Abstract:
A water heater including a water container; a combustion chamber adjacent the water container; a burner associated with the combustion chamber; a blower assembly located to receive combustion products generated by the burner; an intake conduit sealingly connected to the combustion chamber and having a combustion air intake opening located adjacent an upper portion of the water heater; and a dilution air conduit sealingly connected to the blower assembly and having a dilution air intake opening located adjacent a lower portion of the water heater.

Description:
FIELD OF THE INVENTION 
   This invention relates to power vented water heaters, particularly to a power vented water heater that has an air intake and exhaust system to reduce the potential for flammable vapor ignition. 
   BACKGROUND 
   Power vented water heaters are often equipped with intermittent burner ignition devices such as spark or hot surface igniters that ignite the pilot or main burner system only when there is a demand for hot water. Alternatively, the pilot burner may continuously operate in standing pilot type of ignition systems. Standing pilot ignition systems are less energy efficient and are manually re-lit after a power outage. This results in a significant preference in the market place for intermittent ignition systems. 
   However, intermittent ignition systems pose challenges regarding reducing the likelihood of igniting flammable vapors outside the power vented water heater since typical flame arrestor technology using intermittent ignition systems has proven challenging. A power vented water heater uses a blower positioned directly above the flue to move combustion products from the ambient space surrounding the heater into the water heater and exhaust the products of combustion outside. Typical power vented water heaters have two sources of intake air. One source is for combustion, wherein combustion air flows through the combustion chamber and flue. One source causes air to flow directly into the blower to reduce the temperature of the exhaust gases. This allows the vent system to utilize PVC, ABS or CPVC venting. When the water heater burner is off (i.e., in standby mode), the blower does not operate nor is there pilot or main burner operation. When there is a call for heat, the blower typically operates for a short pre-purge period to establish that there is sufficient airflow through the water heater system to support combustion and vent combustion products outside. If there are flammable vapors in the vicinity of the water heater, they may be drawn into the combustion chamber and, upon activation of the pilot ignition device or main burner, the accumulated vapors can ignite in an undesired manner. 
   SUMMARY OF THE INVENTION 
   This invention relates to a water heater including a water container, a combustion chamber adjacent the water container, a burner associated with the combustion chamber, a blower assembly located to receive combustion products generated by the burner, an intake conduit sealingly connected to the combustion chamber and having a combustion air intake opening located adjacent an upper portion of the water heater, and a dilution air conduit sealingly connected to the blower and having a dilution air intake opening located adjacent a lower portion of the water heater. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view of a water heater in accordance with aspects of the invention. 
       FIG. 2  is a partial sectional view of the water heater of  FIG. 1 . 
       FIG. 3  is a partial sectional view of the water heater of  FIG. 1 . 
       FIG. 4  is a partial sectional view of the water heater of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   It will be appreciated that the following description is intended to refer to specific aspects of the invention selected for illustration in the drawings and is not intended to define or limit the invention, other than in the appended claims. 
   This invention assists in reducing the likelihood that flammable vapors outside a water heater will reach the combustion chamber where they may be ignited by the main burner or pilot ignition device. This is achieved in one aspect with a concentric, bi-directional air intake system that directs separate air intake paths to the water heater blower and vent system. One air intake path provides air for combustion and may be located above the dilution air intake for the blower. The intake pipe may be a large diameter pipe that allows air for dilution of the combustion exhaust products to be drawn from below the heater (preferably less than about 18 inches from the floor) and directly into the blower and exhausted to the outside. Inside of the large diameter air intake pipe is a smaller pipe that permits air for combustion to be drawn from the top of the water heater or above the blower and travel down to a sealed combustion chamber. These bi-directional air paths are separate and do not intermix. 
   Turning now to the drawings, a water heater  10  in accordance with selected aspects of the invention is shown. Water heater  10  includes, but is not limited to, a jacket  12 , insulation  14 , tank  16 , combustion chamber  18  and burner  20 . A flue  22  extends longitudinally substantially concentrically within tank  16  from an uppermost portion (tank head) to a lowermost portion (tank bottom). Combustion chamber  18  contains burner  20  which connects to a fuel supply line  22 . Fuel supply line  23  connects to gas control valve  24  that connects to a fuel supply (not shown). 
   A blower assembly  26  is positioned on the top pan  28  of water heater  10  and sealingly connects to flue  22  at its upper terminus. Accordingly, exhaust/combustion gases generated by burner  20  flow upwardly through flue  22  and into blower assembly  26 . Blower assembly  26  has an electrical supply cord  30  that may be “plugged in” a typical electrical residential household socket. Various electric control lines may be contained within a conduit  32  connected between blower assembly  26  and gas valve  24 . 
