. It was a continuation of the study on the fire safety of metal chimneys. The main objective of the study was to reduce the number of fires caused by fireplaces and chimneys by raising awareness of related fire hazards and by participating in the revision of relevant regulations. The management team of the project included Seppo Pekurinen (Federation of Finnish Financial Services), Pekka Rajajärvi (Ministry of the Interior), Jyrki Kauppinen and Matti J. Virtanen (Ministry of the Environment), Kari Siponen (Finnish Safety and Chemicals Agency), Jouni Sorvari (Federation of Finnish Financial Services), Timo Pulkki (RTT), Carl-Gustav Petterson (Hormex Oy), Juha Mielikäinen (Paroc Oy Ab), Ilkka Romppainen (Ekovilla Oy), Kimmo Seppälä (Linnatuli Oy), Juhani Lehikoinen and Johannes Uusitalo (Nunnauuni Oy) and Reijo Hautala (Härmä Air Oy). We wish to thank the management team for their participation in the study.
3 (42) Flue gas temperatures of fireplaces TABLE OF CONTENTS 1 Introduction... 4 2 Tested fireplaces... 5 3 Test methods... 6 4 Testing of wood-burning sauna stoves... 6 4.1 Tests on sauna stoves... 6 4.1.1 Nominal heat output test on sauna stove 1... 6 4.1.2 Temperature safety test on sauna stove 1... 7 4.1.3 Bathing test on sauna stove 1... 7 4.1.4 Temperature safety test on sauna stove 2... 8 4.1.5 Bathing test on sauna stove 2... 9 4.2 Result of sauna stove tests... 9 4.3 Conclusions from the sauna stove tests... 10 5 Room heater testing... 11 5.1 Tests on room heater... 11 5.1.1 Nominal heat output test on room heater + additional batch charges... 11 5.1.2 Temperature safety test on room heater... 12 5.2 Result of room heater tests... 13 5.3 Conclusions from room heater tests... 14 6 Testing of slow heat release appliances... 15 6.1 Tests conducted on slow heat release appliances... 15 6.1.1 Burning rate performance test on slow heat release appliance 1... 15 6.1.2 Temperature safety test + additional batch charge of slow heat release appliance 1... 16 6.1.3 Test on slow heat release appliance 2 with an open ignition damper... 16 6.1.4 Burning rate performance test on slow heat release appliance 2... 17 6.1.5 Temperature safety test + additional batch charges of slow heat release appliance 2... 18 6.2 Results of the tests on slow heat release appliances... 19 6.3 Conclusions from tests on slow heat release appliances... 20 7 Conclusions from the tests... 21 Appendix 1: Test method and performance of tests... 23 Appendix 2: Test arrangement and measurement of temperature, pressure and constituents of flue gases... 27 Appendix 3: Temperatures of sauna stove flue gases and the sauna... 28 Appendix 4: Flue gas temperatures of room heater... 33 Appendix 5: Flue gas temperature of slow heat release appliances... 35 Appendix 6: Measurement of flue gas and hot gas temperatures in fireplace and chimney tests... 40 Appendix 7: Methods of installing chimneys to fireplaces... 41 Appendix 8: Proposed additional measurement point in fireplace tests... 42
4 (42) Flue gas temperatures of fireplaces 1 INTRODUCTION On May 25, 2011 the Ministry of the Environment sent a letter (PG 268 Finnish concern on fire safety risks due to CE marking of appliances fired by solid fuel and chimney products) to the European Commission explaining the deficiencies of harmonised European fireplace and chimney standards. The letter was complemented by VTT's (Technical Research Centre of Finland) research report Flue gas temperature measurements of a slow heat release appliance, a sauna stove and a roomheater. RESEARCH REPORT No. VTT-S-08754-11 December 13, 2011. This report has been presented to the Commission and the member countries. One deficiency of the standard mentioned in the letter is that the flue gas temperature in the CE marking of fireplaces cannot be considered reliable information for dimensioning a temperature class of a chimney. The Ministry of the Environment requested that TUT make one objective of its further research to produce a proposal on how harmonised European product standards should be improve so that the flue gas temperature in their CE marking could be considered a reliable basis point for the selection and dimensioning of chimneys. This research report intends to fill the Ministry s request. The flue gas temperature determined in the tests specified in fireplace standards is the mean temperature meant for determining the heat output of the fireplace. The tests specified in fireplace standard do not provide temperature data required for the dimensioning of chimneys. The purpose of this study is to establish how the flue gas temperature used in dimensioning the temperature class of the chimney should be measured from fireplaces. It was decided to run tests on a sauna stove (EN 15821 Multi-firing sauna stoves fired by natural wood logs), a room heater (EN 13240 Roomheaters fired by solid fuel) and a slow heat release appliance (EN 15250 Slow heat release appliances fired by solid fuel), because they all require a different method of testing the fireplace and the flue gas temperature. The three different test methods cover quite comprehensively the test methods for harmonised product standards. In addition, these products are widely used in Finland where fireplaces are heated more frequently and hotter than in Central Europe due to the climate. The sauna can also be considered part of Finnish culture. Valid versions of harmonised product standards were used in the testing. Tests were made on two wood-burning sauna stoves, one room heater and two slow heat release appliances. Sauna stove 1 was subjected to a nominal heat output test, a temperature safety test and a bathing test (described in Appendix 1). Sauna stove 2 was subjected to temperature safety test and a bathing test.
