Patent Abstract:
The need to maintain the quality of air in a home has become more of a problem in new high efficiency tight houses so that governmental regulations are being proposed for a minimum change of fresh air. If too much cold outside fresh air is introduced into such homes at a single source, the room with the fresh air is usually too cold and/or unbalanced.  
     The present invention avoids cooling any one room while maintaining heat efficiency. When the home has a gas fireplace, the exhaust gases are preferably directed through an air-to-air cross flow heat exchanger which preheats the quality air passing into a forced air furnace system.  
     In modified embodiments of the present invention, make-up quality air is mixed with the room air and heated in the heat exchanger of the fireplace. The preheated room air from the fireplace is preferably connected to the supply/return of a forced air furnace system and distributed to all rooms to provide uniform heating.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to prefabricated fireplaces that provide both radiant heat and convection heat. More particularly, the present invention relates to using heat from a fireplace to mix with cold outside fresh air or to preheat outside fresh air used to raise the air quality in a home.  
           [0003]    2. Description of the Prior Art  
           [0004]    It is known that it is possible to build heat efficient houses so tight that the air inside of a home becomes stale. There is no universal standard in all states which defines the minimum amount of make-up air required to maintain the indoor air quality.  
           [0005]    The State of Minnesota has proposed that the air in a heated house be replaced every two hours. Minnesota has also proposed that a minimum of a set amount of cubic feet of air for each bedroom plus another set amount of air for the remainder of a house be replaced every hour. At present, all known proposed standards leave the solution to builders of custom equipment.  
           [0006]    Heretofore, it was known that an auxiliary air pump could be installed in an old house to pull in a predetermined amount of outside fresh air to make-up or refresh the stale air in a home. Large custom air conditioning systems, if properly designed, introduce into the air conditioning system a small percentage of fresh air, however, there is no standard and the equipment is not mass-produced, thus, imposing a substantial cost to new home builders.  
           [0007]    It would be desirable to incorporate a make-up or air quality replacement system into present mass produced, low cost, prefabricated fireplaces and combination fireplaces/forced air furnace systems and still maintain high efficiency.  
         SUMMARY OF THE INVENTION  
         [0008]    It is a principal object of the present invention to introduce into a fireplace/furnace system outside fresh make-up air in a manner that does not unbalance the heating system.  
           [0009]    It is a principal object of the present invention to mix outside fresh air into a return air duct or ducts and add the convection heat from a fireplace into the same return air duct.  
           [0010]    It is a principal object of the present invention to introduce a predetermined amount of make-up air into a fireplace to produce heated and diluted exhaust air products that are then used in an efficient heat exchanger to preheat fresh outside make-up air being supplied to a return air plenum.  
           [0011]    It is a principal object of the present invention to provide an efficient co-linear fireplace system having hot exhaust gases that are passed through a novel remotely located heat exchanger system for preheating outside make-up air being supplied to a return air plenum of a quality air system.  
           [0012]    It is a principal object of the present invention to provide a novel air-to-air heat exchanger having a pair of separately controlled blower motors for universal use in fireplace/furnace duct systems to supply variable amounts of make-up air in an air quality system.  
