Abstract: A combustion and heating chamber into which a fluid is pumped under pressure is provided. A burner is positioned in the combustion and heating chamber to provide a heat load to the pressurized fluid in the chamber. As the fluid is heated its internal pressure is greatly raised providing a force for driving the heated air through a spiral conduit that encircles the combustion and heating chamber. An insulated outer wall is fitted around the spiral conduit and in contact with it. The individual wraps of the spiral conduit do not lay side by side, but are spaced apart. Relatively cool process air is drawn into the spaces between the separate wraps of the spiral conduit, which is thereby formed as a second spiral space intertwined with the spiral conduit between the combustion and heating chamber wall and the outer wall. The process fluid is therefore in contact with the walls of the spiral conduit.

Abstract: An apparatus (10) for transferring heat to a fluid from combustion gases including a housing (12) extending between a first end (14) and a second end (16). The apparatus further includes a burner (24) in which a combustible gas and oxygen react to form hot combustion gases which flow from the burner to a gas outlet (28) in the second end. The fluid flows in a length of helically coiled tubing (30) extending the length of the housing. The tubing includes a fin portion (36) which is spirally wound about the length of tubing. The apparatus further includes a core member (40) which extends within the coils of the tubing, and which engages the tubing. The core member includes a spirally-wound threaded area (62) about which the tubing is wrapped. The core member further includes a recessed portion (66) which creates stagnant air pocket adjacent the end of the core member.

Abstract: A fuel-fired, forced air, draft induced heating furnace is provided with NOx reduction apparatus associated with a plurality of combustor tubes forming a portion of its heat exchanger structure. In-shot type fuel burners are spaced apart from and face the open inlet ends of horizontal combustion sections of the combustor tubes. The NOx reduction apparatus includes a plurality of metal mesh tubes having diameters substantially less than the internal diameters of the combustion tubes. Each metal mesh tube is coaxially anchored to and telescopingly over the outlet end of one of the burners and extends therefrom coaxially into the associated combustion tube.

Abstract: A heat exchanger which can prevent the increase of an internal resistance by baffle plates, can make the gradient of a heat exchange rate between an inlet side and outlet side more gradual, and can make uniform a temperature distribution of a fluid flowing outside.

Abstract: The present invention involves a combustion box of a gas furnace which experiences oscillating combustion. The combustion box employs an opening in the housing which is tautly covered with a diaphragm made of elastic material such as silicone rubber. The elastic diaphragm transmits noise and vibration generated by the oscillating combustion of the gas burners in the combustion chamber and thereby dissipates that vibration and noise.

Abstract: A forced air furnace (11) has a heat exchanger (35) with one or more tube pack assemblies (10). Each tube pack assembly (10) has a burner (21) situated to fire into a primary fire tube (30) which is mechanically connected through a transition cap (36) to a plurality of secondary tubes (37, 38, 39, 41) returning combustion products from the primary fire tube (30) to a collection manifold (24) at the intake end of a draft inducer assembly (23) for discharge of the combustion products to a flue. In the preferred embodiment, the transition cap (36) is connected to the primary fire tube (30) and to the secondary tubes (37, 38, 39, 41) by a mechanical interlock.

Abstract: An induced draft, fuel-fired furnace having a heat exchanger with an inlet and an outlet includes a vent having an inlet, a burner, and a vented vestibule in fluid communication with the vent. A blower has an inlet in fluid communication with the heat exchanger outlet, and an outlet disposed at the inlet of the vent. The blower outlet has a cross-sectional area smaller than the vent inlet. The vent inlet and blower outlet define a vent inlet opening. A drafthood formed with an inlet is disposed in the vestibule and forms a plenum in fluid communication with the vent inlet opening. A source of combustion products is disposed in the furnace such that combustion products produced thereby are in fluid communication with the drafthood inlet and vent inlet opening. The source of combustion products includes either a standing pilot or electronic ignitor for igniting fuel operably discharged from the burner.

Abstract: A burner unit for heating a gaseous medium includes a heat exchanger provided with tubes, a space between the tubes connected on the upstream side to a feed duct for the gaseous medium; a combustion chamber connected to the downstream side of the space between the tubes; a burner placed in the combustion chamber; and a fuel supply duct connected to the burner. The side of the combustion chamber remote from the heat exchanger is connected to a first end of the tubes; and a flue gas outlet duct is connected to the other end of the tubes. The elongation of the tubes forming part of the heat exchanger renders the use of a conventional tube plate superfluous. Thus, damage resulting from thermal stresses is avoided.

