US005333601A United States Patent [19] [11] Patent Number: 5,333,601 [45] Date of Patent: Aug. 2, 1994

[54] MASONRY HEATER “Finnish Fireplace Construction Manual 1984”, Albert A. Barden, III, pp. 53-57. [75] Inventor: Kerry Hill, Wain?eet, Canada “Finnish Fireplaces, Heart of the Home”, A. Barden et al., pp. 33, 41, 51 and 101. [73] Assignees: Christy Brianna Hill; Andrea Kirsty Brochure by Hearth Warmers. Lee Hill, Wain?eet, Canada Brochure by Dietmeyer, Ward & Stroud, Inc. [21] Appl. No.: 27,493 Primary Examiner-Larry Jones Attorney, Agent, or Firm-Riches, McKenzie & Herbert [22] Filed: Mar. 5, 1993 [57] ABSTRACT [51] Int. Cl.5 F24B 1/ 188 This invention relates to A contra-?ow masonry heater [52] 126/523; 126/500; comprising: a ?rebox having a front opening, an air 126/503; 126/8 intake communicating with a source of fresh air and an [58] Field of Search 126/523, 500, 502, 503 ’ upper flue outlet; at least one vertical contra-?ow heat 126/512, 8 exchange channel communicating between the flue [56] References Cited outlet and an exhaust port, the ?rebox and channel having walls of refractory material for mass absorption U.S. PATENT DOCUMENTS of heat energy from a burning fuel and combustion

wemaaf.wa hC mcmwaoasegml?o bP mdnm?s dmha,dmt rf wuwmmmmMm” 439.1 R Bm@mweaH Unanrnm \e%@./m .Igoemdoe d616y dtgm?bm5 chmndPmh dmmdamwn dhmnpocf 2gQueen Edccv 3,,O,7,4, wfai enema mm“mEsBsP .ngmnmntnm Fmhedm?mQto amthugcab . .andlamg1 mtC.Va.Cd t‘‘ @eTT lme 68mm 4.4.4.5 cnummnmmm nn.comefum;o eamo?lormbV.mmeommm?. , mcthimwuh4 .mimamwmsm iniii; wtoommehc vmnamawewtmdmhooum IauOUeHue comko?emmméwmmdm mmmms_mung \nmmmmwuhh mnmagummw. \ mm- Lu‘-MN>m6 700803 .“moQ‘0 a ms.u1i \Q:, 1nI Ima . \“5wuwlumm1H. nBwooi711M\.I~l \.\I-l<|

11

WA 1

'- \ \ \ \ \\ \ /\ /\ \/\ US. Patent Aug. 2, 1994 Sheet 2 of 14 5,333,601

11 12

14 \23 U.S. Patent Aug. 2, 1994 Sheet 3 of 14 US. Patent Aug. 2, 1994 Sheet 4 of 14 5,333,601

F|G.5. 30

L’

F_ 5'1 6 271 - e 26X. US. Patent Aug. 2, 1994 Sheet 5 of 14 5,333,601

FIG.9. FIGJO. US. Patent Aug. 2, 1994 Sheet 6 of 14 5,333,601

‘ F | 6 -1 1.K' US. Patent Aug. 2, 1994 Sheet 7 of 14 5,333,601

<5:1 "I mm,“‘7 b Hmumm’ F | G I.1 2 .

102 H543‘.

- FIGJ4.

FIG-15. ‘

F's-16. US. Patent Aug. 2, 1994 Sheet 8 of 14 5,333,601

US. Patent Aug. 2, 1994 Sheet 11 of 14 5,333,601

~ F|G.30......

u!!!

WM?‘ I!!!“ ‘ i W! US. Patent Aug. 2, 1994 Sheet 12 of 14 5,333,601

5 mu IIIWml. FIG.33.

