The present invention generally relates to fuel-fired liquid heating apparatus and, in a representatively illustrated embodiment thereof, more particularly provides a fuel-fired water heater having disposed in a combustion chamber portion thereof specially designed heat concentration apparatus operative to reduce standby heat losses and thereby improve overall efficiency of the water heater by concentrating the heat of a standing pilot flame on an underside portion of the bottom wall of the storage tank portion of the water heater. According to a further aspect of the invention, the overall efficiency of the water heater may also be increased by the use and a unique control of a dual input standing pilot burner.
In previously proposed fuel-fired water heater designs, the water heater has, within its combustion chamber, a pilot burner operative to maintain a standing pilot flame during “standby” periods of the water heater in which its main burner is not being fired. The heat from the standing pilot flame may simply escape through the vertical flue of the water heater without adding appreciable heat to water stored in the tank portion of the water which overlies the combustion chamber, or sometimes overheat the tank water during standby periods. From an operational standpoint, neither of these conditions is ideal.
It would accordingly be desirable to provide an improved water heater pilot burner system that addresses these conditions. It is to this goal that the present invention is primarily directed.
In carrying out principles of the present invention, in accordance with a representatively illustrated embodiment thereof, fuel-fired liquid heating apparatus is provided. Illustratively, the apparatus is a fuel-fired water heater having a tank for holding a quantity of water to be heated, the tank having a bottom wall or head portion. A combustion chamber is disposed beneath and upwardly bounded by the bottom wall, and a flue communicates with the combustion chamber, via an open lower end of the flue, and extends upwardly from the bottom tank wall through the interior of the tank. The water heater is provided with fuel-fired combustion apparatus operative to create within the combustion chamber hot combustion products which flow upwardly through the flue and transfer heat therethrough to water stored in the tank. The combustion apparatus representatively comprises a main fuel burner disposed within the combustion chamber in an underlying relationship with the open lower end of the flue, the main fuel burner having a peripheral, horizontally facing side edge.
Also forming a portion of the overall combustion apparatus is a specially designed pilot burner system which embodies principles of the present invention and representatively comprises a pilot fuel burner and a heat concentrating structure. The pilot fuel burner is disposed within the combustion chamber and is operative to create within the combustion chamber, during standby periods of the water heater, a standing pilot flame underlying a bottom surface portion of the bottom tank wall horizontally offset from the open bottom end of the flue. The heat concentrating structure is interposed between the pilot fuel burner and the bottom surface portion of the bottom tank wall, and has a generally vertical, open-ended passage extending therethrough and being operative to upwardly receive the standing pilot flame and concentrate its heat on the bottom surface portion of the bottom wall of the tank. In this manner, instead of merely passing upwardly through the flue, the heat of the standing pilot flame is more efficiently utilized to heat the tank water during standby periods of the water heater.
Preferably, the heat concentrating structure is a generally vertically oriented tube member downwardly offset from the bottom surface portion of the bottom tank wall. According to various aspects of the present invention, the tube member may illustratively have a downwardly and horizontally outwardly flared bottom end portion with a side cutout area extending upwardly the bottom end edge of the tube member and disposed in a facing, horizontally adjacent relationship with the main burner peripheral edge to facilitate pilot flame lighting of the main burner.
In a representatively illustrated alternate embodiment of the water heater, the main burner, the pilot burner and the tube member are carried on a section of a main burner fuel supply line which is inwardly insertable through a combustion chamber side wall opening to operatively position the main burner, pilot burner and tube member within the combustion chamber. The tube member is pivotally supported on the fuel supply line section for pivotal movement relative thereto between a generally horizontal installation orientation, facilitating passage of the tube member through the combustion chamber side wall opening, and a generally vertical orientation to which the tube member may be moved after it is positioned within the combustion chamber. A detent structure is preferably provided for releasably locking the inserted tube member in its generally vertical operating orientation within the combustion chamber.