Abstract: A furnace includes a generally cylindrical combustion chamber that is open at one end for receiving a single port inshot target burner. The target burner includes a flame spreader for lowering the heat energy and temperature of the gas flame so as to reduce NO.sub.x emissions. The flame spreader includes a plurality of rods affixed to the target plate or disc.

Abstract: A low NOx burner assembly of a fuel-fired heating appliance is supplied with an air/fuel mixture having a substantially less than stoichiometric air-to-fuel ratio. The air-rich mixture is partially combusted to create primary combustion products disposed within an open inlet portion of a combustor structure having a catalytic converter operatively positioned within an open outlet portion thereof spaced apart from its open inlet portion. A flow of aspirating air is introduced into the combustor structure between the inlet and outlet portions thereof. The aspirating air mixes with the primary combustion products, cools them, and flows with them outwardly through the catalytic converter. This essentially completes the combustion of the remaining fuel within the cooled primary combustion products, and does so at a temperature not appreciably greater than the initial combustion flame temperature to thereby substantially reduce NOx emissions without the use of flame quenching techniques.

Abstract: A hot air heat exchanger comprises a heat exchanger housing having a floor, which is essentially formed by a ceiling of an outer chamber and has at least one heat exchanger pipe extending from the floor to a ceiling element having exhaust openings, each pipe is secured to an exhaust opening in the upper wall of the outer chamber and a burner is disposed in an inner chamber which is positioned inside of the outer chamber with a spacing between the wall of the inner chamber and the outer chamber to allow air to flow therethrough. The upper wall of the inner chamber is provided with an exhaust gas opening, which is aligned with the exhaust opening of the outer chamber, and both openings have peripheral walls that are tapered to form a Venturi-like nozzle for drawing air in the space between the inner and outer chambers into each pipe as the exhaust gas from the burner in the inner chamber flows into the pipe to pass up through an exhaust element in the ceiling of the heat exchanger housing.

Abstract: A solid fuel burning stove is provided and includes a housing within which a combustion chamber is located. The combustion chamber receives combustion air via an adjustable inlet formed through a channel member running along the base of the housing. The channel member defines a combustion air duct which communicates with a combustion air intake in the rear wall of the housing. Combustion air is drawn into the stove via the air intake and is forced through the combustion air duct by a fan. The combustion air passes through the adjustable inlet into the combustion chamber. A fire box is located within the combustion chamber above the adjustable inlet and holds the solid fuel to be combusted. Hot flue gases heat air flowing through a plurality of heat exchange tubes passing through the combustion chamber. The heated air flowing through the heat exchange tubes is directed into the room in which the stove is located via a plurality of vents in the front wall of the housing.

Abstract: A furnace having a housing, a combustion chamber within the housing, and a burner associated with the combustion chamber is provided with a sound enclosure housing including a muffler portion. The muffler portion comprises an elongated serpentine passage having an air opening at one end.

Abstract: A space heating appliance employing a radiant burner that burns a gaseous fuel and a plurality of heat pipes to transfer heat produced by the burner to the air to be heated. The appliance is adaptable for use in outdoor "packaged" units, together with an air conditioning system, for heating ventilation and air conditioning (HVAC) systems in commercial buildings, and is also adaptable for use in indoor residential or commercial applications.

Abstract: Basically the present invention in its most simple form or embodiment is directed to a heat exchanger which provides for at least two heat exchange surfaces and which has the combustion of the fuel, which generates the heat, take place within the heat exchanger rather than the heat of combustion being introduced into the exchanger from an external combustion chamber and wherein the flame is directed into an opening of a truncated cone which cone has a shape approximating the shape of the flame and wherein the tips or ends of the flame "play" on an arcuate surface which is in thermal energy transfer communication with fluid to be heated which is at the unheated or ambient temperature. Additionally, note that the fluid, air in the case of a hot air system, is introduced into the passages where heat exchange will take place, and directed toward the hottest region of the combustion chamber. That is, the coldest air comes into thermal contact with the hottest region providing for maxinum heat exchange.

