Abstract:
The boiler of the present invention which enables the simultaneous use of heating and hot water includes: an internal heating-water discharge line for heating water, which has a circulation path for heating water forcibly fed by an internal circulation pump between a tank and a main heat exchanger; a supply water discharge line for heating water, which has a circulation path for heating water forcibly fed by an external circulation pump and supplied and returned from/to the tank and an indoor heating mechanism; and a three-way valve provided on a second indoor heating water connecting pipe of the internal heating-water discharge line for heating water, which adjusts the degree to which it is opened according to the indoor heating load and the hot water load in order to supply hot water passing through the main heat exchanger to the tank and a hot-water heat exchanger. The internal heating-water discharge line of the boiler and the supply water discharge line for heating water are connected to the internal space of the tank disposed therebetween.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of International Application No. PCT/KR2013/003121, filed Apr. 15, 2013, which claims the benefit of priority to Korean Application No. 10-2012-0046725, filed May 3, 2012 in the Korean Intellectual Property Office. All disclosures of the documents named above are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a boiler having enhanced heating efficiency and enabling simultaneous use of heating and hot water and, in more particular, to a boiler having enhanced heating efficiency and enabling simultaneous use of heating and hot water, which can supply sufficient heating-water even if heating equipment has a small heating surface area to enhance heating efficiency and can utilize simultaneously heating and hot water in light of a heating load and hot water load. 
     2. Description of the Related Art 
     In general, a heating dedicated boiler is a heating device which heats heating-water to a determined temperature utilizing combustion heat generated when fuel is burned, and supplies heating-water to a place in need of heating. 
     As shown in  FIG. 1 , a conventional heating dedicated boiler includes a tank  10  in which heating-water is stored; a circulation pump  20  for circularly supplying heating-water stored in the tank  10  to a main heat exchanger  30 ; a burner  40  for burning fuel so as to transfer combustion heat to heating-water passing through the main heat exchanger  30 ; a combustion chamber  50  providing a combustion space of the burner  40 ; a heating-water connecting pipe  71  through which heating-water stored in the tank  10  is supplied to the main heat exchanger  30 ; a heating-water supply pipe  72  through which heating-water heated by a heat exchange in the main heat exchanger  30  is supplied to heating equipment  60 ; and a heating-water return pipe  73  through which heating water, which has transferred heat to the heating equipment  60  and has a fallen temperature, is returned to the tank  10 . 
     The conventional boiler constructed as above has the problem in that, if the heating equipment  60  has a small heating surface area, a supply amount of heating-water is limited so that a sufficient heating is not obtained by utilizing this heating equipment  60 . 
     In other words, the conventional boiler has the problem in that, due to the structure in which heating-water heated in the main heat exchanger  30  is directly supplied to the heating equipment  60  through the heating-water supply pipe  72 , an amount of heating-water supplied to the heating equipment  60  is limited to an amount of heating-water passing through the main heat exchanger  30  and then supplied to the heating equipment, and so in a case in which the heating equipment  60  has a small heating surface area, a supply amount of heating-water supplied to the heating equipment  60  is limited and, as a result, a heating is not done properly. 
     In the conventional boiler, therefore, in order that heating-water, whose supply amount is limited, transfers heat while passing through the heating equipment  60  to perform the heating properly, the heating equipment  60  should have a sufficiently large heating surface area. In the ondol heating (Korean floor heating system), for example, a piping of heating having a large heating surface area should be provided on an ondol floor. In a case in which the heating equipment  60  has a large heating surface area as above, a pressure loss of heating-water is also increased so that an efficiency of the boiler is lowered. 
     Meanwhile, depending on the heating surface area of the heating equipment  60 , a supply temperature of heating-water supplied to the heating equipment  60  and a return temperature of heating-water which is returned after passing through the heating equipment  60  are determined. For example, if a high-capacity radiator having a large heating surface area as the heating equipment  60  performs the heating, the supply temperature of heating-water is set to 80° C. and the return temperature of heating-water is set to 60° C., and the heating is performed in the heating equipment  60  in response to the temperature difference of 20° C. between the supply temperature of heating-water and the return temperature of heating-water. If a small-capacity radiator having a small heating surface area as the heating equipment  60  performs the heating, the supply temperature of heating-water is set to 80° C. and the return temperature of heating-water is set to 70° C., and the heating is performed in the heating equipment  60  in response to the temperature difference of 10° C. between the supply temperature of heating-water and the return temperature of heating-water. As compared with the heating performed by utilizing the high-capacity radiator, therefore, in a case in which the heating is performed by utilizing a small-capacity radiator, a supply amount of heating-water, which is twice that for the high-capacity radiator, is necessarily required to perform the heating at the level which is the same as that of the heating performed by the high-capacity radiator. 
