MODULATED TEMPERATURE CONTROL OF STRUCTURES WITH CENTRAL HEATING UNITS

Abstract: A system to control heat-energy transfer between a central unit and a structure consisting of a number of spaces. Heat-energy transfer is accomplished by use of one or more heat valves (10) disposed in each space to control independently the rate at which energy transfer is achieved between that space and the central unit (1). The heat valves are controlled to maximize on time (ton) of the central unit while satisfying room or area temperature requirements: hence, in the usual operation, less than all the heat valves (10) are activated, the number being matched to the capacity of the central unit. The objective of maximizing ton of the central unit is accomplished because use of the heat valves (10) permits the central burner firing rate to be set by the heat load of the structure. Ideally this firing rate is allowed to be variable and is set by the same device that controls the heat valves.

Description: MODULATED TEMPERATURE CONTROL OF STRUCTURES WITH CENTRAL HEATING UNITS The present invention relates to heat transfer mechanisms for residences and the like. The concepts herein disclosed have parti¬ cular value in the context of steam-heat and hot- water systems in use, wherein a hot fluid from a central heater system is delivered to multiple radiators in a family dwelling, commercial struc¬ ture, industrial building or the like. Moreover, the present ideas are especially useful in connec¬ tion with retrofitting activity. In what now follows, the invention is discussed mostly in the context just mentioned, but it is not so limited in scope. A significant problem with respect to the current fuel situation is the intractability of radiator-heated, centrally-fired, steam and hot- ater systems in the northeastern region of the United States where a significant fraction of residences are so heated and the residences often do not lend themselves easily to other solutions (such as insulation). In large, old houses a strategy which has been proposed is that of area (or zone) heating with a lower average temperature throughout the structure. One mechanism proposed to accomplish such area heat¬ ing is, by way of example, to have liquid or steam valves in the hot water pipes to the radia¬ tors, which valves are hand set to effect an area- heating approximation. Such valves, however are often difficult to operate and susceptible to failure, and automatically-activated valves (to permit sequencing) are expensive and difficult and expensive to install. Accordingly, it is a principal object of the present invention to provide a tempera¬ ture-control system that permits facile retro¬ fitting of existing hot water and steam centrally- heated, structures. Another object is to provide a tempera¬ ture-control system that is economical to fabri¬ cate, easy to install, yet efficient and depend¬ able. Still another object is to provide a temperature-control system that does not depend on restricting flow of the primary fluid in the heating system. A further object is to provide a retro- fittable system which provides optixaal control of the flow of heat from the central burner to the individual rooms or areas, A further ob ect is to provide a system which permits the firing rate of the central burner to be matched to the heating load of the structure. Still another object of the present in¬ vention is to reduce the firing rate of the cen¬ tral burner with concomitant reduction in cycling. Still another object is to provide op¬ timized temperature control for each room or area in the structure. A further object is to reduce the trans¬ fer of heat through the exterior walls and win¬ dows of housing. This is accomplished by pre¬ venting the convective flow of hot air set up by the normal placement of conventional radiators. A still further object is to prevent or reduce temperature stratification by means of inducing a circulation pattern which releases hot air at the very lowest levels of the room, A large heat energy expenditure in the usual steam heating system occurs because in such a system the central burner or boiler installed is sized to provide heat energy to each radiator on the coldest days. Hence, the central burner has a firing rate (i.e., rate at which fuel is burned) that is matched to this worst case, where¬ as the heat load of the house is always much less. Two consequences flow from such operationt burner cycling is greatly increased! as a result stack temperature and stack losses are increased. The present inventor has found that the teaching here¬ in permits as much as a 50X reduction in firing rates below those normally recommended--while still satisfying the heating requirements of the heated structure. It has been further found that greatly reduced burner cycling can be effected, that is, the on/off (^oa/^-f-f) ratio is much higher in the present temperature control system. Ideally the firing rate would