Method and System for Controlling an Intermittent Pilot Water Heater System

Abstract

A water heater may include a water tank, a burner, a pilot for igniting the burner, an ignitor for igniting the pilot, a thermoelectric device in thermal communication with a flame of the pilot, a controller for controlling an ignition sequence of the pilot using the ignitor, and a rechargeable power storage device for supplying power to the ignitor and the controller. The rechargeable power storage device may be rechargeable using the energy produced by the thermoelectric device. The controller is configured to selectively run only the pilot for at least part of a heating cycle to increase the recharge time of the rechargeable power storage device while still heating the water in the water heater.

What is claimed is: 
     
         1 . A method for controlling a water heater, the water heater including a water tank, a burner, a pilot for igniting the burner, an ignitor for igniting the pilot, a thermoelectric device in thermal communication with a flame of the pilot, a controller, and a rechargeable power storage device for supplying power to the ignitor and the controller, the rechargeable power storage device is rechargeable using energy produced by the thermoelectric device, the method comprising:
 when the rechargeable power storage device is detected to have a charge that has not fallen below a charge threshold:
 running the pilot and the burner to heat the water in the water tank when the temperature of the water in the water tank falls to a lower temperature setpoint threshold; 
 not running the pilot or the burner when the temperature of the water in the water tank rises to an upper temperature setpoint threshold; 
   when the rechargeable power storage device is detected to have a charge that has fallen below the charge threshold:
 when the temperature of the water in the water tank is at or above the lower temperature setpoint threshold and below the upper temperature setpoint threshold, running the pilot but not the burner to heat the water in the water tank for a first heating segment toward the upper temperature setpoint threshold, and running the pilot and the burner to heat the water in the water tank for a second heating segment toward the upper temperature setpoint threshold. 
   
     
     
         2 . The method of  claim 1 , when the first heating segment occurs before the second heating segment. 
     
     
         3 . The method of  claim 1 , when the first heating segment occurs after the second heating segment. 
     
     
         4 . The method of  claim 1 , further comprising configuring the first heating segment and the second heating segment such that there is sufficient time to fully recharge the rechargeable power storage device using energy produced by the thermoelectric device before the water in the water tank is heated to the upper temperature setpoint threshold. 
     
     
         5 . The method of  claim 4 , wherein the charge threshold is below fully charged. 
     
     
         6 . The method of  claim 4 , wherein the pilot and the burner are run to heat the water in the water tank for the second heating segment toward the upper temperature setpoint threshold before the pilot but not the burner is run to heat the water in the water tank for the first heating segment toward the upper temperature setpoint threshold. 
     
     
         7 . The method of  claim 4 , wherein the pilot and the burner are run to heat the water in the water tank for the second heating segment toward the upper temperature setpoint threshold after the pilot but not the burner is run to heat the water in the water tank for the first heating segment toward the upper temperature setpoint threshold. 
     
     
         8 . The method of  claim 1 , further comprising not running the pilot or the burner when the temperature of the water in the water tank rises to or is above the upper temperature setpoint threshold. 
     
     
         9 . A water heater comprising:
 a water tank;   a burner;   a pilot for igniting the burner;   an ignitor for igniting the pilot;   a thermoelectric device in thermal communication with a flame of the pilot;   a rechargeable power storage device;   a controller operatively coupled to the burner, the pilot, the ignitor, the thermoelectric device and the rechargeable power storage device;   the rechargeable power storage device configured to supply power to the ignitor and the controller, the rechargeable power storage device is rechargeable using energy produced by the thermoelectric device;   the controller is configured to:
 control the pilot and the burner to maintain the temperature of water in the water tank between a lower temperature setpoint threshold and an upper temperature setpoint threshold; 
 detect when the rechargeable power storage device has a charge that has fallen below a charge threshold, and in response, control the pilot and the burner to fully recharge the rechargeable power storage device while maintaining the temperature of water in the water tank between the lower temperature setpoint threshold and the upper temperature setpoint threshold. 
   