     However, in a case in which the heating equipment  60  has a small heating surface area, since a great quantity of heating-water which is circulated is required in order that the heating is performed at the level which is equal to that of the heating performed by the heating equipment having a large heating surface area, an amount of heating-water passing through the main heat exchanger  30  is also increased so that an element such as a heat transfer pin and the like provided in the main heat exchanger  30  for a heat transfer is eroded and corroded by an excessive amount of heating-water to deteriorate durability of and to reduce a service life of the main heat exchanger  30 . In addition, since capacity of the circulation pump  20  provided in the boiler should be increased so as to supply a great quantity of heating-water to the main heat exchanger  30 , an entire volume and weight of the boiler are increased and a great expense is required for manufacturing the boiler. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     The present invention is invented to solve the above-mentioned problems, an object of the present invention is to provide a boiler which prevents a shortage and a pressure loss of heating-water supplied heating equipment to enhance heating efficiency even if heating equipment has a small heating surface area, and delivers some heating-water to a hot-water heat exchanger to heat cold water into hot water if there is a hot water load. As a result, the boiler of the present invention can utilize simultaneously the heating and hot water. 
     Another object of the present invention is to provide a boiler which can supply a sufficient amount of heating-water to heating equipment to reduce a capacity of an internal circulation pump provided therein even if an excessive amount of heating-water does not pass through a heat exchanger and can prevent a corrosion generated by an erosion of a main heat exchanger caused when an excessive amount of heating-water flows in the main heat exchanger to extend a service life of the main heat exchanger. 
     Yet another object of the present invention is to provide a boiler having the structure which can control easily a temperature of heating-water so that a temperature of heating-water supplied to the heating equipment becomes a predetermined supply target temperature of heating-water. 
     Technical Solution 
     In order to achieve the above-mentioned object, a boiler of the present invention has enhanced heating efficiency and enabling simultaneous use of heating and hot water and includes a tank  110  having a space provided therein for storing heating-water, a main heat exchanger  130  for heating heating-water using combustion heat of a burner  140  and a hot-water heat exchanger  180  for heating cold water into hot water through a heat exchange between heating-water heated in the main heat exchanger  130  and the cold water, the boiler of the present invention includes an internal heating-water piping line  160  composed of a first heating-water connecting pipe  160   a  through which heating-water in the tank  110  is supplied to the main heat exchanger  130  and a second heating-water connecting pipe  160   b  through which heating-water passed through the main heat exchanger  130  is supplied to the tank  110 , thereby forming a heating-water circulation flow path for heating-water forcibly fed by an internal circulation pump  120  between the tank  110  and the main heat exchanger  130 ; a heating-water supply piping line  210  composed of a heating-water supply pipe  210   a  for supplying heating-water in the tank  110  to heating equipment  230  and a heating-water return pipe  210   b  for returning heating-water passed through the heating equipment  230  to the tank  110 , thereby forming a heating-water circulation flow path for supplying and returning heating-water forcibly fed by an external circulation pump  220  between the tank  110  and the heating equipment  230 ; and a three way valve  170  provided on the second heating-water connecting pipe  160   b , an opening rate thereof being adjusted depending on a heating load and hot water load to supply heating-water passed through the main heat exchanger  130  toward the tank  110  and the hot-water heat exchanger  180 . Here, the boiler internal water piping line  160  and the heating-water supply piping line  210  are connected to each other via the space in the tank  110 . 
     In this case, a first connecting pipe  191  is installed between the three way valve  170  and the hot-water heat exchanger  180  for supplying heating-water passed through the main heat exchanger  130  to the hot-water heat exchanger  180  and a second connecting pipe  192  for returning heating-water passed through the hot-water heat exchanger  180  to the tank  110  is installed between the hot-water heat exchanger  180  and the tank  110 . 
     In addition, the internal circulation pump  120  is provided on the first heating-water connecting pipe  160   a  and the external circulation pump  220  may be provided on the heating-water supply pipe  210   a.    
     Also, a main heat exchanger connecting port  111  connected to the second heating-water connecting pipe  106   b  and a heating-water supplying port  112  connected to the heating-water supply pipe  210   a  are formed on an upper portion of the tank  110 , and a heating-water returning port  113  connected to the heating-water return pipe  210   b , a pump connecting port  114  connected to the internal circulation pump  120  provided on the first heating-water connecting pipe  160   a  and a heating-water inlet port  115  connected to the second connecting pipe  192  are formed on a lower portion of the tank  110 . 
     In addition, an air/water separator  116  for discharging air contained in heating-water in the tank  110  to an outside of the tank  110  is provided on the upper portion of the tank  110 . 
     Furthermore, a filter  117  for filtering foreign substance contained in heating-water flowing into the tank  110  through the heating-water returning port  113  and the heating-water inlet port  115  is provided on the lower portion of the tank  110 . 