be adjustable to be equal to the requirements of the heated struc¬ ture and the controlled burner would be on, at a reduced firing rate, at all times during the heating season. The present system minimizes the firing rate for any particular structure, and, hence, maximizes the ratio z on / z 0 ff An important trend in the United States is that homeowners have tended toward doing much of the work on. their homes, A still further ob- jective of this invention is to provide a heat control system that can be installed by a pro¬ fessional, but one that can be marketed in kit form for installation by the user-owner. These and still further objects are addressed later. The foregoing objects are achieved, generally, in a method of controlling heat- energy transfer between a central unit and a plurality of discrete spaces, that includes» assigning temperature values to be maintained at each space of the plurality of spaces (pre¬ ferably, but not necessarily, as a function of ti e of day)ι providing a valving mechanism at each space of the plurality of spaces to effect essentially total control of energy transfer be* tween the space in which the valving mechanism is located and the central unit, each valving mechanism including a housing and -an air-moving mechanism that provides the valving mechanism with a torn-down ratio of at least four to one, said turn-down ratio.: being the ratio of energy trans er when the air-moving mechanism is activat¬ ed to deliver air between the housing and the space and energy transfer when the air-moving mechanism is de-activatedj and controlling-the energ trans er of each valving mechanism in a way that maximizes of the central unit, where on is the time that the central unit is on and Qf , is the time that the central unit is off to minimize cycling of the central unit. The invention is hereinafter described with reference to the accompanying drawing in which. Fig, 1 is a diagrammatic representation of a central heating system employing the pre- O H sent concepts and including a plurality of heat valves and a central controller? Fig. 2 is an isometric view, partly cutaway, showing one form the heat valves of Fig, 1 can take* Fig. 3 is an isometric view, partly cutaway, of a modified version of the heat valve of Fig. 2, that includes a flap valve to influence heat flow between the heat valve and the surround¬ ing region; Fig. 4A is a section view taken on the line 4A-4A in Fig. 2 and looking in the direction of the arrowsi Fig, 4B is a section plan view of a modification of the heat valves of Figs, 2 and 4Aϊ Figs, 5A and 5B are respectively a front view on and a section side view of the flap valve Fig. 6 is a diagrammatic representa¬ tion of a portion of the system of Fig. lj and Fig. 7 is a flow chart showing one form that the functions of the central controller in Fig. 1 can take. In the discussion that now follows, the system shown diagrammatically at 101 in Fig. 1, for purposes of simplifying this explanation, is taken to be one in which heat energy is trans¬ ferred from a central unit or furnace (the term "central heat exchanger* is also used herein to denote the element 1) 1 to a plurality of spaces or locations 5A»..5N in a structure 102 to be heated. Also, the heating system 101 is taken to be a steam system, but it is to be understood, as indicated above and as shown in greater detail later, that the invention is not limited to steam systems nor to systems wherein heat-energy is delivered to the spaces 5A...5NJ such heat- energy can be either extracted or delivered accord¬ ing to the present teaching. The heating system 101 is a simple cost effective optimum transfer control for the cen¬ trally-heated structure 102, the central unit 1 at this juncture of the explanation being a central steam furnace 1. A steam furnace, as is well known, includes a burner (called "central burner" herein), a boiler (called "central boiler" herein) and in- ternal piping, all of which are embraced by the designation 1 in Fig. 1. A major aspect of the system 101 according to the present teachings is that of minimizing the firing rate of the central burner—without deleteriously affecting the heat¬ ing comfort within the structure 102, that is, the ratio of turn-on time (t ) of the central burner to turn-off time t Q £f) is maximized by the present invention. It should be pointed out that at the time the burner.is fired and for a time thereafter, heat energy is absorbed totally within the furnace. Some time later heat energy is transferred to the spaces 5A...5N. During this transient situation the heat valves 1GA...10N (discussed below) may be used to control heat transfer to the spaces 5A...5N at a level that matches the heat energy the furnace is capable of providing. Once a steadystate is reached (i.e., after the furnace boiler and internal piping, and so forth, are up to temperature) the heat energy delivered to the spaces 5A...5N is substantially equal to the heat-energy