Abstract: The invention relates to a high performance burner whose performance can be controlled in a stepless manner. To this end, a premixing chamber is upstream of a burner nozzle that extends into a combustion chamber. Fuel is supplied in controllable amounts to the premixing chamber, and a mixture, in the form of an emulsion, is prepared therefrom by means of air supplied from an auxiliary air line. The air-fuel mixture thus prepared is passed to the burner nozzle which diffuses it in the combustion chamber. A high performance burner in accordance with the invention is designed for use as a heating device of high performance, like an independent heating device but, advantageously, can be employed as an exhaust gas afterburner, whereby the high performance burner is disposed in an exhaust gas line of a combustion engine, or a branch line thereto.

Abstract: An induced draft, fuel-fired upflow furnace is provided with a compact, high efficiency heat exchanger having horizontally spaced apart inlet and outlet manifold structures which are innerconnected by a horizontally spaced series of vertically serpentined, relatively small diameter flow transfer tubes. Larger diameter inlet flow tubes are positioned beneath the balance of the heat exchanger, extend parallel to the transfer tubes, and have upturned discharge ends connected to the underside of the inlet manifold. The heat exchanger is configured so that its total vertically facing peripheral surface area is considerably larger than its total horizontally facing peripheral surface area, thereby significantly reducing undesirable outward heat loss through the vertically extending furnace housing side walls upon burner shut off and increasing the overall efficiency rating of the furnace.

Abstract: A fuel-fired, condensing type forced air heating furnace is provided with an improved hot combustion gas-to-air heat exchange system which includes a generally drum-shaped primary heat exchanger having an outlet end connected to a first end of a transfer manifold whose second end is connected the inlet end of a fin-and-tube type secondary heat exchanger which is spaced laterally apart from, faces, and extends generally parallel to the primary heat exchanger. A radial discharge fuel burner end portion is coaxially positioned within an inlet end of the primary heat exchanger and, during furnace operation, a draft inducer fan draws burner combustion gases sequentially through the primary heat exchanger, the transfer manifold and the secondary heat exchanger while air to be heated is flowed externally over these heat transfer elements.

Abstract: A belled orifice inlet plate is provided for an induced draft combustion furnace heat exchanger of the type in which an inshot burner produces a hot gaseous combustion that is injected through an opening in the inlet plate into a combustion zone in the heat exchanger. The inlet plate has a flared collar that surrounds the opening at its periphery, and which extends a predetermined distance into the combustion zone. Preferably, the collar should have a depth on the order of one-quarter inch to one-half inch, and the flared portion should have a radius of curvature on the order of about one-quarter inch.

Abstract: The present invention in its most simple form or embodiment is directed to a heat exchanger which provides for at least two heat exchange surfaces. The two heat exchange surfaces are defined by an inner wall or inner shell which separates a combustion region or combustion passage and at least one fluid passage defined by the inner shell, and an outer wall or outer shell. The space defined between the inner and outer shells being the combustion region or combustion passage. The combustion chamber is configured to provide for full and efficient fuel combustion without any flat surfaces upon which a flame of combustion could impinge. Because of the nature of the construction, the flame forms into a fan configuration allowing thorough mixture with the combustion air and thus providing for complete and efficient combustion.

Abstract: A self-contained, free standing, on-demand, woodburning furnace including a firebox (52), including means to force combustion gases through a manifold (68), a hot air gathering plenum and means to selectively force feed the fire (34, 36, 38, 40, 68) and draw heated air from the furnace (8, 10, 12, 14).

Abstract: A device is disclosed for use in a combustion system to inhibit formation of oxides of nitrogen (NO.sub.x) by the combustion system thereby reducing NO.sub.x emissions from the combustion system. The device is made of a material, such as stainless steel, which is positioned at the periphery of a combustion flame produced by a burner which is part of the combustion system, to temper the combustion flame by absorbing thermal energy from the combustion flame. The device sufficiently tempers the combustion flame to limit peak combustion flame temperatures and residence times at these peak combustion flame temperatures to levels which inhibit formation of oxides of nitrogen while allowing substantially complete combustion of the fuel supplied to the burner.

Abstract: A furnace flue gas draft inducer outlet box assembly is provided for connecting an inducer housing to a vent pipe, and comprises a plurality of differently directed openings to allow the vent pipe to be connected thereto in one of a plurality of different orientations, thereby facilitating ease of installation of the furnace. When incorporated with a condensing furnace, the inducer outlet assembly further comprises a condensate collecting system for collecting a return flow of condensate formed in a vent pipe and for delivering the condensate out of the inducer housing to prevent contact with the inducer motor, wheel and the like.