     Also, the heating-water supply pipe  210   a  is provided with a first temperature sensor  211  for measuring a temperature of heating-water supplied from the tank  110  to the heating equipment  230  and the second heating-water connecting pipe  160   b  is provided with a second temperature sensor  161  for measuring a temperature of heating-water heated in the main heat exchanger  130  and supplied to from the tank  110 , whereby a temperature T3 of heating-water, which is measured by the second temperature sensor  161 , is controlled by adjusting the combustion rate of the burner  140  so that a supply temperature T2 of heating-water, which is measured by the first temperature sensor  211 , reaches a first supply target temperature T1 of heating-water. 
     In the hot water mode of the boiler, the three way valve  170  has a heating-water supply flow path for heating-water to supply all of the amount of heating-water, which flows from the main heat exchanger  130 , to the tank  110 , heating-water in the tank  110  passes through the internal circulation pump  120  via the pump connecting port  114  and is then supplied to the main heat exchanger  130 , heating-water heated in the main heat exchanger  130  passes through the three way valve  170  and flows into the tank  110  via the main heat exchanger connecting port  111 , heating-water in the tank  110  passes through the external circulation pump  220  via the heating-water supplying port  112  and is supplied to the heating equipment  230  and is then entered the tank  110  via the heating-water returning port  113 , some heating-water entered the tank  110  via the heating-water returning port  113  is supplied to the main heat exchanger  130  via the pump connecting port  114 , and the remainder of heating-water is mixed with heating-water entered the tank via the main heat exchanger connecting port  111  and then supplied to the heating equipment  230  via the heating-water supplying port  112 . 
     In the mode for simultaneous use of heating and hot water, in addition, the opening rate of the three way valve  170  is adjusted in proportion to the heating load and the hot water load so that heating-water flowing from the main heat exchanger  130  flows into the tank  110  and the hot-water heat exchanger, heating-water in the tank  110  passes through the internal circulation pump  120  via the pump connecting port  114  and is then supplied to the main heat exchanger  130 , some heating-water heated in the main heat exchanger  130  passes through the three way valve  170  and flows into the tank  110  via main heat exchanger connecting port  111 , heating-water in the tank  110  passes through the external circulation pump  220  via the heating-water supplying port  112  and is supplied to the heating equipment  230  and is then entered the tank  110  via the heating-water returning port  113 , the remainder of heating-water heated in the main heat exchanger  130  flows into the hot-water heat exchanger  180  via the three way valve  170  and is heat-exchanged with cold water and then flows into the tank  110  via the heating-water inlet port  115 , some heating-water entered the tank  110  via the heating-water returning port  113  and the heating-water inlet port is supplied to the main heat exchanger  130  via the pump connecting port  114 , and the remainder of heating-water is mixed with heating-water entered the tank via the main heat exchanger connecting port  111  and then supplied to the heating equipment  230  via the heating-water supplying port  112 . 
     Advantageous Effects 
     According to the boiler having enhanced heating efficiency and enabling simultaneous use of heating and hot water, the boiler is advantageous in that, by connecting the internal water piping line of the boiler and the heating-water supply piping line to each other via the internal space of the tank, it is possible to supply a sufficient amount of heating-water to the heating equipment (a place in need of heating) even if the heating equipment has a small heating surface area to enhance the heating efficiency, and by adjusting an opening rate of the three way valve in proportion to a heating load and a hot water load, a heating and hot water can be simultaneously utilized. 
     In addition, according to the present invention, the boiler is advantageous in that, even if a pump having a small capacity is employed as the internal circulation pump installed in the boiler, a sufficient amount of heating-water can be supplied to the heating equipment and it is possible to prevent an increase of an amount of heating-water passing through the main heat exchanger to prevent a corrosion caused by an erosion of the main heat exchanger, to enhance the durability and to extend the service life. 
     Furthermore, according to the present invention, the boiler is advantageous in that the temperature of heating-water supplied from the main heat exchanger to the tank is controlled so that the supply temperature of heating-water, which is measured by the first temperature sensor becomes the first supply target temperature of heating-water, therefore, the supply temperature of heating-water can be easily controlled. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a view showing a schematic structure of a conventional heating dedicated boiler; 
         FIG. 2  is a view showing a schematic structure of a boiler according to the present invention; 
         FIG. 3  is an enlarged view of a tank provided in the boiler according to the present invention; 
         FIG. 4  is a view showing an operation state in the boiler according to the present invention in a heating mode; 
         FIG. 5  is a view showing a flow of heating-water in the tank of the boiler according to the present invention in a heating mode; 
         FIG. 6  is a view showing an operation state of the boiler according to the present invention in a hot water mode; 
         FIG. 7  is a view showing an operation state of the boiler according to the present invention in a mode for simultaneous use of heating and hot water; and 
         FIG. 8  is a view showing a flow of heating-water in the tank of the boiler according to the present invention in a mode for simultaneous use of heating and hot water. 
     
