Abstract:
A fireplace apparatus for a building includes a firebox, and a plenum arranged with an exterior surface of the firebox. A blower is arranged with the plenum to force air through the plenum and a plenum exhaust vent is configured to release the forced air from the plenum. A method of pre-heating air for a building fireplace includes selecting air admitted from inside the building through an interior inlet port into a manifold and through a plenum until the firebox reaches a selected temperature, and selecting air admitted from outside the building through an exterior inlet port into the manifold and through the plenum when the firebox reaches or exceeds the selected temperature.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/597,511, entitled “X-VENT,” filed on Feb. 10, 2012, which is expressly incorporated by reference herein in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates generally to fireplaces. More particularly, the disclosure relates to heated airflow for wood burning, gas, ethanol, vent free fireplaces, and the like. 
       BACKGROUND  
       [0003]    Generally, modern domestic fireplaces provide a relaxing ambiance. More practically, fireplaces provide warmth to a home by means of radiant heat generated by the fire, but require a large supply of combustion air for this function. In a wood burning fireplace, for example (but not so limited) the fire is contained in a firebox. A chimney or flue allows exhaust gases and smoke to escape. The fireplace may have a foundation, the firebox, a hearth, a mantel, an ash dump door, a damper, a flue, a crown, a spark arrestor, and other ornamental and operational elements. 
         [0004]    The heating efficiency of fireplaces may depend at least on structural materials and design for efficient radiation of heat. Radiant energy may be absorbed by interior surfaces of the room containing the fireplace, as well as the air within the immediate room and throughout the home structure. In a wood burning fireplace, depending on the fuel load and type of wood, about 150 cubic feet of air for each pound of wood consumed is required. This air is typically provided through the front of the hearth opening from the home. This air is heated by the fire and may generally exhaust through the flue up the chimney, thus wasting its energy content. To replace this air outside air will infiltrate through windows and doors due to a negative pressure, forcing colder air into the home. It is not a coincidence that people are drawn to gather around a fireplace for warmth, rather than at a distance, such as near doors or windows. This outside air may be 40° F. or more below inside air depending on the outside air temperature. This replacement of house air with colder outside air can result in a negative heating value of a traditional wood burning (or other fuel type) fireplace. There is a need, therefore, to provide radiant heating to house air while minimizing air replacement with colder outside air. 
       SUMMARY 
       [0005]    In an aspect of the disclosure, a fireplace system for a building includes a firebox, and a plenum arranged with an exterior surface of the firebox. A blower is arranged with the plenum to force air through the plenum and a plenum exhaust vent is configured to release the forced air from the plenum. 
         [0006]    In a further aspect of the disclosure, a method of pre-heating air for a building fireplace includes heating a firebox in the fireplace using at least one of wood, ethanol and gas. Air is admitted to a plenum surrounding the firebox for heating by the firebox. The heated air in the plenum is then exhausted into the building. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a conceptual side-view cross-section illustrating an example of a fireplace with a plenum system in accordance with an embodiment of the disclosure. 
           [0008]      FIG. 2  is a conceptual front view illustrating the fireplace of  FIG. 1 , according to an embodiment of the disclosure. 
           [0009]      FIG. 3  is an illustration of a method of warming outside air using the fireplace of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Various concepts will now be presented with reference to a wood burning fireplace plenum system for warming outside air drawn by a blower and warmed by thermal contact with the fireplace inner firebox. However, the concepts may also apply to gas, ethanol and other fuel types. In the following description of preferred embodiments of the present invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
         [0011]    The detailed description set forth below in connection with the accompanying drawings is intended as a description of various embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the invention. 
         [0012]    Various embodiments of an X-Vent system fireplace for replacing house air exhausted up the chimney will now be presented. In one embodiment, an X-Vent system fireplace allows the flow of outside air drawn through a plenum system in contact with the firebox. This heats the outside air and may provide up to a 75° F. temperature rise once the firebox metal components reach a sufficient temperature. This temperature may be established by burning wood, gas, ethanol or other fuel, and may be generally met within one hour of initial startup. The X-Vent system fireplace may include a blower system that may provide about 3,000 cubic feet of air per hour pre-heated to or above the inside house temperature. This not only replaces the air lost up the chimney, but replaces it with warmer air than would normally be drawn through window and door gaps through the negative pressure effect created with conventional fireplaces that lack the plenum and blower disclosed herein. The net result may be an improved warming rate, for example 4-5° F. per hour rise in the house air temperature, depending on the size of the home, the temperature difference between the inside and outside temperature, the size of the fire and the air transport rate. Since these factors are not standardized, this embodiment is described in the context of a 3,000 square foot home, a 40° F. temperature difference between the inside and outside temperature and a fuel load of 15 pounds of wood per hour as the fuel load. 
