AU2009201219A1 - Room heater - Google Patents

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: ROOM HEATER Applicant: Climate Technologies Pty Ltd The following statement is a full description of this invention, including the best method of performing it known to me: 1 2 ROOM HEATER The present invention relates to a heater for indoor heating, or more 5 particularly, for room heating, such as in domestic housing or office space. A room heater according to the invention employs a heating arrangement to heat air, with the heated air being blown into the room in which the heater is located. 10 Prior art room heaters of the above kind exist but the invention has been developed with the object of increasing the energy efficiency of this type of room heater. According to the present invention there is provided a room heater which 15 includes: - a housing - a heat exchanger and a gas fired air heating facility each disposed within the housing, - the housing including first and second air intakes and an air discharge, 20 - a first fan being located to draw air from outside the housing through the first air intake and to direct that air to flow over the heat exchanger for egress through the air discharge - the second air intake being located in proximity to the air heating facility so that air can be drawn from outside the housing through the second air 25 intake for heating by the air heating facility - the heat exchanger being located in proximity to the air heating facility so that air heated by the heating facility enters the heat exchanger - a second fan being located to draw air through the heat exchanger - a heater exhaust in communication with the heat exchanger, the heater 30 exhaust including a first passage in communication with a second passage, the first passage further being in communication with the heat exchanger and the second passage further being arranged for communication with a flue exhaust, an opening being provided in the heater exhaust and permitting evacuation of air travelling through the second passage toward the first W:\ulie\AndredCompltsRoi Heate (AU).doc 3 passage and further permitting introduction of air into the second passage from outside the heater exhaust as air from the heat exchanger flows through the first passage and into the second passage. 5 A room heater according to the invention is expected to be of improved efficiency compared to existing heaters of a similar kind for reasons that will become apparent from the following discussion. Firstly, by introducing air into the second passage through the opening in the 10 heater exhaust, the temperature within the flue exhaust can be lowered. While this has a positive effect on the efficiency rating of a room heater according to the invention, it also permits the use of unplasticised poly vinyl chloride (UPVC) fluing, which is the type of fluing material that is used with most high efficiency gas appliances. UPVC is not presently employed, because the 15 recommended maximum upper temperature that UPVC can be exposed to is normally exceeded by the temperature of the air which enters the fluing. Because the temperature of that air can be reduced in a heater according to the present invention, the air temperature can be lowered to below the recommended maximum upper temperature, thereby allowing the use of 20 UPVC. The introduction of air into the second passage can be fan induced, but alternatively, the opening can be arranged so that through a pressure differential, air external of the heater exhaust is sucked or drawn through the 25 opening and into the heater exhaust as air flows through the first passage of the heater exhaust to the second passage, i.e. a venturi effect. By employing a venturi effect, the introduction of external air occurs naturally when required, without the expense and complication of a further fan. 30 Secondly, the use of a fan, the second fan, to draw air through the heat exchanger, ensures that proper and consistent air flow through the heat exchanger occurs. Such proper and consistent air flow does not necessarily occur with natural draught systems of prior art room heaters as those systems are reliant on the buoyancy of the heated air in order for the air to flow through W:\leAndrewC npleesR m Heaur (AU) do 4 the heat exchanger and to evacuate through the flue exhaust. When a room heater is first turned on, the air is not initially heated so that there is not sufficient buoyancy for proper flow and evacuation. Thus, there can be spillage of gases into the room in which the heater is located. While low levels 5 of spillage are acceptable, it is nevertheless undesirable and the employment of a fan according to the invention significantly reduces or even eliminates such spillage. The heat exchanger can be a single stage exchanger, but preferably two or 10 more stages are employed. The preference for two or more stages is to increase the energy transfer through the heat exchanger. Where two stages are provided it is preferred that the first and second stages be generally parallel to each other so that the direction of air flow through the second return stage is generally opposite to the direction of air flow through the first away 15 stage. When installed, it is preferred