US. Patent Aug. 2, 1994 Sheet 14 of 14 5,333,601

37

35

36 39

||

39

160 I 101a FIG.38.

I" ‘W5 " _. .; mum-mum_ __ I mm. H ~ ! - 1 40 \ ' J 40 39 107 38.1 F|G.39. 5,333,601 1 2 design there is a dangerous potential for non combusted MASONRY HEATER gas to accumulate in the upper regions of the contra ?ow masonry heater. As a result, such gas ?re contra FIELD OF THE INVENTION ?ow heaters must be operated with the doors open and The invention relates to masonry heaters, and in par may not include a chimney damper. Inef?cient burning ticular a thermostatically controlled gas ?red masonry of the gas fuel results, however the problem of accumu heater. lation of dangerous gases is avoided. A signi?cant dan ger still is presented by such an application since the BACKGROUND OF THE INVENTION home owner may forget to leave the doors open or may Masonry heaters have been used at least since Roman instal a damper without knowing the inherent dangers times to provide radiant heat from a mass of masonry. A of such a modi?cation. conventional masonry heater includes a ?rebox and a The design of conventional masonry heaters also series of maze like channels through which the ?ue often requires that expansion gaskets be installed be gases escape to the chimney. The ?rebox and channels 15 tween various parts of the ?rebox and heat exchange have walls preferably made of refractory material channels due to the differential in temperature during which absorbs heat energy from the burning fuel and operation and relative expansion and contraction. Gas combustion gases. The primary advantage of a masonry kets and cracks in the masonry heater may be accept heater is that a relatively small amount of fuel may be able in a wood burning application, however the danger burned for a short period of time and the mass of the masonry heater absorbs a signi?cant portion of the heat 20 of carbon monoxide poisoning or explosive gases is energy from such a ?re. The masonry mass thereafter present when used in conjunction with a gas burner. radiates heat to the surrounding room over a long per Another disadvantage of conventional masonry heaters iod of time. is that they are of a size which requires the removal of A contra-?ow masonry heater conventionally has a an existing ?replace to install a masonry heater. This is central ?rebox with air intake and upper ?ue outlet. 25 not a particular dif?culty with the construction of a Vertical contra-?ow heat exchange channels communi new home, however the market potential of masonry cate with the ?ue outlet at the top of the ?rebox and heaters is signi?cantly restricted by its inability to be direct the combustion gases downward in the channels adapted to retro ?t in a conventional ?replace. to be exhausted through an exhaust port at a lower SUMMARY OF THE INVENTION level. A contra-?ow masonry heater is preferred since a 30 larger portion of the heat energy may be absorbed by The invention overcomes the disadvantages of the the masonry mass. The heat of combustion is high prior art in a novel manner in the provision of a contra enough to avoid the buildup of creasole and other com ?ow masonry heater which can be adapted to burn bustible products in the channels. wood fuel or to include a gas burner. A down draft In Europe, masonry heaters have been convention 35 hood is provided to prevent down draft in the chimney ally built where a wood burning ?replace is desired. from exhausting carbon dioxide and fuel gas into the The size of the masonry heaters is relatively large and dwelling. Such a down draft hood prevents the serious they are often located in the center of a home to provide problem of back?ow through the air intake. radiant heating throughout the dwelling. The contra-?ow masonry heater of the invention In North America, conventionally an open hearth includes burner control means which operate with a ?replace has been used, however, in recent years due to thermostat in contact with a masonry core. Depending the inefficiencies of such ?replaces, their use has been upon the temperature setting of the thermostat and the discouraged. A conventional ?replace is very inef?cient temperature of the core after burning of the fuel and in that it draws room air for combustion and although heat absorption, the burner control means may be stim radiant heat is felt in the immediate vicinity of the ?re 45 place, in total the heat output of many ?replaces is ulated to ignite the burner ?ame, extinguish the ?ame, negative. In other words, the draft caused by the opera or vary the quantity of gas supplied to the burner to tion of the ?replace exhausts warm air from the dwell achieve the desired room temperature. As described ing and draws in cold