5 (42) 2 TESTED FIREPLACES The CE marked room heater was subjected to a nominal heat output test and a temperature safety test. A test with larger wood batches was also made after the nominal heat output test. Slow heat release appliance 1 was subjected to a burning rate performance test and a temperature safety test. A test with larger wood batches was also made after the temperature safety test. Slow heat release appliance 2 was subjected to a test with an open ignition damper, a burning rate performance test and a temperature safety test. A test with larger wood batches was also made after the temperature safety test. Sauna stove 1 Sauna stove 1 was a conventional commercial sauna stove. It has been designed for an 8 20 m 3 sauna. The height of the stove was 800 mm, width 540 mm and depth 580 mm. The amount of stones in the sauna stove was 60 kg. The manufacturer's operating instructions suggest getting the fire in the stove going with a small initial batch of firewood. When the wood is burning properly, the firebox can be filled to 2/3 of its height. The fireplace does not yet have a CE marking. Sauna stove 2 Sauna stove 2 was a conventional commercial sauna stove. It has been for an 8-20 m 3 sauna. The height of the stove was 760 mm, width 430 mm and depth 510 mm. The amount of stones in the sauna stove was 40 kg. The manufacturer's operating instructions suggest filling the firebox to 2/3 of its height. The fireplace does not yet have a CE marking. Room heater The room heater was a CE marked cast iron commercial room heater with a design nominal heat output of 5 kw. The weight of the room heater was about 134 kg. The declared thermal efficiency of the room heater is 83% at 5.9 kw heat output. The mean flue gas temperature indicated in the CE marking is 260 C. The room heater was granted a CE marking in July 2010. The intervals for adding wood recommended by the manufacturer is about 45 minutes. The amount of chopped firewood to be added (2 pieces at a time) is 1.62 kg (nominal heat output). The maximum quantity of firewood indicated by the manufacturer is 2.9 kg/h (max 3 pieces or 2.2 kg/charge). Slow heat release appliance 1 Slow heat release appliance 1 was a light-weight commercial appliance. Its dimensions were: height 1650 mm, width 594 mm and depth 514 mm. The weight of the fireplace was 495 kg. The thermal energy output of the fireplace indicated in the CE marking is 39.5 kwh. The declared efficiency is 84%. The mean flue gas temperature indicated in the CE marking is 165 C.
6 (42) 3 TEST METHODS Slow heat release appliance 2 Slow heat release appliance 2 was a conventional commercial appliance. Its dimensions were: height about 1750 mm, width 795 mm and depth 585 mm. The weight of the fireplace was 1300 kg. The heating area declared by the manufacturer is 50 to 70 m 2. The fireplace does not yet have a CE marking. Test methods and execution of the tests are described in Appendix 1. The test arrangement and measurement of temperature, pressure and flue gas constituents are presented in Appendix 2. 4 TESTING OF WOOD-BURNING SAUNA STOVES 4.1 Tests on sauna stoves 4.1.1 Nominal heat output test on sauna stove 1 The nominal heat output test on the sauna stove was conducted in a 20 m 3 sauna. The stove was ignited by a 3 kg wood batch. A 3 kg wood batch was added 24 minutes after ignition, followed by another 3 kg wood batch 48 minutes after ignition. The sauna room temperature reached 90 C at 1 h 15 min. The highest flue gas temperature after the first added batch was 616 C and after the second batch 632 C. Figure 1 The 3 kg wood batch used in the nominal heat output test on sauna stove 1 (Firebox loosely stacked to half of opening height.)
