Apparatus for and method of operating a furnace blower to evaporate condensate within an exhaust flue

Abstract

A blower for a furnace is provided where the blower has an impeller that is configured to create a primary air flow of combustion air into the blower housing and a secondary air flow of cooling air through the blower motor. The primary air flow of combustion air into the furnace generates hot exhaust gases for a heat exchanger in the furnace. The secondary air flow cools the blower motor. The secondary air flow is mixed with the hot exhaust gases in the blower housing and cools the exhaust gases before being discharged from the blower housing. A control operates the blower for a time period after each combustion cycle to introduce ambient air into the exhaust flue and chimney to ensure the evaporation of any condensate forming from the products of combustion contained in the exhaust. The blower may be a variable or multi-speed motor so that a different motor speed may be used for combustion than for the run time after combustion.

What is claimed is:  
     
         1 . A method for drying the condensate from an exhaust flue for a fuel burning appliance, said fuel burning appliance having a combustion blower to exhaust the products of combustion from a combustion chamber into the exhaust flue, the method comprising the step of running the combustion blower after the end of a combustion cycle for a time at least longer than a post purge time period but less than continuously.  
     
     
         2 . The method of  claim 1  wherein the running step includes the step of running the combustion blower for at least approximately three minutes after the end of a combustion cycle.  
     
     
         3 . The method of  claim 2  further comprising the step of running the combustion blower after the end of each combustion cycle for the same time period.  
     
     
         4 . The method of  claim 3  wherein the exhaust blower includes an electric motor and further comprising the step of drawing in some ambient air through the electric motor.  
     
     
         5 . The method of  claim 3  wherein the fuel burning appliance further comprises a control, and further comprising the step of setting the control to run the combustion blower for at least three minutes after the end of a combustion cycle.  
     
     
         6 . The method of  claim 5  further comprising the step of running the exhaust blower at a different speed after the end of a combustion cycle.  
     
     
         7 . The method of  claim 6  wherein the motor is a variable speed motor and the step of running the exhaust blower at a different speed comprises the step of changing the speed at which the variable speed motor runs.  
     
     
         8 . The method of  claim 6  wherein the motor is a multi-speed motor and the step of running the exhaust blower at a different speed comprises the step of changing the speed at which the multi-speed motor runs.  
     
     
         9 . The method of  claim 2  wherein the fuel burning appliance further comprises a control, and further comprising the step of setting the control to run the combustion blower for at least three minutes after the end of each combustion cycle.  
     
     
         10 . The method of  claim 9  further comprising the step of running the exhaust blower at a different speed after the end of a combustion cycle.  
     
     
         11 . The method of  claim 10  wherein the motor is a variable speed motor and the step of running the exhaust blower at a different speed comprises the step of changing the speed at which the variable speed motor runs.  
     
     
         12 . The method of  claim 10  wherein the motor is a multi-speed motor and the step of running the exhaust blower at a different speed comprises the step of changing the speed at which the multi-speed motor runs.  
     
     
         13 . A fuel burning appliance having an exhaust outlet adapted for connection to an exhaust flue, an exhaust blower for exhausting products of combustion through said exhaust outlet, and a control for controlling the operation of the exhaust blower, the control being configured to run the exhaust blower after the end of a combustion cycle for a time at least longer than a post purge time period but less than continuously to thereby ensure that the exhaust flue dries of condensate formed therein by said products of combustion.  
     
     
         14 . The fuel burning appliance of  claim 13  wherein said control is configured to run the exhaust blower after the end of a combustion cycle for at least approximately three minutes but less than continuously.  
     
     
         15 . The fuel burning appliance of  claim 14  wherein said exhaust blower has an electric motor, and further comprising a connection between said motor and a blower housing through which ambient air is drawn as the exhaust blower is operated.  
     
     
         16 . The fuel burning appliance of  claim 14  wherein said electric motor comprises a variable speed motor and said control is configured to run said electric motor at a different speed during a combustion cycle than after a combustion cycle.  
     
     
         17 . The fuel burning appliance of  claim 14  wherein said electric motor comprises a multispeed motor and said control is configured to run said electric motor at a different speed during a combustion cycle than after a combustion cycle.  
     
     
         18 . The fuel burning appliance of  claim 13  wherein said control is configured to permit the exhaust blower post combustion cycle run time to be adjusted.  
     
     
         19 . A fuel burning appliance having an exhaust outlet adapted for connection to an exhaust flue, an exhaust blower for exhausting products of combustion through said exhaust outlet, and a control for controlling the operation of the exhaust blower, the control being configured to run the exhaust blower after the end of each combustion cycle for at least about three minutes to thereby ensure that the exhaust flue dries of condensate formed therein by said products of combustion.  
     