air through doorways, windows above, conventional gas ?red masonry heaters have not been thermostatically controlled since for safety reasons and other openings of the dwelling. In modern home 50 construction, insulation and vapor barriers are continu they are required to be operated with the doors open ously provided to substantially increase the heating and cannot include a damper. ef?ciency of the dwelling. A ?replace in such a dwell The relief port of the down draft hood exhausts into ing represents a major source of heat loss, however, the same dwelling space from which the intake air is since many members of the purchasing public still desire 55 drawn. Temperature sensor means are located within a wood burning ?replace in their homes, the level of the relief port and communicate with the burner control energy efficiency is less than optimal in modern con means. When a temperature higher than a prescribed struction. When a gas burning insert is placed in a con value is sensed by the temperature sensor, it stimulates ventional ?replace, the heat ef?ciency is not substan the burner control means to extinguish the burner. Such tially higher than when wood is burned in a conven a rise in temperature would occur when down draft tional ?replace. As a result, such gas inserts are largely through the chimney forces ?ue gases down the chim decorative and are not a practical source of heat for a ney and through the relief port. Without such a relief dwelling despite the quantity of gas burned in such port or down draft hood, the ?ue gases would be forced applications. back into the masonry heater and possibly backwards Attempts have been made to combine the ef?ciency 65 into the dwelling area through the intake port. The of a masonry heater to replace a conventional ?replace danger of carbon monoxide poisoning, poisoning from with the addition of a gas burning insert. Such attempts fuel gas, explosion or ?re hazard are eliminated through have been unsuccessful to date. Due to the contra-?ow the invention. 5,333,601 3 4 As a result of the unique design of the system, it has described by way of example with reference to the been tested as a vented room heater through the Ameri accompanying drawings in which: can Gas Association Laboratories and has received FIG. 1 is a partially broken away perspective trans certi?cation and full approval under ANSI Standard parent view of one embodiment of the invention Z2l.ll.l-l99l. To the knowledge of the inventor such adapted to burn wood fuel showing the flow of intake gas approval has been obtained by any other designer of air and ?ue gases through the masonry heater and (to gas ?red masonry heaters. The ef?ciency of a gas ?red the right as drawn) through the down draft hood which masonry heater in accordance with the invention is such is exploded away from the exhaust port for clarity. that it may be made of such a size to ?t within the hearth FIG. 2 is a like broken away perspective view show of a conventional ?replace. As a result, the masonry ing a second embodiment of the invention adapted to heater may be retro ?t within an existing ?replace include a gas ?red burner showing a thermostat at thereby substantially increasing the potential for mar tached to the core of the masonry heater, gas burner ketplace acceptance. control means and a temperature sensor within the relief The core of the masonry heater is constructed of port of the down draft hood for controlling the opera modular blocks in a vertically stacked series of courses. tion of the gas burner housed within the ?rebox. Every block is of the same vertical height and the walls FIGS. 3 and 4 show details of the down draft hood in of the blocks have substantially the same thickness. As elevation and plan views respectively. a result it has been found through experiment that ex FIG. 5 is a vertical sectional view through the door pansion gaskets are not required between the modular and ?rebox (showing the door exploded away for clar blocks and only high temperature refractory mortar is 20 ity), as indicated by lines 5-5 in FIG. 6. required. Expansion and contraction and differential FIG. 6 is a plan sectional view through the door and temperature between the ?rebox and contra-?ow chan ?rebox as indicated by lines 6-6 of FIG. 5. nels is such that leakage of gas and expansion cracks do FIG. 7 through 9 are all perspective views of the core not occur. of a masonry heater according to the invention showing A further advantage of the modular design is that any 25 height of masonry heater may be constructed from a from left to right the addition of modules to increase the limited number of standard blocks. For example, upper height of the masonry heater thereby