    
    
     
       
         
               
             
               
               
             
               
             
               
               
             
           
               
                   
               
               
                 REFERENCE NUMERAL 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10: Tank 
                 20: Circulation pump 
               
               
                 30: Main heat exchanger 
                 40: Burner 
               
               
                 50: Combustion chamber 
                 60: Heating equipment 
               
               
                 71: Heating-water connecting pipe 
                 72: Heating-water supply pipe 
               
               
                 73: Heating-water return pipe 
                 100: Main body of boiler 
               
               
                 110: Tank 
                 111: Main heat exchanger connect- 
               
               
                   
                 ing port 
               
               
                 112: Heating-water supplying port 
                 113: Heating-water returning port 
               
               
                 114: Pump connecting port 
                 115: Heating-water inlet port 
               
               
                 116: Air/water separator 
                 117: Filter 
               
               
                 120: Internal circulation pump 
                 130: Main heat exchanger 
               
               
                 140: Burner 
                 150: Combustion chamber 
               
               
                 160: Boiler internal water piping line 
                 160a: First heating-water connect- 
               
               
                   
                 ing pipe 
               
             
          
           
               
                 160b: Second heating-water connecting pipe 
               
               
                 161: Second temperature sensor 
               
             
          
           
               
                 170: Three way valve 
                 180: Hot-water heat exchanger 
               
               
                 191: First connecting pipe 
                 192: Second connecting pipe 
               
               
                 193: Cold water pipe 
                 194: Hot water pipe 
               
               
                 210: Heating-water supply piping line 
                 210a: Heating-water supply pipe 
               
