Water heater with forced draft air inlet

Abstract

A water heater includes an air intake assembly that includes a blower for providing primary and secondary air to a combustion chamber at pressures above atmospheric pressure. The primary air is mixed with gaseous fuel and the mixture is combusted at a burner in a partially premixed but substantially diffusion flame having an envelope. Combustion of the mixture is completed within the envelope in the presence of secondary air at elevated pressure. A 24 V controller provides power to a user interface and a powered anode in the tank. The controller receives input from a pressure sensor in the air intake assembly, a flame sensor in the combustion chamber, and a flammable vapor sensor outside the water heater. The controller controls operation of the blower and a gas valve. A flue and baffle arrangement in the tank causes products of combustion from the burner to lose pressure and vent at near atmospheric pressure at the top of the flue. An air distributor plate creates a substantially uniform distribution of pressurized secondary air within the combustion chamber.

1 . A water heater comprising:
 a tank for water to be heated;   a powered anode extending into the tank and creating an electrical current to reduce corrosion of the tank;   a combustion chamber;   an exhaust structure;   a flue in the tank communicating between the combustion chamber and the exhaust structure;   a burner in the combustion chamber operable to burn a mixture of primary combustion air with gaseous fuel in a partially premixed but substantially diffusion flame having an envelope, such that combustion of the mixture is completed at the diffusion flame envelope in the presence of secondary air to produce products of combustion, the products of combustion flowing through the flue to the exhaust structure to heat the water in the tank;   a centrifugal blower forcing primary and secondary air into the combustion chamber at pressure above atmospheric;   a gas valve for controlling a supply of gaseous fuel to the burner;   a user interface for programming operating parameters of the water heater; and   a 24 V controller that provides power to the user interface and powered anode, and that controls operation of the blower and gas valve.   
   
   
       2 . The water heater of  claim 1 , further comprising a pressure sensor operatively interconnected with the 24 V controller; wherein the pressure sensor generates a signal in response to sensing that the pressure of air downstream of the blower is below a minimum threshold; and wherein the 24 V controller closes the gas valve in response to receiving the signal from the pressure sensor. 
   
   
       3 . The water heater of  claim 1 , further comprising a flammable vapor sensor operatively interconnected with the 24 V controller; wherein the flammable vapor sensor generates a signal in response to sensing the presence of flammable vapors outside of the water heater in concentrations above a maximum threshold; and wherein the 24 V controller closes the gas valve in response to receiving the signal from the flammable vapor sensor. 
   
   
       4 . The water heater of  claim 1 , further comprising a pressure sensor sensing the pressure of air downstream of the blower; and a flammable vapor sensor sensing the presence of flammable vapors outside of the water heater; wherein the 24 V controller closes the gas valve upon the occurrence of any of the following: (a) conditions dictated by the user interface, (b) the pressure sensor sensing air pressure below a minimum threshold, and (c) the flammable vapor sensor sensing flammable vapors external to the water heater in concentrations above a maximum threshold. 
   
   
       5 . A water heater comprising:
 a tank for water to be heated;   a combustion chamber;   an exhaust structure;   a flue in the tank communicating between the combustion chamber and the exhaust structure;   a burner in the combustion chamber operable to burn a mixture of primary combustion air with gaseous fuel in a partially premixed but substantially diffusion flame having an envelope, such that combustion of the mixture is completed at the diffusion flame envelope in the presence of secondary air to produce products of combustion, the products of combustion flowing through the flue to the exhaust structure to heat the water in the tank;   an air intake assembly including an air inlet above the combustion chamber and a conduit communicating between the air inlet and the combustion chamber;   a centrifugal blower within the air intake assembly operable to suck air into the air intake assembly through the air inlet and force primary and secondary air into the combustion chamber through the conduit at pressure above atmospheric;   a gas valve for controlling a supply of gaseous fuel to the burner;   a controller that controls operation of the blower and gas valve; and   a flammable vapor sensor external of the combustion chamber and lower than the air inlet, the flammable vapor sensor being operatively interconnected with the controller and operable to generate a signal in response to sensing the presence of flammable vapors outside of the water heater in concentrations above a maximum threshold;
 wherein all primary and secondary combustion air supplied to the combustion chamber flows through the air inlet and conduit; and 
   wherein the controller closes the gas valve in response to receiving the signal from the flammable vapor sensor.   
   