adding secondary blocks may be added to a simple contra-?ow masonry and tertiary combustion chambers and lengthening the heater to add a secondary combustion chamber above heat exchange channels on the sides of the ?rebox. the ?rebox and to increase the heat transfer to the ma FIG. 11 shows perspective views of the individual sonry mass through an extended exhaust route. Further modules which are used to construct the core of the addition of blocks may result in the formation of a ter masonry heater. - tiary combustion chamber and so forth. As with con FIGS. 12 through 37 show a step by step construc ventional masonry heaters, the larger the masonry mass tion of a masonry heater as illustrated in FIG. 8, show that is available to store heat energy, the greater the 35 ing the placement of each module. ef?ciency of heat transfer from the burning fuel to radi FIG. 38 shows the installation of a masonry heater ant heat in the dwelling. core as illustrated in FIG. 8, retro ?tted within the A further advantage of the invention is the provision hearth of a conventional ?replace. of a glass door with diverter plate to divert a portion of FIG. 39 shows a plan sectional view of the retro the intake air against the inward surface of the door. 40 ?tted installation as indicated by lines 39-39 of FIG. The increase of turbulance of air in the ?rebox increases 38. the combustion ef?ciency. Also the diverted air creates DETAILED DESCRIPTION OF PREFERRED an air wash which cools the surface of the glass and EMBODIMENTS OF THE INVENTION prevents the discolorization of the gas from contact with combustion gases. 45 FIG. 1 illustrates the general nature of the invention Accordingly, the invention provides a contra-?ow in relation to a masonry heater utilizing the contra-?ow masonry heater comprising a ?rebox having a front principal. The core of contra-?ow masonry heater 1 is opening, an air intake communicating with a source of shown with a barick facade 2 partially broken away. fresh air and an upper ?ue outlet; at least one vertical The ?ow of air through the ?rebox, secondary combus contra-?ow heat exchange channel communicating tion chamber, vertical heat exchange channels, exhaust between the ?ue outlet and an exhaust port, the ?rebox port, and down draft hood is shown with the arrows and channel having walls of refractory material for through a transparent modular core assembly. The ?re mass absorption of heat energy from a burning fuel and box 3 has a front opening to which is secured an airtight combustion gases contained therein and subsequent door 4. Fresh air from the room enters the heater radiant release of heat energy to an adjacent space, a through an air intake 5 and enters the ?rebox 3 through down draft hood communicating between the exhaust a slot 6 in the bottom ?oor of the ?rebox 3. port and outside air, the down draft hood having a A fuel such as wooden logs as shown, is burnt within plenum communicating among an exhaust inlet, a chim the ?rebox 3 and the combustion gases exit from the ney and a relief port, the relief port being located below ?rebox through an upper ?ue outlet 7. the elevation of the exhaust inlet and communicating 60 In the embodiment illustrated in FIG. 1, the ?rebox 3 with the source of fresh air; and an air tight door se includes a secondary combustion chamber 8 between cured to the front opening of the ?rebox. the upper ?ue outlet 7 and the vertical contra-?ow Further aspects of the invention will become appar heater exchange channels 9 which communicate be ent upon review of the following detailed description. tween the ?ue outlet 7 and an exhaust port 10. 65 As indicated by the arrows of FIG. 1, the burning BRIEF DESCRIPTION OF THE DRAWINGS fuel and combustion gases swirl within the ?rebox 3 and In order that the invention may be readily under secondary combustion chamber 8. As the combustion stood, a preferred embodiment of the invention will be gases transfer their heat to the mass of the masonry 5,333,601 5 6 heater, the combustion gases cool and exit downwardly means with the air tight door closed and need not attend through the vertical contra-?ow channels 9. to the operation of the masonry heater. The masonry core 1 including the ?rebox 3, second Within the relief port 15 of the down draft hood 11 is ary combustion chamber 8, and vertical contra-?ow provided a temperature sensor 23. The temperature heat exchange channels 9 all have walls of refractory sensor 23 communicates with the burner control 21. material. The refractory material provides for mass When a temperature higher than a prescribed valve is absorption of heat energy from the burning fuel and detected, the temperature sensor stimulates the burner