output of the central burner. i / Each space 5A...5N contains one or more of ' the heat valves 10A.,.10N that receive steam through piping 40A,..40N, respectively, and con¬ trol signals by way of conductors 30A...3ON, respectively. Temperature sensors 11A.,,11N may be used to provide temperature information along respective conductors 50A,,.50N to a central controller 2 which delivers control signals on a conductor 51 to the central unit 1 and receives control information from the central unit. Let it be considered at this point in the discussion that the central unit 1 simply has on-off control of the burner. This may advantageously be accom¬ plished by connecting a controlled switching means in parallel with the existing thermostat. The controller 2, as later explained, preferably is a microprocessor adapted to receive feedback tempera¬ ture information on conductors 50A.,.5ON and to provide control signals at 51 and 30A.,.30N, Typically, the heat energy delivered to the struc¬ ture 102 by the burner unit 1 is controlled by controlling the on-time of the unit (assuming the firing rate is fixed). In the usual prior art heating system in fact heat delivery to the spaces 5A...5N is controlled in exactly this way. In the present system, however, heat energy delivered to the spaces 5A...5N is modulated and the rate of such delivery is controlled by the heat valves 10A...ION on the basis of appropriate signals from the controller 2, which may also calculate the fuel consumption from the turner-on time. The heat valves, as explained below, serve as heater control means to control independently the rate at which heat energy is delivered to each of the spaces 5A...5N in such a manner that the steam output of the central boiler is equal to the sum of outputs of the heat valves 1 Q A...10N and that the output of each heat valve is adequate to maintain or move to a predetermined tempera¬ ture each of the spaces 5A.,.5N independently, it being understood that ordinarily less than all the heat valves, at any instant of time, will be delivering heat energy to the associated spaces. Each heat valve 10A,,«10N, as now dis¬ cussed, includes a housing and an air delivery device. Since all the heat valves in any system usually will be identical to one another—or at least similar to one another—either of two varia¬ tions 10 and 10* described below can be taken to be any one of the heat valves in Fig. 1. The hear valve 10, as shown in Fig. 2, includes a housing 3, a fan or blower 12A, and baffles 4A and 4B. The heat valve also works well with only one of the baffles. The housing 3 fits over a local heat exchanger (e.g., a steam or hot water radiator) 8 that exchanges heat from a first fluid (e.g., the steam from the central boiler) internal to the heat exchanger 8 and a second fluid (i.e,, the air drawn over the radiator 8), The housing 3 acts to restrict the natural convective driving force of the radiator 8 and it serves as an insulator with respect to radiation between the radiator 8 and the space or room within which it is located. In the pre¬ sent system, the flow of heat energy between the radiator 8 and the environment is regulated by causing a directed flow of air into the housing 3 (i.e., the second fluid herein), about the radia¬ tor and out into the environment around the heat valve 10, as now explained. -s.- C ?I As above indicated, the heat valve 10 is fashioned to have a large turn-down ratio, at least about four to one, where the turn-down ratio is the ratio of heat transferred between the heat exchanger 8 and the environment when there is no forced air flow into the housing and when there is such forced air flow. Ideally, the housing 3 reduces the transfer of heat between the heat exchanger 8 and the environment to at least half the heat transfer without the housing. A greater . degree of heat- ransfer reduction is desirable. The housing performs the required function by reducing the natural convective driving force of the heat exchanger 8 and by reducing direct radiation to the environment. Regulation of heat transfer, according to the present teaching, is accomplished in the heat valve 10 by the state of activation of the fan or blower 12A which serves to draw air from the surrounding environ¬ ment into the housing 3 through an inlet 6A. As one example, air within the housing is directed by the baffle 4A to move upward in the direction of the arrows labeled 7A, laterally across the top of the heat exchanger 8 to create convection within the heat exchanger, downward in the direc- tion of the arrows labeled 7B, and out to the surrounding environment through the outlet labeled 6B. The present inventor has found that in the absence of baffling there is a thermal short circuit of the heat exchanger 8. Hence, it is vital not only that there be a forced air flow into the housing 3 but also that the air flow within the housing be such that sub¬ stantial convection occurs in and about the