Abstract:
A combined potable water heater and hydronic heating system including: 
     a water tank for holding hydronic heating water; 
     a flue extending through the tank; 
     a burner below the flue so that heat and exhaust gases generated by the burner pass through the flue to heat the water in the tank; and 
     a potable water container mounted in the tank so that the hydronic heating water heats the water in the potable water container and so that the hydronic water is separated from the potable water.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/081,859, filed Apr. 15, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to apparatus for heating potable water and to hydronic heating apparatus. 
     A conventional residential gas water heater includes a potable water tank, a combustion chamber below the tank, a gas burner in the combustion chamber, and a flue extending upwardly from the combustion chamber and through the tank so that heat from the flue heats water in the tank. 
     A conventional residential hydronic heating system includes a boiler connected to radiators by pipes. 
     SUMMARY OF THE INVENTION 
     The invention provides a combined gas potable water heater and hydronic heating system. The system of the invention includes a conventional gas water heater with a flue extending through a tank, except that hydronic heating water, rather than potable water, is heated in the water tank. Potable water is heated in a heat exchanger or potable water container, preferably a coiled conduit surrounding the flue, inside the tank. Thus, the potable water is heated by the heating water in the tank and is maintained separate from the heating water. 
     The combined potable water heater and hydronic heating system is preferably contained in a cabinet having a relatively small footprint and is particularly suited for use in apartments or other small living quarters. The system is adaptable to various types of gas, including natural, LP and manufactured. The system is inexpensive to manufacture and is easy to operate and maintain. 
     The invention also provides a spacer for maintaining the spacing of the coils of the coiled conduit during shipping, the spacer being fixed to the flue. 
     The invention also provides a special union connecting an end of the coiled conduit inlet with a conduit external of the tank. The special union includes an externally threaded spud mounted on the exterior of the tank, the spud having an outer end with an internal chamfer. The end of the coiled conduit extends through the spud, and the special union also includes a ferrule surrounding the coiled conduit end, and a union member having an inner portion which is threaded onto the spud, which surrounds the ferrule and which has an internal chamfer. The ferrule is compressed between the chamfers so that the ferrule seals around the coiled conduit end and seals against both the spud and the union member, thereby sealing the coiled conduit end relative to the tank. The union member also has an outer portion to which the external conduit is sealingly connected, thereby sealingly connecting the external conduit to the coiled conduit end. The external conduit has an inner diameter greater than the outer diameter of the coiled conduit end so that the coiled conduit end can extend into the external conduit if the coiled conduit end extends beyond the union member. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of an apparatus embodying the invention. 
     FIG. 2 is a partial perspective view of the apparatus. 
     FIG. 3 is a front elevational view of the apparatus with the doors removed. 
     FIG. 4 is a sectional view of the tank. 
     FIG. 5 is an enlarged partial sectional view of the tank. 
     FIG. 6 is a sectional view of a special union. 
     FIG. 7 is an electrical circuit diagram of the apparatus. 
     FIG. 8 is a plan view of the cabinet base assembly, including the skirt ring and the header plate. 
     FIG. 9 is an elevational view of the cabinet base assembly and the burner and pilot assembly. 
     FIG. 10 is an electrical circuit diagram of the apparatus. 
     FIG. 11 is a perspective view of a manufactured gas burner. 
     FIG. 12 is plan view of the manufactured gas burner. 
     FIG. 13 is a sectional view of the manufactured gas burner. 
     FIG. 14 is a sectional view of a natural gas burner. 
     FIG. 15 is a view of the flame profile using the natural gas burner. 
