Water heater with intermittent pilot and damper control

Abstract

A water heater includes a gas burner, a thermoelectric element, a pilot, a main valve, a damper, and a controller that actuates an intermittent spark generator to ignite a pilot flame of the pilot after a first predetermined condition is satisfied, moves the damper toward the open position when the energy generated by the thermoelectric element exceeds a threshold value, and opens the main valve to permit flow of gas to the gas burner after the damper is in the open position and after a second predetermined condition is satisfied. The first predetermined condition is different from the second predetermined condition and the first predetermined condition is selected to be satisfied before the second predetermined condition is satisfied.

What is claimed is: 
     
         1 . A water heater comprising:
 a water storage tank defining an interior region configured to contain water to be heated;   a heat source configured to generate heat for transfer to water when contained in the interior region of the water storage tank, the heat source including a gas burner configured to generate combustion gases;   a flue extending through the interior region of the water storage tank and configured to exhaust the combustion gases generated by the gas burner;   a temperature sensor positioned to directly or indirectly sense a temperature of the water when contained in the interior region of the water storage tank;   a pilot associated with the gas burner and configured to fire the gas burner;   a pilot valve configured to supply gas to the pilot;   an intermittent spark generator associated with the pilot and configured to ignite a pilot flame;   a thermoelectric element configured to generate energy from the pilot flame;   a main valve associated with the gas burner and configured to supply gas to the gas burner;   a damper extending within the flue and configured to move between a closed position to restrict the flow of the combustion gases through the flue and an open position to allow the flow of the combustion gases through the flue; and   a controller coupled to the temperature sensor, the pilot valve, the intermittent spark generator, the thermoelectric element, and the damper, the controller being configured to:   actuate the intermittent spark generator to ignite the pilot flame of the pilot after a first predetermined condition is satisfied,   move the damper toward the open position when the energy generated by the thermoelectric element exceeds a threshold value, and   open the main valve to permit flow of gas to the gas burner after the damper is in the open position and after a second predetermined condition is satisfied,   wherein the first predetermined condition is different from the second predetermined condition and the first predetermined condition is selected to be satisfied before the second predetermined condition is satisfied.   
     
     
         2 . The water heater of  claim 1 , the first predetermined condition being satisfied when the temperature of the water when contained in the interior region of the water storage tank drops at a rate exceeding a predetermined rate of temperature change. 
     
     
         3 . The water heater of  claim 1 , the first predetermined condition being satisfied when the temperature of the water when contained in the interior region of the water storage tank drops below a predetermined difference between a setpoint temperature and a first differential temperature. 
     
     
         4 . The water heater of  claim 3 , the second predetermined condition being satisfied when the temperature of the water when contained in the interior region of the water storage tank drops below a predetermined difference between a setpoint temperature and a second differential temperature, the first differential temperature being smaller than the second differential temperature. 
     
     
         5 . The water heater of  claim 4 , the controller being further configured to:
 move the damper from the closed position toward the open position when the energy generated by the thermoelectric element exceeds the threshold value and when the temperature of the water when contained in the interior region of the water storage tank is below the predetermined difference between the setpoint temperature and the second differential temperature.   
     
     
         6 . The water heater of  claim 1 , the controller being further configured to open the main valve to allow ignition of the gas burner using energy generated by the thermoelectric element. 
     
     
         7 . The water heater of  claim 1 , wherein the threshold value of the energy generated by the thermoelectric element is at least 350 mV. 
     
     
         8 . The water heater of  claim 1 , further comprising a damper switch coupled to the controller, wherein the damper switch is configured to send to the controller a “fully open” signal related to the open position of the damper, and wherein the controller is configured to switch power from the damper to open the main valve in response to the “fully open” signal, using only energy generated by the thermoelectric element. 
     