     
     
         10 . The water heater of  claim 9 , wherein the controller is configured to determine when the temperature of the water in the water tank is at or above the lower temperature setpoint threshold and below the upper temperature setpoint threshold, and when the rechargeable power storage device has a charge that has fallen below the charge threshold, and in response, the controller is configured to run the pilot but not the burner to heat the water in the water tank for a first heating segment toward the upper temperature setpoint threshold, and run the pilot and the burner to heat the water in the water tank for a second heating segment toward the upper temperature setpoint threshold, wherein the first heating segment and the second heating segment are configured such that there is sufficient time to fully recharge the rechargeable power storage device using energy produced by the thermoelectric device before the water in the water tank is heated to the upper temperature setpoint threshold. 
     
     
         11 . The water heater of  claim 10 , wherein the controller is configured to detect when the rechargeable power storage device has a charge that has not fallen below a charge threshold, and in response, run the pilot and the burner to heat the water in the water tank when the temperature of the water in the water tank falls to the lower temperature setpoint threshold, and not run the pilot or the burner when the temperature of the water in the water tank rises to the upper temperature setpoint threshold. 
     
     
         12 . The water heater of  claim 10 , when the first heating segment occurs before the second heating segment. 
     
     
         13 . The water heater of  claim 9 , wherein activating the pilot and not the burner is used to fully charge the rechargeable power storage device. 
     
     
         14 . The water heater of  claim 9 , wherein the charge threshold is below fully charged. 
     
     
         15 . A method for controlling a water heater, the water heater including a water tank, a burner, a pilot for igniting the burner, an ignitor for igniting the pilot, a thermoelectric device in thermal communication with a flame of the pilot, a controller, and a rechargeable power storage device for supplying power to the ignitor and the controller, the rechargeable power storage device is rechargeable using energy produced by the thermoelectric device, the method comprising:
 storing a lower water usage period and a higher water usage period;   detecting when the rechargeable power storage device has a charge that has fallen below a charge threshold;   when the rechargeable power storage device has a charge that has not fallen below a charge threshold, and during both the lower water usage period and the higher usage period:
 running the pilot and the burner to heat the water in the water tank when the temperature of the water in the water tank falls to a lower temperature setpoint threshold; 
 not running the pilot or the burner when the temperature of the water in the water tank rises to an upper temperature setpoint threshold; 
   when the rechargeable power storage device has a charge that has fallen below a charge threshold,   during the high water usage period:
 running the pilot and the burner to heat the water in the water tank when the temperature of the water in the water tank falls to a lower temperature setpoint threshold; 
 not running the pilot or the burner when the temperature of the water in the water tank rises to an upper temperature setpoint threshold; 
   during the lower water usage period:
 when the temperature of the water in the water tank is at or above the lower temperature setpoint threshold and below the upper temperature setpoint threshold, running the pilot but not the burner to heat the water in the water tank for a first heating segment toward the upper temperature setpoint threshold. 
   
     
     
         16 . The method of  claim 15 , wherein when the rechargeable power storage device has a charge that has fallen below a charge threshold, and during the lower water usage period, the method further comprises running the pilot and the burner to heat the water in the water tank for a second heating segment toward the upper temperature setpoint threshold. 
     
     
         17 . The method of  claim 16 , when the first heating segment occurs before the second heating segment. 
     
     
         18 . The method of  claim 16 , when the first heating segment occurs after the second heating segment. 
     
     
         19 . The method of  claim 16 , further comprising configuring the first heating segment and the second heating segment such that there is sufficient time to fully recharge the rechargeable power storage device using energy produced by the thermoelectric device before the water in the water tank is heated to the upper temperature setpoint threshold. 
     
     
         20 . The method of  claim 15 , further comprising determining the lower water usage period and the higher water usage period based at least in part on historical water usage.