7 (42) 4.1.2 Temperature safety test on sauna stove 1 In deviation from the standard, the temperature safety test on the sauna stove was performed in a 20 m 3 sauna test room. According to the standard, the test should be performed in the smallest possible sauna test room (8 m 3 for this stove). A larger sauna was used in TUT's test because thereby the stove has to heat a larger space requiring a bigger required heat output is consequently higher. With this sauna stove, two batch charges were required in the temperature safety test to raise the temperature of the sauna test room above 110 C. The sauna stove was ignited by a 4 kg wood batch. One 0.9 kg wood batch was added 30 minutes after ignition and another 0.85 kg wood batch 47 minutes after ignition. The temperature of the sauna test room settled at 60 C when 61 minutes had elapsed from ignition. The temperature safety test was started 69 minutes after ignition. The firebox was filled up to the upper edge of the firebox opening. The mass of the added wood batch was 6.05 kg. Draught was increased to 15 Pa +2 / -0. The temperature of the sauna test room rose to 106 C, which meant that the temperature of 110 C was not reached. For this reason, a new wood batch with a mass of 5.95 kg was added 1 h 48 min after ignition. The temperature of the sauna test room rose to 137 C, which is much higher than the 110 C required for the temperature safety test. Flue gas temperature reached 737 C after the first added batch charge of the temperature safety test. The second batch charge of the temperature safety test raised flue gas temperature to 801 C. 4.1.3 Bathing test on sauna stove 1 The bathing test on the stove was performed in a 20 m 3 sauna. The draught used in the test was 15 Pa, the same as in the temperature safety test. The sauna stove was ignited by a 4.05 kg wood batch. Bathing began 33 minutes after ignition. Wood batches during the test Time Wood batch Ignition 4.05 kg 28 min 30 s 1.8 kg 40 min 1.6 kg 54 min 0.65 kg 1 h 10 min 1.5 kg 1 h 17 min 0.7 kg 1 h 27 min 1.65 kg 1 h 42 min 1.5 kg 1 h 51 min 1.85 kg 1 h 58 min 1.2 kg 2 h 1.05 kg 2 h 4 min 0.95 kg 2 h 12 min 0.8 kg 2 h 17 min 1.0 kg 2 h 35 min 1.35 kg 3 h 3 min 2.05 kg
8 (42) Measured from the point specified in the standard, flue gas temperature reached 767 C in the bathing test and 924 C measured from the flue gas connector. 4.1.4 Temperature safety test on sauna stove 2 In deviation from the standard, the temperature safety test on the sauna stove was performed in a 20 m 3 sauna test room. According to the standard, the test should be performed in the smallest possible sauna test room (8 m 3 for this stove). A larger sauna was used in TUT's test because thereby the stove has to heat a larger space requiring a bigger heat output. With this sauna stove, the volume of the sauna temperature safety test room had no impact on flue gas temperatures because the first batch raised the temperature of the sauna test room to 110 C. The sauna stove was ignited by a 2.5 kg wood batch. One 2 kg wood batch was added 24 minutes after ignition and another 0.5 kg wood batch 47 minutes after ignition. The temperature of the sauna test room rose to 80 C. When the temperature of the sauna test room had settled at 60 C, the batch charge for the temperature safety test was added. The temperature safety test was started 62 minutes after ignition. The firebox was filled to the upper edge of the firebox opening. The mass of the added wood batch was 7 kg. Draught was increased to 15 Pa +2 / -0. The temperature of the sauna test room rose above 110 C. The temperature of the sauna test room reached 125 C. Flue gas temperature rose to 749 C in the temperature safety test. The test ended 93 min after ignition when CO 2 content dropped to 4 %. Figure 2 The 2.5 kg wood batch used for ignition in the temperature safety test and the bathing test on sauna stove 2. (About 1/3 of the height of the firebox opening).
9 (42) 4.1.5 Bathing test on sauna stove 2 Figure 3 Firebox of sauna stove 2 filled from side to side up to about half the height of the firebox opening by a 5.75 kg wood batch. The bathing test on the stove was performed in a 20 m 3 sauna. The draught used in the sauna test was the 15 Pa +2 / -0 used in the temperature safety test. The sauna stove was ignited by a 2.5 kg wood batch. Bathing started 20 minutes after ignition. Wood batches during the test Time Wood batch Ignition 2.5 kg 11 min 30 s 3 kg 23 min 3 kg 42 min 2.95 kg 1 h 7 min 0.9 kg 1 h 20 min 1.1 kg 1 h 27 min 1.4 kg 1 h 36 min 1.4 kg 1 h 49 min 0.56 kg 2 h 4.62 kg 2 h 3 min 2.41 kg 4.2 Result of sauna stove tests In the bathing test, flue gas temperature measured at the point specified in the standard reached 705 C and that measured from the flue gas connector 780 C. The flue gas temperatures of the sauna stove and the sauna temperatures are presented in Appendix 3. The highest flue gas temperatures during the tests on sauna stove 1 are presented in Table 1.
10 (42) The highest flue gas temperatures during the tests on sauna stove 2 are presented in Table 2. Table 1 Highest flue gas temperatures of sauna stove 1. Sauna stove 1 Flue gas connector Measurement point specified in Standard EN 15821 Nominal heat output test (Draught 12 Pa) Temperature safety test (Draught 15 Pa) Bathing test (Draught 15 Pa) 738 C 860 C (After second batch 901 C) 924 C 632 C 737 C (After second batch 801 C) 767 C Table 2 Highest flue gas temperatures of sauna stove 2. Sauna stove 2 Flue gas connector Measurement point specified in Standard EN 15821 Temperature safety test (Draught 15 Pa) Bathing test (Draught 15 Pa) 833 C 780 C 749 C 705 C 4.3 Conclusions from the sauna stove tests The mean flue gas temperature indicated in the CE marking cannot be used as an input value in the dimensioning the temperature class of a chimney. Comparison of the mean temperature and flue gas temperatures in the nominal heat output and temperature safety tests reveals that this temperature is not safe for dimensioning the temperature class of a chimney. Moreover, the nominal heat output test is performed according to the manufacturer's instructions in order to achieve the best nominal heat output. When the fireplace is used in way that corresponds to the normal Finnish way of using it, higher flue gas temperatures are attained. The purpose of the temperature safety test is to ensure fire safety with the largest possible batch charge of the stove. In the temperature safety test, the firebox is filled up to the upper edge of the firebox opening. However, it is not necessary to measure or report flue gas temperatures in the temperature safety test. Besides the nominal heat output test and the temperature safety test, a bathing test was also conducted. The flue gas temperatures of the temperature safety test on a 20 m 3 sauna corresponded to those of the bathing test. In addition to the point specified in the standard, flue gas temperature was also measured from the flue gas connector. The highest flue gas temperature measured from the flue gas connector was 75 157 C higher than the temperature measured from the point specified in the standard.
