초록 ▼

A water heater includes a sealed combustion chamber and one or more fans for raising pressure in the combustion chamber to increase efficiency of the water heater. The pressure permits a more restrictive baffle to be used in the flue compared to baffles used in atmospheric water heaters. The water h

A water heater includes a sealed combustion chamber and one or more fans for raising pressure in the combustion chamber to increase efficiency of the water heater. The pressure permits a more restrictive baffle to be used in the flue compared to baffles used in atmospheric water heaters. The water heater may include a water temperature sensor that activates the fan without activating the burner if water temperature raises above a desired temperature. The water heater may also include pressure and vapor sensors to ensure the combustion chamber is properly sealed and there are no flammable vapors present prior to igniting the burner. The fans are relatively small and run off the same DC power that runs an electric gas valve. The fans may be, for example, 12 or 24 Volt fans with power inputs of about 10 Watts or less.

대표청구항 ▼

The invention claimed is: 1. A water heater comprising: a water tank adapted to contain water to be heated; a flue extending through the water tank and having an inlet end and an outlet end; a combustion chamber in communication with the inlet end of the flue; a plenum upstream of and in fluid comm

The invention claimed is: 1. A water heater comprising: a water tank adapted to contain water to be heated; a flue extending through the water tank and having an inlet end and an outlet end; a combustion chamber in communication with the inlet end of the flue; a plenum upstream of and in fluid communication with the combustion chamber and having an air inlet, wherein the space defined by the combustion chamber and plenum is substantially air-tightly sealed except for the air inlet and the inlet end of the flue; at least one fan sealed with respect to the air inlet such that substantially all air entering the plenum through the air inlet flows through the at least one fan, wherein operation of the at least one fan raises the pressure in the plenum and combustion chamber above atmospheric pressure; a flame arrester sealed between the plenum and combustion chamber such that substantially all air flowing into the combustion chamber from the plenum flows through the flame arrester, the flame arrester permitting ingress of flammable vapors into the combustion chamber but substantially preventing egress of flame out of the combustion chamber into the plenum; and a main burner within the combustion chamber and operable to combust a mixture of air and fuel to create hot products of combustion; wherein the hot products of combustion flow out of the combustion chamber into the inlet end of the flue, heat the water in the tank through the flue, and exit the water heater through the outlet end of the flue; wherein primary air is mixed with fuel prior to combustion at the main burner; wherein secondary air within the combustion chamber combines with the primary air and fuel mixture to complete the combustion process at an outlet of the burner; and wherein the at least one fan pressurizes both primary and secondary air in the combustion chamber. 2. The water heater of claim 1, further comprising a flammable vapor sensor in one of the combustion chamber and plenum; and a controller that initiates ignition of the main burner only after the at least one fan has been activated and the flammable vapor sensor senses an acceptable concentration of flammable vapors. 3. The water heater of claim 2, further comprising a hot surface igniter within the combustion chamber and near the main burner; wherein the controller includes a timer; and wherein the controller initiates ignition of the main burner by first activating the hot surface igniter to heat the hot surface igniter to an ignition temperature hot enough to ignite the air and fuel mixture, and permitting fuel flow to the main burner after the timer indicates that sufficient time has elapsed after activation of the hot surface igniter to enable the hot surface igniter to reach the ignition temperature. 4. The water heater of claim 3, further comprising a flame sensor within the combustion chamber and near the main burner, wherein if the flame sensor does not sense flame at the main burner following the controller initiating ignition, the controller interrupts fuel flow to the main burner, activates the at least one fan to purge the combustion chamber, and again initiates ignition of the main burner. 5. The water heater of claim 1, further comprising a pressure sensor that senses pressure in at least one of the combustion chamber and plenum; and a controller that initiates ignition of the main burner only after the at least one fan has been activated and the pressure sensor senses a rise in pressure in at least one of the plenum and combustion chamber. 6. The water heater of claim 1, further comprising a water temperature probe exposed to the water in the tank, and a controller, wherein when the water temperature probe senses the water in the tank has exceeded a high temperature limit, the controller activates the at least one fan in the absence of fuel flow to the main burner to force ambient air through the flue and reduce the water temperature until the temperature probe senses that temperature of the water in the tank is below the high temperature limit. 7. The water heater of claim 6, wherein the controller includes a timer and wherein the timer deactivates the at least one fan if the at least one fan has run a selected time period without reducing the water temperature below the high temperature limit. 8. The water heater of claim 1, further comprising a base pan supporting the water tank such that the tank and base pan define therebetween a space; a divider dividing the space into the combustion chamber and plenum such that the combustion chamber and plenum communicate with each other only through an opening in the divider; wherein the flame arrester is mounted to the divider across the opening; and wherein the at least one fan is mounted to the base pan over an opening to the plenum. 9. The water heater of claim 1, wherein the at least one fan has an electrical input less than about ten watts. 