     FIG. 16 is a view of the flame profile using the manufactured gas burner. 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An apparatus  10  embodying the invention is shown in FIGS. 1-3. It should be noted that FIG. 1 is not accurate as far the relative positions of and distances between elements of the apparatus  10  but is helpful in understanding the operation of the apparatus  10 . The apparatus  10  is a combined potable water heater and hydronic heating system. The apparatus  10  comprises a cabinet  14  including a generally vertical rear wall  18 , generally parallel, generally vertical side walls  22  and  26  extending forward from the opposite sides of the rear wall  18 , a generally horizontal base  30  extending forward from the bottom of the rear wall  18  and between the side walls  22  and  26 , and a generally horizontal top wall  34  extending forward from the top of the rear wall  18  and between the side walls. The cabinet  14  also includes a generally horizontal shelf  38  extending forward from the rear wall  18  and between the side walls  22  and  26  so as to define an upper space  42  between the shelf  38  and the top wall  34  and a lower space  46  between the shelf  38  and the base  30 . The cabinet  14  further includes a removable upper door  50  (partially shown in FIG. 3) for closing the front of the upper space  42 , and a removable lower door  54  for closing the front of the lower space  46 . The cabinet  14  also includes a panel  56  between the doors  50  and  54 . The panel  56  pivots down to a generally horizontal position (shown in FIG. 2) to allow access to the inside of the cabinet  14  for servicing the water heater and hydronic heating system, and to act as a shelf upon which the service technician may set tools or parts. Preferably, the circuit diagram shown in FIG. 7 is located on the inner surface of the panel  56  so as to be visible when the panel is pivoted down. The cabinet  14  preferably has a width of approximately 20 inches and a height of approximately 66 inches. 
     A generally vertical header plate  58  (FIGS. 2 and 8) is fixed to the base  30  inside the rear wall  18  of the cabinet  14 . The header plate  58  includes (see FIG. 2) first, second, third, fourth, fifth and sixth water or gas connections  61 ,  62 ,  63 ,  64 ,  65  and  66 , respectively, extending through the rear wall  18  of the cabinet. The first connection  61  is connectable to a source of gas, the second connection  62  is a pressure relief outlet, the third connection  63  is an inlet for potable water, the fourth connection  64  is an outlet for potable water, the fifth connection  65  is an inlet for hydronic heating water, and the sixth connection  66  is an outlet for hydronic heating water. The functions of these connections is explained below. 
     The apparatus  10  also comprises (see FIGS. 2-5,  8  and  9 ) a skirt ring  70  fixed generally to the center of the base  30 , the skirt ring  70  having therein air inlet openings  72  and an opening through which the burner assembly passes. The skirt ring  70  provides for support of the water heater tank, creates combustion space, provides combustion air openings, and allows access to the burner and combustion space. 
     A radiation shield  74  (see FIG. 9) sits on the base  30  inside the skirt ring  70 . The radiation shield  74  is designed to shield radiant energy from the burner to minimize floor temperatures. It is also dish shaped to collect condensate. Legs can be provided on the bottom of the radiation shield to set the distance off the bottom of the cabinet  14 . Combined with the burner locator described below, the shield  74  also sets the height of the burner. 
     An inner skirt ring  76  is attached to the radiation shield  74 . The inner ring  76  is designed to allow air flow over the top and bottom of the ring  76  while preventing radiation through the combustion air openings  72  in the skirt ring  70 . This minimizes cabinet temperatures. 
     A water tank  78  is seated on top of the skirt ring  70  so as to define (see FIG. 9) a burner space  82  below the tank  78  and inside the skirt ring  70 . The tank  78  preferably has a height of approximately 48 inches and a diameter of approximately 12 inches. In this appliance the hydronic heating water is stored in the tank  78 . Since the heating water is in a closed system, it is “dead” (minimal oxygen) and will cause minimal corrosion to the steel tank. Therefore a glass liner is generally not necessary. The tank  78  includes a potable water inlet  86  (FIG.  4 ), a potable water outlet  90  (FIG.  4 ), a hydronic water inlet  94  (FIG.  1 ), a hydronic water outlet  98  (FIGS.  1  and  4 ), an expansion tank outlet  102  (FIG.  1 ), and a drain valve outlet  106  (FIG.  1 ). A drain valve  110  communicates with the drain valve outlet  106 . A 3″ thick fiberglass blanket  112  with a vinyl cover preferably insulates the tank  78 . This insulation preferably has a nominal insulation factor of R-10. 
     A generally vertical, generally cylindrical flue  114  extends through the tank  78  so as to define a hydronic water chamber  118  inside the tank  78  and outside the flue  114 . The flue  114  preferably has a diameter of approximately five inches. The flue  114  extends through the shelf  38  so that the upper end of the flue  114  is held in place by the shelf  38 . The lower end of the flue  114  communicates with the burner space  82 . A baffle  120  (see FIGS. 4 and 5) is positioned in the flue  114 . The baffle  120  is preferably a twisted tape baffle with tabs welded to each flat location on both sides of the baffle  120 . The baffle  120  hangs in a slot on the top of the flue  114 . Stainless steel or other high temperature material is recommended for the lower portion of or the entire baffle. 