Abstract: A hot air heat exchanger furnace that uses crop residue as a fuel source is provided for producing the heat required for various purposes, such as the drying of grains, peanuts, soybeans and other materials and for the heating of buildings. The furnace includes a combustion chamber, an upper manifold, a lower manifold, a plenum and a number of exhaust tubes. The exhaust tubes direct the flow of combustion gases from the combustion chamber in a serpentine path in the plenum between the upper and lower manifolds and into a stack. Meanwhile, ambient air passes into the plenum, past the heat transfer surfaces of the combustion chamber and the exhaust tubes as heat transfers to it. Then it passes out of the furnace.

Abstract: A heat pipe heat transfer structure for use in a furnace wherein individual heat pipes are arranged in a series for successive heat transfer association with the hot products of combustion of the furnace. The heat transfer enclosure defines successively a combustion chamber portion, an acoustic decoupling portion, and an input heat transfer chamber portion. The heat transfer chamber portion, in turn, is divided into first and second portions. The first portion of the input heat transfer chamber portion, in the illustrated embodiment, decreases in cross sectional area in a direction away from the burner. The final portion of the input heat transfer chamber portion, in the illustrated embodiment, has a constant cross sectional area.

Abstract: A secondary heat exchanger is positioned within a cold air return plenum of a forced air gas or oil fired furnace to preheat cold air drawn into the furnace through the cold air plenum. A heat recovery flue pipe is connected between a primary flue pipe of the furnace and the secondary heat exchanger, and an exhaust pipe is connected between the secondary heat exchanger and the outside of a structure served by the furnace. A secondary blower coupled to the exhaust pipe draws hot combustion gases from the primary flue pipe through the heat exchanger and exhausts cooled combustion gases to the outside. The secondary heat exchanger comprises a combustion gas inlet plenum and a combustion gas outlet plenum, with a plurality of heat conducting pipes sealingly connected therebetween.

Abstract: This invention relates to a compact high efficiency furnace having a cylindrical combustion chamber and a fin and tube type heat exchanger substantially parallel, transverse to the furnace air flow, and closely spaced in the air flow direction with no other major heat exchange being utilized. Condensation of fluids from the combustion gases occurs at the fin and tube type heat exchanger, whereby a high efficiency furnace results. The fins and tubes of the heat exchanger are of different materials, requiring that the combustion gas temperature at the heat exchanger inlet be limited.

Abstract: A furnace for wood log fuel having apparatus which automatically inserts the logs into the furnace combustion chamber. The log fuel is retained in a sloping ramp storage compartment. Electrical circuitry controlled by a thermostat operates to move a log into an elongated chamber from which a motor driven injector pushes the log into the combustion chamber through a doorway covered by a flexible, segmented flap covering and also a door which is pushed open by the advancing log. The presence of the log on a spring mounted grate operates certain switches to return the injection mechanism to its ready condition and also to operate a fan which provides combustion air to the combustion chamber. The reduced weight on the grate by the consumption of the log by the fire permits the grate to move to a position to re-initiate the log injection cycle.

Abstract: Furnace structure including an outer enclosure divided into a cool air chamber and a hot air chamber separated by a combustion gas chamber through which heat exchange tubes pass air between the cool air chamber and the hot air chamber. The furnace structure further includes a burner in the combustion gas chamber, a blower connected to the cool air chamber and a flue for the combustion gases including a draft diverter therein.

Abstract: A gas-fired, condensing mode, hot air furnace has an exhaust passage for carrying the products of combustion from a gas burner to an exhaust flue. A heat exchanger is provided in the exhaust passage for extracting heat from the products of combustion. An air passage is provided for carrying a flow of air over the heat exchanger and a blower causes a flow of air through the air passage. The gas burner is enclosed and fires into the heat exchanger. A fresh air duct communicates with the burner enclosure for admitting fresh air thereto. A condenser is provided in the exhaust passage for removing water from the products of combustion, the condenser being exposed to the air passage. A second blower is provided in the exhaust passage for causing fluid flow therein from the fresh air inlet duct through the enclosure and the exhaust passage to the exhaust flue.

Abstract: An improvement in a condensing furnace where gaseous products of combustion are ducted through fin tube condensers that act to heat incoming air. The improvement involves spraying water into the products of combustion upstream of the fin tube condenser, so that the sprayed water droplets mix intimately with the products of combustion and are thus vaporized. In this manner, the combined water vapor and gaseous combustion products can condense in the fin tube condenser to create a liquid condensate of which the pH is closer to neutral than would have been the case in the absence of the sprayed water.