combustion gases contained within the masonry heater control to extinguish the burner. Therefore when a core 1. After the refractory material has been heated, down draft condition exists, the exhaust gases from the even after the fuel source has been extended, heat en exhaust inlet 14 are forced through the relief port 15. ergy is radiantly released to the adjacent dwelling The temperature sensor detects a rise in temperature space. and stimulates the burner control to extinguish the The down draft hood 11 communicates between the burner. As a result carbon monoxide or other dangerous exhaust port 10 and outside air via a chimney pipe 12. components of the exhaust gas are not exhausted to a FIGS. 3 and 4 illustrate the detailed construction of signi?cant degree through the relief port 15. the down draft hood 11. A sheet metal down draft hood Of greater importance, due to the provision of a as illustrated includes an internal plenum 13. The ple down draft hood 11, the down draft condition does not num communicates among an exhaust inlet 14, the force outside air backward through the masonry heater chimney 12 and a relief port 15. The exhaust inlet 14 is which would force fuel gas and combustion gases back secured within the exhaust port 10 of the masonry 20 ward through the air intake 5. heater core 1. The relief port 15 is located below the Referring to FIGS. 5 and 6, the details of the door 4 elevation of the exhaust inlet 14 and communicates with are illustrated. The door 4 advantageously includes a source of fresh air within the same area from which the intake air is drawn. A diverter plate 16 is positioned means to divert eh intake air against the inner surface of the door. As shown by the arrows of FIG. 5 the turbu over the opening of the exhaust inlet 14 into the plenum 25 13. A baf?e plate 17 also aids in the redirection of any lence within the ?rebox 3 is increased thus improving down?ow from the chimney 12. A cone 18 is centered the ef?ciency of combustion. A common problem with in the draft hood chimney 12. Under normal operation glass doors on wood burning or gas ?red heaters is that therefore, the ?ue gases are exhausted through the ex the glass accumulates combustion products and be haust port 10 into the exhaust inlet 14 and thereafter comes discolored. Glass also becomes discolored when enter the plenum 13. Under normal circumstances, the high combustion temperatures are used since typically heat of the exhaust gases forces them to rise up the the glass may tolerate only a temperature of approxi chimney 12 and exhaust to the outside air. If however a mately l,400° F. whereas optimal burning occurs at down draft condition exists, outside air is drawn 1,800” F. typically. The ?ow of air past the inward through the chimney 12 into the plenum 13. The down 35 surface of the door therefore has the added advantage draft air is diverted by the diverter plate 16 and baf?e of cooling the door surface, preventing contact between plate 17 to prevent it from ?owing into the masonry the door and combustion gases, and preventing the heater via the exhaust inlet 14. The exhaust gases are buildup of discoloring combustion products. rather forced by the down draft outward through the The door 4 includes a door frame 24 secured to the relief port 15. As will be described in detail below, a 40 front opening of the firebox 3 with an angle iron ?ange temperature sensor is preferably located within the 25 as illustrated. A door panel 26 is hinged to the door relief port 15 to extinguish fuel supply to the ?rebox frame 24 and supports a central glass pane 27. when a gas burner is used. In the case of a wood burning A diverter plate 28 extends over a portion of the masonry heater, adown draft condition would be de ?rebox air intake slot 6 as shown by the arrows in tected by the occupants of the dwelling fairly quickly 45 FIGS. 5 and 6, an air wash portion of the intake air flow by smelling the smoke exhausted through the relief port is diverted upwardly across the width of the bottom of 15. the door panel 26. The air wash portion as illustrated in FIG. 2 illustrates a preferred embodiment of the in FIG. 5 swirls in a clockwise direction opposite to the vention showing a masonry heater fueled by a gas counterclockwise direction of the remaining intake air burner 19 housed within the ?rebox 3. High efficiency ?ow which enters the ?rebox 3. gas burners having an imitation log design are available The door frame 24 includes two hollow tubular side as inserts for conventional ?replaces. The burner 19 is members 29. The interior of each tubular side member supplied with fuel gas via a gas supply pipe 20 and a gas 29 communicates with the interior of a like hollow top