11 (42) 5 ROOM HEATER TESTING 5.1 Tests on room heater The flue gas temperature of a sauna stove should be determined by a temperature safety test. The test should establish the highest temperature. This temperature should be measured from the flue gas connector of the fireplace to make the measurement points of fireplace and chimney standards coincide. The most critical connection is one made behind the stove that penetrates a combustible wall. A problem with the temperature safety test on a wood-burning sauna stove was its short duration. Several consecutive batch charges may result in higher flue gas temperatures. However, the temperature of the sauna room limits the heating of the stove if the stove is located in a sauna of suitable size and the door is closed. 5.1.1 Nominal heat output test on room heater + additional batch charges The room heater was ignited by a 1.6 kg wood batch. A 0.85 kg wood batch was added 27 minutes after ignition. The test period started 1 h 2 min after ignition as the basic firebed was achieved. Chopped birchwood batches weighing 1.7 kg were used as a first batch charge. A second batch of 1.7 kg was added 1 h 47 min after ignition. A third batch of 1.7 kg was added 2 h 34 min after ignition. The nominal heat output test ended 3 h 21 min after ignition as the basic firebed was achieved. Four batches of 3 kg were burned subsequently. The first two additional batch charges were burned using a draught of 12 Pa ±2 and the next two using a draught of 15 Pa +2 / -0. The highest flue gas temperature in the nominal heat output test measured from the flue gas connector was 404 C and that measured from the point specified in the standard was 284 C. During the first two additional batch charges, the highest flue gas temperature in the flue gas connector was 512 C and that measured from the point specified in the standard 376 C. During the burning of the last two additional batch charges the highest flue gas temperature in the flue gas connector was 613 C and that measured from the point specified in the standard 446 C. The mean flue gas temperature determined by the nominal heat output test is 247 C. This is the temperature indicated in the CE marking. The temperature indicated in the CE marking for this room heater was 260 C.
12 (42) Figure 4 The 1.7 kg wood batch used in the nominal heat output test on the room heater. Figure 5 The 3 kg additional batch charge used after the nominal heat output test on the room heater. 5.1.2 Temperature safety test on room heater Fir timber was used for fuel in the temperature safety test on the room heater. The amount of fir timber used is calculated on the basis of the area of the firebox bottom. The room heater was ignited by a 3.3 kg wood batch. The test period started 1 h 2 min after ignition as the basic firebed was achieved. Draught was increased to 15 Pa +2 / -0 in accordance with the standard. In the tempera-
13 (42) ture safety test on the room heater, wood batches are added until the surface temperatures of the trihedron no longer rise. A second 2.5 kg batch was added 1 h 45 min after ignition. A third 2.5 kg batch was added 2 h 30 min after ignition. A fourth 2.5 kg batch was added 3 h 16 min after ignition. The surface temperatures of the trihedron no longer rose. The test was ended 4 h 10 min after ignition as the basic firebed was achieved. Figure 7 Wood batch used in the temperature safety test on the room heater (2.5 kg of spruce batten). 5.2 Result of room heater tests The highest flue gas temperature in the flue gas connector during the temperature safety test was 508 C. The highest flue gas temperature measured from the point specified in the standard was 371 C. The temperatures of the flue gases of the room heater are presented in Appendix 4. The highest flue gas temperatures during the tests on the room heater are presented in Table 3.
14 (42) Table 3 Highest flue gas temperatures of the room heater. Room heater Flue gas connector Nominal heat output test 1 (Draught 12 Pa) Additional batch charges 1 and 2 (Draught 12 Pa) Additional batch charges 3 and 4 (Draught 15 Pa) Temperature safety test (Draught 15 Pa) 404 C 512 C 613 C 508 C Measurement point specified in Standard EN 13240 284 C 376 C 446 C 371 C 5.3 Conclusions from room heater tests The mean flue gas temperature indicated in the CE marking, 260 C, corresponds closely to the flue gas temperatures of the nominal heat output test. However, this temperature cannot be used for dimensioning the temperature class of the chimney. Comparison of the flue gas temperatures from the nominal heat output test and flue gas temperatures from the temperature safety test reveals that this temperature cannot be safely used in dimensioning the chimney. The additional batch test conducted after the nominal heat output test reveals that if a 3 kg wood batch is used instead of a 1.7 kg batch, a draught of just 12 Pa produces flue gas temperatures corresponding to those of the temperature safety test. When draught is increased to 15 Pa with 3 kg wood batches, considerably higher flue gas temperatures are produced. The additional batches can be regarded as overheating the fireplace. The temperature safety test on the room heater is continued until the highest temperatures are attained in the trihedron. In the test, the highest flue gas temperature is attained with the tested wood batch size. The flue gas temperature was measured at the point specified in the standard as well as from the flue gas connector. The highest flue gas temperature measured from the flue gas connector was 120 167 C higher than that measured from the point specified in the standard. The temperature of the flue gases of the room heater should be determined by a temperature safety test. The test should establish the highest temperature. This temperature should be measured from the flue gas connector of the fireplace to make the measurement points in the fireplace and chimney standards coincide. The most critical installation is one made behind the stove that penetrates a combustible wall.