Abstract: A compact secondary heat exchanger, installed above the preliminary heat exchanger in a down draft-type gas burning furnace, so greatly reduces combustion gas temperature as to recover a portion of the latent heat in the water vapor created by burning the hydrocarbon gas.

Abstract: A noise reducing heat exchanger assembly for a combustion system is disclosed. The heat exchanger assembly includes a plurality of side by side heat exchangers each having a single inlet for an inshot burner. An auxiliary port is located just above each burner inlet. A coupling chamber may be used to interconnect the auxiliary ports to allow acoustical coupling between the heat exchangers and to substantially prevent potential fluid flow between the heat exchangers and the surroundings of the combustion system. This heat exchanger assembly is particularly suitable for use as part of an induced draft combustion furnace.

Abstract: A hot air heat exchanger furnace that uses crop residue as a fuel source is provided for producing the heat required for various purposes, such as the drying of grains, peanuts, soybeans and other materials and for the heating of buildings. The furnace includes a combustion chamber, an upper manifold, a lower manifold, a plenum and a number of exhaust tubes. The exhaust tubes direct the flow of combustion gases from the combustion chamber in a serpentine path in the plenum between the upper and lower manifolds and into a stack. Meanwhile, ambient air passes into the plenum, past the heat transfer surfaces of the combustion chamber and the exhaust tubes as heat transfers to it. Then it passes out of the furnace.

Abstract: A solid fuel furnace which includes a housing enclosing a firebox and a heat exchanger chamber. An open grate in the firebox supports solid fuel thereon. Combustion air is admitted to the area below the grate and is preheated and passes upwardly through the grate and fuel and mixes with volatile gases released from the fuel. The air/gas mixture is drawn downwardly through the fuel and exits the firebox through an inlet to an insulated burn-out chamber which is behind the firebox. A metal screen covers the inlet and serves to ignite the air/gas mixture. Hot flue gases exit the burn-out chamber to the heat exchanger chamber.

Abstract: An air heater comprises a plurality of passes, each having tube banks built into a gas conduit through which passes a flow of heating gas. It also comprises a plurality of delivery and collecting air ducts series-arranged one above the other. The delivery air ducts adjoin the tube banks of each pass and communicate therewith through outlets. The collecting air ducts adjoin the tube banks of each pass and communicate therewith by means of inlets. The collecting air duct is connected to the delivery air duct, the next-in-order along the flow of air, by means of interconnecting air conduits, which are positioned in the interspaces between the tube banks of each individual pass. Each interconnecting air conduit has an inlet orifice adapted to admit a flow of air passing from the collecting air duct, and an outlet orifice through which a flow of air passes from the interconnecting air conduit into the delivery duct.

Abstract: A heat exchanger construction for use in a solid fuel burning heating system. A plurality of tubular members are provided for receiving hot, smoke laden gases and directing said gases through the zone in which clean, forced air to be heated is present. The tubes are supported between two parallel, spaced apart support plates having apertures formed therethrough for receiving opposed ends of the tubes. A clean-out box is provided at one end of the heat exchanger tubes and because a predetermined spacing is maintained between the rear surface of the clean-out box and one of the two support plates, it is possible to utilize an inexpensive tack weld to hold the parts in place, rather than a 360.degree. welded seam between the tubes and the support plate through which they pass.

Abstract: The disclosure relates to pulse combustion apparatus generally and to air furnaces of the pulse combustion type. In one aspect, the invention provides a furnace which includes a combustion chamber and an exhaust system disposed in a passageway for air to be heated. The exhaust system includes a primary exhaust pipe, a manifold to which the primary exhaust pipe is coupled, and a plurality of heat exchange pipes which extend from the manifold across the air passageway. The primary exhaust pipe, manifold and heat exchange pipes form a reasonant system with the combustion chamber so that the ignition of successive fuel charges in the chamber causes pressure waves to oscillate throughout said exhaust system including the heat exchange pipes for promoting transfer of heat from the pipes to air flowing through the passageway in use.