           [0013]    According to these and other objects of the present invention, there is provided a fireplace with a heat exchanger/exhaust system for heating or preheating outside fresh air that is then introduced into return air ducts of a forced air furnace system. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a diagrammatic drawing in front elevation of a prior art direct vent fireplace with a convection heat exchanger;  
         [0015]    [0015]FIG. 2 is a diagrammatic drawing in front elevation of a prior art direct vent fireplace with a fire tube air heat exchanger and a high-speed blower;  
         [0016]    [0016]FIG. 3 is a diagrammatic drawing in side elevation of a direct vent fireplace adapted to deliver heat from its heat exchanger to a duct or ducts of a central heating system for distribution to all rooms in a house;  
         [0017]    [0017]FIG. 4 is a diagrammatic drawing in front elevation of a co-linear fireplace having a quiet blower in its heat exchanger and a remote blower for supplying outside fresh air for combustion as well as excess fresh air to the heat exchanger for supplying fresh make-up air in conformance with new air quality standards;  
         [0018]    [0018]FIG. 5 is a diagrammatic drawing in elevation of a fireplace adapted to heat room air in its heat exchanger and to deliver the heated air into the return air duct of a central heating system and is shown having a remote air pump for supplying a predetermined amount of fresh make-up air to the house;  
         [0019]    [0019]FIG. 6 is a diagrammatic drawing in elevation of a draft-assisted or power-vented fireplace adapted to use room air for combustion and to dilute the exhaust gases; and  
         [0020]    [0020]FIG. 7 is a diagrammatic drawing in elevation of a co-linear fireplace adapted to pass its hot exhaust gases through a remote heat exchanger used to heat room air in a house as it passes into the return air duct of a central heating system. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Refer now to FIG. 1 showing a top direct vented fireplace  10  of the type having a coaxial pipe comprising an exhaust pipe  11  and a fresh intake air pipe  12 . The fresh outside air is burned in the center of the fireplace  10  in combustion chamber  13  and subsequently exhausted back out the center exhaust pipe  11  so that no inside air is required for the combustion products. Such gas fireplaces are sold by Heat and Glow Fireplace Products, Inc. of Lakeville, Minn. under Model Number 600DVT. Such fireplaces are provided with a heat exchanger which passes under the combustion chamber around the back of the combustion chamber and comes out at the top to provide an efficient convection and radiant heating system. The intake for the heat exchanger is shown at numeral  14  and the outlet of the heat exchanger is shown at numeral  15 .  
         [0022]    Refer now to FIG. 2 showing a front elevation of a direct vent fireplace  20  having an air intake pipe  12  and an exhaust pipe  11 . The combustion gases produced in the combustion chamber  13  are passed into a plenum  16  which connects to fire tubes  17  which exits into an upper plenum  18  and then passes out through the exhaust stack  11 . To create a heat exchanger, a supply duct from the room(s)  19  is connected to the heat exchanger box and the air is heated by the hot fire tubes  17  and exits into the hot air return duct  21  with the assistance of an induced/forced draft fan or blower which, by nature of its operation and location, is noisy.  
         [0023]    It has been found that consumers who buy prefabricated fireplaces will tolerate low speed quiet blowers in the heat exchangers of the system shown in FIG. 1, but are not quite as tolerant of a noisy high speed blower of the type shown in the prior art fireplace of FIG. 2. Another disadvantage of the FIG. 2 embodiment is that the heat exchanger system is mounted on top of the fireplace  20  and often makes the mantel or top shelf of the fireplace inordinately high and unattractive if it is provided.  
         [0024]    Refer now to FIG. 3 showing a direct vent fireplace  30  adapted to deliver heat from its heat exchanger to a supply duct or return duct of a central heating system for distribution to all rooms or specific rooms in a house. The fireplace  30  is shown comprising an inlet  12 A for supplying fresh air into fresh air passage  24  which extends under floor  25  at burner  26  for burning gases in combustion chamber  13  which surround logs  27 . In the preferred embodiment, the intake air passage  14  and lower passageway  14 A connect into rear heat exchanger passage  23  which connects into upper passageway  15 A for supplying heated room air out of the outlet  15 .  
         [0025]    However, when the system is employed to deliver hot air into duct  28 , damper  29  is opened and hot air can be supplied to the return duct  35 . In the preferred embodiment of the present invention, when heated room air is being supplied via duct  28  into duct  35  the blower motor  32  is not enabled or activated because the return air duct is capable of pulling the air to the central heating system not shown. In the event that the closest duct available is a supply duct, it is necessary to force the air into the supply duct using a forced draft fan  31 .  
         [0026]    The advantage of fireplace  30  is that the blower motor  32  is a very quiet low speed motor and is only used when fireplace  30  is used in its conventional mode to take air in inlet  14  and exhaust heated air out outlet  15 . In all other modes, the motor  32  may be disabled by switches  33  or  33 A. As an alternative, it is possible to connect duct  28  to a direct duct which exits into a remote room having an induced draft fan which is actuated by controller  34 . The controller  34  may actuate the remote controller RC and used to actuate the damper  29 .  