15 (42) A problem with the temperature safety test on the room heater was that with some room heaters the wood batch size used in the test may be small in relation to the volume of the firebox (due to the area of the firebox bottom). A larger wood batch may increase flue gas temperatures. In addition to a calculation based on the area of the firebox, the standard should present a coefficient that ensures the sufficient amount of firewood in such situations. The coefficient could compare the amount of wood to that of the nominal heat output test or the volume of the firebox. 6 TESTING OF SLOW HEAT RELEASE APPLIANCES 6.1 Tests conducted on slow heat release appliances 6.1.1 Burning rate performance test on slow heat release appliance 1 The slow heat release appliance was ignited by a 2.5 kg wood batch besides using 0.5 kg of kindling. A 2.5 kg wood batch was added 15 minutes after ignition. A second 2.5 kg batch was added 45 minutes after ignition. A third 2.5 kg batch was added 1 h 15 min after ignition. The test ended 1 h 59 min after ignition when CO2 content dropped to 3.8%. The highest flue gas temperature in the flue gas connector was 311 C and that measured from the point specified in the standard 298 C. The mean flue gas temperature determined by the burning rate performance test was 246 C. Figure 8 The 2.5 kg wood batch + 0.5 kg of kindling used in the burning rate performance test on slow heat release appliance 1.
16 (42) 6.1.2 Temperature safety test + additional batch charge of slow heat release appliance 1 Temperature safety test on a slow heat release appliance is performed by starting a new burning rate performance test immediately after the first one. The slow heat release appliance was ignited by a 2.5 kg wood batch and 0.5 kg of kindling. A 2.5 kg wood batch was added 15 minutes after ignition. A second 2.5 kg batch was added 45 minutes after ignition. A third 2.5 kg batch was added 1 h 15 min after ignition. The temperature safety test was started 2 h 3 min after ignition when CO2 content dropped to 3.8%. Draught was raised to 15 Pa +2 / -0 in accordance with the standard. The first 2.5 kg wood batch for the temperature safety test was added 2 h 3 min after ignition. The subsequent three 2.5 kg wood batches were added 2 h 33 min, 3 h 3 min and 3 h 33 min after ignition. The temperature safety test ended at 4 h 18 min when CO2- content dropped to 3.9%. An extra 5 kg batch was added subsequently and draught was increased to 20 Pa. Figure 9 The 2.5 kg wood batch used in the normal use and temperature safety tests on slow heat release appliance 1. The highest flue gas temperature in the flue gas connector during the burning rate performance test was 320 C and that measured from the point specified in the standard 310 C. The highest flue gas temperature in the flue gas connector during the temperature safety test was 388 C and that measured from the point specified in the standard was 368 C. The highest flue gas temperature in the flue gas connector during the burning of the additional batch was 435 C and that measured from the point specified in the standard 411 C. The mean flue gas temperature determined by the burning rate performance test was 250 C. 6.1.3 Test on slow heat release appliance 2 with an open ignition damper A test was made on slow heat release appliance 2 with an open ignition damper. The ignition damper is meant to improve draught during ignition. When the ignition damper is open, flue gases flow directly into the chimney without circulating through the smoke canals of the fireplace. The ignition
17 (42) damper can be kept open for 10-15 minutes after ignition. The slow heat release appliance was ignited by a 5 kg wood batch. A 3 kg batch was added 34 minutes after ignition. A 5 kg additional batch was added 45 minutes after ignition. The test ended 1 h 18 min after ignition, when CO2 content dropped to 4%. The highest flue gas temperature in the flue gas connector was 467 C and that measured from the point specified in the standard 432 C. 6.1.4 Burning rate performance test on slow heat release appliance 2 The slow heat release appliance was ignited by a 5 kg wood batch and 0.5 kg of kindling. A 3 kg batch was added 39 minutes after ignition. The test ended 1 h 5 min after ignition when CO 2 content dropped to 2.95%. The highest flue gas temperature in the flue gas connector at 347 C was attained while the ignition damper was still open. When the ignition damper was closed, the highest temperature in the flue gas connector was 260 C and that measured from the point specified in the standard 240 C. Figure 11 The 5 kg wood batch + 0.5 kg of kindling used in the burning rate performance test on slow heat release appliance 2.