supply valve 21. The gas supply valve 21 includes member 30. Each side member 29 has an air wash inlet means to control the burner which actuates the gas 55 31 at a base end of each side member 29. supply valve. As indicated by hidden arrows in FIG. 5 in dotted A thermostat 22 is positioned in contact with the outline, a part of the air wash portion is diverted refractory material of the masonry heater core 1. The through the air wash inlet 31 upwardly through the thermostat is connected to the burner control means 21 interior of the hollow side members 29 and into the and emits a stimulus to the burner control means. De interior of the hollow top member 30. The top member pending upon the temperature of the refractory material 30 has air wash outlets 32 which divert said part of the therefore, the thermostat stimulates the burner control air wash portion downwardly across the width of the to ignite the burner, extinguish the burner, or vary the top of the door panel 26. As shown in FIG. 5 the down quantity of gas supplied to the burner. As a result the ward motion of the air wash through the air wash outlet operation of a gas ?red contra-?ow masonry heater is 65 32 results in a counterclockwise swirling action. The net thermostatically controlled in a automatic fashion simi result of the opposing swirling air masses is increased lar to a conventional furnace. The user of the masonry turbulence-cooling of the door panel 27 surface and heater therefore need only turn on the burner control effective separation of the combustion gases and the 5,333,601 7 8 door panel 27. Discoloration and overheating of the As will be apparent from the description below, the glass pane 27 is thereby reduced. masonry heater illustrated includes two vertical contra In the embodiment illustrated the air wash outlet ?ow heat exchange channels 9 which are laterally adja comprises a longitudinal slot 32 in the bottom face of cent the ?rebox 3. A ?ue gas manifold 34 is formed as the top member 30 however individual openings or 5 shown in FIG. 20 communicating among the bottom nozzles may also be used. portion of both channels 9 and the exhaust port 10. The FIGS. 7 through 10 illustrate the method by which manifold 34 extends beneath the ?rebox 3 from one side the height of the contra-?ow masonry heater core 1 can of the heater to an opposite side. As a result of the be increased. By simply stacking additional courses of manifold 34, the exhaust port 10 may be located in mod modules and alternately inverting them, a secondary 10 ules 1020 on either side of the heater or in the back wall combustion chamber 8 and a tertiary combustion cham of the heater through the use of module 101a as de ber 33 may be formed from standard modules. If de scribed above. sired, the secondary and tertiary combustion chambers Referring to FIG. 21, the construction of a second 8 and 3 may be formed as approximate triangle prisms as and third course of blocks is commenced. As shown in in FIG. 8 or as hourglass prismatic forms as in FIGS. 9 FIGS. 21 through 26, the placement of modules 107 and and 10. The turbulence within the secondary and ter 108 in a second and third course of blocks forms the tiary combustion chambers 8 and 33 and the resultant ?rebox 3 and a lower portion of the channels 9. heat transfer characteristics to the masonry heater core FIGS. 27 through 30 show the installation of a fourth 1 may be varied depending upon the shape of combus course of blocks which forms an upperwardly tapering tion chamber chosen. An additional advantage of 20 upper ?ue outlet 7 and further increases the height of course is that the vertical length of the heat exchange the channels 9 through the placement of modules 109 channels 9 are extended which also results in increased and 102. heat transfer characteristics. As illustrated in FIGS. 31 through 35, the ?fth course For example, as shown in FIG. 10 the ?rebox in of blocks forms a secondary combustion chamber 8 cludes a tertiary combustion chamber 33 between the 25 between the ?ue outlet 7 and the contra-?ow channels secondary combustion chamber 8 and the contra-?ow 9. Module 109 is installed in an inverted position as channels 9. In theory any number of multiple combus shown in FIG. 31. Modules 110 are positioned to form tion chambers may be provided. Outlets ports between the interior walls of the channels 9. It will be noted that such combustion chambers and the laterally adjacent the vertical height of module 110 is marginally less than vertical channels may be provided by simply choosing 30 the height of modules 102 and '109. As a result, module amongst the various components of the system. 