that the first and second stages extend generally vertically. In this arrangement, the employment of the second fan advantageously is operable to draw heated air downwardly through one of the stages most likely the second stage, against the natural buoyancy of the air. Thus the second fan facilitates the use of a two stage exchanger, whereas 20 prior art arrangements which employ the natural buoyancy of the heated air for flow through the heat exchanger, are restricted to a single stage. While the heat exchanger can include one or two stages, it is preferred that a third stage extends from the second stage, so that the heated air flows through 25 three heat exchange stages. Preferably all three stages are generally parallel and are arranged so that heated air flows in a direction firstly away from the air heating facility in the first stage, and then returns in a direction toward the air heating facility in the second stage, and then away again from the air heating facility in the third stage. The stages are preferably arranged so that heated 30 air flows generally upwardly in the first and third stages and generally downwardly in the second stage. Each stage of the heat exchanger includes a chamber and in the two and three stage exchangers, the chambers are interconnected to facilitate flow between W:\hii\AndrewCopletes\Ro Heer (AU).doC 5 them. One or more tubes can extend between the interiors of the chambers to facilitate flow between the stages. While the invention has been described above as having a single, two or three 5 stage heat exchanger, any number of stages as appropriate can be adopted. The chamber or chambers of the heat exchanger stage or stages preferably include interruptions in the air flow path, so that air flow through the chamber is resisted, resulting in greater energy transfer through the heat exchanger from 10 the heated air. Preferably such interruptions are formed or provided in the second return stage and/or in the third away stage, if provided. It is not envisaged that interruptions would be employed in the first stage, as combustion occurs in that stage and such interruptions may reduce the efficiency of heating. Suitable interruptions could be formed by members that 15 bridge between opposite sides of a chamber and these could be formed at one or more positions by depressing opposite sides of a chamber together. Each chamber of a stage typically will be rectangular in cross-section and will be of shallow depth compared to its length and width. 20 In an installed condition of the room heater, the air heating facility and the second air intake are preferably positioned at or adjacent the bottom end of the housing and the heat exchanger extends towards the upper end of the housing. The first air intake and the first fan can be located towards an upper 25 end of the housing, while the second fan can also be located at or toward that end. The second fan is preferably part of an assembly to which the heat exchanger is connected so that air which flows through the heat exchanger is kept separate from air that flows over the heat exchanger. That assembly is preferably interposed between an outlet end of the heat exchanger and an inlet 30 of the heater exhaust. The first and second air intakes can be formed by openings in the housing and in the preferred arrangement, a single opening is provided for each intake. It is preferred that the openings be covered by a safety mesh or grille to prevent W:\hdie\AndrewConplets\Roo Hga (AU).doc 6 objects being inserted through the openings. The first and second fans can be of any suitable kind, although in a preferred arrangement, the first fan is a centrifugal fan which rotates about a 5 substantially horizontal axis and the second fan has an impeller of a backward curve type which rotates about a substantially vertical axis. The heater exhaust can be of a composite construction whereby the first passage is formed in an outlet duct in communication with the heat exchanger 10 and the second passage is formed in a flue connection duct for connection to a flue exhaust. Preferably the outlet duct extends into the flue connection duct. Connectors, for example rivets, can be employed to connect the outlet duct to the flue connection duct if required. Alternatively the outlet duct can be a friction fit within the flue connection duct. Still alternatively, clearance can be 15 provided between the outlet duct and the flue connection duct. In one arrangement, a portion of the outlet duct and the flue connection duct is connected, and a portion remains disconnected. The connection at the connected portions can be of any suitable kind, such as indicated above. The disconnected portion can provide the opening of the heater exhaust. In one 20 arrangement, the disconnected portion comprises a pair of openings, such as on either side of the heater exhaust, so that air can be drawn into the heater exhaust from either side thereof. Where there is no connection between the outlet duct and the flue connection duct, a substantially circumferential opening can be formed. As will be apparent from the foregoing discussion, the opening 25 of the heater exhaust can be formed by a variety of arrangements. The opening of the heater exhaust is provided for permitting evacuation of air from and introduction of air into, the second passage. Evacuation of air is required when air enters the flue exhaust to which the flue connection duct is 30 connected and travels in a direction towards the heater exhaust. This can occur in windy conditions. Evacuation is also required in conditions when the exhaust flue becomes blocked. Introduction of air advantageously cools the air flowing from the heat W:li.eAndrewCmpletes\Ro n Heate (AU).doc 7 exchanger to the flue exhaust and in testing, a temperature drop from 65*C at the exit of the heat exchanger to about 50*C beyond the opening can be achieved. 