     The apparatus  10  also comprises (see FIGS. 5,  9 ,  11 - 13  and  16 ) a burner assembly  121  including a gas burner  122  located in the burner space  82  below the lower end of the flue  114 . The burner assembly  121  passes through the opening  73  in the skirt ring  70 , and a burner door  124  (see FIGS. 2 and 5) closes the opening  73 . The illustrated burner  122  is particularly suited for use with manufactured gas. The burner  122  has (see FIGS. 11-13) a generally cylindrical portion  126  centered on the center axis of the flue  114 , the cylindrical portion  126  having an interior space  130  (FIG.  13 ). The burner  122  also has a frustoconical portion  134  above the cylindrical portion  126 . The frustoconical portion  134  has therein a plurality of outwardly and upwardly angled holes  138  communicating between the interior space  130  and the outer surface of the frustoconical portion  134 . The holes  138  are evenly spaced around the frustoconical portion  134  with a gap between holes at every ninety degrees (best shown in FIG.  12 ). The burner  122  provides a flame that does not, when the burner is operating properly, impinge on any surface outside of the flue  114 , e.g., on the bottom of the tank  78  or the bottom head. As shown in FIG. 16, the irregular spacing, i.e., the gaps between holes  138  of the burner  122  allow air to entrain in the center of the burner flame  140 . This results in improved mixing of air and fuel, reduced recirculation and head temperature, and reduced carbon build-up on the burner  122 . 
     Referring to FIGS. 12 and 13, several variables affect burner performance. The angle “A” of the holes  138  determines the direction of the gas jets emanating from the burner  122 . The orientation of the gas jets changes the shape and size of the flame pattern. Angle “A” can vary from zero to ninety degrees, with the larger angle yielding a smaller flame diameter. At zero degrees, the jets would be horizontal, giving the largest flame pattern. At ninety degrees, the jets would be vertical, giving the smallest flame pattern. In general, angles in the range of thirty to sixty degrees are desired. The number of burner ports  138 , in conjunction with the diameter of each port  138 , determines the maximum input for a given gas and pressure. These can be varied to alter the way the gas mixes with air for combustion, as well as the shape of the flame. In general, higher gas velocities out of the ports  138  provide better mixing of air with the gas. Port diameter is selected based on the input and number of ports  138 . The ports are burr free, and are preferably not chamfered. 
     The burner assembly  121  also includes (see FIGS. 5 and 9) a gas conduit  142  having an outlet end communicating with the interior space  130  of the burner  122 . The gas conduit  142  is supported by a member  144  fixed to the radiation shield  74  so as to fix the burner  122  relative to the flue  114 . It is important that the burner  122  be properly positioned so that the flames do not undesirably contact the flue  114 . The gas conduit  142  has an inlet end communicating with the source of gas via a gas valve  146 , a gas conduit  148 , and the first header plate connection  61 . The gas valve  146  is preferably manufactured by White Rogers. A thermostat  150  (see FIGS. 3 and 5) is mounted on the exterior of the tank  78  and is operably connected to the gas valve  146  via an ignition module  154 . The ignition module  154  is preferably a Honeywell S8600M. The thermostat  150  is preferably set to maintain water temperature at approximately 85° C., which is important for hydronic heating. A manual reset surface mount high limit switch  155  (shown schematically in FIGS. 7 and 10) is preferably located on the side of the tank  78  to control maximum water temperature at 90° C. Upon call for heat from the thermostat, the system powers the pilot valve and initiates spark ignition. After the pilot is lit and flame is sensed, the gas valve  146  is opened. 
     The burner assembly  121  also includes (see FIG. 9) a pilot electrode assembly  156 , which is preferably a Johnson Controls J984DDW. Other pilot configurations could also be used, but should be selected so that they do not affect main burner flames or combustion. 
     A burner  122   a  particularly suited for use with natural gas is shown in FIGS. 14 and 15. The burner  122   a  differs from the burner  122  in the addition of a deflector portion  157  above the holes  138 . Otherwise, common elements have been given the same reference numerals. 
