Patent Publication Number: US-6334411-B1

Title: High efficiency, glass-lined, combination space and hot water heater

Description:
TECHNICAL FIELD 
     The present invention relates to a high efficiency glass-lined combination space and hot water heater provided with a closed circulating circuit through which a predetermined volume of water is circulated and maintained within the tank. The combination heater of the present invention substantially prevents the build-up of deposits and corrosion. Accordingly, a high constant efficiency heater is achieved and the life expectancy of the heater is substantially prolonged. The hot water heater of the present invention provides both space heating and potable domestic hot water. 
     BACKGROUND ART 
     Indirect water heaters are well known in the art wherein a coil is placed within a hot water tank to which city water is fed at one end of the coil and exits at the other end to feed a domestic hot water supply. The hot water within the tank is also fed city water which is heated and used for domestic application such as washing or bathing, whereas the water within the coil is used for consumption or other specific applications such as for heating baseboards connected to a water convection circuit. With glass-lined water heaters which are continuously fed city water, the reservoir and heating coil is continuously bombarded with deposits including calcium, silicas, silts and ferrous materials. This causes several problems such as the formation of bacteria within the coil of the radiators when the water is stagnant therein. In radiators, the water could be stagnant for long periods of time as these are not utilized during the summer months. Accordingly, bacteria will build up during the hot summer months and when the system is placed back in use, these bacterias are flushed back into the tank. If the water within the tank is utilized for bathing or other use where the human body is in contact with such water, then this contaminated water could inflict serious disease to the user. Legionella is known to occur if stagnant water is mixed with potable water. This can occur in summer months when water is stagnant in old casted water heaters which are disposed in hot rooms and exposed to direct sunlight. If such stagnant water is mixed with potable water it could prove deadly to human beings. This risk is amplified if the city water does not contain the proper quantity of chlorine. A further disadvantage is that the build-up of calcium on the glass-lined surface as well as the heat transfer surface and coils greatly affects the efficiency of the heater. 
     U.S. Pat. No. 5,165,472 describes a heat exchanger having fluid injectors therein to maintain the hot water in continuous agitation and this has been found suitable to prevent the formation of deposits on the glass lining of the tank as well as on the heat transfer coils. However, because the system is fed fresh water, deposits and water contamination problems will occur in the heating radiators. The patent is more concerned with the elimination of dead zones or dead spots which cause sediment deposits. A further disadvantage is that these systems corrode the copper pipes due to the use of acid water which contains CO2 and these copper pipes can deteriorate within short periods of time such as five years. Accordingly, such heaters cannot be adapted to old radiator systems which are more fragile and which require hot water in the range of 190° F.-200° F. 
     Combination water heating and space heating apparatus utilizing the hot water from the same tank is described in U.S. Pat. No. 5,544,645. As described the water heating unit and the space heating unit are coordinately controlled such that priority is given to the potable hot water supply over space heating in the event that sufficient hot water is not available to satisfy both demands. Accordingly, all of the above-mentioned disadvantages of the prior art are exemplified by this type of apparatus. A still further example of a combination water heating and space heating apparatus is described in U.S. Pat. No. 4,222,350. 
     SUMMARY OF INVENTION 
     It is a feature of the present invention to provide a high efficiency, glass-lined, combination space and hot water heater which substantially overcomes the above-mentioned disadvantages of the prior art and wherein life-expectancy is greatly improved. 
     Another feature of the present invention is to provide a high efficiency, glass-lined, combination space and hot water heater having a closed water circulating circuit connected to radiators for producing heat and wherein the water consists of a predetermined volume which is continuously circulated during use and wherein the water is substantially free of sedimentary, corrosive and other harmful products. 
     Another feature of the present invention is to provide a high efficiency, glass-lined, combination space and hot water heater having one or more heat exchange coils therein in contact with the hot water for producing domestic hot water independently of the water circulated in the closed circuit. 
     Another feature of the present invention is to provide a high efficiency, glass-lined combination space and hot water heater providing substantially unobstructed heat transfer and having a longer life expectancy than prior art water heaters for such use. 