5 In the above arrangement, both of the outlet and flue connection ducts can be of square or preferably rectangular cross section, with the cross-sectional area of the outlet duct being smaller than the cross-sectional area of the flue connection duct at the region at which the outlet and flue connection ducts are in communication. 10 In a room heater according to the invention, varying levels of condensate can be produced during operation. By incorporation of the opening in the heater exhaust, the dew point of heated air being exhausted through the heater exhaust can be lowered through the introduction of air through the opening. 15 Nevertheless, a condensate catchment system can be included to collect any condensate that does occur and in one arrangement, collected condensate can be fed for discharge into the room within which the room heater is located, for humidifying purposes. A condensate collection tray can be positioned within the housing in proximity to the air discharge, with condensate being fed 20 into the collection tray. Thus advantageously, a room heater according to the invention can produce lower levels of condensate compared to prior art room heaters, while the condensate that is produced can be used usefully to humidify the room being heated. 25 For a better understanding of the invention and to show how it may be performed, embodiments thereof will now be described, by way of non-limiting example only, with reference to the accompanying drawings. Figure 1 is a perspective view of a room heater according to one embodiment 30 of the invention. Figure 2 is a perspective view of the internal components of the room heater of Figure 1. W li\AncCompVlt Heaer (AU).doc 8 Figure 3 is an exploded view of a heat exchanger for use in the present invention. Figure 4 is a part sectioned view of a heater exhaust for use in the present 5 invention. Figures 5 to 7 show views of exhaust fluing for use with a room heater according to the present invention. 10 The room heater 10 of Figure 1 includes a housing 11 which encloses a heat exchanger and a gas fired air heating facility. The housing includes a first air intake 12 through which air can be drawn into the housing 11 for direction over the heat exchanger, for heating that air. The housing 11 includes a second air intake 13 which is positioned in proximity to the air heating facility such that air 15 is drawn into the housing 11 through the second air intake 13 for heating by the air heating facility and for entry into the heat exchanger. The housing 11 also includes an air discharge 14 through which air that has been directed over the heat exchanger can be discharged for heating the room 20 in which the room heater 10 is located. In each case, the first and second air intakes 12 and 13 and the air discharge 14 are covered by suitable grills. 25 Referring to Figure 2, the room heater 10 of Figure 1 is shown with the housing 11 removed, to show the internal components of the room heater 10. The components shown in Figure 2 include a heat exchanger 15 (which is discussed in more detail in relation to Figure 3), a first fan 16 which is operable to draw air through the first air intake 12 of the heater 10 and to direct that air 30 over the heat exchanger 15. By directing the air to flow over the heat exchanger 15, that air is heated. Following heating, the air flows through the outlet 19 for discharge through the air discharge 14 (Figure 1). With reference now to Figure 3, components of the heat exchanger 15 are WNtlie\AndrewCmpletes\Rom Heale (At) doc 9 shown in exploded view. The heat exchanger 15 includes first, second and third stages 20, 21 and 22. In practice, the three stages of the heat exchanger 15 are assembled in close, side-by-side proximity to each other. As will be explained later, air enters the first stage 20 travelling upwardly, and then 5 enters the second stage 21 and is drawn downwardly through the effect of fan force. The air then travels upwardly again through the final stage 22. Each stage is hollow and is of generally rectangular cross-section. The cross section or volume of the first stage 20 is greater than the cross-section or volume of the second and third stages 21 and 22, as the first stage is the stage 10 in which gas combustion occurs. As is apparent from Figure 3, the third stage 22 is of greater length than the first and second stages 20 and 21 and the reason for this will be explained later with reference to Figures 2 and 3. The internal chambers of the stages 20, 21 and 22 communicate through a 15 plurality of hollow tubes 23. Accordingly, the