Thermistor system for temperature measurement in a gas water heater combustion chamber

Abstract

A gas water heater that includes a sheathed thermistor placed into the combustion chamber near a gas burner to provide for more accurate measurements of the temperature therein. The thermistor may be used in combination with a thermopile to provide additional measurements for determination of temperature conditions requiring a closure of a valve controlling the flow of gas to the burner

1 . A gas fueled water heater, comprising:
 a tank for storage of water for heating;   a chamber wall at least partially enclosing a combustion chamber;   a gas burner positioned adjacent to the tank and within the combustion chamber, the gas burner configured for heating the water in the tank;   a thermistor positioned within the combustion chamber near the gas burner, the thermistor not contacting the chamber wall, the thermistor configured for providing temperature measurements of the combustion chamber; and   a sheath positioned around the thermistor.   
     
     
         2 . The gas fueled water heater of  claim 1 , further comprising a controller in communication with the thermistor for the receipt of temperature measurements from the thermistor. 
     
     
         3 . The gas fueled water heater of  claim 2 , further comprising:
 a gas valve for controlling the flow of gas to the gas burner;   wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that the temperature in the combustion chamber as measured by the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX .   
     
     
         4 . The gas fueled water heater of  claim 2 ,
 a gas valve for controlling the flow of gas to the gas burner;   wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that the temperature in the combustion chamber as measured by the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX , for a predetermined period of time, Δ ts .   
     
     
         5 . The gas fueled water heater of  claim 1 , further comprising:
 a pilot burner for providing a pilot light to ignite the gas burner; and   a thermopile positioned adjacent to the pilot burner and configured for detecting the presence of a pilot light at the pilot burner.   
     
     
         6 . The gas fueled water heater of  claim 1 , further comprising:
 a pilot burner for providing a pilot light to ignite the gas burner; and   a thermopile positioned adjacent to the pilot burner and configured for detecting the presence of a pilot light at the pilot burner and for providing a secondary measurement of temperature in the combustion chamber.   
     
     
         7 . The gas fueled water heater of  claim 6 , further comprising:
 a gas valve for controlling the flow of gas to the gas burner;   wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that both i) the temperature in the combustion chamber as measured by the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX , and ii) the temperature in the combustion chamber as measured by the thermopile has reached or exceeded a predetermined maximum temperature, TP MAX .   
     
     
         8 . The gas fueled water heater of  claim 6 , further comprising:
 a gas valve for controlling the flow of gas to the gas burner;   wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that both i) the temperature in the combustion chamber as measured by the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX , for a predetermined period of time, Δ ts , and ii) the temperature in the combustion chamber as measured by the thermopile has also reached or exceeded a predetermined maximum temperature, TP MAX , for the predetermined period of time, Δ tp .   
     
     
         9 . The gas fueled water heater of  claim 1 , wherein the thermistor is supported by the chamber wall. 
     
     
         10 . The gas fueled water heater of  claim 9 , wherein the sheath is attached to the chamber wall. 
     
     
         11 . The gas fueled water heater of  claim 10 , wherein the sheath comprises a metal. 
     
     
         12 . The gas fueled water heater of  claim 11 , wherein the sheath comprises a ceramic. 
     
     
         13 . A gas fueled water heater, comprising:
 a tank for storage of water for heating;   a chamber wall supporting the tank and forming a combustion chamber;   a gas burner centrally located within the combustion chamber and positioned below the tank, the gas burner spaced apart from the chamber wall;   a thermistor located with the combustion chamber and adjacent to the gas burner without being located within a flame of the burner, the thermistor configured for providing a signal representing temperature within the combustion chamber, wherein the thermistor is not in contact with the chamber wall; and   a sheath completely surrounding the thermistor and configured for protecting the thermistor.   
     
     
         14 . The gas fueled water heater of  claim 13 , further comprising
 a controller in communication with the thermistor for the receipt of temperature measurements from the thermistor, and   a gas valve for controlling the flow of gas to the gas burner;   wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that the temperature in the combustion chamber as provided by a signal from the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX .   
     
     
         15 . The gas fueled water heater of  claim 13 , further comprising
 a controller in communication with the thermistor for the receipt of temperature measurements from the thermistor, and   a gas valve for controlling the flow of gas to the gas burner;   wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that the temperature in the combustion chamber as determined from a signal provided by the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX , for a predetermined period of time, Δ ts .   
     
     
         16 . The gas fueled water heater of  claim 13 , further comprising:
 a pilot burner for providing a pilot light to ignite the gas burner; and   a thermopile positioned adjacent to the pilot burner and configured for detecting the presence of a pilot light at the pilot burner and for providing a secondary measurement of temperature in the combustion chamber.   
     
     
         17 . The gas fueled water heater of  claim 16 , further comprising a controller in communication with the thermistor for the receipt of a signal representing temperature measurements from the thermistor; and
 wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that both i) the temperature in the combustion chamber as measured by the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX , and ii) the temperature in the combustion chamber as measured by the thermopile has reached or exceeded a predetermined maximum temperature, TP MAX .   
     
     
         18 . The gas fueled water heater of  claim 16 , further comprising:
 a gas valve for controlling the flow of gas to the gas burner;   wherein the controller is in communication with the gas valve and is configured to close the flow of gas through the gas valve upon determining that both i) the temperature in the combustion chamber as measured by the thermistor has reached or exceeded a predetermined maximum temperature, TS MAX , for a predetermined period of time, Δ ts , and ii) the temperature in the combustion chamber as measured by the thermopile has also reached or exceeded a predetermined maximum temperature, TP MAX , for the predetermined period of time, Δ tp .