               
                 210b: Heating-water return pipe 
                 211: First temperature sensor 
               
               
                 220: External circulation pump 
                 230: Heating equipment 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, a structure and an operation of the preferred embodiment of the present invention are illustrated in detail with reference to the accompanying drawings. 
       FIG. 2  is a view showing a schematic structure of a boiler according to the present invention. 
     In a boiler according to the present invention, a tank  10  in which a space for storing heating-water is provided; a main heat exchanger  130  for heating heating-water through a heat exchange between heating-water and product of combustion generated by combustion of a burner  140 ; an internal circulation pump  120  for circularly supplying heating-water in the tank  110  to the main heat exchanger  130 ; the burner  140  for burning fuel to transmit combustion heat to heating-water passing through the main heat exchanger  130 ; a combustion chamber  150  providing a combustion space of the burner  140 ; a hot-water heat exchanger  180  for heating cold water through a heat exchange between heating-water heated in the main heat exchanger  130  and cold water and supplying hot water; and a three way valve  170  forming a flow path of heating-water so as to supply heating-water heated in the main heat exchanger  130  to the main heat exchanger  130  in proportion to a heating load and hot water load are provided in a main body  100  of the boiler. 
     A boiler internal water piping line  160  is installed between one side of the tank  10  and the main heat exchanger  130  for circularly supplying heating-water. The boiler internal water piping line  160  is composed of a first heating-water connecting pipe  160   a  connected to an inlet  131  of the main heat exchanger  130  at one side of a lower portion of the tank  110  to supply heating-water in the tank  110  to the main heat exchanger  130  and a second heating-water connecting pipe  160   b  connected to one side of an upper portion of the tank  110  at an outlet  132  of the main heat exchanger  130  to supply heating-water heated in the main heat exchanger  130  to the tank  110 , and the internal circulation pump  120  is provided on the first heating-water connecting pipe  160   a  for forcibly feeding heating-water so as to circulate heating-water between the tank  110  and the main heat exchanger  130 . 
     A heating-water supply piping line  210  is installed at the other side of the tank  110  for circularly supplying heating-water to heating equipment  230  such as a radiator and the like. The heating-water supply piping line  210  consists of a heating-water supply pipe  210   a  for supplying high-temperatured heating-water in the tank  110  to the heating equipment and a heating-water return pipe  210   b  for returning heating-water whose temperature is lowered after passing through the heating equipment  230  and transferring heat, and an external circulation pump  220  is provided on the heating-water supply pipe  210   a  for forcibly feeding heating-water so as to circulate heating-water between the tank  110  and the heating equipment  230 . 
     A first temperature sensor  211  is provided on the heating-water supply pipe  210   a  adjacent to the outlet of the heating-water supply piping line  210  for measuring a temperature of heating-water supplied from the tank  110  to the heating equipment  230 , and the second temperature sensor  161  is provided on the second heating-water connecting pipe  160   b  for measuring a temperature of heating-water heated in the main heat exchanger  130  and supplied to the tank  110 . 
     The tank  110  has a space formed therein for storing heating-water so that the internal water piping line  160  and the heating-water supply piping line  210  are connected to each other via the internal space of the tank  110 . 
     The three way valve  170  is provided on the second heating-water connecting pipe  160   b  so that a supply flow path of heating-water which is heated while passing through the main heat exchanger  130  is selectively connected to any one of the tank  110  and the hot-water heat exchanger  180 , or an opening rate of flow path connected to the second heating-water connecting pipe  160   b  from the three way valve  170  to the tank  110  and an opening rate of flow path connected to a first connecting pipe  191  from the three way valve  170  to the hot-water heat exchanger  180  are adjusted in proportion to the heating load and the hot water load. In addition, a second connecting pipe  192  connected to the tank  110  is provided at an outlet of the hot-water heat exchanger  180 , and a cold water pipe  193  into which cold water flows and a hot water pipe  194  from which heated hot water is discharged is connected to and installed at the hot-water heat exchanger  180 . 
       FIG. 3  is an enlarged view of the tank provided in the boiler according to the present invention. 
     Referring to  FIG. 3 , a main heat exchanger connecting port  111  connected to the second heating-water connecting pipe  160   b  is formed on one side of an upper portion of the tank  110 , and a heating-water supplying port  112  connected to the heating-water supply pipe  210   a  is formed on the other side of the upper portion of the tank  110 . A pump connecting port  114  connected to the internal circulation pump  120  installed on the first heating-water connecting pipe  160   a  is formed on one side of a lower portion of the tank  110 , and a heating-water returning port  113  connected to the heating-water return pipe  210   b  and a heating-water inlet port  115  connected to the second connecting pipe  192  are formed on the other side of the lower portion of the tank  110 . 