tubes 23 of the stage 21 extend through openings (not shown) in the stage 20 into the internal chamber of that stage. Likewise, the tubes 23 of the stage 22 extend through openings (not shown) into the internal chamber of that stage. The tubes 23 of the stage 21 are positioned at an upper vertical end of the stage 21 to communicate with 20 the upper part of the internal chamber of the stage 20, while the tubes 23 of the stage 22 are at the lower end of that stage to communicate with the vertical bottom end of the stage 21. Air which is heated by the air heating facility 24 (see Figure 1), enters through 25 the bottom end 25 of the heat exchanger stage 20 and flows vertically upwardly towards the top end 26 thereof. That heated air then flows through the tubes 23 of the stage 21 downwardly towards the bottom end 27 of the stage 21. The air then flows through the tubes 23 of the stage 22 and flows upwardly towards the top end 28 of that stage. The arrows of Figure 3 show 30 the direction of air flow through the heat exchanger 15. Air exits the final stage 22 and enters a heater exhaust prior to entering exhaust fluing for discharge externally of the room in which the room heater 10 is located. It has been described earlier herein, that the invention applies to a three-stage WAmliciAndrwCoplets\R m Hato (AU).doc 10 heat exchanger of the kind shown in Figure 3, but also to two-stage and single stage heat exchangers as well. The employment of three-stage heat exchanger is preferred in order to maximise the efficiency rating of a room heater according to the invention. However, heat exchangers of single or two 5 stage construction also can realise efficiency benefits if constructed according to the invention. Similarly, it is possible to employ further stages such as a four or five-stage heat exchanger and therefore the number of heat exchange stages is a matter for selection dependent on the cost and efficiency requirements. 10 The heat exchange stages 21 and 22 shown in Figure 3 also illustrate from outside of those stages, interruptions in the path of air flow through the respective stages, in order to resist air flow through the respective stages. That resistance facilitates greater heat transfer from the heat exchanger 15 to 15 air flowing over the exchanger so that heat exchange efficiency is increased. The interruptions shown in Figure 3 comprise a plurality of members that bridge between opposite sides of the internal chambers of the respective stages and these can be formed by depressing opposite sides of a stage 20 together at a plurality of discrete positions. Effectively these depressions form bridges from one side of the stage to the other, so that air has to flow around the bridges in order to flow from one end of a stage to another. Only several of the interruptions are indicated by reference numeral 29, although it will be evident that a substantial number of interruptions are shown in Figure 3. 25 However, it is optional as to the number and positioning of those interruptions. Returning to Figure 2, the view of the heat exchanger 15 is such as to show one broad face of the heat exchanger stage 20, as well as the top end 28 of the stage 22. A flange 30 of the stage 20 is provided to locate the bottom end 30 25 of the stage 20, while a further flange 31 applied to the top end 28 of the stage 22 is provided for locating purposes. The air heating facility 24 includes a plurality of in-shot burners 35 and a gas valve 36. In operation, combustion of gas occurs directly beneath the chamber W:Volie\AndrewCopletts\Ra Hea (AU).doc 11 of the heat exchanger stage 20. The heated air will naturally flow through the heat exchanger stage 20 in the direction shown in Figure 3, i.e. generally vertically. However, in a heat exchanger 15 of the kind shown in the drawings, the heated air is required to flow into the adjacent stage 21 and downwardly 5 through that stage. That direction of flow is counter to the natural direction of buoyancy of the heated air and therefore to promote the downward flow, a second fan 37 is provided. In the preferred arrangement, the second fan 37 includes an impeller of backward curve type which rotates about a substantially vertical axis. The second fan 37 forms part of an assembly 38 10 which communicates with the outlet of the third heat exchanger stage 22 at the top end 28. Referring to Figure 3, the stage 22 is of greater length than the first and second stages 20 and 21, in order that the stage 22 can extend upwardly and behind the first fan 16 to the fan assembly 38 of which the second fan 37 is a component. Figure 2 illustrates an electric motor 39 which 15 is also part of the fan assembly 38 and which drives the second fan 37 to rotate. The assembly 38 is connected to the outlet end of the stage 22 and to the inlet of a heater exhaust 32, which is described later herein. Thus, air that flows through the heat exchanger 15, then flows through the assembly 38 and then into the heater exhaust 32, thus being kept separate from air that is 20 directed over the heat exchanger by the first fan. By the use of the second fan 37, travel of air heated by the heating facility 24, through each of the heat exchange stages 20, 21 and 22, most particularly through