   
       6 . The water heater of  claim 5 , wherein the flammable vapor sensor is lower than at least one of the combustion chamber and burner. 
   
   
       7 . A water heater comprising:
 a tank for water to be heated;   a combustion chamber;   an exhaust structure;   a flue in the tank communicating between the combustion chamber and the exhaust structure;   a burner in the combustion chamber operable to burn a mixture of primary combustion air with gaseous fuel in a partially premixed but substantially diffusion flame having an envelope, such that combustion of the mixture is completed at the diffusion flame envelope in the presence of secondary air to produce products of combustion, the products of combustion flowing through the flue to the exhaust structure to heat the water in the tank;   an air intake assembly including an air inlet above the combustion chamber and a conduit communicating between the air inlet and the combustion chamber;   a centrifugal blower within the air intake assembly operable to suck air into the air intake assembly through the air inlet and force primary and secondary air into the combustion chamber through the conduit at pressure above atmospheric;   a gas valve for controlling a supply of gaseous fuel to the burner;   a controller that controls operation of the blower and gas valve; and   a baffle in the flue that restricts flow sufficiently to reduce the pressure of the products of combustion to near atmospheric upon flowing out of the flue into the exhaust structure.   
   
   
       8 . The water heater of  claim 7 , wherein the blower is an axial-intake, centrifugal blower. 
   
   
       9 . The water heater of  claim 7 , wherein the exhaust structure is a category I vent structure. 
   
   
       10 . A water heater comprising:
 a tank for water to be heated;   a combustion chamber;   an exhaust structure;   a flue in the tank communicating between the combustion chamber and the exhaust structure;   a burner in the combustion chamber operable to burn a mixture of primary combustion air with gaseous fuel in a partially premixed but substantially diffusion flame having an envelope, such that combustion of the mixture is completed at the diffusion flame envelope in the presence of secondary air to produce products of combustion, the products of combustion flowing through the flue to the exhaust structure to heat the water in the tank;   an air intake assembly including an air inlet above the combustion chamber and a conduit communicating between the air inlet and the combustion chamber;   a centrifugal blower within the air intake assembly operable to suck air into the air intake assembly through the air inlet and force primary and secondary air into the combustion chamber through the conduit at pressure above atmospheric;   a gas valve for controlling a supply of gaseous fuel to the burner; and   a controller that controls operation of the blower and gas valve;   wherein the air intake assembly includes an interior space, all primary and secondary air being provided to the combustion chamber flowing through the interior space; and   wherein the blower is mounted within the interior space of the air intake assembly.   
   
   
       11 . The water heater of  claim 10 , wherein the blower is an axial-intake, centrifugal blower. 
   
   
       12 . The water heater of  claim 10 , wherein the air intake assembly includes a longitudinal extent; and wherein the air intake assembly includes a two-piece construction divided along the longitudinal extent of the air intake assembly. 
   
   
       13 . The water heater of  claim 10 , wherein the interior space of the air intake assembly is non-cylindrical and has an equivalent hydraulic diameter of a four inch inner diameter tube. 
   
   
       14 . The water heater of  claim 10 , wherein at least a portion of the interior space of the air intake assembly is non-cylindrical to accommodate mounting the blower in the interior space; and wherein the non-cylindrical portion of the interior space defines a minor dimension and a major dimension that is perpendicular to the minor dimension and at least twice the minor dimension. 
   
   
       15 . The water heater of  claim 10 , wherein the air intake assembly includes a partition that divides the interior space into an inlet side communicating with ambient air and an outlet side communicating with the combustion chamber, the partition including a window; and wherein the blower is within the inlet side of the interior space and forces primary and secondary air into the outlet side of the interior space through the window in the partition. 
   
   
       16 . The water heater of  claim 15 , wherein the air intake assembly includes a louvered opening communicating between the inlet side and ambient air; and wherein all air sucked into the inlet side of the interior space by the blower flows through the louvered opening. 
   
   
       17 . The water heater of  claim 10 , further comprising a pressure sensor communicating with the interior space, the pressure sensor operable to disable the gas valve to cut off the supply of gaseous fuel to the burner when pressure within the interior space drops below a minimum threshold. 
   
   
       18 . The water heater of  claim 17 , wherein the air intake assembly includes an exterior surface, a sensor mounting cavity in the exterior surface and a wire routing channel in the exterior surface; wherein the air intake assembly further includes a hole communicating between the sensor mounting cavity and the interior space; wherein the pressure sensor is mounted within the sensor mounting cavity and communicates with the interior space through the hole; and wherein the blower includes a power cord that is received in the wire routing channel. 
   
