Water heater with pressurized combustion

This application is a continuation of U.S. application Ser. No. 11/034,130, filed Jan. 12, 2005, now U.S. Pat. No. 7,032,543 and a continuation of U.S. application Ser. No. 11/329,793, filed on Jan. 11, 2006, now U.S. Pat. No. 7,513,221, the entire contents of which are incorporated herein by reference.

The present invention relates to a water heater having a pressurized combustion chamber.

In one embodiment, the invention provides 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, the combustion chamber having an air intake defining an air inlet, said combustion chamber being substantially air-tightly sealed except for the air inlet and the inlet end of the flue; means for introducing air into the combustion chamber and raising 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 products of combustion. The 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.

In another embodiment, the invention provides 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, the combustion chamber having an air intake defining an air inlet, said combustion chamber being substantially air-tightly sealed except for the air inlet and the inlet end of the flue; means for introducing air into the combustion chamber sealed with respect to the air inlet such that the combustion chamber is downstream of the means for introducing air and air flows through the means for introducing air into the combustion chamber, wherein operation of the means for introducing air 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 products of combustion. The 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.

In some embodiments, the air intake may define an air plenum and a flame arrester may be sealed between the plenum and combustion chamber to contain flames within the combustion chamber. The flue in some embodiments may include a baffle to slow the flow of products of combustion through the flue. The water heater may include a gas valve that is either electric or non-electric, a pressure sensor for sensing pressure in the combustion chamber and/or plenum, a gas pressure switch that activates the at least one fan in response to a change of gas pressure at the gas valve consistent with gas flow to the main burner, a flammable vapor sensor for sensing the presence of flammable vapors in the combustion chamber and/or plenum, and a high-limit water temperature switch for sensing whether the water has exceeded a high limit.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.