heat exchanger 8 when such forced flow is present! and the air heated and convected from within the convector or heat exchanger 8 is caused to flow out of the housing 3 and into the surrounding environment. There are other configurations which will accomplish approximately the same re¬ sult, as already discussed. In this way, the flow of heat energy from the heat exchanger 8, and thus from the central boiler, into the space in which the heat valve 10 is located, is regulated simply by activating and de-activating the fan or blower 12A. In other words, it is the forced air flow into and out of the housing 3 (with appropriate direction of air flow within the housing to assure convection) that modulates heat transfer from the convector 8 to the surrounding environ¬ ment (i.e., one of the spaces 5A...5N in Fig. 1) and heat transfer from the convector 8 is greatly reduced in the absence of such forced flow. Since the heat control system 101 in Fig. 1 contemplates several spaces 5A...5N (typically six to fourteen in a single family residence), heat energy transfer from the central unit 1 can be (and according to the present teaching is) ultimately determined by the rate of heat-energy transfer from the various heat valves 10A...10N and these are turned on and off according to a predetermined algorithm by signals from a micro¬ processor in the controller 2. Several radiators may be left uncontrolled, provided that more or less continuous heating of the spaces in which they are located is desirable. In addition, a number of the radiators in a typi¬ cal house may be permanently disconnected or turned off when the system described is intalled. This is at least partially because of the in¬ creased rate of heat-transfer made possible by the forced convection induced by the fans. An additional point must be made about the disposition of baffles described above. Since the heat valves are to be used in spaces normally occupied by humans, and indeed, in the case of a residential application, where people sleep, it is necessary that the fan means be quiet. By providing a long, wide, obstruction free channel leading to the fans, by directing the output of the fans outward past the screens required by safety regulations, and by locating the fans in the narrowest dimension of the enclosure, noise may be minimized. It is also desirable to insert an in¬ sulating means between the radiator and the exter¬ ior wall to reduce the transfer of heat through that wall to the exterior where it is lost. With¬ out such insulating means, heat transfer to the exterior would be enhanced. In the course of development of the present invention, it has been found particularly advantageous to use a foil- covered cardboard or pulp-board to serve this function, to attach a piece of wood to said foil- covered board, and to attach the baffle required for noise reduction and proper flow of air to this wood, so that the combination of the foil- covered board and the baffle form an "L*f see the L-shaped element labeled 28 in Fig. 4B. The ex¬ terior cover or housing 3 may then be pressed against the deformable baffle to create the obstruction-free channel or passage required for noise reduction and optimum air flow characteristics, By suitably locating the air intake and omitting the second baffle, access to the radiator control val-ve (normally provided in an existing system) may be obtained without impairing system opera¬ tion and the cost of the enclosure may be mini¬ mized. The housing 3 may be constructed either of wood or wood products, or may use a skin and frame construction with an air apace provided be¬ tween the skins (or an air space filled with some light material). For reasons of weight and economy, the use of metal is believed undesir¬ able, though it is feasible from an engineering viewpoint. Since the low of heat into the each room or area is controlled by the state of " acti¬ vation of the fan, the relative proportions of heat delivered to each area may be calculated readily by the central microprocessor. This may be used to provide an allocation and control of heating costs to individual apartments in a cen¬ trally heated apartment building. It is de¬ sirable to line the housing with a reflective material such as,an aluminum foil. In the present system the heat transfer from the radiators 8 is cycled—not the central burner. Such arrangement permits use of much lower firing rates (down as much as 50% of normally recommended) while satisfying the heating require¬ ment of the structure 102 ι studies have shown that a reduction of at least 25% in fuel use (and esti¬ mates go as high as 40%) can result from a properly designed system 101. Before detailing the precise approach for the controlling energy transfer, it may be useful to mention, for emphasis, the im¬ portance of such control in the context of energy saving. The electrical circuitry of Fig. 1 is shown in Fig. 6 for purposes of the explanation below with