Abstract:
There is provided a water heating and storage system, including a heat-insulated main heated water storage tank for storing hot water. The storage tank consists of top, side and bottom walls, has an inlet for heated water entering the tank at a level below the normal level, and a cold water inlet. The system also includes a consumer hot water outlet, and an external water heater having a controlled electrical heating unit, an outlet port for heated water, connectable to the inlet of the tank, and a water inlet port.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a water heater. More particularly, the invention provides a water heating system including an improved electrically-powered water heater and a storage tank. 
   BACKGROUND OF THE INVENTION 
   Conventional solar water heater systems are usually comprised of a solar panel connected by pipes to a hot water storage tank for thermosyphonic circulation of water. The system has been proven to be simple to use and to be an impressive energy-saving device. In cold, cloudy weather, hot water is obtained by actuation of an electric heating element contained in the storage tank. 
   The main drawbacks of existing systems concern maintenance. The present arrangement is that at the base of the cylindrical insulated storage tank there is an opening of about 20 cm diameter which is closed by a flange held tightly by nuts, which in turn, are engaged with a set of firmly welded-on threaded studs. In the common vertical-axis tank, the flange is disposed at the bottom face of the tank. The flange supports the electric heater element and a thermostat, both of which project into the water storage tank. The joint between the flange and the opening is a well-known region for the start of corrosion and eventual leakage. Maintenance activities such as cleaning of built-up scale and accessing the electrical connections in the available restricted space are difficult, and are all the more difficult for changing the flange and/or thermostat, since before any action is possible, all the contents of the storage tank must be drained out, thereby wasting between tens and hundreds of liters of water. Thus, a simple maintenance task such as removing scale, replacing a burnt-out electric element, etc., requires much time and effort. 
   To ensure the availability of hot water in a plumbing system, several devices have been patented. In U.S. Pat. No. 5,072,717, to Laing et al, there is disclosed a priming device upstream from a hot water tap for storing a small amount of water at a continuously maintained temperature. When the tap is opened, the stored water is delivered out of the faucet, while the cold water that has been stationary in the hot water pipe, is fed into the priming device. Similarly, U.S. Pat. No. 5,944,221 to Laing et al, teaches a system of a water heater, a tank and a pump for pre-storing an amount of hot water that is delivered upon demand through a hot water faucet while the equal amount of cold water is pumped into the tank. 
   The above systems do provide hot water on demand until the water from the hot water pipe arrives at a necessary temperature, however, these devices do not render themselves useful for service in solar-radiation water heating systems, since the devices are not capable of continuous operation required to compensate for the cooling effects of wintry, cloudy weather on the water in the hot water storage tank. Moreover, the system is greatly encumbered by the incorporation of valves and pumps. 
   To keep large amounts of hot water available to consumers, U.S. Patent Application No. 2004/0237908 teaches a system composed of a water heater tank and a supplemental tank. The supplemental tank is used to store hot water available for immediate delivery through a hot water faucet. The system, however, fails to be applicable in the solar-radiation water heating systems, because the system fails to address the drawbacks of the solar panels. 
   In U.S. Pat. No. 6,119,682 to Hazan, there is described and claimed a water heater and storage device containing a solar panel and a tank, which further has a heat exchanger piping circuit to facilitate the transfer of heat from the water stored in the tank to cold line-pressure water. An electrical water heating element is disposed in the general proximity to the heat exchanger. The system disclosed in this patent aims to provide a more economical heating of cold water. The design of the system renders the water tank filled unnecessarily with complicated pipe-work of the heat exchanger disposed too close to the heating element 
   In contradistinction to the above prior art systems, the present invention achieves higher energy savings and efficiency by means of an external water heater, and provides for an extremely simple, easy to service system. 
   It is known in practice that heating elements working continuously in non-distilled water become coated with a deleterious layer of insoluble mineral deposits. In common water heater construction, all the more so in the solar panel systems, to change a thermostat or the heating element calls for work performed in awkward, obstructed spaces, and also calls for draining large amounts of water from the water heater being serviced. 
   SUMMARY OF THE INVENTION 
   It is therefore one of the objects of the present invention to obviate the disadvantages of prior art water heaters and to provide a water heater and a solar-radiation water heater which can be serviced in an easier manner, without the necessity of draining the water in the storage tank. 
   It is a further object of the present invention to extend the operating life of the storage tank by eliminating the large opening, the welded-on studs and the flange commonly found on prior art storage tanks. 
   In a further preferred embodiment of the present invention there is provided a water heating and storage system wherein the base of the external tank is detachably affixed into the bottom edge of the side walls for easy cleaning of built-up scale in the interior of the water heater tank. 
   In still a further preferred embodiment of the present invention there is provided a water heating and storage system wherein the water inlet of the water heater tank is connectable to an outlet of a solar collector. 
   In another preferred embodiment of the present invention there is provided a water heating and storage system wherein the storage tank is a part of an existing water heating system wherein the storage tank is connected directly to the solar collector of the existing system, and the external water heater is installed within the existing system such that the water inlet of the water heater is connected to the outlet of the solar collector, and a hot water outlet of the external water heater is connected to the storage tank of the existing system. 
   The present invention achieves the above objects by providing a water heating and storage system, comprising a heat-insulated main heated water storage tank for storing hot water, said storage tank consisting of top, side and bottom walls, said storage tank having an inlet for heated water entering the tank at a level below the normal level, a cold water inlet, and a consumer hot water outlet, and an external water heater including a controlled electrical heating unit, an outlet port for heated water, said outlet port being connectable to the inlet of said tank, and a water inlet port. 