     
         9 . A method of firing a water heater having a gas burner coupled to receive gas via a main valve, a pilot coupled to receive gas via a pilot valve, an intermittent spark generator positioned to spark the pilot, a thermoelectric element, a flue, and a damper configured to move between a closed position and an open position relative to the flue, the method comprising the steps of:
 actuating the intermittent spark generator to ignite a pilot flame of the pilot after a first predetermined condition is satisfied,   generating a threshold value of energy in the thermoelectric element via the pilot flame, moving the damper toward the open position when the threshold value of energy reaches the threshold value thus permitting combustion gases to flow through the flue, and   opening the main valve to permit flow of gas to the gas burner after the damper is in the open position and after a second predetermined condition is satisfied,   wherein the first predetermined condition is different from the second predetermined condition and the first predetermined condition is selected to be met before the second predetermined condition.   
     
     
         10 . The method of  claim 9 , the first predetermined condition being satisfied when the temperature of water when contained in an interior region of a water storage tank of the water heater drops at a rate above a predetermined rate of temperature change. 
     
     
         11 . The method of  claim 9 , the first predetermined condition being satisfied when the temperature of water when contained in an interior region of a water storage tank of the water heater drops below a predetermined difference between a setpoint temperature and a first differential temperature. 
     
     
         12 . The method of  claim 11 , the second predetermined condition being satisfied when the temperature of the water when contained in the interior region of the water storage tank drops below a predetermined difference between a setpoint temperature and a second differential temperature, the first differential temperature being smaller than the second differential temperature. 
     
     
         13 . The method of  claim 12 , further comprising the step of:
 moving the damper from the closed position toward the open position when the energy generated by the thermoelectric element exceeds the threshold value and when the temperature of the water when contained in the interior region of the water storage tank of the water heater is below a predetermined difference between a setpoint temperature and the second differential temperature.   
     
     
         14 . The method of  claim 9 , further comprising the step of:
 opening the main valve to allow ignition of the gas burner using energy generated by the thermoelectric element.   
     
     
         15 . The method of  claim 9 , further comprising the steps of:
 closing the main valve when the temperature of water when contained in an interior region of a water storage tank of the water heater is above the predetermined difference between the setpoint temperature and the first differential temperature and when the temperature of the water contained in the interior region of the water storage tank is above the predetermined difference between the setpoint temperature and the second differential temperature;   routing power from the main valve to close the damper; and   extinguishing the pilot.   
     
     
         16 . A method for retrofitting a water heater having a water storage tank defining an interior region configured to contain water to be heated, a flue, and a heat source including a gas burner, a pilot, a pilot valve, and a main valve, the method comprising the steps of:
 providing the water heater with an intermittent spark generator for igniting the pilot valve, a thermoelectric element, and a damper configured to move relative to the flue between a closed position and an open position; and   providing a controller configured for:   actuating the intermittent spark generator to ignite a pilot flame of the pilot when a first predetermined condition is satisfied,   moving the damper toward the open position when an energy generated by the thermoelectric element from the pilot flame exceeds a threshold value, and   opening the main valve to permit flow of gas to the gas burner after the damper is in the open position and after a second predetermined condition is satisfied,   wherein the first predetermined condition is different from the second predetermined condition and the first predetermined condition is selected to be met before the second predetermined condition.   
     
     
         17 . The method of  claim 16 , the first predetermined condition being satisfied when the temperature of the water contained in the interior region of the water storage tank drops at a rate above a predetermined rate of temperature change. 
     
     
         18 . The method of  claim 16 , the first predetermined condition being satisfied when the temperature of the water contained in the interior region of the water storage tank drops below a predetermined difference between a setpoint temperature of the water contained in the interior region of the water storage tank and a first differential temperature of the water contained in the interior region of the water storage tank. 
     
     
         19 . The method of  claim 18 , the second predetermined condition being satisfied when the temperature of the water contained in the interior region of the water storage tank drops below a predetermined difference between a setpoint temperature of the water contained in the interior region of the water storage tank and a second differential temperature of the water contained in the interior region of the water storage tank, the first differential temperature being smaller than the second differential temperature. 
     
     
         20 . The method of  claim 16 , further comprising the step of:
 opening the main valve to allow ignition of the gas burner using energy generated by the thermoelectric element.