110 acts as a weir over which ?ue gases may escape. The step by step construction of a masonry core as Flue gases ?ow from the ?ue outlet 7 into the secondary shown for example in FIG. 8, will be described below. combustion chamber 8, over the top wall of module 110 FIG. 11 shows detailed perspective views of each pre and thereafter downward through the verticalchannels cast module of refractory material. 35 9. By vertically stacking a series of module‘ blocks, the A second block module 109 is installed in an inverted masonry heater core may be formed. As will be noted position and shown in FIG. 33. every block has the same vertical height and each block The outward walls of the vertical channels 9 are has walls of substantially equal thickness. It will also be completed with the insertion of modules 102 asshown noted that each block is joined to at least one block of 40 in FIG. 34. A double bead of silicon caulking is applied the same course with a dovetail joint. For the purposes to the top surface of the last course of blocks as shown of this description therefore, the modules 100, 105, 106 in FIG. 35. Cap blocks 111 form a cap plate with a and 111 will be described as plates whereas the remain ship-lap joint between them to securely seal the top ing modules of equal vertical height and equal wall surface of the masonry heater core as shown in FIGS. thickness are described as module blocks. 45 36 and 37. The ?rst step in the assembly process is shown in As illustrated in FIG. 10 a sixth and seventh course of FIG. 12 wherein two identical modules 100 are assem block modules 109 may be used to form a tertiary com bled to form a base plate. FIG. 13 shows the next step of bustion chamber 33 between the ?ue outlet 7 and the installing module 101. In the retro?t application illus contra-?ow channels 9. trated in FIGS. 38 and 39, the exhaust port 10 is located 50 As illustrated in FIG. 7 it is not necessary to include in the back wall of the heater. In such an application a secondary combustion chamber 8 for example if module 1010 is installed in replacement of module 101 in height restrictions prevent any increased height for the FIG. 13. masonry core 1. FIG. 14 shows the installation of side wall module Referring to FIGS. 38 and 39 a masonry heater core 102. Next as shown in FIGS. 15 and 16, L-shaped mod 55 1 may be adapted for retro?tting into an existing ?re ules 103 and 104 are inserted to support the ?rebox place hearth 35. The core 1 illustrated in FIGS. 38 and ?oor. 39 correspond exactly to that illustrated in FIG. 8 with Since in the embodiment illustrated the exhaust port the exception that the exhaust port 10 is located in the 10 exists from the right bottom portion of the side wall back wall of the heater as opposed to the side wall of the of the heater, FIG. 17 shows the installation of module heater. As described above, when constructing the ?rst 102a which includes the exhaust port 10. course of blocks, module 101a replaces module 101 to The formation of the air intake 5 and slot 6 is shown include the exhaust port 10 in the 'rear wall of the in FIGS. 18, 19 and 20. The rearward wall of the slot 6 heater. On both side walls, modules 102 are used rather is formed by the insertion of module 105. The ?rebox than module 102a. A chimney liner 36 communicates ?oor is completed as shown in FIG. 19 by the position 65 between the exhaust port 10 and the ?ue 37 of the exist ing of module 106. The forward face of the slot 6 is ing hearth 35. formed by the placement of module 107 as shown in A damper 38 may be provided within the liner 36 to FIG. 20. control combustion. As most clearly shown in FIG. 39, 5,333,601 9 10 a brick facade 39 may be applied to the surface of the tending beneath the ?rebox from one side of the retro?tted masonry heater core 1 to continue the exist heater to an opposite side; ing facade 40 of the hearth 35 to be retro?tted. the ?rebox and channels having walls of refractory It will be understood that, although various features material for mass absorption of heat energy from a of the invention have been described with respect to burning fuel and combustion gases contained one or another of the embodiments of the invention, the therein and subsequent radiant release of heat en various features and embodiments of the invention may ergy to an adjacent space, be combined or used in conjunction with other features a down draft hood communicating between the ex and embodiments of the invention as described and haust port and outside air, the down draft hood illustrated herein. l0 having a plenum communicating among an exhaust The embodiments of the invention in which an exclu inlet, a chimney and a relief port, the relief port sive property or privilege is claimed are de?ned as being located