     On an upper portion of the tank  110 , in addition, an air/water separator  116  is provided for discharging air contained in heating-water in the tank  110  out of the tank  110 , and a filter  117  is provided on the lower portion of the tank  110  for filtering foreign substances contained in heating-water flowing into the tank  110  via the heating-water returning port  113  after passing through the heating equipment  230  and contained in heating-water flowing into the tank  110  via the second connecting pipe  192 . 
     Hereinafter, operations for supplying heating-water heated in the main heat exchanger  130  to the heating equipment  230  and for returning heating-water, which has passed through the heating equipment  230 , via the tank  110  constructed as above are illustrated. 
       FIG. 4  is a view showing an operation state of the boiler according to the present invention in a heating mode, and  FIG. 5  is a view showing a flow of heating-water in the tank of the boiler according to the present invention in a heating mode. 
     In the heating mode of the boiler, the three way valve  170  has a supply flow path for allowing all of heating-water, which flows from the main heat exchanger  130 , to be supplied to the tank  110 . Heating-water in the tank  110  passes through the internal circulation pump  120  via the pump connecting port  114  and is then supplied to the main heat exchanger  130 . Heating-water heated in the main heat exchanger  130  passes through the three way valve  170  and flows into the tank  110  via the main heat exchanger connecting port  111 . Heating-water in the tank  110  passes through the external circulation pump  220  via the heating-water supplying port  112  and is supplied to the heating equipment  230  and is then entered the tank  110  via the heating-water returning port  113 . Some heating-water flowing entered the tank  110  via the heating-water returning port  113  is supplied to the main heat exchanger  130  via the pump connecting port  114 , and the remainder of heating-water is mixed with heating-water entered the tank via the main heat exchanger connecting port  111  and then supplied to the heating equipment  230  via the heating-water supplying port  112 . 
     As some heating-water flowing into the tank  110  via the heating-water returning port  113  is supplied to the heating equipment  230  via the heating-water supplying port  112 , as compared with the flow rate f3 of heating-water flowing into the tank  110  through the heating-water returning port  113  and the flow rate f2 of heating-water supplied to the heating equipment  230  through the heating-water supplying port  112 , the flow rate f1 of heating-water flowing into the tank  110  through the main heat exchanger connecting port  111  and the flow rate f4 of heating-water discharged to the main heat exchanger  130  via the pump connecting port  114  can be reduced (f1, f4&lt;f2, f3). 
     In this case, the temperature T3 of heating-water flowing into the tank  110  via the heating-water returning port  113  becomes equal to the temperature T4 of heating-water supplied from the tank  110  to the main heat exchanger  130  via the pump connecting port  114  (T3=T4) and due to mixing heating-water supplied from the tank  110  to the heating equipment  230  via the heating-water supplying port  112  with returned heating-water, the temperature T2 of heating-water supplied from the tank  110  to the heating equipment  230  becomes lower than the temperature T1 of heating-water heated in the main heat exchanger  130  and flowing into the tank  110  via the main heat exchanger connecting port  111  (T2&lt;T1). However, as the flow rate of heating water supplied to the heating equipment  230  is increased, a heat exchange is smoothly performed in the heating equipment  230 . As a result, it is possible to obtain a high heating performance. 
     Therefore, it is possible to reduce the flow rate of heating-water flowing along the internal water piping line  160  provided in the main body  100  of the boiler and, at the same time, to secure the sufficient flow rate of heating-water supplied from the tank  110  to the heating equipment  230 . Consequently, a permissible capacity of the internal circulation pump  120  can be reduced so that a volume and a weight of the boiler can be reduced, a manufacturing cost can be lowered and it is possible to prevent excessive heating-water from passing through the main heat exchanger  130  to prevent damage of the main heat exchanger  130  caused by a corrosion. 
     In addition, even if the heating equipment  230  has a small heating surface area, since it is possible to supply of heating-water with the sufficient flow rate through the heating-water supply piping line  210  between the tank  10  and the heating equipment  230 , a heat transfer can be smoothly carried out in the heating equipment  230  to enhance heating performance for a place in need of heating. 
     In the present invention, furthermore, a temperature T3 of heating-water, which is measured by the second temperature sensor  161 , is controlled by adjusting the combustion rate of the burner  140  so that a supply temperature T2 of heating-water, which is measured by the first temperature sensor  211 , reaches a first supply target temperature T1 of heating-water. As a result, it is possible to easily control the supply temperature of heating-water. 