   Water heater  10  has a bottom pan  34 , i.e., the bottom of the jacket. Bottom pan  34  has an opening  46  through which passes combustion air and rests on legs  36  that support the entire water heater  10 . 
   An air intake system  38  connects between blower assembly  26  and combustion chamber  18 . Air intake system  38  includes an air intake conduit and a dilution air conduit. The air intake conduit includes a substantially vertically oriented portion  40  that extends alongside or adjacent jacket  12  of water heater  10 . The air intake conduit also comprises a substantially horizontally oriented portion  44  that extends from the substantially vertically oriented portion  40  to opening  46  in bottom pan  34 . Substantially vertically oriented portion  40  may extend upwardly beyond the top of blower assembly  26 . 
   The dilution air conduit includes a substantially vertically oriented portion  42  that extends alongside or adjacent jacket  12 . The dilution air conduit also includes a connector portion  48  that extends between blower assembly  26  and substantially vertically oriented portion  42 . Substantially vertically oriented portion  42  preferably has a perforated cap  52  at its uppermost portion and is positioned to allow ambient air to enter through the perforated cap and through an open end of substantially vertically oriented portion  40 . Portions of substantially vertically oriented portion  40  and substantially vertically oriented portion  42  are preferably concentric. 
   During operation, burner  20  generates combustion/exhaust gases. Blower  50  initiates a flow of air and exhaust gases upwardly through flue  22 . This also causes an upward flow of air/exhaust gases through combustion chamber  18 . This in turn causes flow of air through opening  46  in bottom pan  34 , which in turn causes flow of air through substantially horizontal portion  44  and substantially vertical portion  40 . Combustion air enters air intake and exhaust system  38  by way of perforations in cap  52  as shown by arrows “A” in  FIG. 3 . Then, air flows downwardly through vertically oriented portion  40  as shown by arrow “B”, into horizontally oriented portion  44 , upwardly through opening  46  and into combustion chamber  18 . 
   Substantially simultaneously, as shown by reference to  FIGS. 2 and 4 , blower  50  causes the flow of air to supply air to the blower to mix with exhaust gases entering blower assembly  26  through flue  22 , which decreases the temperature of the exhaust gases and provides for a range of types of exhaust lines (not shown), but which would extend in a direction “away” from water heater  10  in the Figures. The suction created by blower  50  causes dilution air to move through connector  48  and through substantially vertically oriented portion  42 . With particular reference to  FIG. 4 , arrows “C” depict the entrance of dilution air through an opening in the lowermost portion of substantially vertically oriented portion  42 . That lowermost opening is preferably less than about 18 inches from ground level. Dilution air flows upwardly through substantially vertically oriented portion  42 , through connector  48  and into blower  50  for combination with exhaust gases exiting from the terminus of flue  22 . 
   It can be seen, especially as shown in  FIGS. 3 and 4 , that simultaneous intake combustion air and dilution air can occur from different locations and without intermixing. This can be achieved by the seal between combustion air pipe  40  and dilution air pipe  42 . This simultaneous flow reduces the chances of undesirable flammable ignition of vapors that might be located adjacent the water heater and provides for a means to lower the temperature of exhaust gases to increase flexibility of installation of the water heater. 
   Typical gasoline spills or other flammable vapors tend to migrate near the floor and be drawn into the dilution air intake and exhaust harmlessly outside with the products from combustion. Due to the difference in magnitude of the volume of the separate air paths (20% combustion air, 80% dilution air) drawn into each conduit, it is less likely that vapor concentrations will exceed the lower flammability limit at the combustion air inlet. This invention thereby reduces the propensity for flammable vapors to enter the combustion chamber where they could be ignited and can evacuate the flammable vapors from the space during operation, thereby reducing the potential that these vapors will build up and come in contact with another potential ignition source. 
   The size of the concentric portions can be increased or decreased to suit the application and/or size and/or shape of the water heater. The location of the various conduits relative to the water heater may also be varied depending on the size, shape and location of the water heater. The lower portion of the water heater may be the lower half of the water heater, but may be a larger portion so long as the dilution air intake opening is located below the combustion air opening. Conversely, the upper portion of the water heater may be the upper half of the water heater, but may be a larger portion so long as the combustion air opening is above, the dilution air intake. 
   It will be understood that water heater  10  may be constructed with a wide variety of materials, in a wide variety of shapes and sizes. For example, any number of types of burners  20  may be employed, along with various types of blower assemblies  26 , gas control valves  24  and the like. Also, various types of insulation, water containers/tanks and jackets may be employed. Preferably, air intake system  38  is constructed of PVC, ABS or CPVC materials, although other suitable materials may be employed. 
   Although this invention has been described in connection with specific forms thereof, it will be appreciated that a wide variety of equivalents may be substituted for the specified elements described herein without departing from the spirit and scope of this invention as described in the appended claims.