downward stage 21, is assured. In addition, the use of the second fan 25 37 advantageously allows for the velocity of air flow through the heat exchanger 15 to be tuned to an ideal rate relative to the standards governing this type of heater, as compared to prior art heaters, which rely on the natural buoyancy of the heated air. 30 In addition, in prior art heaters which rely on the natural buoyancy of the heated air for flow through the heat exchanger, the velocity of flow through the heat exchanger is dictated by the temperature to which the heated air is heated and at start-up, when the heated air temperature is low, the buoyancy can be insufficient for proper flow to occur. In that situation, combustion gases W ufie\AndeCmplee\Rom He (AU) dor 12 can spill into the room being heated and while it is acceptable for some spillage to occur, excessive spillage can be dangerous given that the spillage can include toxic gases such as carbon monoxide. The use of the second fan 37 has been found in testing to largely eliminate spillage through a room 5 heater according to the invention because the second fan 37 drives the air to flow, regardless of its temperature. It is to be noted that even in a single-stage heat exchanger, in which heated air travels vertically only, the use of the second fan 37 still provides advantages. 10 Those advantages include the controlled velocity of flow through the heat exchanger to improve the efficiency of the heater as compared to prior art natural buoyancy heaters and the reduction or elimination of combustion gas spillage into the immediate environment in which the heater is positioned. 15 Figure 4 illustrates a heater exhaust 32 for use with a room heater according to the invention. A portion of the heater exhaust 32 is shown in Figures 1 and 2 in which an outlet duct 40 is shown. The outlet duct 40 is shown in Figure 4 in partially sectioned view as extending upwardly into a flue connection duct 41, which is shown completely in section. 20 The outlet duct 40 extends into the flue connection duct 41 and a connection between the two ducts can be made if required, such as by a friction fit, or by a rivet connection for example. Alternatively, the respective ducts 40 and 41 might have no connection at all. 25 It is shown in Figure 4 that there is a length of overlap between the upper end 42 of the outlet duct 40 and the lower end 43 of the flue connection duct 41. At least at each of the short sides 44 of the outlet duct 40, a gap G exists between the upper end 42 of the outlet duct 40 and the lower end 43 of the 30 flue connection duct 41. The gaps G permit evacuation and introduction of air, from or into the heater exhaust 32 for the following purposes. The outlet duct 40 defines a first passage P 1 for air flow, while the flue connection duct 41 defines a second passage P 2 . The passage P 1 is in W:\ulie\AneCompleRoa Hewa (AU) doc 13 communication with the passage P 2 while as described above, the passage P, is also in communication with the heat exchanger 15 and passage P 2 is in communication with a flue exhaust (not shown). In relation to evacuation of air, the gaps G form openings such that downdraught air which travels through 5 the passage P 2 towards the passage P 1 , can be evacuated through the gaps G and into the room in which the room heater is located, rather than flowing into the passage P 1 and then into the heat exchanger 15. If downdraught flow of that kind is not exhausted, it would upset the operation of the room heater and potentially could extinguish the burners 35. 10 In relation to introduction of air, flow of heated air through the passage P 1 and into the passage P 2 creates a venturi effect that draws air from the room in which the room heater is located, through the gaps G and into the passage P 2 . That air generally will be of a lower temperature than the air within the passage 15 P 1 and therefore the introduction of air advantageously reduces the temperature of the air which flows through the passage P 2 . Tests have shown that a temperature reduction of about 150C, can be achieved. In that testing, temperatures of air within the passage P, of about 650C are reduced to about 500C in the passage P 2 after the introduction of air through the gaps G. 20 The heater exhaust 32 also includes a condensate catchment system comprising a pair of catchment trays 45 and 46. While it is not shown in Figure 4, these trays collect condensate which forms on the heater exhaust 32 and the trays feed that condensate to a collection tray which is enclosed within the 25 housing 11 in proximity of the air discharge 14 so that the condensate can be employed to humidify the room within which the room heater is located. It is to be noted, that in a room heater according to the invention, the amount of condensation is expected to be less compared to prior art room heaters, as a result of providing one or more openings in the heater exhaust 32 (by way of 30 the gaps G), because the dew point is lowered by the introduction of air into the heater exhaust 32. The heater exhaust 32 also includes a circular deflector or restriction 47 which is provided to deflect a downdraught flow of air through the flue connection W\hl\Ade omee\Rm Heate (AUJ) do.