below the elevation of the exhaust follows: inlet and communicating with the source of fresh 1. A contra-?ow masonry heater comprising: 311'; a ?rebox having a front opening, an air intake com 15 an air tight door secured to the front opening of the municating with a source of fresh air and an upper firebox. ?ue outlet; 5. A masonry heater according to claim 4 wherein the at least one vertical contra-?ow heat exchange chan exhaust port is located in a back wall of the heater. nel communicating between the ?ue outlet and an 6. A masonry heater according to claim 4 wherein the exhaust port, exhaust port is located in a side wall of the heater. the ?rebox and channel having walls of refractory 7. A contra-?ow masonry heater comprising: material for mass absorption of heat energy from a a ?rebox having a front opening, an air intake com burning fuel and combustion gases contained municating with a source of fresh air and an upper therein and subsequent radiant release of heat en ?ue outlet; ergy to an adjacent space, 25 at least one vertical contra-?ow heat exchange chan a down draft hood communicating between the ex nel communicating between the ?ue outlet and an haust port and outside air, the down draft hood exhaust port, having a plenum communicating among an exhaust the ?rebox and channel having walls of refractory inlet, a chimney and a relief port, the relief port material for mass absorption of heat energy from a being located below the elevation of the exhaust burning fuel and combustion gases contained inlet and communicating with the source of fresh therein and subsequent radiant release of heat en ergy to an adjacent space, alr; a down draft hood communicating between the ex an air tight door secured to the front opening of the haust port and outside air, the down draft hood ?rebox; 35 having a plenum communicating among an exhaust a gas burner housed within the ?rebox, the burner inlet, a chimney and a relief port, the relief port communicating with a source of fuel gas via a gas being located below the elevation of the exhaust supply valve; inlet and communicating with the source of fresh burner control means for actuating the gas supply 311'; ‘valve; an air tight door secured to the front opening of the thermostat means in contact with the refractory ma ?rebox, said door comprising: a door frame se terial and the burner control means, for stimulating cured to the front opening of the ?rebox; a door the burner control means to ignite, extinguish, and panel hinged to the door frame, the door panel vary the quantity of gas supplied to the burner; and supporting a central glass pane; and diverter plate temperature sensor means, within the relief port of 45 means, extending over a portion of the ?rebox air the down draft hood and communicating with the intake, for diverting an air wash portion of intake burner control means, for stimulating the burner air ?ow upwardly across the width of the bottom control means to extinguish the burner when a of the door panel; temperature higher than a prescribed valve is de wherein the door frame includes at least one hollow tected. tubular side member, the interior of which commu 2. A masonry heater according to claim 1 wherein the nicates with the interior of a hollow top member, ?rebox includes a secondary combustion chamber be each side member having an air wash inlet at a base tween the upper ?ue outlet and the contra-?ow chan end thereof, the top member having air wash outlet nel. means for diverting a part of said air wash portion, 3. A masonry heater according to claim 2 wherein the 55 from the air wash inlet, downwardly across the ?rebox includes a tertiary combustion chamber be width of the top of the door panel. tween the secondary combustion chamber and the con 8. A masonry heater according to claim 7 wherein the tra~?ow channel. air wash outlet means comprises a longitudinal slot in 4. A contra-?ow masonry heater comprising: the bottom face of the top member. a ?rebox having a front opening, an air intake com 9. A contra-?ow masonry heater comprising: municating with a source of fresh air and an upper a ?rebox having a front opening, an air intake com ?ue outlet; municating with a source of fresh air and an upper two vertical contra-?ow heat exchange channels ?ue outlet; laterally adjacent the ?rebox communicating with two vertical contra-?ow heat exchange channels the ?ue outlet; 65 laterally adjacent the ?rebox communicating with a ?ue gas manifold having an exhaust port, the mani the ?ue outlet; fold communicating among a bottom portion of wherein the ?rebox and channels are constructed of both of the channels and the exhaust port and ex pre-cast modules comprising: a base plate; a verti