     As one embodiment, if the first supply target temperature T1 of heating-water to be supplied from the tank  110  to the heating equipment  230  is set to 80° C., the temperature of heating-water passing the heating equipment  230  and returned to the tank  110  is determined by the heating surface area of the heating equipment  230 . For example, the temperature of heating-water to be returned may be set to 80° C. In this case, in order that the temperature T2 of heat-water, which is measured by the first temperature sensor  211 , reaches ° C. which is the first supply target temperature T1 of heating-water, the second supply target temperature T4 of heating-water supplied to the main heat exchanger  130  to the tank  110  is set to 90° C., and in order that the temperature of heat-water, which is measured by the second temperature sensor  161 , reaches the second supply target temperature T4 of heating-water, the combustion rate of the burner  140  is controlled. 
     As described above, in the present invention, the temperature T2 of heating-water is measured by the first temperature sensor  211  provided on the heating-water supply pipe  210   a  and the combustion rate of the burner  140  is adjusted so that the measured temperature T2 reaches the first supply target temperature T1 and the temperature T3 of heating-water, which is measured by the second temperature sensor  161 , becomes a second supply target temperature T4. As a result, it is possible to easily control the temperature of heating-water. 
       FIG. 6  is a view showing an operation state of the boiler according to the present invention in a hot water mode. 
     In a case in which there is no heating load when the boiler is in the hot water mode, the three way valve  170  closes the flow path connected to the second heating-water connecting pipe  160   b  extending to the tank  110  and opens the flow path connected to the first connecting pipe  191  extending to the hot-water heat exchanger  180  so that all heating-water heated in the main heat exchanger  130  is supplied to the hot-water heat exchanger  180 . After transferring heat to cold water entered the hot-water heat exchanger  180  through the cold water pipe  193 , heating-water supplied to the hot-water heat exchanger  180  flows into the tank  110  through the second connecting pipe  192  and is then stored in the tank  110 . Heating-water stored in the tank  110  is circularly supplied to the main heat exchanger  130  via the first heating-water connecting pipe  160   a.    
       FIG. 7  is a view showing an operation state of the boiler according to the present invention in a mode for simultaneous use of heating and hot water, and  FIG. 8  is a view showing a flow of heating-water in the tank of the boiler according to the present invention in a mode for simultaneous use of heating and hot water. 
     In the mode for simultaneous use of heating and hot water of the boiler, the opening rate of the three way valve  170  is adjusted in order that heating-water flowing from the main heat exchanger  130  to the three way valve  170  is dividedly directed to the tank  110  and the hot-water heat exchanger  180  in proportion to the heating load and the hot water load. Heating-water in the tank  110  flows into the internal circulation pump  120  via the pump connecting port  1140  and is then supplied to the main heat exchanger  130 . Some heating-water heated in the main heat exchanger  130  passes through the three way valve  170  and flows into the tank  110  through the main heat exchanger connecting port  111 , and heating-water in the tank  110  flows into the external circulation pump  220  via the heating-water supplying port  112  and is then supplied to the heating equipment  230 . Finally, heating-water is entered the tank  110  via the heating-water returning port  113 . The remainder of heating-water heated in the main heat exchanger  130  passes through the three way valve  170  and flows into the hot-water heat exchanger  180 . After heat exchanging with cold water in the hot-water heat exchanger, heating-water flows into the tank  110  via the heating-water inlet port  115 . T5 and f5 in  FIG. 8  indicate a temperature and a flow rate of heating-water flowing into the tank  110  through the via heating-water inlet port  115 , respectively. 
     Some heating-water entered the tank  110  via the heating-water returning port  113  and the heating-water inlet port  115  is supplied to the main heat exchanger  130  via the pump connecting port  114 , and the remainder of heating-water is mixed with heating-water entered via the main heat exchanger connecting port  111  and is then supplied to the heating equipment  230  through the heating-water supplying port  112 . 
     When heating-water and hot water are simultaneously utilized, as illustrated in the description for the mode for simultaneous use of heating and hot water of the boiler, since the present invention as described above prevents excessive heating-water from passing through the main heat exchanger  130 , a service life of the main heat exchanger  130  extends, a capacity of the internal circulation pump  120  can be reduced, it is possible to prevent a lack of heating-water supplied to the heating equipment  230  and a pressure loss, and heating-water and hot water can be simultaneously utilized by adjusting the opening rate of the three way valve  170 . 
     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.