14 duct 41 to prevent the downdraught from applying pressure to the opening at the upper end 42 of the outlet duct 40. Such pressure could affect flow of air through the outlet duct 40. Advantageously, the deflector 47 deflects air towards the gaps G, but does not unduly impede the flow of air through the 5 heater exhaust 32 from the outlet duct 40 to the flue connection duct 41. The deflector 47 could have other shapes. The deflector 47 surrounds an opening 48. In practice, the deflector 47 extends fully from one broad side 49 of the flue connection duct 41 to the other 10 (not shown). Airflow through the heater exhaust 32 is therefore prevented from entering the opening 48. The opening 48 can be made in order to reduce the amount of material of the flue connection duct 41, to reduce overall cost. Figure 5 illustrates the upper end of the room heater 10 of Figure 1 as well as 15 an installation bracket 50 through which the flue connection duct 41 of the heater exhaust 32 extends. Figure 5 further illustrates a twin skin flue attachment 51 which attaches to the flue connection duct 41 and which includes a flue exhaust 52. Each of Figures 6 and 7 show the arrangement of Figure 5, but with the attachment 51 attached to the flue connection duct 41, 20 although Figures 6 and 7 differ by the configuration of the flue exhaust 52. Figure 6 shows a flue exhaust 53 which comprises a horizontal section 54 and a vertical section 55, while Figure 7 shows a flue exhaust 56 having only a horizontal section 57. Figures 6 and 7 illustrate that the flue exhaust can have different configurations for exhausting combustion gases. The Figure 6 25 arrangement allows downward exhaust such as through the eaves of a house, while the Figure 7 arrangement is for exhaust though a wall (not shown). It is to be noted that the use of the second fan 37 assists exhaust by driving flow through the flue exhaust. 30 Very positive results have been achieved through testing of room heaters according to the invention. In particular, under some testing conditions, excellent suction has been achieved through the heater exhaust 32 via the gaps G so that there was no monitored spillage of exhaust gases. Such results were achieved with flue exhaust configurations of the kind illustrated in W:\ lie\Andrewcom \Ro Hene (AU) doc 15 Figures 6 and 7. Moreover, it is an industry requirement in Australia that under all operating conditions of gas heaters, that the gas ratio between carbon monoxide and 5 carbon dioxide remains below a 0.02 limit. Thus, gas heaters are constructed so that the 0.02 ratio limit is not exceeded, which means that heaters are designed to meet the ratio limit under extreme operating conditions, and that means that under normal operating conditions, the heater does not operate at peak efficiency. The present invention alleviates this problem by utilising the 10 second fan (see fan 37 in Figure 2), as well as one or more openings in the heater exhaust (see the openings provided by the gaps G in Figure 4). The opening or openings facilitate compliance of the heater to meet the ratio limit under extreme operating conditions, and because of this, the second fan can be tuned to peak efficiency in which it provides consistent performance with 15 respect to air velocity through the heat exchanger. Clearly this is a highly advantageous outcome. The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be 20 understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the above description. W:Vulie\AndrewCompletcsRon Hcae (AU).doc