     A T-shaped conduit  158  (see FIGS. 2 and 3) is mounted on the upper end of the flue  114  above the shelf  38 . The T-shaped conduit  158  has a lower or flue exhaust inlet  160  (see FIG. 4) communicating with the upper end of the flue  114 , an ambient air inlet  162  communicating with the upper space  42 , and a mixed flue exhaust/ambient air outlet  164  communicating with the inlet of a blower  166 . The inlet  162  is preferably a fixed air orifice with its size determined by setting CO/CO2 limits during combustion testing at overfire. An exhaust conduit  170  has an inlet communicating with the blower outlet. The conduit  170  extends through the top wall  34  of the cabinet  14  and through the wall  172  of the building and has an outlet communicating with the atmosphere. The T-shaped conduit  158  mixes cool air with the flue exhaust so that relatively cool gases pass through the conduit  170 . In an alternative construction (not shown), the T-shaped conduit  158  is replaced by an elbow (without the ambient air inlet  162 ), and the flue  114  has therein openings above the shelf  38  for admitting ambient air to cool the flue gases. 
     An air inlet conduit  174  extends through the wall  172  of the building and has an inlet communicating with the atmosphere. The conduit  174  also extends through the top wall  34  and the shelf  38 , and, as shown in FIGS. 1 and 3, has an outlet  176  communicating with the lower space  46  near the skirt ring  70 . The placement of the outlet  176  near the skirt ring improves the supply of air to the burner  122 . Otherwise, it is possible that the air would get sucked out through T-shaped conduit  158 , thereby inhibiting combustion. 
     The apparatus  10  also comprises a pressure switch  178  connected to the blower  166  and to the gas valve  146  for closing the gas valve when the pressure in the blower  166  is below a set point. The pressure switch  178  is mounted on top of the shelf  38 . In general, all of the components mounted above the shelf  38  are strategically positioned to facilitate servicing of the apparatus. A water pump  182  is also mounted on top of the shelf  38 . The pump  182  has (see FIG. 3) an inlet  184  communicating with the hydronic water chamber  118  via an air bleed valve  186  and the hydronic water outlet  98  of the tank  78 . The pump  182  has an outlet  188  communicating with the header plate connection  66  via a hydronic water outlet conduit  190 . 
     A pressure relief conduit  194  communicates between the expansion tank outlet  102  of the tank and the header plate connection  62 . The pressure relief conduit  194  has therein a pressure relief valve  198  and communicates with an expansion tank  202  mounted above the shelf  38 . A hydronic water inlet conduit  206  communicates between the header plate connection  65  and the hydronic water chamber  118  via the hydronic water inlet  94  of the tank  78 . The hydronic water inlet conduit  206  has therein (see FIGS. 1 and 2) a gate valve  210  for opening and closing the hydronic water inlet conduit near the hydronic water inlet  94  of the tank  78 . 
     An auto-fill valve  214  has (see FIG. 2) an outlet  216  communicating with the hydronic water inlet conduit  206  between the gate valve  210  and the header plate connection  65 . The auto-fill valve  214  has an inlet  217  communicating with the header plate connection  63  via a conduit  218  so that the auto-fill valve  214  supplies additional water to the hydronic heating system when the pressure in the hydronic heating system is below a set point. Most hydronic systems experience a minor water loss due to evaporation or leakage at valve packings, pump seals, air vents, etc. To maintain system pressure the water must be replaced. An automatic fill valve is used for this. These valves are available from many companies. 
     The apparatus  10  also comprises (see FIG. 4) a potable water conduit  220  coiled around the flue  114  within the hydronic water chamber  118 . The coiled potable water conduit  220  has an inlet end  222  extending through the potable water inlet  86  of the tank  78  and has an outlet end  226  extending through the potable water outlet  90  of the tank  78 . A spacer  230  (FIG. 4) maintains the spacing of the coils of the conduit  220  during shipping. The spacer  230  is fixed to the flue  114  so as to maintain the position of the conduit  220  relative to the flue  114 . 
     A conventional mixing valve  234  (see FIG. 2) has a cold water inlet  235  communicating with the header plate connection  63  via a branch of the conduit  218 , a cold water outlet  236  communicating with the coiled conduit inlet end  222  via a cold water conduit  238 , a hot water inlet  240  communicating with the coiled conduit outlet end  226  via a hot water conduit  241  (FIG.  1 ), and a mixed hot and cold water outlet  242  communicating with the header plate connection  64  via a conduit  244 . In alternative embodiments of the invention the mixing valve can be omitted. 