         [0027]    Refer now to FIG. 4 showing a co-linear fireplace  40  having a conventional heat exchanger where the inlets and outlets  14  and  15  are shown and are connected by a passageway like passageway  23  in the rear of the combustion chamber  13 . In this embodiment, a remote blower  37  is shown having an intake pipe  36  connected to an outside source of fresh air which is pumped into the fireplace  40 . The necessary amount of combustion air is supplied by supply pipe  38  and the remainder of the outside fresh air which comprises the make-up air is supplied into the heat exchanger by branch  39 . Thus, the outside fresh air being forced into the heating system is preheated by the heat exchanger and supplied directly into the same room with the heat exchanger. When the fireplace  40  is of sufficient capacity, all of the outside air is heated above room temperature so that the system operates efficiently to preheat the make-up air as well as supply diluted heated room air to the room in which the fireplace  40  is located. In this embodiment, a control  42  in fireplace  40  operates the remote blower motor  37  at a predetermined speed to supply the necessary make-up air into the chamber shown at inlet  14 ,  14 A.  
         [0028]    Refer now to FIG. 5 showing a direct vent fireplace  50  having a supply duct  43  which connects into the heat exchanger of the fireplace  50 . The duct  43  supplies room air at approximately 270 degrees Fahrenheit to the return air plenum or duct  44  which terminates at the central hot air furnace  45 . The furnace  45  is provided with a blower (not shown) and heats the air received and supplies it in the supply duct  46  to the rooms to be heated. An air conditioning coil  47  is shown connected into the supply duct  46 , but is not used during the heat season. After supplying the heated air to the rooms, the individual return ducts from the rooms are connected back into the return air plenum  44  and since there is a negative pressure provided at the central heating system  45  no additional fan is needed to pull this return air back to the central air furnace. The furnace blower is preferably on when fireplace  50  is on.  
         [0029]    In order to supply the necessary make-up air or quality replacement air for the home, a remote air pump  48  is shown connected to an outside source of fresh air. In the preferred embodiment, the remote air pump  48  is located in a basement area. Basement air and the fresh air enter the return  44  and do not overly cool any particular isolated room. In this embodiment, the fresh air in a tight home is circulated through the duct system to the individual rooms and is preheated with the air in the return duct  44 . Further, the outside fresh air that is passed into the room in which the fireplace  50  is located passes through the heat exchanger  14 ,  15  and is heated before it passes into duct  44  and the return air plenum duct  44 . Since the remote air pump  48  can produce a positive pressure in a tightly sealed house, it is preferred that a bleeder  49  be located at an area completely remote from the air pump to relieve this positive pressure inside of the house.  
         [0030]    Refer now to FIG. 6 showing a diagrammatic drawing in elevation of a draft assist or power vent fireplace  60  adapted to use room air for combustion and for dilution of exhaust gases which in turn are passed through a novel heat exchanger. The fireplace  60 , like fireplace  30 , has a heat exchanger with two inlets  14  and  15 . The bottom grill  15  supplies stale room air for combustion in combustion chamber  13  as well as dilution of the exhaust gases. The inlet  14  supplies room air for dilution of the mixed exhaust gases which pass into the exhaust duct  11 B at approximately 270 to 500 degrees Fahrenheit, depending on the amount of excess combustion air and dilution supplied in inlets  14  and  15 . As will be explained later, this amount of dilution may be controlled in a tight house. The exhaust gases in exhaust duct  11 B are cooled to approximately no more than 220 degrees Fahrenheit before being passed into a novel cross flow air-to-air heat exchanger  51 . The arrows in the heat exchanger show the exhaust gases pass diagonally downward into in-line blower  54  and force the cooled exhaust gases out of duct  55  at approximately 118 degrees Fahrenheit. There is shown a fresh air intake duct for outside air  56  supplying air into the heat exchanger  51  via in-line blower  57  which forces the preheated outside air into duct  58  which is connected to the aforementioned plenum  44 A that serves as the supply to the central hot air furnace  45 . The furnace  45  has its own blower and heats the air which is supplied to supply duct  46  through air conditioning coil  47  into the previously explained supply duct  46 . The air conditioning system  53  is shown having a supply S and a return R even though the air conditioning coils  47  are not cooled during the heating season. The novel heat exchanger  51  is preferably made from a high heat conductivity metal such as aluminum and comprises a plurality of spaced plates sealed one from another to permit an efficient cross flow heat exchanger. Such heat exchangers made of aluminum are capable of operation as high 500+ degrees Fahrenheit in the preferred embodiment.  