     According to the above features, from a broad aspect, the present invention provides a high efficiency, glass-lined, combination space and hot water heater which comprises an inner tank. An outer casing is spaced about the inner tank and insulation is provided between the outer casing and the inner tank. The inner tank has a glass-lined inner surface. Heater means is provided for heating a predetermined volume of water within the inner tank. An anode extends within the inner tank. A closed water circulating circuit is connected to the inner tank for circulating hot water from the inner tank. Heat exchange means is connected in the closed water circulating circuit. A pump is connected to the closed water circulating circuit for convecting hot water from the inner tank through the heat exchange means. The predetermined volume of recirculating water provides for minimal deposits to accumulate in the inner tank thereby substantially preventing the build-up of deposits on heat exchange elements within the tank and the formation of harmful bacteria and corrosion and further wherein high constant efficiency is achieved and the life expectancy of the hot water heater is substantially prolonged. At least one heat exchange coil is disposed in the inner tank and immersed in the water contained therein. The heat exchange coil is connected at one end to an outlet coupling to which a domestic hot water line is connected. An opposed end of the heat exchange coil is connected to an inlet coupling. The inlet coupling is connected to a pressurized water supply. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     A preferred embodiment of the present invention will now be described with reference to the examples thereof as illustrated in the accompanying drawings in which: 
     FIG. 1 is a cross-sectional schematic view of a high efficiency, glass-lined, combination space and hot water heater using a gas or oil burner and constructed in accordance with the present invention and connected to a closed loop water circulating circuit and illustrating the optional use of one or more heat exchange coils provided in the inner tank to supply hot domestic water; 
     FIG. 2 is a section view showing the disposition of the one or more heat exchange coils; 
     FIG. 3 is another cross-sectional schematic view of a high efficiency, glass-lined, combination space and hot water heater constructed in accordance with the present invention and wherein the heating means is constituted by electric resistive elements; 
     FIG. 4 is a fragmented perspective view showing an agitating conduit disposed adjacent the bottom wall of the water heater for agitating the hot water therein; and 
     FIG. 5 is a section view illustrating a still further embodiment of the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings and more particularly to FIG. 1, there is shown generally at  10  one example of a high efficiency, glass-lined, combination space and hot water heater constructed in accordance with the present invention. It consists essentially of an inner tank  11  having a cylindrical side wall  12 , a top wall  13  and a bottom wall  14 . A combustion chamber  15  is provided below the bottom wall. A gas or oil burner  16  is connected to the side wall and has a combustion nozzle  17  extending within the combustion chamber  15  to produce a flame  18  therein to provide a heat source to heat the same predetermined volume of water  19  contained within the inner casing  12 . The tank  11  is not continuously fed by the city water supply and accordingly does not use fresh water which contains sedimentary particles. 
     An outer casing  20  is secured about the inner casing  11  and an insulating material, such as wool or foam insulation  21  is disposed between the outer wall of the inner tank and the inner surface of the outer casing. An anode  22  is secured in the inner casing and extends within the inner chamber  22  in contact with the water  19  contained therein, to protect the tank from the corrosive effects of hot water, as is well known in the art. 
     As hereinshown a flue pipe  23  extends from the combustion chamber  15  and exits through the top wall  13  of the tank to release products of combustion into outside atmosphere. The inner side wall as well as the inner surface of the bottom wall  14  of the tank are lined with a glass lining  24 , as is also well known in the art. The flue pipe  23  also has a glass lining  24  thereabout and the top wall  13  may also be glass-lined. As hereinshown the same predetermined volume of water  19  within the inner chamber  22  is heated by heat transfer between the bottom wall  14  and the cylindrical side wall  26  of the flue pipe  23 . 
     A low-pressure closed water circulating circuit  27  operating within the range of from about 5 to 35 psi is connected to the inner tank  11  and it consists of a conduit  28  usually constituted by copper piping connected to an outlet coupling  29 . One or more heat exchange means, herein baseboard heaters or radiators  30 , are secured to the closed circuit either in series, as hereinshown, or in parallel, so that the hot water from the inner chamber  22  of the inner tank is convected therethrough to generate heat to warm a space. A pump  31  circulates the water within the closed water circulating circuit  27  with the return conduit  28 ′ being connected to the inlet coupling  32 . 
     It is important to note that the inner chamber  22  contains the same predetermined volume of water which is continuously heated and recirculated. Therefore, fresh water is not continuously added to the inner tank. The advantage of this is that a predetermined small volume of deposits will take place when the heater is initially placed in use and small deposit only may accumulate in the corners  33  between the cylindrical side wall  12  of the inner tank and the bottom wall  14  and will substantially not interfere with the heat transfer surfaces. If fresh water was admitted in the inner tank the sedimentary deposits would continue to build up over the bottom wall and greatly reduce the efficiency of this heat transfer. Also, hard fresh water is known to have sedimentary material such as calcium, silicas, silts and ferrous materials and some of these products cause oxidation of exposed metal even through a pin hole in the glass lining. The anode  22  substantially reduces this corrosive effect but seeing that the volume of water is always the same volume, it cleanses itself and the chance of corrosion taking place is practically eliminated. Also, if harmful bacteria was to originate in the radiators  30  during stagnant periods, these bacterias would have no effect on the potable heated water which is not mixed with the volume of water in the tank. Usually, known combo systems have a life expenctancy of 5-6 years whereas with the present invention the life expectancy is extended to about from 25-35 years. 