10. The water heater of claim 1, wherein the at least one fan includes a twelve or twenty-four volt direct current permanent magnet fan. 11. The water heater of claim 1, further comprising a pilot burner near the main burner and adapted to maintain a constant flame to ignite the mixture of fuel and air flowing out of the main burner; a thermocouple generating a voltage in response to heat from the pilot burner flame; a voltage sensor sensing the voltage in the thermocouple; and a controller that activates the at least one fan to purge the combustion chamber in response to the voltage sensor sensing a voltage drop in the thermocouple indicative of oxygen depletion in the combustion chamber. 12. The water heater of claim 11, wherein the controller deactivates the at least one fan and prevents main burner ignition in response to the voltage sensor sensing a voltage drop in the thermocouple indicative of pilot outage. 13. The water heater of claim 1, further comprising an electrically-powered fuel valve, the valve and at least one fan being powered with electricity from a single source. 14. The water heater of claim 13, wherein the single source of electricity provides A/C power; wherein the valve includes a power transformer and inverter turning the provided A/C power into one of 12-volt and 24-volt D/C power; and wherein the valve and at least one fan operate on D/C power provided by the power converter. 15. A water heater comprising: a water tank adapted to contain water to be heated; a flue extending through the water tank and having an inlet end and an outlet end; a combustion chamber in communication with the inlet end of the flue; a plenum upstream of and in fluid communication with the combustion chamber and having an air inlet, wherein the space defined by the combustion chamber and plenum is substantially air-tightly sealed except for the air inlet and the inlet end of the flue; at least one fan sealed with respect to the air inlet such that substantially all air entering the plenum through the air inlet flows through the at least one fan, wherein operation of the at least one fan raises the pressure in the plenum and combustion chamber above atmospheric pressure; a flame arrester sealed between the plenum and combustion chamber such that substantially all air flowing into the combustion chamber from the plenum flows through the flame arrester, the flame arrester permitting ingress of flammable vapors into the combustion chamber but substantially preventing egress of flame out of the combustion chamber into the plenum; and a main burner within the combustion chamber and operable to combust a mixture of air and fuel to create hot products of combustion; wherein the hot products of combustion flow out of the combustion chamber into the inlet end of the flue, heat the water in the tank through the flue, and exit the water heater through the outlet end of the flue, further comprising a baffle in the flue operable to slow the rate at which products of combustion flow through the flue to thereby increase heat transfer through the flue wall to the water in the tank. 16. A water heater comprising: a water tank adapted to contain water to be heated; a flue extending through the water tank and having an inlet end and an outlet end; a combustion chamber in communication with the inlet end of the flue and having an air intake, the combustion chamber being substantially air-tightly sealed except for the inlet end of the flue and the air intake; at least one fan sealed with respect to the air intake such that all air entering the combustion chamber flows through the at least one fan, wherein operation of the at least one fan raises the pressure in the combustion chamber above atmospheric pressure; and a main burner within the combustion chamber and operable to combust a mixture of air and fuel to create hot products of combustion; wherein the hot products of combustion flow out of the combustion chamber into the inlet end of the flue, heat the water in the tank through the flue, and exit the water heater through the outlet end of the flue; further comprising a pilot burner near the main burner and maintaining a pilot flame to ignite the mixture of air and fuel flowing out of the burner; and a temperature probe measuring the water temperature within the water tank; wherein the temperature probe permits the air and fuel mixture to flow out of the main burner and activates the at least one fan when the water temperature drops below a set point; and wherein the temperature probe activates the at least one fan in response to water temperature being above the set point but below a temperature indicative of a low-oxygen condition within the combustion chamber. 17. The water heater of claim 16, further comprising a flame arrester in the air intake, the flame arrester permitting ingress of flammable vapors into the combustion chamber but substantially preventing egress of flame out of the combustion chamber through the air intake. 18. The water heater of claim 17, wherein the air intake includes a plenum and an inlet opening to the plenum, wherein the at least one fan is sealed across the inlet opening such that substantially all air flowing into the plenum must flow through the at least one fan, and wherein the flame arrester is sealed between the plenum and combustion chamber such that substantially all air entering the combustion chamber from the plenum flows through the flame arrester. 19. A method for operating a gas-fired water heater having a water tank, a combustion chamber, an air intake for the flow of combustion air into the combustion chamber, a main burner in the combustion chamber, and a flue within the water tank for conducting a flow of hot gases out of the combustion chamber and heating water stored in the water tank, the method comprising: substantially air-tightly sealing the combustion chamber except for communication with the air intake and flue; sealing at least one fan in the air intake such that all combustion air flowing through the air intake into the combustion chamber flows through the at least one fan; and raising the pressure in the combustion chamber above atmospheric pressure in response to operation of the at least one fan during main burner operation to improve the heat transfer efficiency of the water heater, further comprising mixing primary air with fuel prior to combustion at the main burner; combining secondary air with the primary air and fuel mixture to complete the combustion process at an outlet of the burner; and pressurizing with the at least one fan both primary and secondary air in the combustion chamber. 