18 (42) Figure 12 The 3 kg wood batch used in the normal use and temperature safety tests on slow heat release appliance 2. 6.1.5 Temperature safety test + additional batch charges of slow heat release appliance 2 A temperature safety test on a slow heat release appliance is performed by starting a new burning rate performance test immediately after the first one. The slow heat release appliance was ignited by 5 kg wood batch and 0.5 kg of kindling. Ignition was performed with an open ignition damper. The ignition damper was closed 10 min after ignition. A 3 kg wood batch was added 40 minutes after ignition. The temperature safety test started 1 h 6 min after ignition. Draught was raised to 15 Pa +2 / -0 in accordance with the standard. The first 5 kg wood batch for the temperature safety test was added 1 h 6 min after ignition. A 3 kg wood batch was added 1 h 30 min after ignition. The temperature safety test ended at 1 h 49 min. A 10 kg wood batch was added subsequently and draught was increased to 20 Pa. When flue gas temperatures had reached their peak, the ignition damper was opened to attain the highest temperatures.
19 (42) Kuva 13 The 10 kg wood batch added after the temperature safety test on slow heat release appliance 2. The highest flue gas temperature in the flue gas connector during the burning rate performance test was 266 C and that measured from the point specified in the standard 243 C. The highest flue gas temperature in the flue gas connector during the temperature safety test was 371 C and that measured from the point specified in the standard 350 C. The highest flue gas temperature in the flue gas connector during the burning of the additional batch before the opening of the ignition damper was 452 C and that measured from the point specified in the standard 426 C. After the opening of the ignition damper, the highest flue gas temperature in the flue gas connector during the burning of the additional batch was 581 C and that measured from the point specified in the standard 530 C. 6.2 Results of the tests on slow heat release appliances Flue gas temperatures of slow heat release appliances are presented in Appendix 5. The highest flue gas temperatures during the tests on slow heat release appliance 1 are presented in Table 4. The highest flue gas temperatures during the tests on slow heat release appliance 2 are presented in Table 5.
20 (42) Table 4 Highest flue gas temperatures with slow heat release appliance 1. Slow heat release appliance 1 Flue gas connector Burning rate performance test 1 (Draught 12 Pa) 311 C Measurement point specified in Standard EN 15250 298 C Burning rate performance test 2 (Draught 12 Pa) Temperature safety test (Draught 15 Pa) Additional batch (Draught 20 Pa) 320 C 388 C 435 C 310 C 368 C 411 C Table 5 Highest flue gas temperatures with slow heat release appliance 2. Slow heat release appliance 2 Flue gas connector Measurement point specified in Standard EN 15250 With open ignition damper (Draught 12 Pa) 467 C 432 C Burning rate performance test 1 (Draught 12 Pa) Burning rate performance test 2 (Draught 12 Pa) Temperature safety test (Draught 15 Pa) Additional batch (Draught 20 Pa) Additional batch with open ignition damper (Draught 20 Pa) 260 C 266 C 371 C 452 C 581 C 240 C 243 C 350 C 426 C 530 C 6.3 Conclusions from tests on slow heat release appliances The mean flue gas temperature indicated in the CE marking corresponds rather well to the flue gas temperatures of the burning rate performance test. In these fireplaces, the highest flue gas temperature in the burning rate performance test was only about 50 C higher than the mean temperature. However, this temperature cannot be used for dimensioning the temperature class of the chimney. Comparison of the temperature from the burning rate performance test with temperatures of flue gases from the temperature safety test reveals that this temperature is not safe for dimensioning the chimney. The highest flue gas temperature in the temperature safety test was more than 100 C higher than the mean temperature in the burning rate performance test.
21 (42) The additional batch test made after the temperature safety test reveals that using a double wood batch and a draught of 20 Pa produces about 50 C higher flue gas temperatures than those measured in the temperature safety test. Leaving the ignition damper open during the heating of the slow heat release appliance may increase flue gas temperatures in the chimney even more. Additional batches may be regarded as overheating the fireplace. In addition to the point specified in the standard, flue gas temperature was also measured from the flue gas connector. The highest flue gas temperature measured from the flue gas connector was 10 51 C higher than that measured from the point specified in the standard. The biggest difference in temperatures occurs when the ignition damper is open. The flue gas temperature of a slow heat release appliance should be determined by a temperature safety test. The test should establish the highest temperature. This temperature should be measured from the flue gas connector of the fireplace to make the measurement points in fireplace and chimney standards coincide. The most critical connection is one made behind the stove that penetrates a combustible wall. A problem with the temperature safety test on slow heat release appliances is that they use the wood batches of the normal use test specified by the manufacturer. In some cases, the batch sizes specified by the manufacturer may be small in relation to the volume of the firebox. A larger wood batch may increase flue gas temperatures. Another problem lies with the ignition dampers of slow heat release appliances. If a slow heat release appliance has an ignition damper, the temperature safety test should be performed while it is open. The measurement of flue gas and hot gas temperatures in fireplace and chimney tests is described in Appendix 6. Methods of installing chimneys in fireplaces are presented in Appendix 7. A proposal for an additional measurement point in fireplace tests is presented in Appendix 8. 7 CONCLUSIONS FROM THE TESTS The mean flue gas temperature determined by the nominal heat output and burning rate performance tests on fireplaces cannot be used in the dimensioning of chimneys. Fireplaces should be used according to the manufacturer's instructions to ensure that flue gas temperatures stay within the design limits and the efficiency of the fireplace corresponds to tests. However, the test specified by the manufacturer cannot be used as a starting point in the measurement of flue gas
23 (42) Appendix 1: Test method and performance of tests Appendix 1 (1/4) Test methods: Sauna stoves: Standard EN 15821:2010 Multi-firing sauna stoves fired by natural wood logs - Requirements and test methods. Room heater: Standard EN 13240:2001/A2:2004/AC:2007 Roomheaters fired by solid fuel. Requirements and test methods. Slow heat release appliances: Standard EN 15250:2007 Slow heat release appliances fired by solid fuel. Requirements and test methods. Measurements: Draught and flue gas temperature is measured by a Kimo MP 200 micromanometer with a TPL-06-300-T measurement sensor. In addition to the measurements specified in the standard, flue gas temperature is measured from the flue gas connector of the fireplace with a type K thermocouple wire Ø 0.5 mm. Flue gas temperature and composition is measured and recorded at intervals of 1 minute. Mean flue gas temperatures during normal use and nominal heat output tests are calculated and reported. Fuel: The fuels used in the tests conform to Appendix B of the standards. The wood amounts used in the nominal heat output and burning rate performance tests correspond to those used in the tests for the CE marking or which the manufacturer intends to perform to earn the CE marking.