   
       19 . A water heater comprising:
 a tank for water to be heated;   a combustion chamber;   an exhaust structure;   a flue in the tank communicating between the combustion chamber and the exhaust structure;   a burner in the combustion chamber operable to burn a mixture of primary combustion air with gaseous fuel in a partially premixed but substantially diffusion flame having an envelope, such that combustion of the mixture is completed at the diffusion flame envelope in the presence of secondary air to produce products of combustion, the products of combustion flowing through the flue to the exhaust structure to heat the water in the tank;   an air intake assembly including an air inlet above the combustion chamber and a conduit communicating between the air inlet and the combustion chamber;   a centrifugal blower within the air intake assembly operable to suck air into the air intake assembly through the air inlet and force primary and secondary air into the combustion chamber through the conduit at pressure above atmospheric;   a gas valve for controlling a supply of gaseous fuel to the burner;   a controller that controls operation of the blower and gas valve;   an air distributor plate having a generally horizontal top surface defining a plurality of edges, and a bottom surface at least partially defining a secondary air distribution space and a primary air plenum;   wherein all primary and secondary air flows into the respective primary air plenum and secondary air distribution space;   wherein the air distributor plate defines a primary air opening for the provision of primary air from the primary air plenum to the burner; and   wherein the air distributor plate includes a plurality of secondary air openings for substantially axisymmetric distribution of secondary air around the air distributor plate.   
   
   
       20 . The water heater of  claim 19 , wherein the air distributor plate has first, second, third, fourth, fifth, and sixth edges; wherein the air distributor plate has generally vertical surfaces extending from the first, second, third, fourth, and fifth edges to at least partially define the secondary air distribution space; wherein the generally vertical surfaces define the secondary air openings; and wherein the substantially axisymmetric distribution includes secondary air flow rates through the plurality secondary air openings with standard deviation less than 0.88 from average secondary air flow rate. 
   
   
       21 . The water heater of  claim 20 , wherein the standard deviation is less than 0.10. 
   
   
       22 . The water heater of  claim 20 , wherein the standard deviation is about 0.08. 
   
   
       23 . The water heater of  claim 19 , further comprising an air diverter secured to an edge of the air distributor plate to direct all primary and secondary combustion air from an air intake to the respective primary air plenum and secondary air distribution space. 
   
   
       24 . The water heater of  claim 19 , further comprising a plenum pan mounted to a bottom surface of air distributor plate to at least partially define the primary air plenum. 
   
   
       25 . The water heater of  claim 24 , wherein the plenum pan includes a plurality of tabs; wherein the distributor plate includes a plurality of slots through which tabs extend; and wherein the tabs are bent against the top surface of distributor plate to secure the plenum pan to the bottom surface of the distributor plate. 
   
   
       26 . The water heater of  claim 19 , wherein the distributor plate includes an integral first locating member, an integral burner locating member, an integral manifold pocket, and an integral manifold clearance indentation; wherein a portion of the burner mates with the burner locating member; the water heater further comprising a gas manifold for the provision of gaseous fuel from the gas valve to the burner, the manifold extending into the manifold clearance indentation during installation, and the manifold extending into the manifold pocket when installed; and a condensation tray including a first mating portion that mates with the first locating member, and a second mating portion that extends around the manifold pocket. 
   
   
       27 . The water heater of  claim 19 , wherein the distributor plate includes first and second locating members; the water heater further comprising a condensation tray having first and second clocking points that mate with the respective first and second locating members; wherein the condensation tray is secured to the distributor plate with a single threaded fastener in combination with mating of the first and second clocking points with the first and second locating members. 
   
   
       28 . The water heater of  claim 19 , further comprising a condensation tray mounted in the combustion chamber; wherein the burner includes a condensate drain that directs condensation to the condensation tray. 
   
   
       29 . The water heater of  claim 28 , wherein the condensation tray has a containment capacity at least equal to the volume of condensate predicted during heavy condensation cold start of the water heater. 
   
   
       30 . The water heater of  claim 28 , wherein the condensation tray is dimensioned to cause a sufficient surface area of condensate in the condensation tray to be exposed to heat in the combustion chamber to result in total evaporation of the condensate upon the water heater reaching steady-state combustion and normal operation.