         [0031]    In this embodiment, a controller  59  preferably is capable of operating the blower motors  57  and  54  at predetermined speeds to achieve predetermined desired cubic foot displacements of make-up air and exhaust air in the system. For example, if motor  54  is run at a slower speed the exhaust gases in exhaust stack  11 B increase in temperature. The exhaust motor  54  only needs to be operated to a speed which exhausts the desired amount of make-up air plus combustion air into the system. Similarly, the blower motor  57  only needs to supply the amount of fresh air needed for combustion and make-up. It is not intended that motors  54  and  57  be operated at variable speeds over a long period of time. It is preferred that the motors be set to operate at desired displacement speeds when the fireplace  13  is on and the blower in central air furnace  45  may be operated independently of the make-up system which passes through the fireplace.  
         [0032]    Refer now to FIG. 7 showing a diagrammatic drawing in elevation of a co-linear fireplace  70  adapted to pass its exhaust gases through the aforementioned novel air-to-air cross flow heat exchanger  51 . When the fireplace  70  is on, it takes outside fresh air in through duct  61  and burns the air in the combustion chamber  13  and passes the undiluted exhaust gas into exhaust duct  11 B at approximately 600 degrees Fahrenheit where it cools on its passageway to the novel cross flow heat exchanger  51 . The exhaust gases pass through the in-line blower  54  and are exhausted through exhaust duct  55  to the outside. In this embodiment, the blower  57  sucks in air from the house at 60 to 80 degrees Fahrenheit and passes it into the return duct  58  after being preheated in the heat exchanger  51 . The preheated house air is passed into the central hot air furnace  45  where it is heated again and forced into the supply duct  46  by air conditioning coils  47  and into the rooms.  
         [0033]    In the preferred embodiment of this invention, it may be possible to control the blower motor  57  in a manner where it creates a negative pressure in a room or area in which it is located so that either the bleeder  49  or leaks in a loose house supply the sufficient make-up air desired for air quality. However, if the house is new and of tight construction it could be necessary to place a remote heat pump in the system as shown and described in FIGS. 4 and 5 in order to supply the deficiency of make-up air for quality air conditions. Blower  54  acts to induce outside combustion air into combustion chamber  13 .  
         [0034]    Having explained a preferred embodiment of the present invention and modifications thereof, it will be understood that presently designed and manufactured high production fireplaces may be coupled into existing heating systems in homes that have forced air furnaces so as to create not only an efficient heating system, but a system which supplies make-up air for a quality air system in a very efficient manner. The preferred embodiment of the present invention is provided with variable speed motors and controls which allow the installers of such systems to use universal equipment to achieve precise and exacting predetermined standards for different types of houses made to different tightnesses and specifications. Thus, the present invention permits a builder of houses to select universal components that are produced at high efficiency and low cost for installation without having to engineer and manufacture a custom system.  
         [0035]    Having explained the problem of maintaining heat efficiency in tight houses having hot air fireplaces and hot air furnaces, it will be appreciated that the introduction of a required amount of cold outside air to maintain air-quality can decidedly reduce the heat efficiency of the fireplace and/or the heating system. Accordingly, there is provided a high efficiency heat exchange system that preheats the fresh air using the hot exhaust gas from a gas fireplace and/or the fireplace heat exchanger is employed to preheat the air without unbalancing the temperature of the rooms or the system. The outside fresh is preheated in a manner which will permit easy modification of existing fireplace/furnace systems as well as the installation of the present novel system in new homes.

Technology Classification (CPC): 8