20. The method of claim 19, wherein the air intake includes a plenum, the method further comprising using a flammable vapor sensor to sense the presence of flammable vapors in one of the combustion chamber and plenum; activating the at least one fan without initiating ignition of the main burner if flammable vapors are sensed by the flammable vapor sensor; and initiating ignition of the main burner only after the flammable vapor sensor senses an acceptable concentration of flammable vapors. 21. The method of claim 20, wherein initiating ignition of the main burner includes first activating a hot surface igniter near the main burner, then waiting a time sufficient for the hot surface igniter to reach a temperature hot enough to ignite an air and fuel mixture, and then permitting flow of the air and fuel mixture out of the main burner. 22. The method of claim 21, further comprising monitoring with a flame sensor whether flame is present at the main burner; and, if the flame sensor does not sense flame at the main burner, deactivating the hot surface igniter, stopping the flow of air and fuel mixture out of the burner, then activate the at least one fan to purge the combustion chamber, then repeat the steps for initiating ignition of the main burner. 23. The method of claim 19, wherein the air intake includes a plenum, the method further comprising monitoring with a pressure sensor pressure within at least one of the combustion chamber and plenum; and initiating ignition of the main burner only after the at least one fan has been activated and the pressure sensor senses a rise in pressure in at least one of the plenum and combustion chamber. 24. The method of claim 19, further comprising monitoring with a water temperature probe the water temperature within the tank; activating the at least one fan without initiating ignition of the main burner in response to the water temperature probe sensing a water temperature in excess of a high temperature limit; and deactivating the at least one fan when the water temperature probe senses that the temperature of the water in the tank is below the high temperature limit. 25. The method of claim 24, further comprising deactivating the at least one fan if the at least one fan runs a selected time period without reducing the water temperature below the high temperature limit. 26. The method of claim 19, wherein the water heater includes a pilot burner and thermocouple near the main burner, the thermocouple generating a voltage in response to being heated by a flame on the pilot burner; the method further comprising monitoring the voltage in the thermocouple; and activating the at least one fan to purge the combustion chamber in response to sensing a voltage drop in the thermocouple indicative of oxygen depletion in the combustion chamber. 27. The method of claim 26, further comprising deactivating the at least one fan and preventing main burner ignition in response to the voltage sensor sensing a voltage drop in the thermocouple indicative of pilot outage. 28. The method of claim 19, wherein the water heater includes an electric fuel valve that operates on a direct-current valve power source not greater than 24 volts, the method further comprising operating the at least one fan off of the valve power source. 29. The water heater of claim 19, wherein the water heater includes a pilot burner near the main burner and maintaining a pilot flame to ignite a mixture of air and fuel flowing out of the burner, the method further comprising: measuring the temperature of the water within the tank; in response to the water temperature dropping below a set point, permitting the air and fuel mixture to flow out of the main burner and activating the at least one fan; and in response to water temperature being above the set point but below a temperature indicative of a low-oxygen condition within the combustion chamber, activating the at least one fan. 30. A method for operating a gas-fired water heater having a water tank, a combustion chamber, an air intake for the flow of combustion air into the combustion chamber, a main burner in the combustion chamber, and a flue within the water tank for conducting a flow of hot gases out of the combustion chamber and heating water stored in the water tank, the method comprising: substantially air-tightly sealing the combustion chamber except for communication with the air intake and flue; sealing at least one fan in the air intake such that all combustion air flowing through the air intake into the combustion chamber flows through the at least one fan; and raising the pressure in the combustion chamber above atmospheric pressure in response to operation of the at least one fan during main burner operation to improve the heat transfer efficiency of the water heater, further comprising positioning a baffle within the flue to slow the rate at which products of combustion flow through the flue to thereby increase heat transfer through the flue wall to the water in the tank. 31. A method for operating a gas-fired water heater having a water tank, a combustion chamber, an air intake for the flow of combustion air into the combustion chamber, a main burner in the combustion chamber, and a flue within the water tank for conducting a flow of hot gases out of the combustion chamber and heating water stored in the water tank, the method comprising: substantially air-tightly sealing the combustion chamber except for communication with the air intake and flue; sealing at least one fan in the air intake such that all combustion air flowing through the air intake into the combustion chamber flows through the at least one fan; and raising the pressure in the combustion chamber above atmospheric pressure in response to operation of the at least one fan during main burner operation to improve the heat transfer efficiency of the water heater, further comprising mounting a flame arrester within the air intake downstream of the at least one fan such that all combustion air flowing into the combustion chamber through the air intake flows through the flame arrester; and further comprising substantially preventing with the flame arrester the escape of flame from the combustion chamber through the air intake. 32. The method of claim 31, further comprising activating the at least one fan prior to igniting the burner to create positive pressure upstream of the flame arrester to assist in containing flame within the combustion chamber.