respect to Fig. 1, it being noted here that the connections 30A...30N can be accomplished along the ac lines labeled 15A...15N, respectively. In other words, on-off signals to an on-off switch within each of the blocks 12A...12N can be carried by the 120 volt ac conductors that carry electri¬ cal power to the respective fan or blower 12A... (see United States Letters Patent 4,070,549). When heat is called for by signals to the controll¬ er 2 from the various room (or space) temperature sensors, the controller 2, along a multi-conductor 51, determines the temperature of the water (either directly or from its past firing history) in the central unit or furnace 1. If the temperature there is below some predetermined value, the unit 1 is fired and shortly thereafter some of the fans or blowers 12A.., are energized, the number being matched to the central heating unit 1 such that the heat extracted by the combined heat valves 10A,., matches the heat input to the system by the central boiler. In this way the ratio t /t __ of the central burner is maximized. Let it be assumed, for example, that the structure to be heat controlled is a seven- room house. Each room is assigned a temperature level for different times of the day. The controller (e.g., a micronrocessor) scans the temperature values over inputs 50A...50N in Fig. l! assume all the rooms are below temperature. Signals move between the controller 2 and the central burner unit 1, the fans or blower 12A...12N and the temperature sensors 11A...11N, At this juncture the controller makes a number of decisions in accordance with a pre-established pattern which may be of the type shown in Fig. 7 which is an exemplary flow chart for the microprocessor. Typi¬ cally, the fans or blowers 12A * .,12N in three to four rooms will be energized in some pre-arranged schedule until all rooms in the house come up to temperature. In this way the firing rate of the central burner is minimized, as is, also, cycling of that central burner, and the temperatures with¬ in the rooms are determined by the heat valves— rather than the central unit—on the basis of user supplied information to the controller 2. The - - coήtrol pattern in Fig, 7 is based upon a closed- loop control system. The central controller should be adapted . to control the burner and the heat valves so that, over the period of a day, the temperature in each of the rooms or areas most closely approximates the desired temperature for such time of day. To illustrate this point, consider the case of a room which is supposed to be at 60°F at 5p.m. and at 70°F at 6ρ.m, The room cannot be wa med up in¬ stantaneously. On the other hand, any control algorithm employs a series of trade-offs result¬ ing, at any given time, in rooms being hotter or colder than the precise set temperature. By "looking ahead,- * the direction of the "errors" can be made to be consistent with the future desired temperature. Likewise burner control decisions may be impacted by a consideration of future desired temperature settings. A more sophisticated control scheme allows for the con¬ sideration of variables such as outside tempera¬ ture and the rate of change thereof and the re¬ quirements for domestic hot water for those syste s that heat domestic hot water in the central heating system. An open-loop system can also be used,, as now explained * In the open-loop system, the user again establishes the temperature for each room. There is only one temperature sensor in one roomi the temperature in the other rooms is maintained on the basis of experience. The length of time each fan is allowed to be on in each room is set to be a function of the time required to heat the room with the temperature sensor, the desired set tempera¬ ture of each other room. An experimentally used open-loop algorithm found to give reasonable re¬ sults is presented below. The user sets the desired temperature for each room in degrees Fahrenheit. The micro¬ processor subtracts 60 from the number entered, calling all results less than zero equal to zero and all results greater than 20 equal to 20, If the temperature sensor is below the set tempera¬ ture of the controlled room, a heating cycle is begun. During this cycle each fan is turned on for a number of minutes equal to the result of the subtraction described above, A fixed percent¬ age of radiators are "on" at any instant in time. A cycle is completed when each radiator has been turned "on" and then "off," At this point, a check is again made to see if the controlled room still requires heat. If so, a new cycle is initiated. If the controlled room no longer requires heat, the central burner is turned off—but at least one additional cycle » is performed to extract the heat remaining in the system. This algorithm may be modified for maxi¬ mum performance by making the percentage of radia¬ tors turned "on" a function of the past operating history of the central burner--i.e., if the burner has been