24 (42) Tests on sauna stoves: Appendix 1 (2/4) Nominal heat output test The fireplace to be tested is installed in the sauna test room specified in standard EN 15821 at the safety distances from walls specified by the manufacturer. Fuel batch charges specified by the manufacturer are added in testing at nominal heat output; they should suffice to raise the temperature of the sauna test room to 90 C. The draught used in the test is 12 Pa ±2. The air exchange rate is 6 times per hour. The test is used to determine the mean flue gas temperature. The nominal heat output test of a sauna stove corresponds to a situation where the sauna is heated ready for bathing, and heating is then stopped. In reality bathing starts when the sauna gets warm, and the fire is kept burning in a multi-firing sauna stove throughout the bath. Temperature safety test In a temperature safety test, the temperature of the sauna test room should first settle at 60 C, then the draught is raised to 15 Pa and the firebox is filled to the upper edge of the firebox opening. If the first batch charge does not raise the temperature of the sauna test room to 110 C, another batch is added. The purpose of the temperature safety test is to determine safety distances to combustible materials. According to the standard, it is not necessary to measure flue gas temperature as part of the test. Bathing test In addition to the tests specified in the standard, a sauna test was carried out. The nominal heat output and temperature safety tests on a sauna stove are short in duration. The standard fails to consider baths of long duration. This is why the bathing test was made. A sauna stove is very different from other kinds of fireplaces. During the bath, the temperature of the sauna is kept at 80 100 C; some prefer even hotter temperatures. Moreover, the stones in the stove must be sufficiently hot (about 300 C) throughout the bath. A sauna bath may continue for several hours. In the bathing test, people took a bath in the test sauna during which water was thrown on the sauna stove to produce steam. Wood batches were added to keep the sauna temperature comfortable. The air exchange rate was 6 times per hour according to the standard. The purpose of the bathing test was to describe the Finnish way of using a sauna stove, for use as a starting point in determining the temperature of the flue gases of the stove.
25 (42) Tests on the room heater: Appendix 1 (3/4) Nominal heat output test The fireplace to be tested is installed on a weighing apparatus at safety distances specified by the manufacturer from the trihedron specified in standard EN 13240. Testing at nominal heat output consists of ignition, pre-test and test phases. The pre-test phase ensures that the basic firebed is achieved. The test phase starts when the basic firebed has been achieved. Fuel batches specified by the manufacturer are added during the test phase. The test phase ends when the weight of the basic firebed is the same as at the end of the pretest phase. The draught used in the test is 12 Pa ±2. The test determines the mean flue gas temperature. Temperature safety test The test fuel of the temperature safety test is fir timber with cross-sectional dimensions of 4 cm x 6 cm or 5 cm x 5 cm. At first, a sufficient amount of fuel is added in the room heater to ensure the ignition of the fuel. When the fuel has ignited, the calculated fuel batch is added. The next fuel batch is added as the basic firebed has been achieved. Fuel batches are added until the walls of the trihedron have reached their highest temperature. A draught of 15 Pa is used. The purpose of the temperature safety test is to determine the safety distances of the fireplace to combustible materials. According to the standard, it is not necessary to determine flue gas temperatures as part of the test. The weight of a fuel batch in the temperature safety test on a room heater is calculated by the formula: where Bfl = weight of the test batch, kg Sc = area of firebox bottom, m 2 Hu = lower calorific value of fuel at moisture content at burning, MJ/kg c = 400 MJ/m 2
26 (42) Appendix 1 (4/4) Additional heating test In a temperature safety test, the size of fuel batches is calculated on the basis of the area of the firebox bottom. However, the standard does not consider the height of the firebox. The large size of the firebox of many room heaters allows using larger wood batches than those calculated in the temperature safety test. Larger wood batches may increase flue gas temperatures. After the nominal heat output test, we conducted a test with larger wood batches. Tests on slow heat release appliances: Burning rate performance test The fireplace to be tested is installed at safety distances specified by the manufacturer from the trihedron specified in standard EN 15250. Fuel batches specified by the manufacturer are used in the burning rate performance test. The draught used in the test is 12 Pa ±2. The test establishes the mean flue gas temperature. Temperature safety test In a temperature safety test, a burning rate performance test is performed first, then draught is raised to 15 Pa, and wood batches corresponding to those of the burning rate performance test are added. The purpose of the temperature safety test is to determine the safety distances of the fireplace to combustible materials. According to the standard, there is no need to measure flue gas temperatures as part of the test. Additional heating test Although twice as many wood batches are used in the temperature safety test, the wood batch sizes are specified by the manufacturer. In reality, considerably larger wood batches may be used in many slow heat release appliances. Larger wood batches probably increase flue gas temperatures. After the temperature safety test, an overheating test was conducted using a wood batch twice the size specified by the manufacturer. The second fireplace had an ignition damper. When the ignition damper is open, flue gases flow directly into the chimney without circulating through the furnace flue of the fireplace. This results in higher flue gas temperatures in the chimney. The ignition damper may be kept open for a short time during ignition. Its purpose is to promote the formation of draught in the chimney. Fireplace 2 was tested also with an open ignition damper.