According to a further aspect of the invention, which may be used in conjunction with or in place of the aforementioned heat concentrating structure, an improved standing pilot burner system is provided that increases the efficiency of a fuel-fired water heater in which it is incorporated. The standing pilot burner has dual firing rates—a high firing and a low firing rate. Four representative modes of controlling the dual firing rate pilot burner are provided. In all four modes, during periods that the main burner is operating in response to a demand for heat the pilot burner is set to its high firing rate, and when the main burner shuts off in response to satisfaction of the heat demand the pilot burner is set to its low firing rate.
In the first mode the pilot burner is maintained at its low firing rate during the entire standby period, and is returned to its high firing rate in response to the next heat demand. In the second mode, the pilot burner is reset from its high firing rate to its low firing rate at the onset of a standby period, but is returned to its high firing rate during portions of such standby period in which the sensed tank water temperature is less than the water heating set point temperature by a predetermined amount. In the third mode, the pilot burner is reset from its high firing rate to its low firing rate at the onset of a standby period, but is returned to its high firing rate during the standby period in response to a sensed predetermined rate of decrease in tank water temperature. In the fourth mode, the pilot burner is reset from its high firing rate to its low firing rate at the onset of a standby period, but is returned to its high firing rate during the standby period after being at its low firing rate for a predetermined time during such standby period.
The present invention generally relates to better utilization of energy available to a fuel-fired water heater and, in a representative embodiment thereof provides an improved pilot burner system 10 for a fuel-fired liquid heating apparatus which is representatively a gas-fired water heater 12. Water heater 12 includes an insulated tank 14 having a bottom wall or head 16, a cold water inlet fitting 18 and a hot water outlet fitting 20. Tank 14 is adapted to hold a quantity of water 22 to be heated. The bottom head 16 overlies a combustion chamber 24 in which a main gas burner 26 is operatively disposed. Main gas burner 26, which, along with the pilot burner system 10, forms a part of a fuel-fired combustion apparatus portion of the water heater 12, underlies the open bottom end of a flue pipe 28 which communicates with the interior of the combustion chamber 24 and extends from the bottom head 16 upwardly through a central portion of the tank 14.
The main burner 26 is supplied with gas from a source thereof, such as a main supply line 30, via a conventional gas valve and control 32 coupled to the main burner 26 by a gas supply line 34 having a main gas valve 34a therein. Gas valve and control 32 senses the temperature of the water 22 in the tank 14 by means of a sensing element 36 extending into the tank interior. Firing of the main burner 26 creates a main burner flame 38 which, in turn, creates hot combustion gases 40 that flow upwardly through the flue 28 and transfer heat therethrough to the tank water 22.
Pilot system 10 is a standing pilot system including a pilot burner 42 disposed within the combustion chamber 24 adjacent the main burner 26 and supplied with gas via a supply line 44 interconnected between the pilot burner 42 and the gas valve and control 32 and having a pilot gas valve 44a therein. During “standby” periods of the water heater 12 (i.e., periods when the main burner 26 is not being fired), the pilot burner 42 continues to generate the indicated pilot flame 46 within the combustion chamber 24, the pilot flame 46 being used to ignite the main burner 26 when the gas valve and control 32 supplies gas to it the next time the main burner needs to be fired.
In many conventional standing pilot systems, most of the heat from the standing pilot flame 46 simply goes up the flue 28 without adding appreciable heat to the tank water 22. However, in the standing pilot burner system 10 of the present invention, this waste of standby pilot flame heat is reduced by the provision within the combustion chamber 24 of a heat concentrating structure representatively in the form of a generally vertically oriented tube member 48 having an open upper end 50 positioned downwardly adjacent the bottom head 16, and a downwardly and horizontally outwardly flared open lower end 52 disposed above the standing pilot flame 46.
Representatively, but not by way of limitation, the upper end 50 of the tube member 48 is downwardly offset from the tank bottom wall 16 by a distance D of about 0.5 inches, and the flare angle of the lower tube end is approximately 10 degrees. The length and diameter of the non-flared upper body portion of the tube member 48 may be varied as necessary to suit the configuration of the combustion chamber 24 and the vertical location of the pilot burner 42.