off for a protracted period the initial "on" percentage should be low (and possibly zero) and increase with each cycle. The baffled heat valve 10 of Fig. 2 may be replaced by the heat valve designated 10 • in Fig. 3 wherein a flap valve 13 replaces the baffles 4A and 4B in Fig. 2. As shown in Figs. 5A and 5B, the flap valve 13 has a flap 18 that opens, i.e., pivots counterclockwise in Fig. 3 and clockwise in Fig. 5B, to permit air to flow into the housing labeled 3A and over the top ^f the radiator 8, again to avoid a thermal short circuit which occurs if the incoming air were directed, for example, below the radiator 8 between input and output of the housing 3A. The housing 3 or 3A, as shown in Fig. 4A » can be fabricated of fiberboard which serves as a the-qmal insulator. The top and sides of a housing can be secured together by screwing each into a wood strip as shown. A weather stripping 23 and foil 24 serve to insulate the interior of the housing against heat transfer to a wall sur¬ face 25 or the room area. The numerals 26 and 27 represent respectively the floor and walls of the room being heated. The foregoing explanation is made with reference to a system wherein the first fluid, i.e., the fluid within the radiator 8, is a vapor (steam), but the system 101 in Fig. 1 can be a hot-water system with results at least as good as derived from a steam system. Furthermore, the central unit can be or can include a cooler (i.e., an air conditioning unit) in this case the first fluid will be cooler than the second fluid and heat valves 10A...10N will cool the structure 102. The design of the heat valves must now be re¬ versed, as would be obvious to one skilled in the art. Again, matching the heat transfer to the structure 102 to the capacity of the air condition¬ ing unit results in large energy savings, as is known, . The temperature sensors 11A...11N may be temperature-to-frequency converters, for example, with a phase locked loop being used as a detector. In such an arrangement, the variable frequency sig¬ nal can be transmitted over ac building wiring and the phase locked loop would be located in the controller 2. The temperature sensing means can provide a signal which is converted to a coded sequence of digital pulses for transmission over the ac wiring (or ulti-component lines). A microporcessor in the block 2, in addition to the functions above described, can provide information on firing rates, room heat requirement, and so forth. The microprocessor transmit/receive unit may be a chip similar to GI AR-38470 or GI AR-38475 marketed by General Instruments, or it may be a general purpose microprocessor which also per¬ forms the transmit/receive function. These chips can be programmed to provide the above-mentioned functions and other functions can be easily pro¬ vided, e.g., input data to the controller means can include the outside temperature or the need for domestic hot water and these data can be factored into the decision-making process. In the controller 2, batteries may be supplied to protect against ac system outages and crystal- controlled timing may be used. The present system permits active manage¬ ment of heat transfer to, among other things, free the firing rate and cycling of the central unit— whether it be a heater and/or cooler, e.g., a heat pump— rom pulsed requirements thereby, for this reason alone, giving substantial savings. It permits a reduction in window losses (due to altered air circulation patterns) and other losses as well as reduced stack (and other transient) losses and lower stack temperatures. Zone heat¬ ing control is greatly simplified and the equip- ent is simple to install, low cost, reliable, easy to repair, and retrofittable. The system permits use of readily available materials which can be marketed in kit form for installation by the user in existing central heating systems. Furthermore, the forced convection enhances heat transfer from individual radiators to the surround¬ ing region and acts to reduce stratification and favorably alter room air circulation patterns. Efficiency can be enhanced by having continuously- variable central burner or a multi-level firing rate. In this situation, control of the firing rate of the central heat exchanger may be effected in part, by using a multi-speed forced-air burner with higher speeds corresponding to rarely used but less efficient modes of operation. The heating system may also be a hot air system, in which air is heated in a central heat exchanger and delivered to the various spaces by ducts. In this case, the advantages described may be achieved by remotely controlling the flow from the ducts on a room-by-room basis. The same principle, of course, may generally be applied to a central air-conditioning system, as previously indicated. The foregoing and other modifications of the present invention will occur to persons skilled in the art and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.