27 (42) Appendix 2 (1/1) Appendix 2: Test arrangement and measurement of temperature, pressure and constituents of flue gases Appendix 3 (1/5)
28 (42) Appendix 3: Temperatures of sauna stove flue gases and the sauna FLUE GAS TEMPERATURES AND THE SAUNA IN NOMINAL HEAT OUTPUT TEST ON SAUNA STOVE 1 Date of test 17.2.2012
29 (42) FLUE GAS AND SAUNA TEMPERATURES IN SAFETY TEST ON SAUNA STOVE 1 Appendix 3 (2/5) Date of test 20.2.2012
30 (42) FLUE GAS AND SAUNA TEMPERATURE IN BATHING TEST ON SAUNA STOVE 1 Appendix 3 (3/5) Date of test 23.2.2012
31 (42) Appendix 3 (4/5) FLUE GAS AND SAUNA TEMPERATURES IN TEMPERATURE SAFETY TEST ON SAUNA STOVE 2 Date of test 20.6.2012
32 (42) Appendix 3 (5/5) FLUE GAS AND SAUNA TEMPERATURES IN BATHING TEST ON SAUNA STOVE 2 Date of test 21.6.2012
33 (42) Appendix 4: Flue gas temperatures of room heater Appendix 4 (1/2) FLUE GAS TEMPERATURE IN NOMINAL HEAT OUTPUT TEST ON THE ROOM HEATER AND WITH ADDITIONAL BATCH CHARGES Date of test 6.3.2012
34 (42) Appendix 4 (2/2) FLUE GAS TEMPERATURE IN TEMPERATURE SAFETY TEST ON ROOM HEATER Date of test 7.3.2012
35 (42) Appendix 5 (1/5) Appendix 5: Flue gas temperature of slow heat release appliances FLUE GAS TEMPERATURE IN BURNING RATE PERFORMANCE TEST ON SLOW HEAT RELEASE APPLIANCE 1 Date of test 6.6.2012
36 (42) Appendix 5 (2/5) FLUE GAS TEMPERATURE IN TEMPERATURE SAFETY TEST ON SLOW HEAT RELEASE APPLIANCE 1 Date of test 7.6.2012
37 (42) Appendix 5 (3/5) FLUE GAS TEMPERATURE OF SLOW HEAT RELEASE APPLIANCE 2 WITH OPEN IGNITION DAMPER Date of test 11.6.2012
38 (42) Appendix 5 (4/5) FLUE GAS TEMPERATURE IN BURNING RATE PERFORMANCE TEST ON SLOW HEAT RELEASE APPLIANCE 2 Date of test 12.6.2012
39 (42) Appendix 5 (5/5) FLUE GAS TEMPERATURE IN TEMPERATURE SAFETY TEST ON SLOW HEAT RELEASE APPLIANCE 2 Date of test 14.6.2012
40 (42) Appendix 6 (1/1) Appendix 6: Measurement of flue gas and hot gas temperatures in fireplace and chimney tests EN 15821 EN 1859 Multi-firing sauna stoves fired by natural wood logs, Chimneys. Metal chimneys. Requirements and test methods Test methods Measurement of flue gas and hot gas temperatures
41 (42) Appendix 7: Methods of installing chimneys to fireplaces Appendix 7 (1/1) 1: Exit from top 2: Exit from back directly into chimney EN 15821 Critical point 3: Exit from back through wall EN 13240 Three principle drawings for connecting a fireplace to a chimney. In installation methods 1 and 2, the critical point is the penetration of the chimney through a combustible roof. The critical point in installation method 3 is the penetration through a combustible wall. Flue gas temperature measurement in installation method 3 is after the critical point. This causes uncertainty. Temperature measurement Critical point
42 (42) Appendix 8 (1/1) Appendix 8: Proposed additional measurement point in fireplace tests Additional measurement point for measuring flue gas temperatures EN 15821 The purpose of the additional measurement point is to ensure the fire safety of installation method 3 presented in Appendix 7.