     As shown in FIG. 6, a special union  246  connects the cold water conduit  238  with the coiled conduit inlet end  222 . The special union  246  includes an externally threaded spud  250  mounted on the exterior of the tank  78  over the potable water inlet  86  of the tank. The spud  250  has an outer end with an internal chamfer  254 . The coiled conduit inlet end  222  extends through the spud  250 . The special union  246  also includes a ferrule  258  surrounding the coiled conduit inlet end  222 , and a union member  262  having an inner portion which is threaded onto the spud  250 , which surrounds the ferrule  258  and which has an internal chamfer  266 . The ferrule  258  is compressed between the chamfers  254  and  266  so that the ferrule  258  seals around the coiled conduit inlet end  222  and seals against both the spud  250  and the union member  262 , thereby sealing the coiled conduit inlet end  222  relative to the tank  78 . The union member  262  also has an outer portion to which the cold water conduit  238  is sealingly connected by a fitting  270  and a cap nut  274 . This sealingly connects the cold water conduit  238  to the coiled conduit inlet end  222 . The cold water conduit  238  has an inner diameter greater than the outer diameter of the coiled conduit inlet end  222  so that the coiled conduit inlet end can extend into the cold water conduit  238  (as shown in phantom in FIG. 6) if the coiled conduit inlet end  222  extends beyond the union member  262 . A substantially identical special union  246  (FIG. 4) connects the hot water conduit  241  with the coiled conduit outlet end  226 . 
     The auto-fill valve  214  is a pressure regulator with a bypass valve. Under normal system operation, if there is a leak in the hydronic system the valve will maintain a substantially constant pressure in the system. The valve  214  also has a setting to bypass the pressure regulator of the valve so that it allows the system to be filled quickly. When the tank is empty and the water is first turned on, because there is atmospheric pressure in the tank chamber  118  and inside the hydronic circuit, the auto-fill valve  214  will allow water to enter the system. When the system is turned on, the tank chamber  118  begins to fill and air escapes upstream of the pump  182  through the air bleed valve  186 . When the water reaches the top of the tank the water level raises a float and shuts the air bleed valve  182 . The tank is now full. The pressure relief valve  198  will dump water if the water exceeds its setpoint, usually  30  psi. This could be caused by excessive water temperature or water pressure with the autofill valve in the fast-fill or bypass mode. 
     There is usually, however, a significant amount of trapped air in the heating circuit in the radiators (shown schematically and represented by numeral  300  in FIG.  1 ). This trapped air creates an air-lock which will prevent the water from entering the system. The air bleeds on the radiators can be opened, but the water coming in the auto-fill valve  214  wants to take the path of least resistance, i.e. the water will want to go into the tank and out through the pressure relief valve  186  instead of going backwards through the hydronic system. The water comes up through the tank and, instead of going out through the pump  182  and flushing the air through the system in the other direction, the water exits from the pressure relief valve  198 . 
     The gate valve  210  solves this problem. With the gate valve  210  in between the auto-fill valve  214  and the tank  78 , the gate valve  210  is directly attached to the tank and then, on the other side of the gate valve, to the auto-fill valve  214 . The hydronic water inlet conduit  206  is teed in between auto-fill valve  214  and gate valve  210 . Once the tank is full and the air is completely bled out of the tank, then the gate valve  210  is closed. This prevents water from going into the tank through the hydronic water inlet conduit  206  and taking the path of least resistance and going out the pressure relief valve  198 . The water now must flow through the radiator system, and the water pushes most or all of the air backwards through the heating system and back in through the pump  182  where the air hits the air bleed valve  186  which is plumbed at the very highest point in the system. This evacuates enough air to eliminate a vapor lock in the system. The pump  182  will circulate water and any additional air will bleed out through the air bleed valve  186 . 
     Two on-off switches  304  and  308  (see FIGS. 3,  7  and  10 ) are located on the panel  56 . The switch  304  controls power to the apparatus  10 . When the switch  304  is on, the water heater will operate for potable water heating. The switch  308  operates the hydronic system. When the switches  304  and  308  are on, the pump  182  will operate when the thermostat calls for heat. The switches are preferably lighted when on. An indicator lamp  312  is also located on the panel  56  and indicates burner operation. 
     Various features of the invention are set forth in the following claims.