Abstract: Improved furnaces are described in which secondary and tertiary heat exchanges are incorporated into new and existing hot-air furnace systems for controlled cooling of hot combustion products by co-current and countercurrent heat exchanges. Hot combustion products are cooled to a temperature at which latent heat of water vapor contained in combustion gases are substantially recovered.In one embodiment of our invention, a secondary heat exchanger comprises inter alia a closed hollow annular drum concentric with and spaced from a cylindrical combustion chamber, said annular drum having an upper annulus preferably filled with randomly packed refractory material.A second embodiment of our invention comprises a closed double-annuli drum heat exchanger concentric with and spaced from a cylindrical combustion chamber.Finned tube or thermosiphon heat exchangers can be arranged sequentially with the primary heat exchanger combustion chamber to function as a secondary heat exchanger or as a tertiary heat exchanger.

Abstract: A warm air furnace including a plenum, a blower, heat exchanger disposed within the plenum and an air distribution chamber. The heat exchanger includes an encasement surrounding a plurality of vertically extending heat exchanger tubes. The tubes are in communication with the plenum and with the air distribution chamber. A fibrous refractory inorganic tubular flame chamber is positioned within the encasement and is partially surrounded by the vertically extending tubes. The tubes are positioned in a generally U-shaped pattern and one of the tubes contacts the flame chamber. The tubes along the sides of the pattern are interconnected by upper and lower side baffles. The baffles are vertically spaced from each other to define exhaust outlets. A rear baffle extends between the tubes along the base of the pattern. A flue extends from the encasement for exhaust of combustion gases.

Abstract: A wood burning furnace includes a combustion enclosure made up of a lower closed generally rectilinear fire box which is defined at an upper portion thereof by a semicylindrical roof dome and a top cylindrical-shape smoke chamber supported on a rearward upright cylindrical smoke conduit and a forward upright smoke conduit, these conduits being supported on the fire box roof dome and open between the smoke chamber and fire box. The combustion enclosure is supported inside of a furnace shell above a fan compartment in that shell. The furnace shell and heating air baffles fastened to it are so constructed as to provide a heating air passage between the combustion enclosure and shell, and a blower in the fan compartment forces air from outside of the shell over the surfaces of the combustion enclosure and out the top of the shell to a location for use of heated air.

Abstract: A solid fuel burning system which may be readily combined with a conventional fluid fuel burning furnace in a forced air heating system. The solid fuel burning system comprises, in combination, a draft inducing blower which directs air for combustion into the furnace at a point proximate the burning fuel. Baffle walls are provided which separate the smoke and other products of combustion from the clean air to be heated and a novel heat exchanger comprised of a plurality of elongated tubes provide a relatively large heat transfer surface. The furnace is specifically designed to facilitate periodic cleaning of the interior walls of the heat exchanger where creosote and other products of combustion may accumulate. In addition, the system employs a novel electronic control circuit which is tied in with the room thermostat and with a thermocouple disposed within the solid fuel burning furnace.

Abstract: In a home heating system having a furnace with a combustion chamber for burning fuel and creating heat, and a chimney with a draft therein, an improvement comprising, an exhaust flue connected between the combustion chamber and the chimney for venting heated exhaust products from the furnace, a heat reclaimer connected into the exhaust flue between the combustion chamber and the chimney for reclaiming heat from the heated exhaust product, and an outside air line for supplying air from the outside of the house to the combustion chamber. A first flue portion of the exhaust flue is connected between the combustion chamber and the heat reclaimer, and a second insulated flue portion of the exhaust flue is connected between the heat reclaimer and the chimney. An outside air by-pass or balancing line is connected between the outside air line and the chimney for satisfying the chimney suction at flame-out.

Abstract: A heating boiler having a combustion chamber, a chimney and preferably curved channels connecting the chamber to the chimney. The combustion chamber is preferably of good aerodynamic shape on the outside and located next to the chimney. The channels preferably join the chimney tangentially, and means are provided for blowing a fluid over the entire heating surface of the chamber and the chimney.

Abstract: An energy storage and distributing device having a heat storage chamber arranged for retaining heat which can be received from a solar collector arrangement or from a furnace or furnaces disposed within the chamber itself. Mounted on the chamber is a plenum arrangement disposed for directing warm fluid to a space to be heated, such as a room or rooms of a house, while a fluid distribution system is associated with the plenum and the chamber for alternately directing a fluid current directly into the plenum and directly into the chamber, and thereby supplying the plenum selectively with warm fluid from one of the chamber or from a source disposed outside the chamber. In this manner, solar energy, and the like, can be fed directly to the plenum, or stored in the chamber, or if solar energy is not available for whatever reason, and insufficiient heat energy is present in stored form within the chamber, a furnace or furnaces can be employed to supply the requisite heat energy.