         [0013]      FIG. 1  illustrates a conceptual side-view cross-section representation of an example of an 
         [0014]    X-Vent fireplace  100 .  FIG. 2  illustrates a conceptual front view of the X-Vent fireplace  100  of  FIG. 1 . The fireplace  100  includes an inner firebox  16  including a floor, side walls, a back wall, a ceiling, and having a front opening  26  and a flue  36  to vent burning fumes from wood, gas, ethanol and the like, hot air and flying ash up a chimney (not shown), where a spark arrestor (not shown) limits fire hazard due to flying hot ash. The floor, side walls, back wall, and ceiling create the front opening through which a flame from burning wood (or, e.g., gas fired artificial logs, ethanol, etc.) within the firebox  100  may be viewed. The floor, side walls, back wall, and/or ceiling may be made of metal, cement panels or masonry products or any combination of these or equivalent non-flammable materials. Preferably, the inner firebox  16  is constructed of metal or other high thermal conductivity material. 
         [0015]    The front opening  26  of the fireplace  100  may be covered with a transparent plate, such as glass or screen mesh, or an equivalent to allow radiant heat to project into the room, while preventing sparks, glowing embers or hot ash from being ejected from the firebox  16 . 
         [0016]    The X-Vent fireplace  100  may have a selector switch  3  that will allow air flow  1  from the inside of the home through an interior inlet port  11 , or allow air flow  2  selected from outside the home through an exterior inlet port  12 . In general the position of the selector switch  3  will be chosen to allow inside air to flow through a plenum  6  until the inner firebox  16  of the fireplace  100  has heated to provide a temperature rise adequate to cause outside air to be heated above the inside air temperature before passing into the room through a plenum exhaust vent  7 . Alternatively, the selector switch  3  may be set to admit outside air to the plenum  6  when a fire is initiated, and then set to admit inside air when the fireplace is not in use. 
         [0017]    Once the selection is made, air will be drawn into a manifold  5  where a blower  4  forces this air supply into the plenum  6  to travel around the exterior of the walls of the inner firebox  16 . The plenum  6  may provide a path several feet in length for air to flow to come in contact with the wall of the inner firebox  16 . This plenum  6  may have a channel depth of approximately one inch to insure adequate heat transfer from the inner firebox  16  to the air supply. The air may be moved, for example, at approximately 275 feet per minute, however, the depth dimension may be greater or smaller, and the velocity of air motion may be greater or smaller, depending on various parameters that may include, the volume of home space to be heated, the dimensions of the firebox  16 , the rate at which the temperature of the heated space is desired to rise, size and power rating of the blower  4 , and the differential between inside and outside air temperature. The plenum exhaust vent  7  may be located on one or more sides of the opening  26  of the inner firebox  16  so it does not draw flue products into the home by static pressure created by its velocity. 
         [0018]    The air supply selector  3  can operate manually, by a remote control, or by a thermostat control. In addition the blower  4  can also be operated by the same options, and the blower  4  may also be powered by AC (house) current or by batteries. 
         [0019]    In an aspect of the disclosure,  FIG. 3  illustrates a method  300  of pre-heating air from outside a home, including enabling a lit wood, ethanol or gas burning fireplace to reach a sufficient temperature above a desired interior temperature (block  301 ), where the fireplace includes an inner firebox burning wood (or gas, ethanol, etc.) with a plenum in contact with the exterior walls of the firebox. A selector  3  in a first position (block  302 ) blocks outside air and admits inside air if the firebox has not reached sufficient temperature. Air from inside the home may be circulated (block  303 ) by a blower  4  through the plenum  6  in contact with the firebox  16  by action of the selector switch  3  to heat the inside air while the selector switch  3  is in a first position. If the firebox  16  has reached a sufficient temperature (block  304 ), the selector switch  3  is placed in a second position (block  305 ) to block inside air and admit outside air that is circulated by the blower  4  through the plenum  6  to heat the inside air while the selector  3  is in the second position. With the selector in either first or second position, heated air is circulated around the firebox through the plenum  6  and forced through plenum exhausts  7  to be expelled into the room and/or building heated by the fireplace. 
         [0020]    The selector switch  3  and blower  4  may each be controlled by one or more of a thermostat, a remote controller and manual switches. The blower  4  may be further controlled by a variable speed control device, which may be automatically (e.g., thermostatically), remotely and/or manually adjusted. 
         [0021]    It may be readily appreciated that the preheating of air obtained through the interior inlet port  1  during warm-up of the firebox  16  will increase the rate at which heated air is provided from the plenum exhaust vent  7  because the temperature differential between interior air and the firebox  16  is less than the temperature differential between exterior air and the firebox. Furthermore, it may be readily appreciated that air obtained from outside the home through the exterior inlet  12 , when the firebox  16  is at operating temperature, reduces or eliminates an airflow that may occur due to negative pressure with conventional fireplaces that cause colder exterior air to be drawn into the home through small openings around doors and windows, and the like. Thus, the fireplace heats interior air that has already been heated, and functions more efficiently by heated air that is warmer than if colder exterior air drawn in through small openings must be heated over a greater differential temperature to reach a desired room temperature. 
         [0022]    The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”