     In the specific embodiment as shown in FIG. 1, domestic hot water is supplied by providing one or more, herein four, heat exchange coils  40  as shown in FIGS. 1 and 2. These heat exchange coils are immersed in the predetermined volume of hot water contained within the inner chamber  22 . The coils  40  are connected at one end, herein  41 , to an outlet coupling  42  to which a domestic hot water line  43  is connected. An inlet coupling  44 , to which an opposed end  45  of the heat exchange coils  40  is connected, supplies pressurized water from the city supply conduit  46  which is pressured at about 65 psi. Because of the use of the same predetermined volume of hot water, there will not be any build-up of deposits on the heat exchange coils  40  and substantially 100% heat transfer is achieved. This permits for a supply of hot domestic water at a constant temperature and at high efficiency per b.t.u. Accordingly, the hot water heater of the present invention can be adapted to old steel-casted radiators where there is a need to supply hot water at constant high temperatures in the range of from about 190° to 200° F. If one of the coils was to puncture, then the potable water would flow into the tank due to the difference in pressure. This would cause the relief valve of the tank to release water indication that a coil is defective and the coil assembly would be changed or else the combo unit replaced if it has been in operation up to its life expectancy. 
     FIG. 3 illustrates a further embodiment of the high efficiency, glass-lined hot water heater  10 ′ of the present invention. As hereinshown, the heat source is provided by one or more, herein four, electric resistive heating elements  50  extending within the inner chamber  22 ′ of the inner tank  11 ′. Although not shown the inner tank is protected by an outer casing and insulation as shown in FIG.  1 . The closed water circulating circuit  27 ′ is similarly connected to the inner chamber  22 ′ of the inner tank  11 ′ as with the embodiment described in FIG. 1. A plurality of heat exchange coils  40 ′ may also be conveniently disposed within the inner chamber  22 ′ to feed the domestic hot water supply line  43 ′. 
     If desirable to enhance heat transfer, there may be provided at the bottom of the inner tank  11  or  11 ′ an agitating means in the form of a partly circular conduit-like chamber  55  provided with orifices  56  therein oriented at predetermined angles to agitate the water within the inner chamber  22  or  22 ′. This agitating chamber would be connected to the return line  28 ′ of the closed water circulating circuit  27  as shown in FIG. 1. A similar agitating means is described in U.S. Pat. No. 5,165,472 referred to hereinabove and is shown herein as an auxiliary or optional device that may be connected at the base of the inner tank to obtain some of the benefits as described in the aforesaid patent. 
     Referring to FIG. 5 there is shown a still further embodiment of the high efficiency combination space and hot water heater of the present invention and generally indicated by reference numeral  10 ″. As hereinshown the water heater is a gas heater provided with a combustion chamber  60  at the base thereof adjacent the bottom wall  61  whereby to provide heat to heat the water contained within the inner tank  11 ″. A heat exchange coil  62  is wound along a major portion of the flue pipe  63  and has an inlet end  62 ′ and an outlet end  62 ″ exiting from the top of the tank. The inlet end  62 ′ connects to the base portion of the heat exchange coil  62  so that the potable water as it enters the coil is heated as it is convected spirally from the base of the hot water heater to the top portion of the hot water heater. 
     A tubular sleeve  64  is formed about at least a major portion of the heat exchange coil  62  and spaced from the flue pipe  63  to define an annular jacket about the flue pipe to retain heat, thus acting as a super heater. The base of the tubular sleeve  64  is provided with a skirt portion  65  which is spaced above the bottom wall  61  to channel the water heated against the bottom wall  61  into the annular jacket. The tubular sleeve  64  is spaced a predetermined distance to provide for the water to shoot up into this annular jacket, thus providing an upward convection of hot water from the bottom wall  61  to the top portion  66  of the inner tank  11 ″. The water temperature at the bottom portion of the tank is at about 140° F. and at the top it rises to about 175° F. 
     As hereinshown a further spiral heat exchange coil  67  can be supported horizontally in the top portion  66  of the inner tank  11 ″ and connected to the inlet and outlet pipes  62 ′ and  62 ″ whereby to extract further heat from the hot water within the tank and particularly in the top portion  66  where the water is hotter than in the bottom section when the closed water circulating circuit  27  is not in use. When the pump  31  is operated to circulate hot water through the closed circulating circuit, then the water temperature in the tank is fairly constant throughout the tank. 
     The inlet coupling  32 ′ connected to the inner tank could also be located in a lower portion as indicated by reference numeral  68  and have an extension pipe  69  extending within the inner tank  11 ′ and directly under the annular skirt  65  so that the cooled return water from the closed circuit can be warmed quickly as it moves up into the annular jacket where it is superheated. 
     This particular embodiment as shown in FIG. 5 for use with gas or oil burners has been found to be extremely efficient as a combination space and hot water heater. 
     Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.