Claims: What is claimed isi 1. For use in a heat-energy transfer system where¬ in energy transfer is between a central unit and a plurality of spaces in a structure com¬ prising a multiplicity of such spaces each space of the plurality of spaces having a local heat exchanger located therein to re¬ ceive a fluid from the central unit and to exchange energy between the fluid and the associated space, energy valving means for installation in each said space which is activated and de- ctivated to control energy transfer between the central unit and the space in which particular energy valving means is located, comprising a housing adapted for installation over and about the heat ex¬ changer in each said space operable to effect a large turn-down ratio on the associated heat exchangers, wherein the turn-down ratio is the ratio of heat transferred between the associated heat exchanger and the surrounding environment when the energy valving means is energized and de-energized, respectively, said energy valving means further including air moving means operable, when activated, to direct air with respect to the associated heat exchanger in a manner that greatly in¬ creases the energy transfer between said associated heat exchanger and the environment, essentially total control of energy transfer between said associated heat exchanger and said environment being accomplished by energy the valving means. , Apparatus as claimed in claim 1 in which said turn-down ratio is at least four to one. , Apparatus as claimed in claim 1 in which the central unit is a furnace, in which the associ¬ ated heat exchanger receives a hot fluid that serves to heat the air drawn over the heat exchanger by the air moving means associated therewith, the air moving means being operable to create an air circulation pattern that minimizes by-pass of the associated heat ex¬ changer and directs hot air into the space at a low level to reduce temperature stratifi¬ cation. 4.> Apparatus as claimed in claim 1 that includes controller means operable to permit selective transfer of energy between the central unit and said spaces at a level that matches the capability of said central unit to maximize the ratio wherein t Qn is the on time of the central unit and t Qf ^ is the off time of the central unit, 5. A system to control temperature in a structure comprising a plurality of individual spaces, each space of the plurality of individual spaces having disposed therein a heat ex¬ changer connected to receive a first fluid from a central system and adapted to ex¬ change heat energy between the first fluid internal to the heat exchanger and a second fluid external to the heat exchanger, that comprisesi a heat valve comprising a housing adapted to enclose the heat exchanger located in an associated space and fluid moving means which when activated is operable to direct the flow of the second fluid relative to the heat exchanger in such a way that there is no substantial natural convective driving force with respect to the heat exchanger in the absence of a flow of the second fluid into the housing effected by action of the fluid moving means but there is substantial con¬ vective driving force effected by flow of the second fluid with respect to the heat exchanger when the fluid moving means is activated in order that energy flow between the heat exchanger and the space within which the heat exchanger is located is essentially controlled by the fluid moving means, and means to control the operation of said heat valve. method of controlling temperature within certain spaces in a structure comprising a plurality of discrete spaces, that comprises) assigning temperature values to be maintained at each space of the plurality of spaces as a function of time of day providing a heat valve at each said space of the plurality of the spaces to deliver and control transfer of heat-energy to the space in which the heat valve is located, each heat valve having a heat exchanger, an enclosure about the heat exchanger, the enclosure being operable to * inhibit natural convection with respect to the heat exchanger and an air-moving mechanism to deliver air into the enclosure to effect forced convection about the heat exchanger to provide the heat valve with a turn-down ratio of at least about four to one, said turn-down being the ratio of heat-energy transfer to the associated space when the air-moving mechanism is activated to deliver air into the enclosure and from the enclosure to the space and heat-energy transfer when the air-moving mechanism is de-activated, and controlling the air-moving mechanism in each said heat valve to maintain the tempera¬ ture in the associated space, in accordance with a predetermined pattern in which less than all the air- oving mechanisms are ener¬ gized at any instant of time, \

Inventors: HAMMOND O
Applicants: HAMMOND O
Application year: 1981
Main classification: F24D19
IPC codes: F24D19, G05D23