Claims (16)

1. A room heater including: - a housing 5 - a heat exchanger and a gas fired air heating facility each disposed within the housing, - the housing including first and second air intakes and an air discharge, - a first fan being located to draw air from outside the housing through the first air intake and to direct that air to flow over the heat exchanger for heating 10 by the heat exchanger and for egress through the air discharge - the second air intake being located in proximity to the air heating facility so that air can be drawn from outside the housing through the second air intake for heating by the air heating facility - the heat exchanger being located in proximity to the air heating facility 15 so that air heated by the heating facility enters the heat exchanger - a second fan being located to draw air through the heat exchanger - a heater exhaust in communication with the heat exchanger, the heater exhaust including a first passage in communication with a second passage, the first passage further being in communication with the heat exchanger and 20 the second passage further being arranged for communication with a flue exhaust, an opening being provided in the heater exhaust for permitting evacuation of downdraught air travelling through the second passage toward the first passage and further permitting introduction of air into the second passage from outside the heater exhaust as air from the heat exchanger flows 25 through the first passage and into the second passage.

2. A room heater according to claim 1, wherein the heat exchanger is a two stage exchanger. 30

3. A room heater according to claim 1, wherein the heat exchanger is a three stage exchanger.

4. A room heater according to claim 2, wherein the first and second stages are generally parallel to each other so that the direction of air flow through the W:aJid re~m pleP\Rom Heae (AU) do 17 second stage is generally opposite to the direction of air flow through the first stage.

5. A room heater according to claim 4, wherein each of the first and 5 second stages extend generally vertically.

6. A room heater according to claim 3, wherein the three stages are generally parallel and are arranged so that heated air flows in a direction firstly away from the air heating facility in a first of the three stages, and then returns 10 in a direction toward the air heating facility in a second of the three stages, and then away again from the air heating facility in a third of the three stages.

7. A room heater according to any one of claims 1 to 6, wherein the heat exchanger defines a chamber which includes interruptions in the path of air 15 flow through the chamber, so that air flow through the chamber is resisted.

8. A room heater according to claim 7, wherein the interruptions are formed by members that bridge between opposite sides of the chamber. 20

9. A room heater according to any one of claims 1 to 8, wherein the second fan forms part of a second fan assembly which is interposed between an outlet end of the heat exchanger and an inlet of the heater exhaust, such that air which flows through the heat exchanger flows into and through the second fan assembly and into the heater exhaust, and is kept separate from 25 air that is directed by the first fan to flow over the heat exchanger and through the air discharge.

10. A room heater according to any one of claims 1 to 9, wherein the first fan is a centrifugal fan which rotates about a substantially horizontal axis. 30

11. A room heater according to any one of claims 1 to 12, wherein the second fan has an impeller of a backward curve type which rotates about a substantially vertical axis. W:\ulie\Andre0CmpIcets\R Hea (AUdcC 18

12. A room heater according to any one of claims 1 to 11, wherein the heater exhaust is of a composite construction including an outlet duct and a flue connection duct, whereby the first passage is formed in the outlet duct and the second passage is formed in the flue connection duct, the outlet duct being 5 in communication with an outlet of the heat exchanger and the flue connection duct being arranged for communication with a flue exhaust.

13. A room heater according to claim 14, wherein the outlet duct extends into the flue connection duct. 10

14. A room heater according to claim 12 or 13, wherein the opening of the heater exhaust is formed between the outlet duct and the flue connection duct.

15. A room heater according to claim 14, wherein the opening of the heater 15 exhaust comprises a pair of openings formed between the outlet duct and the flue connection duct.

16. A room heater according to claim 15, wherein the pair of openings are disposed on opposite sides of the heater exhaust. W:\ ki\AndrewCmpete\RooHeA. (AU) doc