   The present invention also provides a water heater for operationally interconnecting with a hot water storage tank comprising an enclosure having a top, side and bottom walls enclosing a volume for containing about 1 to 3 liters, and a water heating arrangement at the top of side walls of the enclosure for controllably heating water inside said enclosure, wherein said bottom wall being detachably attached to said side walls, facilitating access to the interior of the enclosure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood. 
     With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
     In the drawings: 
       FIG. 1  is a schematic view of a preferred embodiment of the water heating and storage system, according to the present invention; 
       FIG. 2  is a detailed schematic view to an enlarged scale of an external water heater, according to the present invention, and 
       FIG. 3  is a schematic view of a preferred embodiment of the water heating and storage system, inter-connected with a solar collector panel. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   There is seen in  FIG. 1  a water heating and storage system  2  composed of a thermally insulated, hot water storage tank  4 , e.g., a cylindrical tank, having a top  6 , a side wall  8 , a bottom or base  10  and an external water heater  12 . The tank  4  has a pipe  14  for delivering hot water to a consumer, typically reaching at one end adjacent to the top  6  and exiting the base  10 , and a cold water inlet  15 . There is also provided at the upper portion of the tank  4  a heated water inlet  16 . Advantageously, the water heater  12  is cylindrically shaped and has a capacity typically of 1 to 3 liters and includes heated water outlet port  18  leading through pipe  20  to the inlet  16  of the tank  4 . 
   The external water heater  12  is also provided with an electrical heating element  22 , and advantageously, a thermostat  24  both attached to the upper wall of the heater, and a water inlet port  26  at the lower end portion thereof. The inlet port  26  is interconnected by a pipe  28  with a water outlet  30  of the tank  4 . There are also provided valves  32  and  34  fitted in pipes  20  and  28 , respectively. 
   Referring now to  FIG. 2 , there is seen a water heater  12  having a thermo-insulating double-walled jacket  36 , the space  38  between the double walls may be filled with insulating material or be utilized for circulating hot water for heating the water inside the heater, as per se known. One of the most practical features of the water heating system according to one embodiment of the invention, is the construction of the heater  12  which has a removable bottom lid  40 , which is held water-tight onto the jacket  36  of the main body of the heater  12 , by a screw  42  passing through a thread in a frame  44  attached to the jacket  36 . The outlet and inlet ports  18  and  26  are fitted with valves  32  and  34 , respectively, for preventing water flow into the heater or water draining from the heater when the heater is opened while still installed. When the heater must be opened for servicing, such as for draining or otherwise removing any mineral sediments, cleaning scale built-up on the heating element  22  and the inner walls of the heater, or changing either of the thermostat  24  or the heating element  22 , the liquid communication to and from the heater  12  is cut off using valves  32  and  34 . The bottom lid  40  is conveniently unscrewed and any water contained in the external tank  12  is drained. Due to the small capacity of the water heater  12 , during the opening of the bottom lid  40 , only a minimal amount of water is spilled, unlike the copious amounts of water spilled when the flanged sleeve nuts are loosened on the water heater tanks in the prior art. Yet another advantage is in the compactness of the water heater  12 , rendering same simple and quick to install into the existing, old solar panel collector heating systems. This case would typically call for removal of the flanged sleeve supporting the old heating element and thermostat, sealing the existing water heating tank, thereby converting the existing main storage tank into the tank  4 . In one embodiment of the invention, the heating element and the thermostat, if both relatively clean, or having been cleaned of mineral scale, can be removed from an existing deployed water storage tank and installed in the water heater  12 , thus easily forming the system of the invention by retrofit. 
   There is seen in  FIG. 3  a water heating and storage system  2  including one or more solar collectors  46 , typically containing water pipes or channels for absorbing solar radiation, thermally insulated hot water storage tank  4  and a water heater  12 . The inlet port  26  of the heater  12  is connectable via the valve  34  to an outlet  48  of the collector  46 . The water storage tank  4  is connected via outlet  30  and pipe  50  to the inlet  52  of the solar collector  46  for allowing the water stored in the storage tank  4  to flow to the solar collector  46 , in order to complete the thermosyphonic path. The storage tank  4  is also connectable to a cold water inlet  15  for introducing cold water from the main water supply. 
   It will thus be realized that the novel device of the present invention serves to: 
   a) provide a system for a fast, economical heating and storing of hot water, without the need for a sleeve inside the storage tank; 
   b) provide compact, easily serviceable electrical components of the system; 
   c) facilitate easy and unobstructed access to the components of the system; 
   d) provide a longer lasting storage tank not requiring either an internal sleeve or a flange opening, and 
   e) avoid freezing of the water in solar collectors during cold weather by causing warm water from the heater to circulate through the collectors. 
   While some of the advantages of the present invention can be realized in retrofit applications, and a retrofit kit would be a profitable product, nevertheless it will be understood that maximum benefits are obtained when the main water tank is replaced. The idea of replacement of the prior-art main storage tank by a new longer-lasting main storage tank costing less than the cost of the present day tank will be attractive to consumers. The new tank will have an extended life due to elimination of the rust-inducing flange, flange opening and welded-on studs. Insulation will be improved and simplified as no access flange is required. 
   It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.