     
         20 . The fuel burning appliance of  claim 19  wherein said exhaust blower has an electric motor, and further comprising a connection between said motor and a blower housing through which ambient air is drawn as the exhaust blower is operated.  
     
     
         21 . The fuel burning appliance of  claim 20  wherein said electric motor comprises a variable speed motor and said control is configured to run said electric motor at a different speed during a combustion cycle than after a combustion cycle.  
     
     
         22 . The fuel burning appliance of  claim 20  wherein said electric motor comprises a multi-speed motor and said control is configured to run said electric motor at a different speed during a combustion cycle than after a combustion cycle.  
     
     
         23 . A method for drying the condensate from an exhaust flue for a fuel burning appliance, said fuel burning appliance having a combustion blower to exhaust the products of combustion from a combustion chamber into the exhaust flue, the method comprising the step of running the combustion blower after the end of a combustion cycle for at least about three minutes but less than continuously.  
     
     
         24 . The method of  claim 23  further comprising the step of drawing at least some ambient air into the exhaust blower at least during the time period after the end of the combustion cycle.  
     
     
         25 . The method of  claim 24  wherein the exhaust blower includes an electric motor and wherein the step of drawing in some ambient air includes the step of drawing in some ambient air through the electric motor.  
     
     
         26 . The method of  claim 25  wherein the fuel burning appliance further comprises a control, and further comprising the step of setting the control to run the combustion blower for at least three minutes after the end of a combustion cycle.  
     
     
         27 . The method of  claim 26  further comprising the step of running the exhaust blower at a different speed after the end of a combustion cycle.  
     
     
         28 . A method for drying the condensate from an exhaust flue for a fuel burning appliance, said fuel burning appliance having a combustion blower to exhaust the products of combustion from a combustion chamber into the exhaust flue, the method comprising the step of running the combustion blower after the end of each combustion cycle for a fixed period of time equal to at least three minutes but less than continuously.  
     
     
         29 . The method of  claim 28  wherein the exhaust blower includes an electric motor and further comprising the step of drawing in some ambient air through the electric motor.  
     
     
         30 . The method of  claim 29  wherein the fuel burning appliance further comprises a control, and further comprising the step of setting the control to run the combustion blower for at least three minutes after the end of each combustion cycle.  
     
     
         31 . The method of  claim 30  further comprising the step of running the exhaust blower at a different speed after the end of each combustion cycle.  
     
     
         32 . A method for drying the condensate from an exhaust flue for a fuel burning appliance, said fuel burning appliance having a combustion blower to exhaust the products of combustion from a combustion chamber into the exhaust flue and a control configured to control the operation of said blower, the method comprising the step of determining a duty cycle for said combustion blower to thereby ensure that the exhaust flue dries of condensate formed therein by said products of combustion.  
     
     
         33 . The method of  claim 32  wherein the determining step includes the step of determining either of the frequency or duration of blower run time after appliance combustion cycles.  
     
     
         34 . The method of  claim 33  wherein the control is configured to perform the determining step.  
     
     
         35 . The method of  claim 34  wherein the determining step includes the step of determining blower run time after combustion.  
     
     
         36 . The method of  claim 34  wherein the determining step includes the step of determining a frequency for blower run time after combustion.  
     
     
         37 . The method of  claim 32  wherein the step of determining said blower duty cycle includes determining blower run time after combustion to be a time greater than a post purge time period but less than continuously.  
     
     
         38 . The method of  claim 32  wherein the step of determining includes the step of determining the duty cycle for the exhaust blower in response to the appliance duty cycle.  
     
     
         39 . A fuel burning appliance having an exhaust outlet adapted for connection to an exhaust flue, an exhaust blower for exhausting products of combustion through said exhaust outlet, and a control for controlling the operation of the exhaust blower, the control being configured to determine a duty cycle for the exhaust blower to thereby ensure that the exhaust flue dries of condensate formed therein by said products of combustion.  
     
     
         40 . The fuel burning appliance of  claim 39  wherein said control is configured to determine a post combustion blower run time greater than a post purge time period but less than continuously.  
     
     
         41 . The fuel burning appliance of  claim 39  wherein said control is configured to determine a frequency for blower run time after combustion.  
     
     
         42 . The fuel burning appliance of  claim 39  wherein said control is configured to determine the duty cycle for the exhaust blower in response to the appliance duty cycle.