During standby periods of the water heater 12, substantially all of the heat of the pilot flame 46 is funneled upwardly through the tube 48 and, as indicated by the arrow 54, is transferred to and concentrated on the bottom surface of an overlying portion 16a of the bottom head 16 instead of simply flowing upwardly through the flue 28 and essentially being wasted. In this manner, the heat of the standing pilot flame 46 is more efficiently transferred to the tank water 22 through the bottom head 16, thereby better utilizing the energy available from the pilot flame 46. Depending on the design parameters of the water heater 12, the firing rate of the pilot burner 42 may be appropriately selected so that the heat its flame 46 transfers to the bottom head 16 during standby periods is insufficient to cause overheating of the tank water 22.
As best illustrated in
Extending downwardly from a bottom wall 60 of the combustion chamber 24 is a circular skirt wall 62 that rests on a horizontal support surface, such as the illustrated floor 64. A circumferentially spaced series of combustion air inlet openings 66 extend through the skirt wall 62 into an air inlet plenum 68 that it horizontally bounds. An air transfer opening 70 formed in the bottom combustion chamber wall 60 communicates the plenum 68 with the interior 72 of a raised platform structure 74 disposed within the combustion chamber 24 and extending upwardly from the bottom combustion chamber wall 60 beneath the main burner 26. Platform structure 74 has a top side wall 76 disposed directly beneath the main burner 26 and having a generally diamond-shaped air supply opening 78 formed therein.
During firing of the water heater 12 (as well as during standby periods in which only the pilot burner 42 is being operated), combustion air 80 from outside the water heater 12 sequentially flows inwardly through the skirt air openings 66 into the plenum 68, and then upwardly through the openings 70 and 78 into the combustion chamber 24 for delivery to the burners 26,42.
Representatively, the pilot burner 42 is operatively supported within the combustion chamber 24 by a bracket 82 secured to the main burner gas supply line 34, and the tube 48 is operatively supported within the combustion chamber 24 by a bracket 84 secured to the top side wall 76 of the platform structure 74. However, as will be readily appreciated by those of skill in this particular art, a variety of alternative supporting structures could be employed if desired to operatively secure these components within the combustion chamber 24.
As previously described, the tube member 48 functions as a heat concentrating structure for receiving pilot flame heat and concentrating it on a bottom surface of a portion 16a of the bottom head or wall 16 of the tank 14. Tube member 48 additionally helps to stabilize the pilot flame 46 and shield it from condensate which may drip from the underside of the bottom tank wall 16. While the heat concentrating structure has been illustratively depicted as having a tubular configuration, it will be readily appreciated by those of skill in this particular art that it could have a different configuration, if desired, without departing from principles of the present invention. Moreover, while the present invention has been representatively illustrated and described herein as being utilized in conjunction with a fuel-fired water heater, it will readily be appreciated by those of skill in this particular art that it could alternatively be utilized in conjunction with other types of fuel-fired heating apparatus without departing from principles of the present invention.
With reference now to
In order to facilitate the inward installation insertion of the burner assembly 86 through the combustion chamber side wall opening 90, the heat concentrating tube 48 may be mounted on the main burner gas supply line 34, in a subsequently described manner, for pivotal movement relative thereto between a downwardly pivoted horizontal installation position (see
In the alternate burner assembly embodiment 86 shown in
As can be seen in
As illustrated in
According to a further aspect of the present invention, which may be utilized with or in place of the previously described heat concentrating structure, the standing pilot burner 42 is of a dual input type having a low firing rate and a high firing rate depending on the degree of opening of the previously mentioned pilot gas valve 44a (see
Utilizing the control algorithm of the first operating mode, shown in
Steps 112-124 in the second through fourth representative operating modes of the control algorithm depicted in
Specifically, in step 128 of the second representative control algorithm mode shown in
The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.